III ~ ~pB1.0 I.ii IIIII~I~ Ij,iW .2IW WIi. IIIoi

:"1 wI 1.1 ........

11111 1.8

111111.25 111111.4 111111.6

MICROCOPY RESOLUTION TEST CHART NA,IONAL BUREAU D' STANOARDS1953.A

I~ 12B ~F5 ~ II!Iii iii1i1II!iI1.0 :: Iii 12.2 ... W ~ IIIoi

..1.1 ..... :: ~

""1~8 111111.25 111111.4 IIIII 1.6

MICROCOPY RESOLUTION TEST CHART NATIONAL BUR[AU Of SlANDARD51963A

http:111111.25http:111111.25

Technical Bulletin No. 730 July .1940 '1-'

\1 ' ,

;1 -VNI8. 'STATES ..EPAI!iT.BN....... AGBIVI..TV"c~

'.ASIUNGTON!lB~~~ , '. '.

Market Quality and Condition of California

Cantaloups as Influenced by Maturity,

Handling, and Precooling 1 !!

By W. T. PEXTZER, physiologist, and J.UIES S. WIAXT, associate pathologist,

Division of Fruit and 1'egetable Crops and Diseases, Bureau of Plant Industry, and JORX R. MACGILLlVRAY, associate olericlIltllrist ('alifornia Agricultural Experiment Station 3

enited States Department of Agriculture, Bureau of Plant Industry, in cooperation with the California Agricultural Experiment Station

CO:\TEl'iTS

Pllge PageIntroduction_____ ._ ... _ _____________.. __ .. _ Itesults and discussion-('ontiuUld.:Mctbods and materials......__ ...._.... __ _ 3 I Relation of pre(1)oling and transit tempera

]'Ian of work .. 3 tures to the condition and quality of _oo.......... ____ ..... ..

S~lrction of test melons _______......____ .. a cllntaloups after arrh'a] in elL'tern Loading d test crates_. '. ____ ~~ .. __ ~~~ ___ _ 9 markets "__ ._ Type ofrefri~prator car used ___ ... _____ _ 9 ft"lation of picking maturity to the market Determination of temperatures of air and bcha\"ior of cantaloups_ __ .. _ 62

melons_. _. ______ . _____ .. __ ... __ 9 Relation of variety to the Ulllrk~t beba ,-ior Metbods of analyzing temperature data __ 13 of cantaloups -. _ 65 _Metbods of waxin!' t('st melons ___ . _ 18 I EfT"ct of waxing upon the market IWb'l\'ior "fetbods of fumil!!ltinl! cantaloups witb i of cantaloups_ - - - - '- 6ti nitro~en triebloride ______. .. _____ _ IS EfTect of fumhmtion with nitrog('n trio

"'[ptbods of inspecting melons on tbe ; cbloride upon tbe market bebaviur ofmarket_. ____________ _________ . __ ___ _ 18 i cantaloups __ "__ "". ______ ._ 6SResults and discussion________________. ___ . __ Z~. SUIDIuary. . *_~~.~ ___ .. _~~~ .. ~~~. ,,~~~_ 69

Precoolingstudies..______________ __ . __ 2"2 i Literature cited .~.~~_~~ . _.~_ 72 Temperatures in refrigerator ears intmnsiL.______ .. _._. ___________ .___ 38;

1 Recl'i\-ed [or puhlicntion J)ecemt ... r 20. 1939. 2 Although tl st.rict taxonomic usage of thr term "Cfiotaloup" would limit it to memh('TS of CuerLl/li.'f 1IIt/U

,-ar. canta{up .. ".i. it has come to be generally used in tbe Cnited States to designn!, the ):rt'(!n-skinnrd, netted muskmclons (C. melD yar. reticuLalll.'). and it is employed in th,' Jatter sense in tlds bulletin,

