The Leaves We Eat

SOUTH PACIFIC COMMISSION

The Leaves We Eat

John M. B a i l q

PACIFIC FOODS SPC Handbook No. 31,1992

Cover picture

The boy issittin amongsweetpotatoes. In the fore round thereisa young%nthosoma taro plant and near his 7 eet are some 'weed' seedlings - possibly amaranth or nightshade. On the right are stems of cassava.

Technieal Centre for Agricultural and Rural Cooperation (ACP-EU)

The ACF-EU Technical Centre for Agricultural and Rural Cooperation (CTA) was established in 1983 under the Lomé Convention between the African, Caribbean and Facific (ACP) States and the European Union Member States.

CTA's tasks are to develop and provide services that improve acceçs to information for agricultural and rural developrnent, and to strengthen the capacity of ACP countries to produce, acquire, exchange and utilise information in these areaç. CTA'ç programmes areorganised amund threeprincipal themes: strength- ening ACP information capabilities, pramoting contact and exchange of information among partner or- ganisationsand providing informationondemand.

CTA, Fostbuç 380,6700AJ Wageningen, The Netherlands

SPC Handbook No. 31,1992

Pacific Foods

The Leaves We Eat by

John M. Bailey

Food Composition Co-ordinator South Pacific Commission

Iiirst priiited in 1992 with findiicial dSSistancc from the United States Ageiicy for International 1)evelopmcnt (USAID)

lieprinted in 1997 witli financial assistancc from the Technical Centre for i\gricultural and Rural C<iirpcration (AC1'-I:U)

Soutli Pacific Commission Noumca, New Caledonia

1992

'i: Ci,~~yri&IiI 5~1uili I',iciii, Coinniissiiiii, I t j Y 2

' 1 Iic Soutli r.iiifii C'<~iiimi.ii~iti ,iiitli,nriic,s th,, rcpri,Jiiitic,ii s ~ f 1 1 ~ s m,itcri,il, whole or in part, iii aiiy form, provided appropriate acknowlcdgmcnt is givcn

Origiiial text: Eiiglisli

Soutli Pacific Commissii~ii Cataloguiiig-iii-publicatit)~~ data

Bailcy, Joliii M. Pacific f««ds : Tlic Icaves wc cat / by Joliii M. Bailcy (SPC li,iiidbouk ; ii0.31, 1992)

1. Grcciis, Ediblc 1. l'itle II. Series

641.353 ISBN 982-203-245-5

Prcparcd for publicatioii at South Pacific Commission Headquarters, Noumea, New Caledonia, and priiited by

Stredder Print Limited, Auckland, New Zealand, 1992

PREFACE

1. About leaves

II. Leaves for health - composition and handling

General compositioii Caiicer protectioii Flavours and aromas Toxic substanccs Maximum healtli bctiefits Other cookirig effects Darker the bettcr Nutrieiit value Reduciiig iiuhieiit loss

III. Use of leaves

As a food source For colour and flavour III food preparation and storage Food processiiig In mediciiic Protein source aiid preserved food supply Summary

IV. Composition of some leaves eaten in the Pacific Islands

1. Lcttucc 2. Taro 3. Papaya shoots

(iii)

CONTENTS Page

vii

1

3

3 3 3 4 5 6 6 6 7

10

11 11 13 14 14 15 15

16

16 18 20

4. Cabbage 5. Nightshade 6. Winged bean 7. Chayote 8. Jointfir Y. Water spiiiacli 10. Pumpkin 11. Chiiiesc cabbagc 12. Drumstick 13. Cassava 14. Kale seedliiigs 15. Water dropwort 16. Watercress 17. Tropical spiiiacli 18. Swcct potato 19. Taro (leaves) 20. Fern 21. Edible hibiscus 22. Basella

V. Nutrient composition

Cwkiiig and iiutrieiit value Differciiccs iii lcaf compositioii Improving nutrient valuc Comparison of iiutrieiit compositioii of leaves

VI. Composition of lettuce leaves

W h y lettuce? Frotein Fat Carboliydrate Fibre Minerals Vitamins Otlier substances

VII. Future for leaves

VIII. References

Appendices

1 . Nutrient compositioii of some greeii Ieafy vegetables eateii iii the Pacific

2. Aiialytical metliods

Acknowledgments

Figures

1. Water 2. Fat 3. Eiiergy 4. Protciii 5. Carboliydrate 6. Fibre 7. Sodium 8. Potassium Y . Calcium 10. Magncsium 11. lron 12. Zinc 13. Thiamine 14. Riboflavin 15. Niaciii 16. Vitamin A 17. Vitamin C

(vii)

PREFACE

issues wliicli arc iiow of growirig iniport'jiice in tlic I'acifii.

I l > < , ! I ! ~ I ~ ~ L , I , . : . ~ i t t . ~ ~ ~ i . , ~ i l < , ! i \ I L ;:i , IL . r . , r \ ,, ;r<.,c . \ < . I I , l L , ~ , . , : t ~ ~ ~ ~ ,; ,I, i l ) . i i l . ,,r t.jrl<,!i dc

~,l.iiii .,ii.i ;r.ii\.iii; . . > i > . I i i i . i i i . 1 I . i . i.,tr~.~liiliti. i i i i i - i i.. iolls , l l , : ,r<, I.I!. . l . I I I . ~ .>;lii>~,.l

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I l i L i i i i .~r :~i l i i .~i i > r i . nis I I , < I~ i - : : i : 1 . 1 . . l ( . m . or.. f i i i i i - t ~ l ' l 1, . ! r : .. :1 ' L I - I\ I I h II : l i . I I .

i.i.,,i- iii.lr.i,.rr.i/iL~~l 't i~i: ; i i i . i t i : . i . :~ i . i , i : r . ; i : I i i i r .~ l i~ i~~ i i . . .r.i,::.~~ i i i r~ .m.<.I.:s i . i.11.. i i - r i i i , i

i ~ , , ~ t ji lL~:,iIl~ l>r~).iu:..l ;.,.:II 1 . . , i \ v ; . t . t l>l, .

The nrany aiici valuable coiitributioiii i,f earlicr workers arc arkiiowlcdgc~i aiid .i brief Iiistoriçal b a c k ~ o u n d is tlicreforc iiicluded tur tlic rcader's heiicfit.

otlier witli niatcriial aiid iiifdiit wclf.rre

111 1950, tiicsc projects wcrc turtlier cxp?iidcd to iiiclude tlicitudy o t infant fo<ids, cspecially the prcpûratiuii frrirn local resourceiufa suitahlc focid for tlic weaiiiiig pcriod aiid dctcrniinatioii r i f

tlic nutritive \p.ilue uf islaiid fciods. TIic SI'ï's dictitiâii and ii~itritionist carried uut extensive rcsearçh ii i 1'apu.i Ncw Cuiiic'~, aloiig the East Coast uf Ncw 1ri.lati~i aiid i i i the Trobriaiid Archipelago.

A bioclieiniit, F. E. I'ctcrs, appoiiiteci i i i May 1931, cdrricd out rescarcli oii tlic iiutritioii.il valut of l'acific lslnncl fuods, espcc~ally coc,,iiut and saiiiples of brcast rriilk collected fruiii tlic Ncw Hcbridcs (now Vanuatu) by Miss Malcolin, the nutritionist.Tlic,xii.ilytical wrirk wasdi ,~ici i i tlie Instituti. o f Aiiatoniy in Canberra, Australin. Tiie SI'C âlsii gave a graiit to tlie Laboratory of Bioclieniistry, Ott1 ,O Utiivcrsity, New Zealniiii, for a rcscarcli study on tlie aniiiio-acid c impo- sitir~ii of IJacific ~ s k n d foods.

During 1952, tlie hioci~cmist contirrued iiis w»rk in Cai~ùcrra oii tliccomposition of cocoiiut and breûst milk and the thiamine coiitciit r i f Fiiaii rice. Ap roval wns giveii fur a n cxpaiisiriii of the food cumprisitiriii prnject to includc a ..tud i i f tlie u s e h n e s s of ruteiii fruin ci>ci>nut a s a food sourcc. Rctwccii Marcli aiid Çcptciiibcr, 1&3, MT Peters visited Ihc Uiiitcd States, EiigIaiid rliid Iiidia. On his return, Iiebepiii aiialytical work tit tlic ORSTOM labor,iti)ry in Noumca on water, ail,, fats, st,lrihei, rcduciiig sugar aiid fibre.

foods wcrc givcii tlie highest priority

Dy April 1956, tlie laborator was fullv staffed aiid cquippci . I t w'is t i i~w able tu aii.ilysc fixids for 'proximatei', amiiio acii?s and sonic vitamins.

(viii)

Most of the foods aiial x d were from Ncw Caledoiiia. All tlie tubcrs cxamincd (taros, sweet potatocs, yani.;) werc JLflcicnt iii oiic or niorc essential amiiiu acids. Gciicrally spcakiiig, tlic proteins wcre reasonably good aiid a niixed dict of taro and yams, or taro and sweet potato, or eachof thcscwitligreen leavcs, would supply the balaiiceofamiiiu acidsnccded for a satisfactory dict. Coconut !vas fouiid to bc low iti the sulphur arniiio acids. Tlic protcin and carotene (pro- vitaniinA)ofswectpotato varicd widcl withvarieties,butthe arniiio-acid profilesdid nntdiffcr significaiitly. Çago coiisistcd inaiiily "?starch and water.

During Iiis scrvicc witli SI'C, tlic biochciiiist compiled a lliblio rn iliy of rit,frifior~nl flspects of flic coc<iiruf,(Sl>CTecliiiicalI'apc.r No.58,1954), arevised editioii($ecAnical I'apcr Nri. 95,1956)aiid ai1 annotatcd bibliograpliy, Chcriricnl cil>ii~>i~s~fi~>l o SoirfIr IJncificfi~o<i (Tccliiiical Paper No. 100, 1957). This publicatioii çoiitaiiis 105 pages witli i 26 rcfcreiiccs (niaiiy with food coiii oiition data), ai? autlior iiidcx, ail iiidcx of furid laiits rlussary uf sçieiitific nanies anJ)afuod composition tablec<iiitaiiiiiigdata iiii sceds( f 4),starrliy . ', " foods(l71, lcafy vegetables (10) and frcsli fruits-(14). Allfouds;ircgivcii tlicirsçiciitificiiaiiicsaiid figurcsarc prcseiitcd foreiiergy, water, protciii,fat,carholiydratc,fibrc,calciuiii, p\iuspliorus,iron, carutciie, tliiaiiiiiie,riboflaviii, iiiaçiii and asccirbiç açid.

Tlic aiialytical wcirk was suspciiiled at tlic eiid of 1956 1i i 1957, the bioclicniical laboratory was closcd aiiii its p~crsi,tiiicl di~~~,iiicled.

Duriiig tlic t i c ~ t 211 ycars, f o i ~ i .in.ilysis rcçeivcii i i c i furtlwr attciitioi~ froiii tlic SI'C Healtli Services.

By 1979, scveral surveys i ~ f licaltli problciiis anioiig Melanesiail aiid Polyiicsiaii populatioiis Iiad bcciicarricdout.Tlicri~sultsiiitliescsurvcyssuggcstcd tliatçcrtaiiipopulatioiiswcrcsuscc.ptiblc to a varict of cliroiiic diseascs coiiiiiioiily associatcd witli urbaiiisatioii, westerii lifcstyle aii<l dict. ~ l ic?I 'C rcçcivcd fiii,iiicial support iii 1980 fora stud i ~ f t l i ~ and iiutritional status <if Pacific Islaiidcrs. Duriiig 1981, witli fu~idiiig providcd {y tlic;t%&atioiis Devclopnieiit I'rograiiinic, al1 tlii. varirius survcy results .iiid iiiforiliatioii oii tlic cffect of urbaiiisatioii and wcsterii dict oii the Iicaltli of 17.icific Islaii~lc.rs wcrc brouçlit h>xctlier. Scvcr'il iii-ciiuiitry

of I'acific Islaiid populatioiis'.

A workirig rroup, oii fiiod coiii xisitioii t,ihlcs, coiiveiicd by SI'C in Nciveiiiber 1982, io~isidcrcd tliat SIJC's kooii oi>rlposifii,rl fnthcs f<,r tusi, i i i flic Si~iifii I>nci,ii iu.is the iiiost suitable set of tables available for routiiic dietetic aiid public Iiealtli practicc i i i tlie I'acific rcgiuii aiid sliuuld he used uiitil a bettcr set of tablcs was roduccd. I t recr~iiinieiidcd tli.jt CI iiutrieiit databascof iiidi 7eiious aiid iniported fc~odç C<>llsUnlC~iil the I>ncifiç bcestablisliecl. Italso rcçoiiiiiieiidcd tliat adkitional iiutrieiit coiiipositioii data oii iiidigciious and in1 wrtcd foocis c<iiisumcd in the I'acific be produced. and suggestcci tliat niucliof tliis food aiia/yiiscoulci aiiù sliiiuld beperfornicci witliin the Pacifie TL< > -1oI1.

Mcctiiigs of Paciiii Island Heads of Health Services (1983) and Heads of Agriculture aiid Livestock (1984) rccommcnded tliat SPC once agaiii pron~tltc food composition studics for the benefit of people in the Pacific rcgioii. As a result, a roject eiititlcd 'Developmeiit o f food composition tables iii thc iJacific region' was includef iii thc Crimmission's nutrition work programme in 1985.

Thc followin year, thc South Pacific Commission o r p s e d the First Technical Workshop on Pacifie Food Poiiipositioii Tables, with fundiii from t e Uiiitcd States Agency for Iiitcriiatii>iial hvcl»pmciit(USAID). Rc rcsentativesfrom kur~acificanalyticallaboratc1rieswere rcseiit- tlic lnstitutc uf Natural &sources of the University of the Çuutli Pacific (INR, ES;, Fiji); Departmciit o f Prirnary Iiidustr I'apua New Guiiiea; the National Anal tical Laborator Uiiiversit of Tcclinulo~y, Lac, ?apua NEW Guiiiea; aiid tlic Iiistitutc of Aedical ~ e s e a r c l : Madaiig, Fapua New Guinca. Nutritioiiists,dictitiaris, hoineecoiirii~iists,agriculturistsandfood tccliiiologists froni tlii' regiiiii took part, aluiig witli observers froiii ititeriiatiuiial, rcgioiial and national organisations.

The worksliop dcfincd tlic niaiii ainis of tlic I'acific Islands Food Coiiiposition I'rograiiiiiie (P1FCP)andaskcdSPC toappoiiita full-tiiiiero-ordiiiator tnirnpleiiic.nt tlic pro rramiiic. Itdrcw up listsuf priority foods furiiiclusioii iii the PIFCP, iiutriciits and aiialytical mehiods to beuscd, aiialytiç.il equipmciit nccdcd and putciitial rescarcli projects wliicli cr~ulii fl«w froiii tlic ,ro r i i . T e reonitiieiidatiiis aiid r lai~s wu! kt11 iwn rcl~ctisive aiid ainhitiuus. $11; i i ia~or~ty of participants uiifortuiiately iad uiirealistiçall hio[ cxpectations of wliat cciuld be ~~cliicvcd by tlic liiiiitcd tccliiiicâl rcsuurccs available in tJe Facific.