3 Report ofnjoint in\'esti~ation planoed and ronductN! by the authors and the followillg(1)workers as u cooperati\"(' proj!'ct of the Burrau of Plant Indostry and the California A~cultural Experiment Scallon: C_E. Asbury. W. R. Bar~er, C. 0_ Bratley. D. F. Fisher. and R. C. Wri~t, Division of Fruit and Vegetable CropE and Diseases, Bureau of Plant Industry, r. S, Dppartment of _~.".icultun. Th,'y were wsisted in som~ of the shipping tests by G. W. Scott and Allen Younnnn, formerly r~l'farcb assistants in the California station. Acknowledpnent is gratefully made of tbe assistance of other assOC'ia!es, namely, tbe late Ivan C. Jagger in snpplying test melons and of G. B. Ramsey in inspecting melons on the Chien carried on. Acknowledgments are also due to officials of the various railroadsowr wbich the transportation fes!s were routed, and to fmitprocessing companies and precooling agencies for facilities supplied and for eool}('rntion dnring the COUrse of the test work.

2]8~~4>--4O----1 1

http:EPAI!iT.BN

2 TE('HN"H'AL neLLETIN" 730, 1'. ~. DEPT. OF ACRIUeLTI~RE

INTRODGCTJON

The uwestigations on handling, preeooling, and shippillg California cautaloups that form the subject of this bullptin \\,pre IH'gun in 1934 and were COil tinued through the seasons of 1935~3S. TIl(' purpos!' of the study, stn.ted briefly, was the improvenwut of qUillity !lnd C01Iclition of C'H.lltaloups on tllP Illfl.rkrt throllgh modificatioll" ill picking, handling, n.nd shipping practices.

A brief considern.tion of somp of tIll' nwthodR in lise at tht' tin1' th{' investigations ,nol'l' initiatNl will bl' hl'lpful to n clPlU' 1Ind{'rstanding of some of the problpUls confronting tht' industry. 1'1H' gC'IH'l'n.l Iw,l'Y, ".-h1Ch RllpC'rs(,c\f'd all othl'l' Yn.rif'tiC'R in rommpJ'cial importanc(' in 19~7. Tlw work covC'f'('{l thC' qUC'RtionR of whC'n to piek pantnJollpR, how much .... to prl'eool thpm, tlw trmppratur(' npC('R!';arT for thcif' trallRportatioll to rastern markds without ]05RC'R, and thp valuC' of wn,xC's nne! gil!'; trC'n.tmC'ntR in tbp Rhipmpnt of rantalollp!';.

I Itnlir nurnh(lr~ in pnrl'nth('$~s f{\(pr to Literature' Cited, IJ.72. I C'oused hy the lun!(us Rrvsiphe richoracearum DC.

3 L'A.LlFOR:81A CAXTALOUPS

METHODS AND MATERIALS

PLAN OF ~WORK

The genrral pl!1n followed throughout the investig!1tions W!1S to compare thr condition and quality of special test lots of nwlolls ilftpr transport!1tioll to ('!1stern mark(ts in commercial carlot sliipmpnts. The test lots were made up of several crates of melons of ('11ch of thp maturities, varieties, or trr!1tments under test, or, where precooling!1nd transit rei'rigemtion W!1S the problem being investig!1trcl, melons alike in maturity, varirty, and treatment were shipprd with and without precooling. An outline of thr test shipments mnde during the course of the inv'stigation is presented in table 1. Twenty-fin' of the thirty-onE' shipments mad' were from the ImpE'rial VaUey, the rpmainder from ~tf('ndota, Turlock, and :Modesto, Calif., and Yuma, Ariz. All but threr of tlll' tpst cars WE'Te unloadrd at the New York market. Cars L, 11, N, !1nd 0, shipped in 1936, and cars U, V, W, X, and Y, in 1937, wpre accompanied to XC'w York by obsrrvers who recordpd tempera turps in transit. In the othE'r cars listpd, trilllsit tpmpf'ra.turE's wprp obtaill('d at onr or two positions by nwans of recording thrI'monH'tprs.

SELECTION OF TEST MELONS

In splpctill

Jo!:>.TAIII,F] 1.-8hi/llllt'lIls of lesi cllrs'in canill/ou/l hll'lll/l-in(J, 711"I'cooii1l(J, lind irrrn'~/lorl(lii()n investi(J(lti(}n.~, 19.'14-37

I I 'I'tlgl1'esl Dalool Hhll.plll~ poillt DesIllIlIUIIII l'roo'hIPPIII~ IronllllOIlI\ erntcs 'l'oSI R i lI\'ol\'od J RnUl!II:- -~I' M otholl of refrl~erntion ~ l'nr shlplllollt shlppod, I: _I - .,.,. _I .. -~~.-- . ----_._---- @---.--.-~

I ' I ~ 111.1,1 I I-t;.Vumlwr A,\ A I Jlllle IO-IB IIrllwlo~', ('11111 Now York, N Y Pro('onlmi n~.i h(lIlrs . In I Prllcooling, IIIntu- i AouthQl'1l ~.)ncin(!; 'I'UXtl~ ProlcOlI; precoolod with portIIble enr IIIIIS; slnmlllrd redi.y, "flrloly. I 1,'II";flc; Mlssollri 1'11- ~

I llin('; \Vuhm;h; Erie. frigeration.

b:j(III .1111 NOtIIIft,(,tlololl III till . lIn I'roieell; stnll(\nrd rolrigem111111 (h. lion, @

('('0 Juno 1I!!1 YIIIIIII, ,lrl1. 110 NOTlprl!('onlod; I \l I\'II,h!~ Do. tIwnxtHI. t".lDl.m I Sopt. 11-18 MllIulola, ('nlll t 'hil'H~O, 111 Prceooied U!Jii honrs 5; Pn!t'nollll~, 11111\11- I SOllthem I'neillc; Wosl l'rolcoll; precouiod wilh port 1-'3rily. (,rn Pncif1l': Denver & able cur fnns; stnndara ra I-t

IlIn (lrnmlo 1I'0storn; Irl~erntion. 2:I\'lIhnsh.

--.11135 t:I.:>

A JUliO :tHS IIrllwl,.}', ('alii Now York, N. Y 1 I'n",oolotl:l hOllrs 18 1 Proconlllif,;, :ltl\i,u- Simlhom [,ncltlc; Roek Prelcetl; llfecotllell wIth Irnck o

I rltY.l'lIrlol)'. fslllnd; \Vnhnsh; mrie. sltlo II owor; stlllldnrd re

frlgerntloll; a percent snIt \~ullln IIIIli 'rUlISon. ~

)I do dn ,10 NOIII.rll(,lmIB,1 II 110 ell) Prolced; stundllrd relri~emtiOll. ?lj Preiced; precooled with portC' Juno 1:1-21 gl COli1m, ('1,111 dj) ,I1'ro""ol(lIl II)H hours 1\ do Southorn I'lIcltlc; Oot

ton nelt; Nickel Plale; IIble cnr Inns; stllndar!! reErio. Iri~eration; a percent salt ~

Yuma llnd 'rUCSQll. Do.do ... __ ...lll rceOOllJd f1,'!!" hotIrS I I.; rio _ .-.- -.---1----110 - .. _ -- ~ 1> i JUllO IJ-ZI do

g ,J!llIoIS 20 d'l do _ _ Pro"oolml I()~~ hours I II tI.. ... . ___ . __ tlo. Do. F do do tin . l'roellnlod 7tli hours IX Do. o o Jill)' 2;\:11 ')'urIUt,k I Clllir tit.. LOllis, I\fo .1 Prm'(lIllod S"n hnllfs 13 pre~~:~lInf(,' illlltll-I'S(jut\~om PIlclflc;irnlt;n' Proh!otl; precooled with port "Jt rit )-. I'llrille; Wnbllsh. able car 1'105; stlllldllrd re t>-I I Irlgemtlon. II ! JIII}'2(h\II~. 2 11101",,10, Onlil (,)hiCII~o, ilL . Prcf!ooiod 8} 2 hours JoI '-_ 110. __________ Tldowntor SOllthorn; Prelced; precooled with port @