The first Ford Comnositioii Co-orciiiiatur. Dr Heatlier Greenfield. froiii tlic Uiiivcrsitv of New Soutli Wales. ~us t r a l i a . was aonriiiitcd ir; November 1987 for a terni <if oiic vcar. d s ~ i t c tlic

Aftiir tlie departurc (if Dr Grceiificlii, tlic p rog ran~n~c contiiiued uiider tlie guid'iiicc of tlic SI'C Nutritioiiist, Dr Jaccui Badcuck, ~ i i i t i l a IICW c~>-ordinatur, MT J U I I I I Baile fruiii tlic Uiiitcd Kingdom (fornicrly hic Cliicf Agricultiiral Clien~ist for tlie Coveriimeiit of l%pU.i Nciv Guiiical was appointcd in April 1989.

foods, fruits; iiuts, mixed &>oked I'acific fonds, siiaçk~urids, br&stmilk, cereals,~lie~~ercigcs, iiieats, Iierbs aiid spices, poultry, iiiilks, eggsaaiid coiifcctioiiery.

c<imirioiily eatcii g;ccii lcafy vcgct.iblcs. Tlic rc;ults Lf tliese aiialys~s, togetlier wiih colour lliotog~a 115 anii infc~rn~ation ab«utgrceiiIc,ify vrgetables, are puL>lislicd for tlic first tiiiic iii tliis

aiidbuof. '

1. ABOUT LEAVES

Leaves of oiic kiiid or anotlicr arc al1 arouiid us. They are usually greeii. This is ni) accidciit.Tlie green colour isgivcn by substaiicescalled chlori)pliylls.Tliescare vital fur the miraculous process callcd pliotosyntliesis, wliich uses tliem tu capture ciicrgy from tlie suii. This energy causes carboii dioxide from tliea tniosplierc to combiiie witli wa ter, creatiiig organic matter or 'food' aiid oxygcii. /,--',

Grcciii lcavcs arc dcsigiicd aiid positioiied oii eacli plant i i i sucli a way tliat tliry caii in,iki> the bcst possible use of eiiergy comiiig froni the sui1 iii a groit iraricty iif

eiivirciiimciits ovcr tlie eiitire globe.

The 'food' formcd in lcaves caii Lie used dircctly (by aiiimals wlricli eat llic leaves) or iiidircctly (after accumulatiiig in diffcrciit parts of tlie plaiit, sucli as fruits, tubcrs or iiuts, in ,i varicxty of forms - starcli, fat and protciti).

Tlic lnrgcr the Ieaf area a plaiit isablc tr) expose to daylight, tliemt>re 'food' it produces. I t c«iiseqiic.iitly requires iiot oiily more water and carbon dioxide, but also morc < > f a ivliolc range LI! elements from the suil in wliich it is growing.

Plants ,iildptcd to a desrrt cxistciicc gciierally Iiavc very sni,ill leavrs diid dcep roots, ivliilc ,iiludtic plants Iidvc Iarger leaf areas aiid rclatively iiisigiiificaiit rootiiig systcnis.

Food plantsof tlie same family illustrate the wide range of eiiviroiimeiits tliat tliey caii exploit. The swcet potato (1;~oino~a batatas) necds excclleiit drainage for success, while its relative kangkoiig (Il?oinoi.a aqiraticai thrives in water.

Leavcs from decp-rootcd trees or otlicr well establislied peri.iiiiia1 p1,ints arc loss affected by abrupt changes in tlic weather. Aiinual crops, on tlie otlier Iiaiid, Iiavc sliallow root systems and more delicatc leavcs which respoiiù quickly to cliaii~es in ., eiiviroiimeiital conditions. Sliallow-rootcd secdliiigsaiid most fast-growiiiggrceii Ic.ify vcgetablcs are particularly vuliierablr to lack of water.

Animal life, ailotlier miraculous process, depends eritircly oii the grecii plant aiiii Iiumaiis are iio exccptioii. Leaves eaten by animals are one of the inost efficiciit converters of the sun's ciierhy tliat exist on earth.

Piigç 2 SV<: liniidb-ik Ni,. il. IV92

II. LEAVES FOR HEALTH - COMPOSITION AND HANDLING

General coinposition

Frcsli lcavcs gciicrally contai11 a lot of water, some Iiigli-iluality protciii, a littlc fat (mostly uiisaturatcd), some cticrgy, fibre, miiierals, aiid a wide raiige of vitamins, cspccially the pro-vitamin A pigments called caroteiioids (see Appcndix 1). According to Becclicr aiid Iiis collcagues (19901, the most usual caroteiioids fouiid in comm~iily eateii Pacific foods, espccially grecn vcgetables, wcrc lutcin niid beta-caroteiic. Yelltibv, oraiige aiid red fruits and vcgetables coiitaiiicd tlic widcst varicty of caroteiioids. All Pacific fruit and vcgetables ci>iitaiiied bcta-carotene togetlicr witli at least i~iic otlicr carotciioid. Pale-colourcd foods sucli as taro flesh, liglit-ycllow swect pcitato flcsli, aiid liglit colourcd piiicapplc coiitaiiicd vcry littlc beta-caroteiie.

Cancer protection

Caroteiioids scem to play an important role iii protectiiig aiiinial cclls from ciiiiccr. Accordiiig tu Mathews-Roth (198Y), skin tumeurs iiiduced by ultra-violet B radiation wcrc sigiiificaiitly delayed by car»tciioids. He concludcd tliat carotcnoid pigments, irrespcctivc of their pro-vitamin A activity, could preveiit or dclay the growtli of skiii tumeurs especially tliose iiiduced by ultra-violet B aloiie.

Dark grreii leafy vegetables als~i coiitaiii a wide raiige of utlicr Iiiglily clicinically iictivc subst~iiices wliicli iiiteract witli 11tlier iiutrieiits tomake tlicm mi~rea\,ailablc tu aiiiiii,ils. Vitamiiis C aiid E are botli described cliemically as 'reduciiig agciits'. TIi~>sc ni,iki miiicrals sucli as ir«n morr available to the animal. Tliey tu« arc tliouglit to pldy a n~l i . in caiiccr pri~tectioii, becausc of tlieir capacity tu iieutralisc active oxygeii.

Flavours and aromas

Some plants coiitaiii a lot of 'essential «ils', known cliemically as terpeiies. Tlicse substaiicrs arc prescnt in higlicr conceiitrations in hcrbs and spiccs but thcy arc also to

--- Ik 1 ~ 8 ~ 3 WC Ca,

be found in the different fruitsand vcgetableseateii by man aiid give them their special smells or flaveurs. These 'essential oils' caii be extracted from leavcs and are uscd iii flavourings, perfumes and for traditional medicine. WC can smell these 'oils' because tliey are higlily volatile. This means that tliey are easily lost to the atmospherc wlieii leaves coiitaining them are cruslied or cookcd.

Toxic substances

Uiifortunately some substances fouiid iii leaves are Iiarmful or prevciit the propcr absorption of otlier iiutrieiits. Examples of tliese are oxalate crystals in taro leaves, cyaiiidc in cassava, phytates iii cereals, goitrins in cabbage, aiid eiizyme iiiliibitors iii beaiis.

Oxalate crystals in taro leaves aiid tubers caii make the moutli and tliroat sure. The oxalate also makes calcium less available and may Icad tu the poor absorption of iroii, magiicsium aiid copper (Beier, 1990). Large quantitics are also poisoiious to animals. Tliey caii be removed fr»m taro lcaves by boiling well aiid pouriiig off tlic liquid.

Cassava leaves also nced to be properly boilcd to get rid of aiiy cyaiiidc prescnt i i i the leaf. 'Bitter' varieties contaiii more cyaiiide compounds tlian 'swcet' varieties. Swect cassavas usually have a lower cyaiiide content, wliicli is coiifiiied to a layer just uiider the skin, aiid softer and whiter flesh tliaii the firm yellow flesh of tlie higlicr cyaiiidc types. Tliey mature earlicr (6 months) and oiily kcep about oiie year iii tlie grouiid, compared witli over three years witliout deterioratioii for the bitter or Iiigli cyaiiide cassavas (Purseglove, 1968). The leaves usually contaiii more cyanide thaii the tubers.

Pliytates make iroii less available aiid goitrins interfcre with tlic uptake of iodiiie, an essential elcmeiit for the thyroid hormoiie, tliyroxin. Certain eiizymcs iiibeaiis prevciit tlie digestion of protciiis, but tliese caii be removed by soakiiig the beaiis in wnter aiid pouriiig away the watcr before cookiiig.

Traditional Pacificfood prcparatioiimctliodshaveelimiiiated or rcduced maiiy of tlicsc. unpleasaiit substaiices by a prosess of trial and error over the ycars.

Boiling docs, howevcr, destroy %)me of the otlier vitamiiis, such as Vitamin C and folates, aiid pouriiig away tlic water will mcan tliat water-soluble minerals and vitamiiissucli as potassium, sodiumaiid some of the B group vitamiiis will be lost also. Pro-vitamiii Acarotenoidsarereduced by boiling but iiot to thesameextentas theotlier vitamins.

Page 4 SFC liuii~biuk N,,. I I . I Y Y ~

Food processing, storage and haiidling also seric~usly affect the nutrient levels in grccii Icavcs. As soon as the leaf is removcd from the plant, itscnzymes begin to break dowii many substances. The degree of enzyme action depends on the extent of tlie damagc suffered by the leaf.

Maximum health benefits

111 order to obtaiii maximum hcaltli bcnefits from green Ieaves, tliey shoiild bc eaten fresh or as liglitly cooked as possible. Cooking methods wliicli are quick and retaiii al1 tlie cookiiig watcr are tlie best, but of course thcy are iiot suitablc for lcaves wliich contain cyariides or oxalates. At cvery stage froin Iiarvestiiig the leaf to the cvcntual coiisumptioiisomevitamii~sand minerals will belost. Mostof tliesubstaiiccs ivliicli are said to bc Iicaltli-protectiiig, except protcins, are extremcly vuliicrablc to loss or degradation.

Grccii lcaves iieed to be haiidled very carefully. Physical damagc, whetlier causcd by cuttiiig, bruisiiig, freezing, over-heating, excessive cxposure t« light (cspccially suii- light) during dryiiig or storagc, insects or disease, should bc miiiimised for maximum iiutrieiit reteiitioii.

As ' 3 gaicral rule, the most active substances are the ones wliicli are lost Iirst. Uiifortunately maiiy of tliese special Iiealth-protectiiig substances arc alw very activc clicmically. Green leavcs iiecd to be washed very carefully before being eatcii fresh. This is iiot always possible when water is in short supply or is pollutcd. Cc~oking the greciilcavcsis tlicn the bestmetliod of processing,especially for youngchildren. Grecii leavesarcstill alivcand respiriiigshortly after gathcring.Tliatmcans they need oxygen, so grccii lcafy vegetables should never bc scalcd in air-tight coiitaiircrs. Wlieii scaltd, tliey quickly start prt~duciiig clicmicals which damage the cells, cause bn~wri spots, change the flavour aiid ge~ierally make them incdiblc.

/ Lid 5 t h Container

srna11 holei ,O PIIOW

are, to ari in a"J""t

Other cooking effects

Some greeii leaves are changed chemically during the cooking process. This caii increase their smcllsor flavours (McGee, 1984). Herbs havcstrong smells and flavours wlien raw, but a cabbage Ieaf caii dcvelop very strong odours wheii it is cooked for a long timc. These odours come from a family of substances wliich contaiii sulpliur and are called isotliiocynatcs. Hydrogeii sulpliide is also produccd - giviiig the smcll of rotteti eggs. So a geiicral rule wlieii cookiiig the cabbage farnily (mustard, brussels sprouts, cauliflowcr, broccoli, turiiips) is tliat fewcr iiutrieiits will be lost witli sliorter cookiiig periods aiid fcwer objectionable sulpliur compouiids will bc forined. Stir- fryingorcatingraw iiisaladsare two waysof usiiig vegctablesfroin tliccabbagc farnily that will reduce nutrient losses and uiipleasant smells.

Darker the better

Auseful guideline forestimatiiig thcrelativciiutritioiial valueof green leafy vcgetables is "ïhedarker tlicir colour, the more vitamiiis tliey contain'. This is bccause plants makc Vitamin C from simple sugars supplied by the lcaves from pli«tosyiithcsis, the eiicrgy- trappiiig process meiitioiied earlier. The m«rc liglit the leaf receivcs, the more plio)to- syiitliesis tlicrcis aiid tliusmorc sugarsare produced, wliicli iii turii givc niore Vitamiii C. In addition, in order to Iiandle more liglit-eiiergy input, tlic plant iiccds inorc pigments, sucli as cliloropliylls aiid carotciioids, in the leaves and tliereforc the Icavcs and stems arc a mucli darker greeii.

Thcpalciiiner leavcsof lettuceaiid cabbagecoiitainoiily a fraction of the carotciieof tlic dark green outer leaves-possibly 30 or 40 timcs less. The trouble is tliat tliesc outer Ieaves are more likely to be damaged cither by insccts or the weather and probably ciid up beiiig tlirowii away or used as animal food.

Nutrient value

Some final commcnts about the iiutritioiial value of green lcafy vegetables are worth repcating. As meiitioned at the bcgiiiiiitig of this section, greeii lcafy vegetablcs suyply vitamiiis, cspecially Vitamiiis A, 8, C and E, aiid some miiicrals. Vitamiii A prccursors, tliccaroteiiepigmeiitsaiid substances with Vitarniii E activity arciiot water-solublebut fat-soluble, wliileBaiid Cgrciup vitamiiis, togetlier with tliemiiierals, are water-soluble and arcliable tobelostiii tliecooking water if itispoured away.Caroteiiesarerelative1y stable, white thiamine and folates are heat-sensitive and Vitamin C and Vitamiii E substances are very sensitive to both oxygeii and heat.

Page 6 SPC iluicihuii Na. i l , ,991

Reducing nutrient loss

For cooking green vegetables, therefore, use the shortest possible cooking time and the leastpossible water, with undamagedor uncut piecesof vegetable. Inother words,cook the leaves intact and only add salt to taste after cooking. Salt added during cooking increases the loss of soluble nutrients.

A useful list of green leaves is shown in the table below (taken from South Pacific Fmds Leafirt 6,1983) together with their photographs. Some of the leaves shown have now been analysed in more detail and the results are shown in Figures 1-17 and in Appendix 1.