I\'oston! 1"11'1 lie, Den nble cnr fnns; stnndard re I-t I'er ,\: Rio Orlllltlo Irigerntion; :J pcrc""t snit o Wost.orn; Missouri 1'11- Slockton nnd Portoln. cille; Alton.I !I~~lj ~

I, I JIIIIO ~>() 28 IIrllwlo)" ('nlll Nuw York, N. Y } NUllpnwoo)od o _ dn SouUlllrll Pllcltl,, Oot Preleed; stllOdnrd rolrlgeratlon; tOil 1I01t,; BIIllJlllore 2 percent snIt Brnwley nnd ~ .I:. Uhio. YUlIln,

M ~:I ('1m1m, Cnlll do PrOt.'nuit.HI i,1 ~ hOllrs . do ----------1I Southern Pnclfic; Oot Preleetl; precooled with rort lOll nlllt; Niekol PIIIlo; nhle enr fnns, slnndnr< regrie. Irigorntlon; :I percont snIt gl

C~ntro nnd YJllIlq. I ".

http:PrOt.'nuit.HI

N Juno 2(}-21l do

0 IJUlie 211 28 lIoltl'lllo, ('nm

I' I JUIl02\July U limn-loy. cllm

Q I JUlle2hluly2 do

S IJUI10 211 July 8 : ~;I ('011 I reI, l'nllf

'I' do do.... ,

'l".P JIII",:I() July II i C\O

'1"),'1' t July :!2- Aug. a . rl'urlfl('k, (lnlir

'l'1~'1"l' I Jul>' 28 ,\ug. (\ tlo lMr

II JtlllO 12..:'J() Bmw I"),, CIIUf

V do do

IV do 1,1 ('oll\rl), CnUf

110 , Precooled 101~ hOllrs..

do............. I]'r~COl)led Il'~ hours . t\II.............1NUllproconled.

do ..... 1 J'roc(ll)lo(\ lI'. hours

... do............ ll'flll'lIolod 1;1 hours

do .... .1 1'rocooI01\5':( hours

.do............. 1 COIlllllort!lllUy procooled

do ....I.....do

do "" do

do ..........1NOlI\lweolllod

do ... 1'rel'oolOiI nli hours ,,

. i do.. Pret:(}ult~d 8 hours

(\ I. ....do ... _....1. . do.

fl L ...do............... I.. do

(\ I. ....do. Southern Pllclfle; Hock Isla lid; Missouri Pa cllIc; Nickol 1'lute; l~rJo.

12 I )'re"oolinl':, 1II11tU 8mlthoru l'neltle; Oot rlt,y t wnxirl~. tOil Belt; Wuhush;

J~rio.

l'rocooling, IIIII\,U' I Southorll I'lleiflc; Oot rlt>" " tOil llolt; l3l1ltllllore& Ohio.

20 Procooling, IIIIItU'[ Southorll 1'lIelllc; Hock rity, vllrlol,y, wn~~ !sluud; Minneul,olis inl-{. & St. Lonis; rpo ado,

Peorill

TABLE 1.-Shipments of lest cars in canlalollp handlino, pl'ecooz.ino, and transportation i1westigations, 1934-37-Colltillued 0;,

--. 'festTest ])"to of Shipping point Dost.llliltion l'reshipping treatmont craLes 'rosts invol \'od Routing MothotI of refrigerution t;3cllr shiplllont shipped 0

------.--- I ~ ~ 1937 H

~VumlJcr X June 12-20. Brnwley, CllliL .. , New York, N. Y.. Precoololl 8% hours_ . (I Prccoding, mlllu- Soul horn PuoiOc;

7 CALIFORNIA CAXTALOUPS

00

~ G ~ ~ ~,... ;:;. ,.... ..... ::... ~ ..., ~

-I ::..:

? ~

'f.