SPC ~ a n d h ~ k NO. 3 1 , 1992 Page 7

EYOW* NAML Y i lEYnlC * M E L r X A L N U I iW0 VALUE OEBCIIPTION OF PU*, P I E P A U M H U m O D 0. hl

1. aibika. ~be!moschus w le maniho,

V ~ R W small v m d y buîh; ESSY ~ e t w (no many ditlemnt kindî longer than 5

ml""teS, turn 1eaveo once1

2. amiranth. Amsran<hus Impical species

"eV gmd plant with rfmd-up Easy Methm or Sfir

aplnsîh, stems and spiker of Fiying

csyion Ilaera: man

spinach dlfferenf kind;

3. basella. Bssella alba crssping Barella n ian

omd climbin or burny ~ i u y eth hm ho rpinach

Plant Wyth Pink or longer than 5 ",nile fiOwen minutss,. stir

F"i"9, or iaw in salads

4. bmadlwlt Ariocarpus 1-"ea 11,1,1$

VBV gmd large fruit-bearlng tree Chmss very young 1ea"es. wnenad Ove, a Il-; mmve stetk. then cm* 4 Eiuy MetMd for 20 minute8

5. caasava Maniho, leami SSCUk9"U

MV g d rmt-karing rnrub ch- ieavea; cmk by Special Methm. Oa not sst rsw

Bcni l l i Cspgkum bava n " t a m

vw DDod ;;:Al fruitharing Easy Methm w stir Frying

7. ml- Brssska ubbspe. Chi"S"sls

gmd da* oieen leavss wlth Eiuy ~s thad . stlr

Pak chol lighf sta1lu Fiyi"9. or raw in

salaas B. m p s vlgns

IWve6' unOuhuldld 9Ood dlmblng or hshy Eaay Methm or Sfir

plan! with long pea FVI~Q W S

8. dwmîtlck Mdngs t m . mirera

vsiy o d =mal trse wifh plloviahuh#fe Eiuy MmMd or Slir

hDRB FViW

MlSh lowen and long pads

Ires 10. Eumpeui Bns& fair

ubbspe o*nni . *a,. aolid muM heada of Easy Methd, Stlr

capitat* llght orsen 1-ves Fv iw. or rau in

salads I I . lem Alhydum

e5e"b"lum DDod large vild fsrn fhat use top of 3talks.

amui in wel placsi apllt into four ~ k e % t h cmk &, Esly Msfhcd

12. wtum, Gwlum &l"t,l, g M m M

veiy g d mail nul-karino trse CMdse ue<y young

rplnash lhat uirunlly gmwa In lurui, use E u y the DYlh Mslhad a Stir

Fiyin9 O no, eat .a",

13. IMlan M W mu1bary c,tti,oiia

veiy W rmrll Ires r l f h white Vi- veiy young

1- flowem and bumw laaver and use fwita Eaay Msfhd

14. kaqlwig, lpomoes 9md tnlllno plant lhat Eaay ~ e f h m . stlr 01WS in uatw or on Frylno, w rsv In dV land MIMS

1 5 pumpkin Cucumlfs gmd lrulf-hepring vine 1-m8 m > l a t a %2YPd"

use -y ~ m h a d 8, Stlr F i y l q

16. -11s. wbireus rsd SORS1 YDLWflS

small with h s y ~ m h m or stir DDod d y Mmchss Wlog

37. suaet 1pomoes t """ Qmd mnbenilng vine Essy Methad or Stli

FVI"0

18. taro m a s U I leama assumtl

wv g d r m t k i n g shnib Cho- WH w n g

rnlhoMUi 1- wlfh stalks, use g l e d

rpsW Mnhad. O no! eaf n w

18 ustw. NaslwWum cm- 0llk~"ale.

W tislllno plant fhat Collecf only from g m w in watsr c h " w s , a EDay

W P a ruslu,,l"m-

Methm (only 3 m 1 n w SI,,

4usflcum Firina 4 raw In salads

W. vlnped m w u r M'Y g d cllmMno plint vith ~ n r y ~ m h a d sur Man f0IW-9 1-

imo fovrsided ws ~iy inp, or in salads

'NO PMtwnph 1s à,mn

Page 8 SPC H i o h k Na 31. 1992

Page 9

III. USE OF LEAVES

Leaves are widely eaten in the Pacific. They are also used to wrap other foods, usually the root crops and protein foods sucli as fish or meat, duriiig cooking.

As mentioned earlier, green plants are able to absorb eiiergy from the suil with their special coloured pigments and store it iii different forms sucli as carbohydrates, fats, waxes and proteins.

Humans caii sytithesise Vitamin D in tlieir outer skins when exposed to sunlight, but animals do iiot Iiave special pigmeiits to capture the suii's eiiergy and make their owii food as plants do.

Animals tlierefore Iiave to depend entirely, either directly or iiidirectly, oii plant food for their energy supplies. Reptiles, such as some types of lizards, do need the sun's direct warmtli, Iiowever,iti order toliaveeiiouglienergy todigest tlieir plant food. They can't eat if tliey are too cold!

Page 10 SPC k m m k N% 31,1992

Humans use leaves for food either indirectly, by eating the herbivoreç-sheep, cows, rabbits, etc. which have obtained their energy by eating grass and other plants, or directly, by eating green leaw vegetables.

In man'searly days he wasdescribed asa 'hunter and gatherer'. He hunted, fished and gathered leaves, nuts, tubers and fruits. Later he kept animals under his control and grew his own crops - what we now cal1 agriculture.

As a food source

A greater variety of leaves was probably eaten in the days before agriculture, because the different herbs, bushes and trees would have been widely distributed throughout the area where the early Pacific Islanders lived and hunted.

Eating a large variety of leaves is a good practice, because no particular leaf contains everytliing that is needed for good health. Man's sumival must have depended a lot on the variety of leaves eaten. Nueition studies in the Pacific in the early 1950s stated that green leaves were generally considered a substitute for meat. Meat or fish was only eaten on average about three times a week.

Settled agriculture with domestic animals and cultivated vegetables probably resulted in a reduction in the vanety of leavesconsumed, either because not al1 the plants would beable to grow on the farmsorbecause people would tend toeatmore leaves from those plants which could be grown more easily or took less space. Perhaps people began to grow more of certain food crops for status reasons, or for security against natural or other disasters. The yam, for example, is given high prioriiy as a root crop in many Island couniries.

For colour and flavoui

Ashumansbecame more sophisticated, leaves were used to make food moreinteresting and acceptable. Leaves were used to add colour, flavour, moisture and different textures to food.

- Kangkong with tinned meat, onions and baby tomatoes (top left) -Green salad (lettuce, watercress, spring onions and nightshade leaves) (top right) - Pumpkin tips in coconut milk (bottom left) - Snapper, bele leaves and yam, steamed (bottom right)

Page 12 SPC H U ~ ~ L NO. 31. 1992

In food preparation and storage

Banana or other green leaves are often used in the Pacific to wrap up root vegetables such as yams, taroand sweetpotatoesand meat or fish forbakinginearthovens('lovo', Fiji; 'umu', Tonga; 'mumu', Papua New Guinea). Breadfruit leaves can be used for this purpose, but, like al1 green leaves, they must always be washed well with clean water before use. The leaves are often softened slightly over the fire or hot Stones to prevent them cracking or splitting when they are wrapped around the food. Sago and cassava leavesare alsousedas wrap food beforecooking. 'Leaf laplap',Heliconiasp. and 'burao' ('fao'), Hibiscus tiliacrus are used in some island countries for the same purpose.

Coconut frondscanbe woveninto baskets to holdlargefishorpiecesof meat. Pandanus is commonly used to wrap seafood such as beche-de-mer. Banana mid-ribs or panda- nusand coconutleaf frondsaregenerally used for tying up the food bundlesbefore they are placed in the earth oven.

The wrapping leaves seal in moisture and nutrients duritig cooking. Flavours are retained and the cooked food more palatable as a result.

Wrapping leaves also have additional effects on the food. Some leaves, such as papaya, contain the protein-splitting enzyme papain and tenderise any meat they are covering.

SPC ~ i n k k NO. 31. 1992 Page 13

Fat-soluble Provitamin A and Vitamin E are partially extracted from the enclosing leaves by fatty food, thus improving the overall food value. The leaves also act as a protective bufferbetween thefoodand thefire or hot Stones, thus helping toretainmore heat-sensitive vitamins in an active state and protecting food from contaminants.

Some of the larger leaves from plants such as breadfruit, taro and banana were commonly used as 'plates' in the old days before Captain Cook arrived in the Pacific with his ceramic plates, crockery and other European customs. Plaited coconut leaves can be used as food bowls and storage baskets to store large quantities of baked food from the 'umu, or to contain food for traditional feasts ('pola', Tonga).

Food processing

Some simple food processing techniques use leaves. For example, many cocoa produc- ersin thePacificandGhana, Africa,utilise banana leaves toproduce high quality cocoa. The freshly harvested cacao fruits are removed from the& pods and wrapgd with banana leaves in largebundles. The bundles are left to ferment forabout seven days, and then, after drying, =an be ground or pounded to produce a kind of cocoa pasté.

Certain leaves are used directly to make hot and cold beverages. The young tips and leaves from a particular type of camellia bushareplucked, partially fermented and then dried to make the familiar drink, tea. Lemon grass and orange and lemon leaves are al1 widely used in the Pacific tomake pleasantly flavoured dnnks. Oneor two small blades of lemon grass are infused with a cup of hot water for about five minutes to give a refreshing hot drink.

In medicine

Many of today's modern drugs or medicines have been developed from the thousands of natural products found in plants. Either they have been extracted directly from the leaves or organic chemists have synthesised them in the laboratory from the appropriate organic molecules. More than 20 percent of commercially prepared dmgs originate from plants (Beier, 1990).

A commonly used pain-killer has its origins in the willow tree - Salix sp., hence acetyl salicylate and the familar dmg 'aspirin'.

Two classes of chemicals regularly employed in medicine and found in plants are the alkaloids and terpenes. Alkaloids often have quite remarkable effects on the body and

Page 14 SPC H m h t Na 31. 1992

the group includes quinine, extracted from the bark of the cinchona tree and is used to treat malaria; atropine, which comes from a member of the solanum family, and is used to treat organo-phosphorous insecticide poisoning; morphine, a powerful painkiller made from poppies; and many others. Terpenes, which are used in perfumes and medicaments, are found in the essential oils of herbs and spices such as cardamom, pepper, chilli and cloves. They are also in the leaves of eucalyptus and melaleuca trees (known in New Caledonia as niaouli). Niaouli leaves infused with hot water are said to relieve aches and pains. The niaouli oils in the vapours from a hot-water infusion also help to relieve an asthma attack. Other substances found in leaves or flower petals and seeds are pyrethrins, from the pyrethrum daisy, which are used in rapid-acting insecticides, and cineol and terpineol from cardamom, a member of the ginger family.

Readersinterestedinfindingoutmoreabout medicinal plaiitsin thel'acificshould refer to the hvo excellent SPC technical papers by Petard (1972) and Holdsworth (1977), details of which are given in the list of references at the end of this booklet.

Protein source and preserved food supply

Processes have been developed, especially in India, to extract protein from leaves. The process involves crushing the leaves, extracting the juice and heating it to coagulate the protein. This is then separated, dried and ground. The resulting green powder is added to baby foods and other foods to increase their protein and carotene content (Fellows, 1987). Many leaves are sun-dried in African countries, ground and then stored to be used later in the year as a food,supplement. Some of the more sensitive vitamins will have been lost, but most of the food value will have been retained. More information about leaf protein, its preparation and use, can befound in a handbook produced by the International Biological Programme and edited by Pirie (1971).

In conclusion, it is stressed that leaves should be used in people's diet as often as possible. The greater the variety of leaves eaten, the more likely it is that daily vitamin and mineral requirements will be satisfied. An interesting and valuable account of the useandnutrilional valueofgreen leaves isgiven by Oomenand Grubben (1977), should additional information be needed.

The next section deals with certain commonly eaten Pacific Island green leafy vegetables which have been analysed by the three PIFCP laboratories.

SPC ~ u i h k N- 31,1992 Page 15

IV. COMPOSITION OF SOME LEAVES EATEN IN THE PACIFIC ISLANDS

Twenty-two commoniy eaten leafy vegetables are described in this section. Each vegetable is illustrated by a colour photograph or line drawing. The chemical composition of these vegetables is presented graphically in Figures 1-17 and in tabular form in Appendix 1.

Lettuce is the most widely grown of al1 the green leaf salad crops. It can also be eaten m k e d . It belongs to the Compsitae family, one of the largest in the plant kingdom, which contains, sunflower, chicory, endive, pyrethmm and many ornamental flowers. Lettuce is a ppular salad vegetable in most parts of the world. The plant probably originated in the Middle East. According to Purseglove (1968), a long-leaved form is depicted on Egyptian tombs dated 4500 BC and there is evidence that lettuce was eaten by the ancient Greeks and Romans.

Lettuce grows best at higher altitudes or in the cooler season in the tropical region. Light, well-drained, well-watered and adequately fertilised soi1 promotes the most vigorous growth. When water is limited or the temperafure is too high, the leaves not only become bitterbut thereisalso a strong tendency for the plant to 'bolt' or go toseed. Several varieties of lettuce exist, including the upright cylindrical cos lettuce, cabbage or head lettuce, curled-leaf lettuce (some with pink tips) and asparagus or stem lettuce from China. Local departments of agriculture can be contacted for the names of recommended varieties.

Lettuceis usually grown fromseed and 1 ozor28 gof çeed producesabout3,000 plants. Theseedsgerminatebestat about20"C withinP5daysof sowing. Lettuceseedsdonot store wellin the tropics and if stored, they are best kept in the body of a refrigerator, an air-conditioned room, or a dry, well-sealed container (tin or bottle) in a cool place.

Lettuce must be well washed with clean water, especially if it has been fertilized with animal manure. The leaves should be shaken well to remove water. This enables the oil used for salad dressing to stick to the surface of the leaves. The additionof a little oil helps to extract the fat-soluble carotenes present in the leaves and probably improves their absorption during digestion. About 100 g or 4 oz of lettuce, especially the darker outer leaves, will supply about 30 percent of a child's daily Vitamin A requirements.

Page 16 SPC ~omao* ~a 31.1992

Lettuce is nsually eaten raw as salad after being washed in clean water. The leaves are best eaten with a little oil and uinegar to imprme palability and extract uitamins. A Cos type is

shown in l a and a pink-coloured opm-headed type in 1 b.

SE ~ u i m m k N~ 31.19% Page 17

2. TARO: Colocasia esculenta

(Taro stalks and leaves appear as nos. 2 and 19 in Figures 1-17 and Appendix 1)

The Colocasia taro is one of the most important edible aroids in the Araceae family and probably came from India more than 2000 years ago, according to references cited by Bradbury and Holloway (1988). The family includes giant taro (Alocasia macrorrhiza), elephant foot yam (Amorphophallus campanulatus), giant swamp taro (Cyrtosperma chamissonis) and tannia (Xanthosaa sp.). These are described by Massal and Barrau (1956), whoalso give a simple identification key. After cooking, a single taro leaf which weighs about 20 g would supply about 20 percent of a small child's daily requirement for Vitamin A.

Taro is grown throughout the tropical region, including the Pacific. The major variety eaten is Colocasia esculenta, which produces a large edible corm with a few suckers or cormels. Taro livesquite a long timeand producesuseful food after about eight months in the warmer lowland areas of the Pacific. The leaves are heart-shaped and the leaf veins do not join directly with the petiole or stalk as those of the other comrnon taro, tannia, Xanthosoma sugittifolium, do. The plant stands about one metre from the ground and hasanormalproductivelife of about tenmonths.There are many varieties and each has its particular colouring, taste, yield, disease resistance and vigour (Hale and Williams, 1977).

The leaves and young stems of the non-acrid varieties which do not irritate the mouth are widely uçed asa greenvegetable insaladsandmany traditionalpacific Island dishes (Standal, 1983; Parkinson, 1984; both cited by Bradbury and Holloway, 1988). The best leaves for eating are said to be the first four produced (Hale and Williams, 1977). The upperpartsof larger leaves, especially those varieties withapurplish tinge,and thelong white shootsproduced by tubers which have been stored in a dark damp place are also eaten (Herklots, 1972). The older leaves are more likely to have sharp, needle-like crystalsof calciumoxalate whichmake themvery acrid evenaftercooking. In thepacific both leaves and stems are commonly cooked with coconut cream.

Taroneedsa deep, fertilesoil and plenty of rain-at least 2000mmper year. It isusually planted in the best areas of newly cleared land. As a Pacific example, the sequence of &oppingin ~ o n ~ a , according to chr roder et al. (1983), usually begins with 'ufi'or sweet yam, (Discorea esculenta) followed by 'talo futuna' or kong-kong taro (Xanthosmna sagittifo1iiriii)and 'talo tonga' or Colocasiaesculenta, sweet potatoes, cassava and bananas or plantains (cooking bananas).

Page 18 SPC Hioamk Na 31,1992

In the highland areas of Papua New Guinea, on land just out of fallow or newly cleared from forest, the first crops to be planted, at about the same time, are usually the yams and taros, together witha variety of greenvegetables. As thesoil fertility declines, more sweet potatoes are planted and these are commonly followed by cassava.

Local names for tarosand other food plants are given in SPC Information Document No. 35 (1974), Kulu, kuru, uni, by Claude Jardin.

Taro (Colocasia esculenta)

Both stalks and Ieaves can be eaten.

SPC HiuirBaok No. 31.1992 Page 19

3. PAPAYA SHOOTS: Carica pnpaya

Papaya or pawpaw trees are foundin tropical and sub-tropical America and Africa. The species probably originated in southern Mexico and Costa Rica. About 40 species of papaya are cultived in America for their fruit.

The papaya belongs to the small Caricaceae family, which also includes the small egg- shaped mountain papaya and several small shrubs and trees.

The sap or latex of papaya is rich in papain, an enzyme which breaks down protein.

TheSpaniards took papaya to Manila in the middle of the sixteenth century, according to Purseglove (1968) and it reached Malacca in Malaysia soon afterwards.

The plant probably spread to the Pacific region during this time

Papaya is a tropical plant and doesnot withstand frost. It iieeds full sun and adequate protection from wind. Low temperatures produce poor-flavoured fruits.

The treegrows beston well-drainedand fertile soils, withabuiidaiit water, but it cannot tolerate standing water arouiid its roots.

Papaya is a short-lived tree with very soft wood. Young shoots aiid leaves are eaten as a green vegetable, especially in South-East Asia.

Papaya can be grown from seed but can also be propagated vegetatively by cuttings or grafting. The trees may live as long as twenty-five years.

Fruitingbeginsafteraboutone year'sgrowthand trees arcsuitable for latex production for a period of about three years.

Shoots and leaves can be Iiarvested for about tliefirst tliree years or until the tree grows too high to reach the new young shoots.

More information about husbandy, major pests and diseases and papaya productioti can be found in Purseglove (1968) or obtained from local departments of agriculture.

Page 20 SPC t h b k No. 31. 1992

Papaya shoots (Carica papaya)

The ymlng shoots and leaues are eaten a5 a g m wgctable, cspecially in South-East Asia This uegetable could supply a useful ainount of uitamin A

and other uitamins to the Pacific diet.

SPC ~ m - k NO. 31.1992 Page 21

4. CABBAGE: Brasçica olrracea. var. capitata

Cabbage belongs to the plant family Cmciferae, with most of its members having their centre of origin in temperate countries.

The familiar round, compact cabbage has been grown in Europe for about 4500 years and was probably spread to many European countries by the Romans.

Theplantisnow grown throughout the world,including thePacific whereithasbecome a very popular vegetable.

Cabbages prefer a well-drained, fertile soi1 and temperatures between 10°and 25°C but fairly good yieldscanbe obtained withsome varietiesat temperatures between 25" and 30°C.

Cabbages respond rapidly to the addition of manures containing plenty of nitrogen, which isneeded to support the satisfactory development of healthy, dark green leaves. The greener the leaf the more vitamins and minerals it will contain.

Page 22 SPC H M ~ L N* 31, 1992

Cabbage (Brassica oleracea, var. capitata)

The hard drum-head cabbage keeps well and is a popular uegetable in the Pacific. The pale inside leaues are notas rich in uitamins as the darkrr outer ones.

SPC ~ u i - k NO. 11.1992 Page 23

5. NIGHTSHADE: Solanu~n nigrum

The Çolanaceae family gives us many useful plants such as potatoes, tomatoes, egg- plants, capsicums and chillies, tree tomatoes and tobacco, to name just a few common ones. Tobacco is mentioned here because it contains the substance nicotine which is used as an insecticide on pepper (Piper nigrum) and other cash crops suitable for the Pacific.

NighBhade is an annual, known as 'karakap' in Papua New Guinea, which probably grows throughoutthePacificregion. Itlikescool, wet weatherandgenerally seedsitself, but the seeds can be broadcast. The plant thrives in damp, shady places and among other vegetables and grows like a weed. It rarely reaches a height of one metre and is usually found growing to about 30 cm. The leaves are best eaten young and should be harvested just before flowering and before they harden. The unripe berries are poisonous and should not be eaten.

A similar plant from the same iamily found in Europe (Atropa belladonna) is called 'deadly nightshade' because of its poisonous bernes. They contain the alkaloid, atropine -atropine sulphate is used as an antidote for organo-phosphorus insecticide poisoning. Ophthalmologists use atropine to dilate the pupils of their patients' ey es in order to make examination easier. The name 'belladonna' cornes from the Italian for 'beautiful woman'; the plant was used by women in some countnes to emphasise their eye and make them more attractive.

Page 24 SPC Hanmmk No. 31,1992

Nightshade (Solarium nigrum)

The tender new leaues from the youngeçt plants are the beçt.

Page 25

6. WNGED BEAN: Psophocarpus tetragonolobus

Theplantprobably originated in tropical Asia butit hasbeen known fora very long time to the Melanesians in Papua New Guinea, where it is called 'arsebean' or 'bin'. Other names for it are Goa Bean, four-angled bean, Manila bean, asparagus pea and princess pea. It beloiigs to the plant family called Leguminosae, one of the largest of the plant families.

Theyoungleaves, shootsand flowerscan beeatenasa vegetable,but theplantisusually grown for its immature pods which are consumed like French beans.

The winged beaii also has edible tuberous roots which are eaten, raw or cooked, especially in Burma. Eating the leaves and plant Sap is also said to cure tropical yaws (Holdsworth, 1977).

The wiiiged ùeaii grows well in a hot wet climate, although it suffers less from disease in drier weather. Tlie plant does not tolerate waterlogging and prefers a deep, well- drained soi1 of almost any type.

The planthas tlieabiliiy tofix atmosphericnitrogen withitsexceptionally large nodules or lumps formed on the roots. Tliese lumps of plant tissue contain large colonies of nitrogen-fixing bacteria which livesymbiotically with the winged bean. As a result, the winged bean can grow in relatively low fertilily soils and is therefore more successful than most other commonly eaten plants of the bean family.

Usually the appropriate bacteria are already preseiit iii the soil, but if the plant fails to nodulate special inoculation is needed with the correct rhizobium bacteria.

The nitrogen fixed by tlienodulesin the rootsisleft after the plant is harvested and thus improves soil fertility. The yields of any following non-nodulating crops are significantly increased and it is therefore a very valuable crop to iiiclude in aiiy form of crop rotation system.

Page 26

Winged bean (Psophocarpus tetragonolobus)

The drawing shows the pod and leaues. The Young leaves, shoots and fiowers can be eaten as a uegetable but the plant is usually grown for i fs younggreen pods.

SPC b m m k NO. 31. 1992 Pagç 27

7. CHAYOTE: Sechium edule

Thechayoteorchokocomes from çouthern Mexicoand Central Amenca and waseaten by the Aztecs long before the Spanish arrived in South America. It has now spread widely throughout the tropics and the Pacific. It is a member of the Cucurbitaceae family which contains gourds, water melons, gherkins, melons, cucumbers, pumpkins, squashes, marrows and loofahs.

Chayote is a strong climbing plant with relatively hairless leavesand stems. The vine is herbaceous and perennial. The young leaves and tender growing points and climbing tendrils are eaten as a vegetable in the Pacific. The fruits are also eaten, usually boiled, as are the large tuberous roots.

The plant grows best with moderate rainfall and in the slightly cooler areas of the tropics. It is well suited to the Pacific region and prefers the cooler months of the year.

Page 28 SPC Hmdkmk Na 31,1992

Chayote (Sechium edule)

The young leaves and climbing tendrils are eaten as a vegetable. The wrinkled, ofteri slightly pricklyfnrits are also eaten after being cwked in stews.

SPC ~in-r NO. 31. ,992 Page 29

8. JOINTFIR: Gnehtm gnemon

This is a long-lived, forest tree found in Papua New Guinea, where it is known as 'tulip' or 'two leaves'. It should not be confused with the West African Tulip Tree, Spathodia campanulata, which alço grows in Pacific countries and is common on old fallow areas or as a decorative tree in urban areas.

w The young leaves are eatenas a vegetable or boiled with chicken in coconut cream. The leaves are available in the local markets, especially on the New Guinea side of Papua New Guinea. It is not commonly eaten or found in other Pacific Island countries.

The new young leaues frorn this forest trec are eatcn aç a uegetable. l t is known as 'tulip' or 'two leaues' in Papila New Guinea because of the distinctive twiri-leaf arrangement.

SPC ~ui-r NO. 31.1992 Page 3 1

9. WATER SPINACH: lpomwa aquatica

This belongs to the same family, Convolvulaceae, as the sweet potato. It is called 'kangkong' in Asia and the Pacific region. The plant resembles sweet potato, especially in its leaf shapes and twining or creeping habit, but does not produce tubers.

Water spinach, as the name suggests, is an aquatic, floating or trailing herbaceous perennial which is found throughout the hopics and the Pacific region. Dry land types also exist. The young leavesand shootsare usually eaten as a leaf vegetable. The hailing vines can be fed to pigs and cattle.

It is propagated from cuttings or from seed and usually takes about six weeks after planting before enough leaves are available for harvest.

The leaves have a sharp taste and a sticky, glutinous texture, especially if over-cooked. The leaves are best cooked with coconut cream or fried, Chinese style, with different meats. They can also be used fresh in salads.

The plantis easy to grow and lastsa long timein swampy areas or neara plentiful water supply. The flowers are pink or white and have the familiar shape of 'morning glory' fl&e;s (Ipomoea purpur&). The dry-land types require very fertile soils which are rich in nitrogen and humus or organic matter.

Page 32 SPC nui&k NO. 11.1992

Water spinach (Ipomoea aquatica)

This is a close, water-louing, relative of sweet potato. The young leaues and shoots can be eaten cooked with cocoriut creain or fried Chinese style with lneat or other urgetables.

SPC Hsn-k No. 31. 1992 Page 33

10. PUMPKIN: Cucurbita pepo

Pumpkin leavesare knownas lippamken' inPapua New Guinea Pidgin and Vanuatu Bislama. In Samoa the shoots are called 'tumutumu maukeni' or green vegetable.

Cucurbita pepo belongs to the family Cucurbitaceae and provides summer squash, winter squash, pumpkin, vegetable marrow and ornamental gourds.

The plant probably originated in North America and the oldest recorded archaeologi- cal specimen was growing in Mexico about 9,000 years ago (Purseglove, 1968).

The young leaves, growing points and climbing tendrilsareeaten as a green vegetable. The pumpkin tips shown in the photograph weigh about 25 g and would supply about . . 20 percent of aêhild's daily r&uire&ent for vitamin A.

-

The pumpkin grows throughout thepacific region and prefers the cooler period of the year. Pumpkins do not do well in theconstantly wet and humid tropical areas because of fungal diseases. They grow best on well-drained and highly fertile soils which contain plenty of organic matter.

Pumpkins are usually grown from seed, but they can also be propagated from cuttings because they can produce roots from their nodes.

Page 34 SPC Hart&* NO. 31. ,992

Pumpkin (Cucurbita pepo)

The tender yotrng leaues, growing points and tendrils can be eaten as a green vegetable in many Pacific dishes.

SPC ~ i n d b m k NO. 31. 1992 Page 35

11. CHINESE CABBAGE: Brassica chinensis var. pekinmsis cylindrica

This is a member of the large family called Cmciferae which contains several hundred different groups or genera such as horse-radish, radish, garden cress, watercress, cabbage, turnip, broccoli, cauliflower, brussel sprouts, kohlrabi, kale, rape and mustard.

Chinese cabbage belongs to the Brassica group and the variety represented in the photo is pekinensis cylindrica or 'pe-tsai' in Chinese. It resembles a giant lettuce and the leaves are eaten eitlier as salad or stir-fried Chinese style witli differeiit meats.

It comes from East Asia, is grown exteiisively in China and Japan and has now spread throughout the tropics and the Pacific. It is a very easy aiid productive green leafy vegetable to grow and is suitable for al1 altitudes.

As with al1 large-leaved fast-growing vegetables, a fertile, well-drained and well- watered soi1 is needed to produce the best plants. It usually takes about 2-3 months from the seedling stage to reach a size suitable for harvest. It is a biennial plant but is grown as an annual.

Page 36 SPC ~ a n < ~ m k NO. 31.1992

Chinese cabbage (Brassica chinensis var. pekinensis cylindrica)

A tasty vegetable, especially for Chinese stir-fry cooking and stews. As with the head cabbage, the white inner leaves confain fewer vitamins than the darker green outer leaves.

SPC b m m k N- 31.1992 Page 37

12. DRUMSTICK: Moringa oleifera

Also known as liorse-radish tree' and 'suijan' in Fiji, drumstick is a native of India. Its m t s have the same sharp flavour as horse-radish and can be used as a substitute if needed. It belongs to the family Moringaceae.

Dmmstick is a small tree which grows throughout the tropics and the Pacific. The young tops, leaves, immature tender pods (which hang dowii like dmmsticks) and the middle of the maturepods can be eaten and even the roots are eaten by Philippinos. The tree is low-growing and can withstand long dry periods. This makes it a convenient standby vegetable for al1 seasons and conditions. A popular addition to Asian dishes, it is generally propagated from stem cuttings.

Drumstick (Moringa oleifera)

The young tops, leaves and green podsfrom this small Pacifie tree can al1 be eaten. This makeç it a convenient vegetable for al1 seasons.

SPC ~(m-r NO. 31.1992 Page 39

13. CASSAVA: Manihot esculenta

Also known as manioc, tapioca and tavioka, it belongs to the family Euphorbiaceae, a very large and diverse family which contains many useful plants that give us castor oil, tung oil, rubber, laxatives, fruits and many different ornamental shrubs.

Cassava is not found in the wild state, but it probably originated in Çouthem Mexico, GuatemalaandNorth-Eastern Brazil. Cassava wasprobably spread to thepacificdirect from Mexico by the Spanish or from Brazil by Portuguese traders. lt would have most likely been introduced to the Philippines by the Spanish in the 16th century.

The sweet cassavas or low cyanide types are more widely dishibuted in the American tropics than thebittercassavas. Sweetcassavasusually have softer, whiter flesh and the cyanidecontent islower. Thecyanide is present just under the skin. Sweet cassavasalso mature earlier (sixmonthsearlier than thebittervarieties) and do not keepas wellin the ground (one year versus over three years for bitter types).

The cassava produces tubers which are an important source of carbohydrate food. The young leaves are eaten as a vegetable. Sweet cassava can be fed to livestock.

Cassava will grow on the poorest soils and can tolerate wide extremes of rainfall, although it is essentially a lowland tropical plant. When there are long periods without rain, cassava sheds its leaves asa survival mechanism. It grows best, however, on light sandy loam soils of low to moderate fertility.

The bush grows to about 1-5 m and there are many varieties with different stem colours and leaf shapes. The leaf stalk or petiole is usually longer than the leaf, which is deeply divided into 3-9 fingers or lobes.

Cassava is propagated from stem cuttings 2&30 cm long, preferably taken from the middle section of the stems. Care is needed to avoid virus diseases, the only serious problemof cassava, whichare morelikely to be spread if cuttings are used from the base of the stem near soi1 level. Cassava can be planted on its own or inter-planted with annual food crops, usually with about 1-2 m between plants.

Cassava is veryeasy to grow in home gardens and a plot measuring about 10m2 should produce 1-2 kg of young leaves per week, enough pro-vitamin A for a family of six for a week, depending on the rainfall and general growing conditions. An average-sized cassava leaf, as shown in the photograph, weighs about 5 g and would supply after cmking, about 10 percent of a child's daily needs of Vitamin A.

Page 40 SPC ~ i o h r NO. 31. 1992

The food value of cassava leaves, especially the iron and pro-vitamin A content, is very high becauseof therelatively low water content. Theaverage Pacific greenleaf contains 86 per cent water, compared with 72 per cent for cassava. The presence of any poisonous cyanide is not a problem because it disappears in the steam during cooking orispoured away in thecooking water.Itshouldberemembered thatif toomany leaves are harvested from the plant, smaller tubers will be formed.

Cassava (Manihot esculenta)

The leaues are u e y rich in vitamins, especially A and C, but need to be cooked well to get rid of the bitterness. The leaues should be boiled with waterfor about 10 minutes and the water

then poured away. Cmk in fresh water until tender.

SPC ~uia-~ N- 3 1 , 1992 Page 41

14. KALE SEEDLINGS: Brassica oleracea var. acephala

This isin the same family asordinary round cabbage but does not forma head. It issaid by Purseglove (1968) to be closer to the wild species of cabbage which is indigenous to the Mediterranean region, south-western Europe and southem England.

The kale seedlings eaten in Papua New Guinea are immature plants which are harvested a relatively short time after being sown direct from seed in nursery beds. Plants are allowed to grow about ten centimetres or more before hamesting.

Like ordinary cabbages, they prefer a well-drained and highly fertile soi1 rich in nitrogen with cool to moderate growing temperatures.

Page 42 SPC HuicU-mk Na 31, 1992

Kale seedlings (Brassica oleracea var. acephala)

Page 43

15. WATER DROPWORT: Oenanthe javanica

This is widely eaten in Papua New Guinea. It belongs to the Umbelliferae family together with vegetables and herbs such as parsley, parsnip, carrot, dill, anise, celeriac, celery, caraway, coriander, cumin and fennel.

The leaf shape is very like celery or a large-leaved parsley and the plant grows in clumps quite close to the soi1 surface. It spreads out to about 1-2 m and roots easily from the nodes.

The main stem is hollow and slightly ribbed and has a distinct purplish tinge towards each end of the nodes. It can be propagated from cuttings taken from the middle of the . * - - stem.

The plant grows in both wet and dry areas and several varieties exist which Vary in colour from purplish-green to yellowish-green.

Water dropwort can be eaten as a salad vegetable or cooked with other foods. The leaves have a slightly sharp but fresh and bitter taste.

In theSouthemHighlandsof PapuaNew Guineaitisused asan antidote for poison and to cure headaches and coughs (Holdsworth 1977).

Theleavesareready for harvestabout 10 weeksafter planting. After a further 10months orso, the plant stopsproducingnew shootsandfreshcuttings have tobe taken toensure a continuous supply of leaves

Page 44

Water dropwort (Oenanthe javanica)

A close relative ofparsley and celery which can either be eaten as a çalad vegetable or cooked with other foods.

SPC ~ u i - k NO. II. 1992 Page 45

16. WATERCRESS: Nasturtium officinale

This plant belongs to the Cruciferae family, which includes radish, tumip, cabbages, cress and mustard. It is known as 'cress' in Papua New Guinea, Fiji, 'cresson' in New Caledonia and 'kapisi vai' in Samoa.

Watercress is an aquatic perennial herb which exists in the wild state throughout Europeand Western Asia and by the 1960s had alsobecome a seriousriver weed in New ~ea l and following its introduciion by settlers from Great Britain and Europe.

The plant has now spread to many parts of the world including the Pacific region. The leafy stems are eaten as a salad vegetable or cooked with other foods. It has a sharp, fresh and tangy taste.

The stems are hollow and roots grow easily from nodes. Watercress is usually propagated from cuttings but it can also be grown from seed.

Clear running water provides the best growing conditions but it can be grown in well- watered, almost flooded soil.

Regular harvestingencourages the plant to producemoresmall branches, which in tum provide more leaves and thus a better quality vegetable.

Extra careisneeded with watercress when the water it is growinginappears to be dirty or polluted. The leaves and stems should be thoroughly cleaned by washing them carefully several times in clean water, especially if they are to be eaten raw as a salad.

It is worth repeating as often as possible that al1 green leafy vegetables should be washed very well if they are to be eaten without cooking. R i s advice is especially relevant when any form of organic manure is used which contains animal excreta or when any form of chemical spray has been used to control pests and diseases.

SPC Hndbm* Na31.1992

Watercress (Nashirtium officinale)

Can be eaten raw as a salad after careful washing in clean water, or cooked as a vegetable.

SPC h d b o o k No.31.1992 Page 47

17. TROPICAL SP1NACi-k Amaranthus viridis

This is known as in 'tubua' in Fiji, 'aupa' in Papua New Guinea and 'bhaji' (Indian). It belongs to the family Amaranthaceae, most of whose members are grown for grain or as green leafy vegetables. They are herbaceous annuals with single leaves and small densely spiked flowers.

It probably originated in Central and South America and there are now many different types found throughout the tropics including the Pacific region.

Tropical spinach, also known as amaranth, will most likely be found in many Pacific Island gardens growingas a weed, like nightshade. It is a relatively short-lived plant and the young leaves and tops are the parts usually eaten, cooked, as a green vegetable.

Tropical spinach is relatively easy to grow directly from seed if it has not already self- seeded. Transplantingseedlings from a nursery isalso a g w d way to produce this plant.

It is a good vegetable to have in any garden crop rotation system because it is not affected by the usual soi1 problems such as fungal infections or nematode attack. Diseases such as 'damping-off' or pests such as caterpillarsand stemborers also do not seem to trouble it.

Tropical spinach needs a lot of water and a well-cultivated mil. It thrives in a garden environment and because it self-seeds it tends to grow al1 over the place like a weed.

The young shoots and leavesnear thegrowing point canbe harvested about one month after sbwing and the plant continues to produce new shoots for about two months before developing flowers.

Page 48 SPC Hindbmk No. 31. 1992

Tropical spinach (Amaranthus viridis)

An easily grown uegetable for a well-watered garden. The young shoots and leaues near the growing point are eaten as a uegetable.

SPC ~ u i h k NO. 11.1992 Page 49

18. SWEET POTATO: lpomoea batatas

Sweetpotato isa memberof theConvolvulaceae family.Thisincludesmany annual and perennial herbaceous twining plants such as kangkong (Ipomomea aquaticn); moming glory (Ipomoea purpurea) a blue flowering creeper, at its best in the mornings; and moonflower (Ipomoea alba), a large, white, sweet-scented flower which only blooms at night.

Although sweet potatoes havenot been found growing wild, they probably originated in Cenhal America. They were eaten in Mexico before the first European explorers visited America and had found their way to the Pacific at about the same time.

The plant subsequently reached Polynesiaand New Zealand. Themethod of transfer is not exactly known. One idea (suggested by Purseglove, 1968) was that the plant had been carried as seeds by ocean currents from Cenhal America to Hawaii. Another, perhaps more plausible, theory is that they were carried over from South America in çailing canoes as a food supply.

Columbus retumed to Spain in 1492 with the sweet potato nearly 80 years before the arriva1 of the ordinary potato (Solarium tuberosum). The name potato cornes from the Carib word 'batata' whichhad beenused originally tonamelpomoea batatasor thesweet potato. TheSpaniards then took sweet p t a t w s to their Settlements in Africa and Asia. TheChineseand Japanesesubsequently obtained the plant from the Philippines, in 1594 and 1698 respectively.

By the middle of the nineteenth century, sweet potatws were commonly grown throughout the tropics and in some counwies they were replacing yams and taros as a source of energy food because they were quicker and easier to grow. They are now the main staple root crop in the highlands of Papua New Guinea. The young leaves are eaten as a green vegetable and they also ha\e several medicinal uses. In Papua New Guinea chewed leaves are wrapped around wounds to promote healing (Holdsworth, 1977). The small branch of sweet p t a t o leaves held by the child in the photograph weighs about 5 g and would supply about five per cent of a child's daily requirement for Vitamin A.

Sweet potatws are usually grown from cuttings and less often from tubers. The plant does not need a highly fertile soi1 but does need plenty of moisture, without Ming waterlogged. It cannot tolerate poorly-drained mils. The young leaves and growing tips are eaten as a vegetable. The stalks and older leaves can be fed to pigs.

Page 50 SPC n m b k N~ 31, 1992

Sweetpotato (Ipomoea batatas)

This plant is iisually grownfor its tuber but the young leaves cal1 also bc eaten. The cover picture also shows sweet potato leaves.

SPC H M ~ W X N* 31,1992 Page 51

19. TARO LEAVES: Colocasia esculenta (Leaves are descnbed in (2), together with stalks)

Taro (Colocasia esculenta)

An average taro leaf similar to theone held by the boy in the photo would contain about 20 percent of the boy's daily requirement for Vitamin A.

Page 52 SPC ~ ~ b k NO. 31.1992

20. FERN: Athyrium esculenta

This fern is eaten in Fiji ('ota' and 'sukau') and in Papua New Guinea, together with severalothers, includinga heefern (Cyathea sp.) whichgrows toabout 2 4 min height andof whichonly the1eafletsareeaten;acreepingfern (Marattiasp.) whichclimbsover hees; and a river fern (Asplenium sp.), which is found along the edges of riversgrowing in clumps up to one mehe high.

Generally, ediblefernsgrow wild and arenotusually found orplanted ingardens. They Vary in size, shape and type and are traditionally eaten cooked with pig meat in an earth oven.

Fem (Athyrjum esculenta)

Thisfern is commonly eatcn in Papua New Guinea, Fij i , New Caledonia and Vanuatu

SPC ~indbook ~0.31.1992 Page 53

21. EDIBLE HIBISCUS: Hibiscus manihof

This is called 'aibika' in Papua New Guinea, 'bele'in Fiji and 'pele' in Samoa. It belongs to the Malvaceae family which also includes Cotton, kenaf, okra or 'Lady's Finger', ros- elle,fibreplantsand ornamentalsh~bs.Thefamiliar hibiscus flowerof thePacificisHi- biscusrosa-sinensis. Anextractfrom theleavesof thisissaid torelievefever (Holdsworth, 1977).

A small hee,Hibiscus tiliaceus, which is found eve~ywhere in the tropics, isused to rnake mats and ropes and wrap food in the Pacific. d i s also used to treat coughs and sore throats (Holdsworth, 1977).

Edible hibiscus (Hibiscus manihot)

This is a uery popular leafy uegetable in the Pacifie, especially among Melanesians. There arc many different types with various Ieaf shapes, colours and forms. Photos show the

full-leaf type and the cassaua-leaf type.

SPC H ~ ~ , ~ W L NO. 31. ,992 Page 55

The fruitsof okra and roselleareedibleand the leavesof Hibiscus manihot can be cooked as a green vegetable with other foods. The leaves are slightly glutinous or sticky when cut or broken, but are made more appetising by cooking in coconut cream or with a mixture of curry spices.

Edible hibiscus is a small shrub which grows to about one metre in height. Many varieties exist, with very different leaf shapes, coloursand flavours. Leaves are usually ready for harvest about four months after planting from a stem cutting - the most common metliod of propagation.

The plant continues toproduce leaves for about two years. The leaves are soft and veiy attractive to insects, which frequently attack them and cause severe damage. A beetle of the Nisotra species, possibly rose beetle, eats many small holes in the leaves, producing the appearanceof gun-shot damage, but tliis is generally not a big problem. A caterpillar of the Spdoptera species, together with snails and a stemborer, a form of burrowing grub, also eat into the stems of the plants. In Samoa a white scale insect sometimes causes problems.

Edible hibixusisan easy plant togrow in the vegetablegardeii and thrives best on well- drained, well-watered fairly fertilesoil which is regularly cultivated. Anaverage leaf as shown in the photograph weighs 5 g and would supply about six percent of a child's daily requirement for Vitamin A.

Page 56 SPC H M ~ W ~ ~0.31.1992

22. BASELLA, CEYLON SPINACH: Basella alba

Alsn known as Malabar nightshade or vine spinach, this is a climbing perennial with very dark green, oval or nearly round leaves.

The flesh of the leaves is succulent and sticky. The vines grow to about three metres in length and produce jet-black berries which, when boiled in a little water, will produce an acceptable ink for writing. The plant grows almost anywhere, including poorly drained soils. There are no insect pests and the leaves are ready for harvest about five weeks after the seeds are sown. The usual life-span of a plant in the tropics is about six months. It is a very productive and nutritious leafy vegetable for home gardens in the Pacific. About 100g of leaves, whencooked,easily supply thedaily Vitamin A needsfor a child.

Basella is usually grown from seed or stem cuttings and the young leaves and growing tips are most commonly eaten as a cooked vegetable in Chinese-style recipes.

Basella (Basella alba)

This is a popular leafy uegetable in South-East Asia and also for ~nany people in the Pacific. Theflesh of the leaves is succulent and slightly sticky. It is a very prodilctive vegetable.

SPC Huidbok No.31.1992 Pagï 57

V. NUTRIENT COMPOSITION

Each nutrient is displa ed on a separate pa e in the form of bar gra hs (Figures 1- K 17,Appendix 1) for al1 t e vegetablesexce t f or basella leaf (No. 22 in g 0th the text and Appendix 1). This allows each vegetabye to be compared within the group for a particular nutrient and also makes it easier to prepare enlargements or overhead projection hansparencies for health education purposes.

The average iiutrient levels of the green leafy vegetables are iven below in Table 1. Vitamin A contents com are favourably with typical values7685 micro Vitamin A retinol equivalent) foun f for leafy vegetables worldwide (Ball, 1988). 8tamins and minerals are present at vew satisfactorv levels and show that Pacific leaves are a moderiitcly ri?hwurceof ri> vitamin A, VitarninC, iron. ziiic,caliiumand potassium. Analytical mcthods usedKy iic. PlFCP laboraturies arc~cl~~xribcd in Appriidix 2.

Table 1: Average nutrient composition of some green leafy vegetables eaten in the Pacifie (Values are per 100 g edible portion, raw)

Water (g) Energy (kcal) Protein (g) Fat (g) Carbohydrate (g) Fibre (g) Ash (g) Sodium (mg) Potassium (mg) Calcium (mg) Iron (mg) Zinc (mg) Vitamin A (pg) n iamine (mg) Riboflavin (mg) Niacin (mg) Vitamin C (mg)

Average Range

Page 58 SPC ~ u i e ~ k NO. 31,1992

The values given in Appendix 1 are for vegetables in the raw state, with the exce tion of taro leaves where the Vitamin A figure has also been determined after cooRing. Cassava leaves have a verv hieh content of ~ro-vitamin A carotenoids, but it needs to br emphasised that cassaGa le%ves contain hisonous cyanide compounds and there- foreshould neverbeeaten raw.Taro leavesalsoneed tobecooked becausethey contain oxalate, another unpleasant and poisonous substance.

Cooking unfortunately deskoys some vitamins and reduces others. Minerals and water-solublevitaminsarealsodissolved out of theleavesand lostin thecooking water when it is poured away. Losses of over 30 per cent were found for pro-vitamin A carotenoids of taro leaves after cooking, according to one PIFCP laboratory (INR, Fiji).

Cooking and nutrient value

If one assumes that about 30 per cent of the pro-vitamin A carotenoids are lost after boiling, cassava leaves still contain the highest concentration of pro-vitamin A carotenoids of the entire group of green leafy vegetables. Vitamin C is very susceptible to oxidation and most cooking methods reduce the level significantly.

It should be remembered that reen leafy ve etables should be cooked for the shortest time oossible and in the smal ? est volume o f water to ensure maximum retention of r~~~ nutric,nts. Thc cooking tirne depends on individual tastes and prrferenccs but, gibner- .illv s~c; ik i i i~ , rrecn v~~~etablrsshi~uld only bt,c,>okrd until iust tcndereiiuugh tomakc

Most green leafy vegetables eaten in the Pacific are eaten as tas& side dishes or used as wrappingsand additions to the main food items suchas sweet potatoes, yamsand fish. Vegetables are rarely eaten separately in large quantities as is the custom in Western countries. The Pacific custom of wrapping foods in a leafy vegetable during cooking means the leaf is kept at a higher temperature longer than necessary because the main food needs more cooking.

Minerals probabz go fromtheleaf to theother food, but thelevels of Vitamins A, Cand E and possibly O er vitamins in the B grou , such as folacin, are substantially reduced after rolonged cooking (Tver and ~usselP1989). According to Souci and colleagues (1989f the maximum losses of vitamins due to cooking are estimated to be:

Vitamin A 40%, carotene 30%, Vitamin D 40%, Vitamin E 55%, Vitamin K5%, thiamine 8006, riboflavin 75%, niacin 70%, pantothenic acid 50%, Vitamin 86 50%, biotin 60%, folic acid 100%. Vitamin 812 50%, Vitamin C 100%.

The Chinese cooking method of rapid stir-frying in a little oil robably retains more Y nuhients tlian most other methods. Boiling cabbage leaves in a arge volume of water fora long timeand then discardin thecooking waterisvery wasteful, not only because minerals and vitamins are lost ut also hecause it produces unpleasant-smelling sulphur compounds.

%

SPC ~anamr NO. 31.1992 Page 59

Cooking losses are probably the most sedous form of nuhient loss, especially for the ereen leaves which are eaten in the Pacific. If few meen leafv veeetables and fmit are - eaten, these losses have evcn morc serious health ~ n s e q u c ~ c e s , ~ e c a u s c about half of the human dietary intakc of Vitamin A is usually derived from fruit and ve etable carotenoids (Hsich and Karcl, 1983). Infants are ccrtainly the most vulnera % le y u p because the are cntirely dependent on the food they arc given. Vegetablcs coo ed in coconut mil{ or includd in stews retain most of the water-soluble nutrients.

Differences in Ieaf composition

Green leafy vegetables are an important source of minerals and vitamins and differences in their levels are therefore of some significance. Unfortunately, these components show the largest variations in quantities present.

The concentrations of minerals found in Ieafy vegctables are particularly variable because they dcpend on theinicractionsof many factors, the moin ones bein environ- mental andgenetic. Thcse iiiclude thc ty eof soi1 the plantsaregrowing in, t % e quality of available watcr, nearness tothesca, l n t varie orspcciesand other factors. Crops

own immediatcly followin a long- urahon fa1 ow or after the clcaring of primary i $ . Y grcst will contain a much hie cr concentration of most minerals. cs~eciallv the soluble forms such as potassium anYnitrate-nitrogen. Some plaiitscan také u p mbre nutrients than thcv need - 'luxury uptake'. This is true for wtassium and nitrate-nitrozen, - especialry in green leafy Gegêtables.

Vitamin levels also varv more than those of the maior components mentioned earlier because they are closefy linked to variety and the genera'l vigour of plant growth. Healthy, pst-frce, fast-growing, dark green lea vegetables will contain far more active substancessuch asoru-vitamin A carotcnoi 2 S. Vitamin C. Vitamin Eand folacin than pale green, slow-gr;wing, diseased or drficient plants. Thcre arc 30- tu 50- fold differcncesbctwren the vitaminand mineral contentsof ualc inner leavesof lcttuceand cabbage and dark outer leaves, as mentioned earlier in the section on composition

Green lcafy vegetables should prefcrably t>e considcred as a group and not cach on its own as a uotential 'suocr ve~etable'. niere is eenerallv too much ovcrlap in nutrieiit contents, 'duc to thc many ;riables rcsent,ïo be a61e to sa with ceiiainty that a % particuiar Ieafy vegetable will t?e k t nutritionally he best way tocnsurc a satisfactory intakeof mineralsan vitaminsis toensure that as widea varieN of lcafy vegetables as possible is eaten, within the limits of the environment or income of thé people concerned.

Eatinqa wide variety ofgrc~ii leavcsevensout someof the ciifferencesanci compcnsatcs forde icienciesina ~arhcularnutrient or tlie~rcsenceof anti-nutritional factor5 whiçh may be present in &me leaves.

Page 60 SPC Haodbwk No. 31. 1992

Improving nuîrient value

Thcnuhitional valueof leafy vcgetab~scanbc improved by cnsuring the plants receivc adeouatc nutrients. water and ieht in their erowinr cnvironmcnts. Prolcction from wind or animaldamage, suchasfënccsand wi'id breals, may alsobc nceded.Nutrients can be supplicd by some form of manure made from compost, animal droppings and urine, wood ash, plant refuse, waweed, fish and animal wastr or, if money is availablr, from a small quantity of a balanced compound fertilizer which contains nitrogen, phosphorus and potassium in available forms. The quantity of fertilizer material to apply dcpcnds on the type of material and thc agc or stage of dcvclopment of the vcgetablc. In general, largt-leaved, fast-growing vegetablcs will rcquire more than seedlin~s. Great careis needed with conccniratcd manurrs bec.iuse thcy can eabily bum voune Ülants if too much is used. The best thine to do is obtainadvice fr6m an &xpe$cfced manure user before applying anythinU Wrll-rottcd compost which has 7' k n prepared for at lcast thrw monthscan be used rcelv onall rreen lcafv veeetableb " , .. at a n i time.

Comparison of nutrient composition of leaves

The values shown in thebar graphsare the weights of nutrient present in 100 gof fresh, uncooked leaves. In terms of everyday quanhties, 100 6 is the weight of bvo avera e hen's e s or about the weight of one third of a tin of Coca-Cola drink. About 1 b Tl lleaves o bele' or 'aibika' - edible hibiscus - would give 100 g but this of course depends on the size of the leaves. An average-sized taro leaf weighs about 20 g. Good kitchen scales or a simple scientific balance are needed to obtain accurate weiehts. In practical terms, a good estimate is al1 that is needed. %me of the leaves in thëcolour photographs were weighed and the figures are given whcrc ûvûilable.

The 'averageleaf',asshowninTable l,contains87percent 'water'and 11.2 r cent 'dry matter' with ranges of 72-96 per cent and 4-28 percent respectively. TE so-called 'drymatter'ismadeup of3.4 protein, 0.6gfat,3.4 gcarbohydrate,3.0g fibreand about 0.5 g mineralsand vitamins. f; or comparisonlettucecontains95 per cent 'water' and4.8

matter'madeupof 1.25g rotein,O.ZZgfat, 1.1 gcarbohydrate, 1.52gfibre and percent about 'd'l 7 g minerais, vitamins an a other substances.

SPC ~ u i a ~ k ~0.31.19~2 Page 61

VI. COMPOSITION OF LETTUCE LEAVES

The average m n leah, veeetable also contains manv other substances which have or may havc<i@ificant nbtri<onal or hcalth-related pr6perties. In order to illustratc this, somc additional nutrient com osition data of lettuce leaves, frorn thc Ccrman Food Tables produced by Souci et a/?(1989), arc presented below in Table 2.

- Why lettuce?

The reader will no doubt immediately ask why lettuce has been chosen to illustrate the point. The main reason is that lettuce has been analysed in laboratories al1 over the world and in greatdetail. Mostof thei'acific green leavesin thisbooklet have never been analysed before or, if they have, not in any great detail.

Another reason for choosing lettuce is that it probably contains the least amounts of al1 thenubientsand thereforeit issafe toassume that mostPacificgreenleaves will contain more of everything. Lettuce is usuall eaten raw, although it can be eaten cooked or made into soups, and therefore it is a K ealthv veeetable to eat. The onlv ~rob iem with eating lettucc Ar any other raw s i a d vc ctabies~uch as watrrcress is thàt lhey have to be wash~d very carefully inclean water %e forebe~ngeaten.Thisiscxh~cmcly important because raw &lad can Carw the cvsts of ~arasitesand bacterial swres. ésoehallv if animal manures have been bsed a i fertiligers or polluted water fo;irrigitiÔn.

Many of the hcalth problerns in Pacific Island counhics are asstxiiated with oor sanitationand ~oor food safeht habits. Younechildrcn suffcr themost from thcse i o d - and water-borie diaases and they are the ones who would bcncfit most from catlng more green leafy vegetables.

Page 62 SPC n u i h k NO. 11.1992

Table 2: Nutrient composition of leMice leaves

A. Major nutrients (Values given are per 100 g edible portion.)

Isoleucine* (mg) Leucine* (m ) Lvsine* (me 7

Constituent

Water (g)

~ r y ~ t o ~ h a n * (Gg) T osine (mg) a i n e * (mg)

Average

95.00

Fat (6) Palmitic acid (mg) Stearic acid ( m ) Palmitoleic aci a (rnd - Oleic acid (m ) Linoleic acid ?mg) Linolenic acid (mg)

Carboh drate (g) Starch &)

F%Eee Sucrose (g

Dietary fibre (g) Total Dietary fibre (g), water-soluble Dietary fibre (g), water-insoluble Pentosan ( ), water-soluble Hexosan (7, water-insoluble Cellulose g), water-insoluble Polyuronic acid (g), water-insoluble

SPC ~andbaok NO. 31.1992 Page 63

B. Mineral elements (Values given are per 100 g edible portion)

Sodium (mg) Potassium (mg) Magnesium (mg) Calcium (mg) Manganeçe (mg) Iron (mg) Cobalt (pg) CoplJer (pg) Zinc (mg) Nickel (pg) Chromium (pg) Molybdenum (pg) Phosphorus (mg) Chloride (mg) Fluoride (pg) Iodide (pg) Boron (pg) Selenium (pg) Silicon (mg) Nihate (mg)

Constituent

Page 64

Average Range

C. Vitamins and other health-related substances (Values given are per 100 g edible portion)

Constituent

Carotene (pg) Vitamin A equivalents (pg) Vitamin E activity (pg) Vitamin K (pg) Vitamin BI, thiamin (pg) Vitamin B2, riboflavin (pg) Niacin (pg) Pantothenic acid (pg) Vitamin 86, pyridoxine (pg) Biotin (pg) Folic acid (pg) Vitamin Bi2 (pg) Vitamin C (mg)

Citric acid (mg) Oxalic acid Total (mg) Femiic acid (pg) Caffeic acid (mg)

Sterols total (mg) Campesterol (mg) Beta-Sitosterol (mg) Stigmasterol (mg)

Purines total (mg) (as uric acid)

Average Range

SPC Huidbwk No. 31,1992 Page 65

In Table 2A. orotein has been analvsed into the comwnent amino acids. All eiaht 'essential' a&oacidsarepresent and although theyare'only present in small amounis, the rcsultant protein in leituce leaves can make a contribution to the protein supply. Other erecn leafv veeetables would rnost Iikelvmntainat least thesame raneeof amino - acids 2 lettuce and &me probably contain Gger quantities.

Fat

The fat mntent of lemice leaves is well below the average levcl found for the group uf green leaves analyseci by the PlFCP laboratones. lt is, however, of excellent quality when theomstituent fanvacidsareexamined. Mono-and mlvunsaturated fath, acids. oleic, limleicand linoledcacidsmake up more than 70 cehi of the total fat &>nient. The last two mentioned are also known as Omega 6 and Omega 3 fatty acids because of their s d a l chernical smicture. Thev could be considered as 'vitamins' because thev are neéded in small amounts and aie thought to be involved in man wide-ran in biochemical activities in cell walls and bld-clottin mechanisms dettleton, ïg87h

fatty acids found in fish and seafood. 5 l Omega 3 fatty acids from plants can be converted in t e body to the type of Omega 3

Carbohydrate

Carbohydrate, especiall starch, is very low in the lettuce shown in the table. The main carbohydratesaresolub Y esugars, withglucoseand fructosebeingdominant. Thislevel of carbohydrate is well below that found for Pacific green leaves such as cassava and amaranth.

Fibre

Dietary fibre ismuch lower in lettuce than in theother Pacific reen leavesand ismainly

polyuronic acids. B in the form of water-insoluble fibre. This is made up O cellulose, hexosan and

Çomeof themany different mineral elemcntsin lettucearegiven inl'able2B.Thr major componcnts are potassium, calcium, chloridc, phosphoms and nitrogen.

Potassium is present in relatively hi h amounts in lettuce. Levels of over two per cent are possible in some lants. Green eaves are generally nch in potassium. It occurs in P F the soluble or ioNc orm and lays an important role, with sodium, in balancing the water content of cells and celluyar fluids. Potassium also plays a similar role in animals and an adequate supply helps to regulate b l d pressure.

Page 66 SPC h m m k NO. 3 1 . 1992

Potassium aiid especially nitrate-iiitrogcn can Vary tremendously witli cliangcs in uiil fcrtility. Tlie large iiicrease in soi1 otassium followiiig forcst buriiiii and clearin ,, or tlic fiusli of iiutrieiits made availagle in soi1 after opetiirig u p laiid a p ter a long fahow period,are twocxamplesof thedramaticchangesinsoil fcrtility wliiclicaiioccur. Plants rcsoond ouicklv to tliis releasc of iiutrients and hcaltliv. fast-rrowine. erccii lcafv

for tlie weeds, ~ ~ i r ~ b s ~ i i d ' ~ o u i ~ ~ fhrest trces t i ~ regencrate oncc ;gain.

Wlierc tlicre is sevcrc populatioii ressurc aiid the land shorta .c the laiid is farmcd maiiy timcs before rcturning to falrow. Wlicn th? time allowcd k,; fallow is tao short, the vegetablc gardeiis bccomc impovcrislied aiid tlie grccii Icavcs ?rown iii them arc

from t 1 iree to tliirty tiines duc to tliis change in soi1 fcrtility. 'I coiise ueiitly of lowcr iiutritiiliial quality. Nutriciit composition in t ie 1c;ivcs caii vary

Vitainins

Table 2C sliuws tlie vitamiiis and somc othcr substances fouiid in lettuce leavcs whicli have bccn sliowri to have important roles in iiutritioii and healtli. Lettuce, in commoii witli ,III grccii leafy ve etables, is a good source of carotciic or Vitamiii A, Vitamiii E, Vitainiii C ;ilid some O 7 tlic B voup vitamitis. Folie acid is 1. rexiit iii lettucc and iitlicr grccii leafy vegctables.'It reprcsciits a iiumbcr of relate clicmical substances wliich lielp preveiit certain forms of anemia. Tlie nutritioiial, bir~chemical and clinical aspccts of the vitamiiis listcd arc3 discussed in detail by Macliliii (1984).

Other substances

stcrols are similar cliemically tu cholestcrol but do riot liavc the samc capacity t6 form dcposits or plaque oii the sides of tlie blond vessels in the body. Puriiics are low iii lcttuce and green leaves~enerally compared with other foods such as liver and kidney which contaiii up to 40 times as mucli.

Lettuce, likc al1 grceii lcafy vegetahles, coiitaiiis a widc varicty of iiutrients. The Ievcls fouiid in lcttuce as usually consumed arc, however, probably among tlie lowest of al1 grcen leaves. Tliis is mainly duc to the wa lcttuce is preparcd. Tlie outside leaves arc probaùly tlirowii away or fcd to aiiirnals lecause the arc damagcd or too dirty. Tlic outcr, dark green Icavcs are kiiowii to contai11 u p to 4 g or 50 timcs as mucli carotcne as the pale iniier Ieaves. Otlier iiutricnts a lw will be present in tlicsc outer leavcs in many timcs tlie conccntratioii of the iiiiicr Icavcs.

SPC H a i d b o l Nu. il. 1992 Page 67

VII. FUTURE FOR LEAVES

n i e kiiowii liiiks bctwceti g « d Iicalth aiid eatiiig plciity of grceii lcaiy vegetablcs and fruit evcry day grow stroiiger as timc passes aiid our kiiowlcdgc is increascd.

Tlie oraiigc colour in fruits aiid root vcgctahlcs sucli as swcet pcitatiIcs and carrots Iias loiig becii kiiowii to bcduc tobcti-car«tciic,a molecule wliicli fiivesusabout half of our daily rcquircmciitof Vitainiii A. Tliissuhstaiicc isalw prcsi,iit iii grccii Icavcs, altliougli its colour is masked by tlir grceii pigment clilor«phyll.

Rccciit rcsearcli Iias sliowii tliat certaiii forms ~ ) f caiiccr arc significantly reduçcd i>r prcvciitcd by catiiig a dict ricli i i i grccii Icafy vcgctables ,iiid iruit. I t Iias iiorv becii provcd tliat beta-caroteiic is iiijt tlic oiily m~)lccule associatcd witli tlicsc cancer- prutcctivc cficcts, aiid tliat a vcry large iiurnbcr of otlicr substaiiccs fouiid iii lcavcs aiid fruits arc also iiivolv'd. Maiiy r ~ f tlicsc substaiiccs are iiatural aiiti-cixidaiits and arc kiiuwn to iiiliihit certaiii rcdctii~iis wliicli çaii damagc 'iiiiinal cells (Fraiikel, 1989).

Tlic buildiiig brick. of tlic Icaf arc iiiicroscoyic cclls wliicli çc>iitaiii mniiy teiis oi tliousaiids of diffcrciit orgiiiic mi)lccules, al1 takiiig part iii a ci>niplcx cliaiii of clicmical rcactioiisivliiclieiiiihlc~ tlii.iii t i~usc tlicriicrgy rcccivrd at tliesiirf'iccoi thcleaf toçrcatc i>rfi"iiic m'ittcr froni c.irboii diiixidcps i i i tlic air aiid absorbcd ivnti.r (tliat rniraculoiis pruccss of pliotosyiitlicsis oiicc agtiii).

Sorncof tl icsccliemicalsarealsi) toxic todiiimalsaiid Iielp protcct tliclcaf agaiiist pcsts diid diseases (Bci'r, 1990). TIie%> 'magic molccules' Iiave in'iiiy 'iiid varicd prupcrties aiid wlieii wc rat a Icaf, sonir of tlics~tspccial molcculcs pass iiito uur blc~od rclatively uiicliaiiged. A comrnoii fcaturc of tlicsc molcculcs is tlicir ahility to scavciigc or rcact witli oxygcii iii somc way (iiatural aiiti-oxidaiits). Si)mc miiicral elcmciits sucli as sclciiium aiid Vitainiiis C aiid E aiid maiiy of tlic vcry large group of car«tcii»ids fouiid in grcciileaves al1 Iiavc tlic capacity iii varying degrces to rcact rapidly aiid easily witli aiiy sparepoteiitially daiigerousactivesubstaiiccs,«r 'frecriidicals', '1s tliey are kiiowii. Aiiti-oxidaiitsarc uscd asadditives iii maiiy proccsscd fi)ods to prcvciit iiutriciit Ioss and spoilagc. Aiiti-oxidaiitsare pri)b,ibly «ne class «iclicinicnl .idditives for wliicli tlic advaiitagcsof theirusctoprotect iiatiiralaiitioxidaiitsinay outwcigli tlicdisadvaiitages of iiot usiiig tlicm i i i fooci processiiifi.

As you would cxpect from thc namc, 'frce radicals' arc Iiiglily reactive. Receiit researcli shongiy suggcsts that frce radical reactioiis iiivolviiiglipid ycroxides preseiit iii Iiumaii tissues arc part of tlic cause of skiil cancer followiiig loiig or excessive exposurc to suiishiiie (Mergeiis aiid Bhagavaii, 1989).

Page 68 SPC ~ ~ d b ~ ~ ~ NO. 3 1 . IVVZ I

Green leaves lose tlieir iiutricnt quality very quickly once they are removed from the plant. Poor handling, storageand overcookingall result in hugc lossesof the mostactivc substances as mcntioiied in an earlier section. Natural anti-oxidaiits sucli as Vitamiiis C and E aiid many carotenoids are among these active substaiices.

Anew analy tical technique known as HighPressure Liquid Cliromatography isalready being used to separate some of the many different active substances in leaves.

Itiiivolves theuseof extremcly high pressures toforccaleaf extracf iiiaspccial solvent, through a small staiiiless steel column coiitaining a uiiiformly packed material such as aluminium oxide or fine silica beads. The pressure applied (2000 p.s.i.1 would be about the same as that produccd wlieti an elepliant stamps 011 ,i tomato! The differeiit mc)lccules in the leaf extract travel tlirough the tube or cc)luinii uf powdcr at differeiit spccds depending on thcir size and cllemical iiaturc. Most completc separatioiis take about haIf ail Iiour.

k-4 1 ,"ch square

As each different substance leaves the column it is measured by special detector cells and a series of peaks is produced on a recorder. The sizc of the peak indicates the quantity of the substance coming off the column at that prccise time. Substances of knowii compositioii are also iiitroduced ont0 the column and tlieir peak positions and sizesareused asstandard refercnces toidentify tlieunkiiown substancesiii theextract.

SPC ~ u i d l i ~ o r NO. ~ i , ,992 Page 69

Future rcsearch into the healtli-giviiig and prutective properties of green leavcs will ccrtaiiily coiitiiiue to be dirccted nt tlie idcntificatioii of al1 tlie diffcreiit Iiighly active chemical substances found iii tlieir cclls and the dcterniiiiati~~ti of tlieir rclationsliip to the diffcrciit ciiviroiimciital discascs. l'licsc iiiclude cancer, Iicart dixvise, diabctcs, hypertciisioii aiid gi)u t - the SI)-callcd iioii-commuiiicable or 'lifc style' diseases wliicli arc n t ~ w becomiiig a scrious problem among Pacific peoplcs.

Tlic effcct of c«<iki~ig, processing and storiiig çould also be studicd by aiialysiiig leiives by HPLC beforc and after tlic leavcs Iiavc bceii trcated. Cliaiigcs in tlie levels of tlie diffcrent active substances would bc iiidicatcd by thc prcseiicc or absence of tlieir spccific pcaks oii tlie cliromatograms.

VIII. REFERENCES

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Wills, R.B.H. and H. Grceiificld (1988). Laborutor,y irisfrrrcfioii rrruiiiralfur fwii cui~i)ii~sitiuri sfiidies. Departmciit of Food Science and Technology, Uiiiversity of New Soutli Walcs, Australia.

-- ~ ~-

l)c Ir;a".l WC cal

APPENDIX 1

Page 74 si2r biaii,ikm* NU. J I , 1992

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APPENDIX 2

ANALYTICAL METHODS

The three PIFCP laboratories, Institute of Natural Resources (INR), University of the SouthPacific,Suva, Fiji; National Agricultural Chemistry Laboratory (NACL), Dcpart- meiit of Agriculture and Livcstock, Papua New Guinca; aiid National Aiialytical Laboratory (NAL) used the Laboratory iwstrirctiori ~riariiiul for food n~irr~~ositioiz stiu.iii,s compiled by Willsand Greenfield (1988) as a guide for the aiialysis of their grecii leaf samples. For somc componeiits, however, differeiit metliods werc used or modifica- tions werc madeby the individual laboratorirs. n i e metliods used are outliiied below for each component determiiied.

Sample preparation

lmmediatcly upon rcacliiiig the laboratos., the samplc buiicli of leaves was waslicd well witli tap water, riiiscd with distilled or deionised watcr to removc dust and soi1 particlesand tlieii drained and shakcn to elimiiiatcexcess watcr. The ediblepartsof tlir plants were separatcd and wciglied. Tlie iiicdiblcportioiis wcre alm weighcd aiid the11 discardcd. Tlie sample selectcd for aiialysis was quickly homogeniscd in a blciider to the consisteiicy of a pulp. The samyles wcre fiiially stored in stroiig plastic bags iii tlic decp frceze until needcd for subsequciit aiialysis.

All analyses were duplicatcd aiid standard rcference matcridls wcre ruii at the samc time.

Moisture

III the NACL the leaves wcre wcighed aiid tlieii dricd to coiistaiit weiglit in a vacuum oven set at 80°C. Tlie NAL dried the leaves in a fan oveii set at 135°C for 2 hours beforc cooling in a dessicator. The weiglit loss was then dctcrmiiied (Association of Officiai Analytical Cliemists, Official Mctliods of Analysis, 1990, Mctliod 930.15).

Protein

The standard kjeldahl digestion method with selenium catalyst was used by al1 three laborat(iries. The NAL measured the total ammoniacal nitrogen, using an automated 'Büclii' 322/342 Kjcldahl Apparatus, accordiiig to the British Standard 5766, Fart 4,1981. INR and NACL used manual and 'Tecator' equipmeiit respectively for the measurement of total ammoniacal nitrogen. The standard factor 6.25 was used to convert total nitrogeii to 'crude protciii'.

Fat

INR and NACL used the acid Iiydrolysis method. A weiglied lcaf sample was boilcd witli dilute Iiydrocliloric acid to free the bouiid lipids. These were extracted witli a mixture »f peh.oleuni etherand diethyl etlier. Fat wasdetermiiied gravimetrically after the complete cvaporation of the etliers.

NAL extractcd a 5-10 g sample witli hexaiie usiiig a 'Tecator Çuxtcc' Appra tus . The fat remaiiiing aftcr evaporatioii of the solvent was determiiicd gravimetrically (Asso- ciation of Official Aiialytical Cliemists, Official Metliods of Analysis I Y Y O , Mctliod 920.39 B).

Ash

INR and NACL followed the Wills and Greenfield metliod usiiig a muffle furiiacc set at 530°C. NAL aslicd a 2 g samplc for 2 hours at 500°C in a mufflc furnace (Association of Official Aiialytical Cliemists, Official Metliods of Analysis, 1990, Metliod 942.05).

Minerals (Sodium, Potassium, Calcium, Magnesium, Iroii aiid Zinc)

Tlie asli wasdigested withliot, dilute hydrochloric acid and the solutioiiaiialysed using the atomic absorption technique. NACL added cacsium cliloride to prevciit ionisation of sodium and potassium and strontium as a releasing agent for calcium aiid magrie- sium.NALuçed lanthaiiumat 0.1 percent asspccified in the British Standard 5766 par. 4.1984, and Australiaii Analytical Cliemists Committee Mcthod 40-70, 27.10.82.

SI'C i ir i idlr><>i hii. i l . , 9 9 2

Available carbohydrates

NACL extracted sugars witli ethanol and after removal of tlie cthanol scparated thcm by HPLC (High Pressure Liquid Cliromatography). NAL and INR did iiot deterniiiic. available carboliydrates. Dietary fibre

OiiIy NACL determincd 'dietary fibre'. Tlie rcsiduc left froni tlie determination of available carbuhydrates was hydrolyscd with the enzyme, amyloglucosidasc and tlie resultiiigglucoscmcasurcd by HPLC.Tliefiiialglucosc-frecrcsidue followiiig tliisstcp, after allowiiig for asli aiid protcin, was coiisidcred t i ~ b e 'dictary fibre'.

Vitamin C

Oiily INR detcrmined Vitamiii C. Tlie Association of Official Aiialytical Clicniists, Official Metliod of Aiialysis, 1990, Metliod 43.069-43.073, was cmployed.

Carotenes

Thcse precursors i>t Vitamiii A werc oiily determilied by INR. Tlie carotciics werc scparated by columii cliromatograpliy iiitu tliree main fractions consisting of alplia- carotene, bcta-caroteiie and cryptoxarithiii. Each fraction was measurcd by '3 visible absorption metliod as described by Wills and Greenfield (1988).

ACKNOWLEDGMENTS 1 am grateful to Nick Currey, Walter Bciigko and lan Walsh of tlie National Aiialytical Lahoratory, University of Tcchnology, Lac, Papua New Guiiiea; Dr Mary Mcfarldiic, Fred Gricsliaber, Kevin Gubag, Pah.ick Olou aiid Maima Sine of tlic Natic>iial Agricul- tural Clicmistry Laboratory, Dcpartment of Agriculture aiid Livestock, Papua New Guiiiea; and to Dr Bill Aalbershcrg, Ms Rohiiiee Singli and Praveeii Ravi of tlic Food SLudies Uiiit, Iiistitute i ~ f Natural liesources, University of tlicS<)utli Pacific,Suva, Fiji, for tlic iïutrieiit aiialysis rcsults of most of tlie Pacific grceii lcafy vcgetables dcscrihcd iii tliis booklct.

Tlie riutriciit data for lettucf wcre used with permissioii friliii tlie Gcrmari Food coi~i}~ositiiori arid riirfritiori tables 1989/Y0 by Souci ct al. (1989). Most additioiial supple- meiitary data for tliciiutrieiit tables in Appendix 1 werc tnken witli pcrmissioii from the Nl~f r i~nt co~~i)~ositiori of Mulaysiu foods (1988) by Sioiig et al. of tlie ASEAN Food Habits Priijcct, National Sub-cornmittee on Proteiii, Malaysia.

1 tliaiik Jcair-Paul Gnudcclioux for figures 1--17aiid Jeail-I'icrr<> Le Bars for iniist of tlic colour pli«tc>graplis aiid illustrati«iis. The vital partsplayed by tlie 'modcls' Lilctteaiid J~>clic Maseiig and Çiutaisa Fuavao arc gratefully ackriowledg~:d. 1 ivoiild also likc tu tliaiik 'Cliez Mariii', Paul Triiili Ngoc Boii aiid Feldali Maseiig for ,ill«wiiig us t i ~ pliotv- grapli tlieir vcgctablc gardeiis.

1 Iinvc supplementcd my owii kiiowledge of the botaiiy diid agroiiomy of tlie differcrit plaiits witli inuch valuableinf«rmati«n from Purseglove (1968) and Haleaiid Williams i1977). Mc Gee (1984) alsosupplicd me with fascinaying ha~k~oui id i i i fo rmat ion about tlie cffccts of cookiiig on tlie iiutritioiial quality of greeii leafy \,egctables.

1 very mucli appreciatcd tlie support aiid patience of all tlie SI'C typists wlio Iiclped preparc tl~is boi~klct for publication, esyecially Yvana Routier, E\,clyrie Gras, Marielle Ceorget, Maria Lourciico, Hcatlicr Jncksoii niid Odile R~lllaiid niid Elisc Knmisaii. l tliaiik tlic Publications Officer, Cartiliiic Nalo, for iiitcrcsting discussiuiis about Icavcs, for her liclpfiil commciits and for cditing tlie rvork. For tlir I,iyc~iit 1 tliaiik Martial Dosdaiic.

1 am gratcful to Dr Çitalcki Fiiiau, Co-ordinûtor of the Community Health Services, for liis good idcas aiid many constructive commcnts and support. I i i particular 1 apprcci- ated tlie 'Pacific flavour' added by Mrs Melc'ofa Malolo, Nutrition Educatioii aiid

Training Officer, and her frequent valuable comments during the writing of this booklct. Thedraft wasalso read by SPC Management, Dr Malcolm Hazelman (Agricul- ture Co-ordinator, Food and Materials Programme) and other members of the Commu- nity Health Services. Their comments and suggestions are gratcfully acknowledgcd.

The South Pacific Commission greatly appreciatcd the financial support from tlie United States Agency for International Developmciit (USAID) provided to the Pacific Islands Food Composition Programme to pay for tlie production and dishibution of this booklet.

Joliii M. Bailey

Page 80 SYC llandbwk Nu. II. ID92

Ilr 1çrrrs ue rrr

loinair Watei Spinaçh

Pumpkin Chinese Cabbage

Dmmslick Cassava '<

- Lettuce -

Taro Stalks - Papaya shoots -

Cabbage - Nightshade

r

Figure 1: Weight of water, in grams, in 100 g edible portion, raw.

iPC liaiiilhiik Nn 3 , . 1992

- Water Dropwon -

Waiercress - Tropical Spinach -

Sweet Potato - Taro - Fern -

Edible Hibiscus

I

1 1 50 75 100

, > .:@ !.'a; -- Ilr ,~>"CS uc cai

Figure 2: Weight of fat, in grams, in 100 g edible portion, raw.

- Lettuce -


Cabbage - Nightshade -

Winged Bean - Chayote - Jointfir -

Water Spinach - Pumpkin -

Chinese Cabbage - Dmmstick -

Cassava - Kale Seedling

SPC Ilriidbiiiak No. J I . ,992

i - i - - i

i

i

Water ~ r o ~ w o r t * Watercress -

Tropical Spinach - Sweet Poiato -

Taro - Fem -

Edible Hibiscus

- i - i

i

, l ~ ~ ~ ' 1 ~ ~ ~ ' 1 ~ ' ~

O 0.5 1 1.5

Lettuce Taro Stalks

Papaya shoots Cabbage

Nightshade Winged Bean

Chayote loinair

Water Spinach Pumpkin

Chinese Cabbage Drurnstick

Figure 3: Energy content, in kCals, in 100 g edible portion, raw.

Multiply by4.184 t o convert t o kilojoules

cassava- - Kale Seedling -

Water Dropwon - Watercress -

Tmpicai Spinach - Sweei Potato -

Taro - Fern -

Edible Hibiscus

SIC ~ ~ ~ d t ~ ~ * NO. 3 1 , ,992 Page 83

- r

I 1 O 50 100

- Lettuce - -

Taro Stalks i - Papaya shoots -

Cabbage - Nightshade - '


Water Spinach - - Pumpkin -

Chinese Cabbage - Drumstick -

Cassava - Kale seedling -

Water Dropwon - Watercress - '

Tropical Spinach - Sweet Potato -

Taro - Ferri

Edible Hibiscus I 1

O 5 10

Figure 4: Weight of protein, in grams, in 100 g edible portion, raw.

Protein w u s ciilculated by using the factor 6.25 x totul nitrogen.

Page 84

Kale Seedling Water Dropwort

Tropical Spinach Sweet Potato

Taro

Lettuce Taro Stalks

Edible Hibiscus 1 Tr l i i i i , i i i l , i i i i l i , -

O 5 IO 15 20

- Papaya shoots -




Chinese Cabbage - Drumstick

Figure 5: Weight of carbohydrate (CHO), in grams, in 100 g edible portion, raw.

Tr Tr Tr Tr Tr Tr i

Tr indicates tliat the quantity of carbohydrate present is be low the detection litnit of the analytical method used.

si2c >iuiilluui NO 31. 1192 Page 85

Figure 6: Weight of dietary fibre, i n grams, i n 100 g edible portion, raw.

- Lettuce -


Cabbage

The da t a for 5, 6, 7, 8, 9, 10, 16, 19, 20, and 21 are from the National Agricultural Chemistry Labora toy , PNG (See Appendix 1).

m i - 1

Page 86 SPC IIN,C~~~UX ND. 31, ,992

Nightshade Winged Bean -

Chayote - Joinffir -




i

r œ - -

Water Dropwon Watercress -


Taro - Ferri -

Edible tlibiscus

r.

- I I

O 5 10

Lettuce Taro Stalks



Chayote Jointfir

Figure 7: Weight of sodium, i n milligrams, in 100 g edible portion, raw.

SPC H ~ C I ~ ~ O L NO. 11. 1991 Page 87

- Pumpkin -


Cassava - Kale Seedling -

i

i

œ Water Dropwort b -

Watercress - Tropical Spinach -

Sweet Potato - T a o - Fern -

Edible Hibiscus

- i

œ - - 1 I

O 25 50

Lettuce- - Taro Stalks -

Papaya shoots - Cabbage -

Figure 8: Weight of potassium, i n milligrams, i n 100 g edible portion, raw.

- i

d


Sweet Potato - Taro - Ferri -

Edible Hibiscus

Page 88 SPC ~ u i d 6 - k NO. 3 1 . ,992

r

Nightshade Winged Bean -

Chayote - Jointfir -


Chinese Cabbage - D~mst ick -


1 " " l " " l " " l O 300 600 900

- œ

Water ~ r o p w o n l

'Ili- Iri<"ïn u i cri

Sweet Potato

Fem

- Lettuce -







Water Dropwon - Watercress

Figure 9: Weight of calcium, in milligrams, in 100 g edible portion, raw.

si^ ~ r ~ i l l ~ ~ ~ i NU. I I , I Y Y Z I'agc X9

- I

i - œ - i

i

i

f

Edible Hibiscus 1 1 1 1

O 200 400

- Lettuce

Taro Stalks- - Papaya shoots -

Cabbage Nightshade- -

Winged Bean - Chayote

Figure 10: Weight of magnesium, i n milligrams, i n 100 g edible portion, raw.

i

No data No data i - -

Page 90

'No data' indicates that magnesium w a s not detertnined in the PIFCP laboratories and that a suitable literature

source could not be fouttd.

1ointfir-b -

SPC Handb-k No. 11. 1992



Cassava - Kaie Seedling

Water Dropwort-- -

I - i

No data N o data i

Watercress Tropical Spinach

Sweet P o t a t o - i - Taro - Fern

r

Lettuce Taro Stalks

Papaya shoots - Cabbage - i

Nightshade - Winged Bean - -

Chayote - Joinfir -

Water Spinach - - Pumpkin - -

Chinese Cabbage - - Dmmstick - -


Water Dropwort - - Watercress - -


Taro - - Fem -

Edible Elibiscus I 1 I

O 10 20

Figure 11: Weight of iron, in micrograms, in 100 g edible portion, raw.

SPC ~u id tnok NO. 31, 1992 Pagï 91

. ., ',lx , ~ l x ~ r s cai

- Lettuce -


Cabbage - Nightshade No data -

Winged Bean No data - Chayote No data - Jointfir -

Water Spinach r - Punipkin -

Chinese Cabbage Dmmstick- -


Water Dropwoti - Watercress -

Tropical Spinach Sweet Potato

Taro Fem

Edible Hibiscus l ' ' ' ~ l ' ' ~ ' l ' ' a ' l O O. 1 0.2 0.3

Figure 12: Weight of zinc, in micrograms, in 100 g edible portion, raw.

'No data' indicates that zinc w a s not detennined in the PlFCP laboratories and that a suitable literature source could not be fonnd.

l'agc 92 SPC HU?<U~W~ NO JI. 1992

Ilr ,ca,Cr xr cal

Lettuce

Cabbage Nightshade

Winged Bean Chayote Jointfu

Water Spinach Pumpkin

Chinese Cabbage

Water Dmpwort Watercress

Tropical Spinach Sweet Potalo

Taro Fern

Edible Hibiscus

Figure 13: Weight of thiamine, in milligrams, in 100 g edible portion, raw.

'No datu' indicutes tliut tliiurnine w u s not deteriiiincd in tlie PIFCP laboratorics and tliut a suituble literuture source corild iiot be found.

Figure 14: Weight of riboflavin, in milligrams, in 100 g edible portion, raw.

- Leuuce -

Taro Stalks - Papaya shoots

c a b b a g e W i - Nightshade -



Chinese Cabbage - Dtumstick

'No data' indicutes tliat riboflavin was not determined in tlre PIFCP laboratories and tltat a suitable literature source could not be found.

i

No data No data No data - No data

rn

Page 94 SPC i l î ~ i ~ l l i a i k Nu 11. 1992

Cassava Kale Seedling -

Water Dropwon - Watercress -

Tropical Spinach - Sweet Potato

I - T m - Fem -

Edible Hibiscus -

1 1 O 0.5 1

k n u c e Taro Stalks


lointfu Water Spinach

Pumpkin Chinese Cabbage &

Figure 15: Weight of niacin, in milligrams, in 100 g edible portion, raw.

- Cassava -

Kale Seedling - Water Dropwort -



Edible Hibiscus

'No duta'indicates tliat niucin w a s not detertnined in tlie PIFCP laborutories und tllat a suitable literatzire source could no t be found.

r

i - 8 - -

1 I

SPC i ~ ~ ~ ~ ~ i i ~ ~ ~ k NO 31. 1992 Page 95

O 2.5 5

Figure 16: Weight of Vitamin A, in micrograms retinol equivalents, calculated from the weight of carotene divided by six, in 100 g edible portion, raw.

Dmmstick - Cassava -

Kale Seedling

Page 96 SPC liuidbmk Ni i3 I . IYYL

8

Edible Hibiscus 1 1 I 1 1

O 500 1000 1500 2000

. . ~p

l i r 1ca\.er uc crr

Lettuce Taro Stalks



Jointfir Water Spinach

Chinese Cabbage Dmmstick

Figure 17: Weight of Vitamin C, in milligrams, in 100 g edible portion, raw.

Cassava Kale Seedling

Water Dropwon

'No data'indicates that Vitutnin C w a s not dctcrmii~ed in the PIFCP laboratories and tliat a suitable literature source coirld not be found.



Edible Hibiscus

r

I

l " r ~ l ' ~ ' l l ' l ' r l ' l " l r " l l ' l l l l l L " l O 50 100 150 200 250 300 350

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The Leaves We Eat