..... '"' ~ ~ o r'%j

>=:I ;,;.... G,....

~ t:-j ~

FWUllE 2. "-Culltlliollp of the hurd-ripe 01' "full-8lip" llllLtllrity: A, With Htem uttachl'dj H, aHol' l:lcpamtiun from l:ltelll. A cruck t:j

don'lops IIround the stcm uttllchmcnL!L8 the lIIolons reach lh{' full-iilip stuge of lllat.urity, pruviding vi:;iblc e"idollCC thut they urc ripl' cnough to bo pirkL'd.

9 C,\.LTFOHXlA CAX'r.\LOlTP:-;

LOADING OF TEST CRATES

The cantruollp load of 288 jumbo cratt'S was used in the test cars whene,pr possible. In this load the crat('s are stowl'd on th('ir sides, 6 rows wide, 3 layers high, and 8 sLacks long in each end of the cm', with a spnce left at the dool'wny where the lond is braced to prevent shifting in transit. As the crates are all of one size in this type of load, the air channels are continuous, and more effective refrigern,tion cnn be obtained than when crates of different sizes are used. It was sometimes necessary to use test cars con taining se\'ernl sizes of crates, and then the test crates were loaded with other jumbo crates in one end of the car. The e:xperimentru crates of melons were usually placed in the top layer of the doorway stacks where they would ordinarily be exposed to the warmest temperatures in the car.

FIGURE 3.-Crew of pickers in an Imperial Valley field. When the pieking bags have been filled they are carried to the end of the row and emptied into field crates by opening the bottom of the bag.

TYPE OF REFRIGERATOR Cm USED

Refrigerator cars equipped with basket-type bunkers, solid insulated bulkheads, and permanent floor racks were used for all of the tests. For each transportation test, cars in good condition and of similar construction were select('d to minimize differenc('s in tigiltn('ss n;nd insulation. The cars used in the tests were f('presentatiYe of the average equipment then available for the tmnsportation of can talou ps. They w('re made of wood with insulation for the most part as follows:

FloOT_________________________ 2 inches of Hairinsul. RooL__ _.. _______________ 2 inches of Hairfelt or Flaxlinum. Sides and ends_ .. ______________ 2 inches of Hairinsul, Balsam Wool,

or Flaxlillulll.

DETERMINATION OF TE;\lPERATURES OF AIR AND ~[ELONS

In tll(' prrcooling and transportation stud irs it was necessary to read temp('ratmf's of melons in various parts of tIl(' loaded car at

!:!1.m2~"-40-!:!

10 TEt'llXll',\L lll'LLETIX ,:10, l'. :->, HEl'l', OF ,\UHllTL1THE

\ c \

Frl" J:r:L ,I, hij.l C'ra7p.; IIf ('a',lUlo',!I~ I"'il-!! c!"!i\l"rl"r1 II) I~ />/((,1-,1' 1.( j"'1!~(' ('q'~;JJIJf'fl \\ 'th fr'Ht-\~:l~ d~I-' !.! lU:.Hfb:T.fr:-.; 15, (Irat(:: }'(ir.g IJ!:u't d (I'. a hl'lt tl.at d..ji\.'r~ l1"'Ui 11) 11 r1 ..\i ..1' II at lilt~ \hl" I'fatl', InLJi.~f'rrI: e: 1l.1' (/II.1a1"''!,, In tIll' "'ftrtirlg I ,,It ; r'o (-nl1djtd ("ralf':-: b('ilJ~ (+f)!'\'('){'d frotH tLf' II~u*~~iI;g IHJ,l .... t to tlH~ n,Il tf'l"h1I1adit!! ;,ard

11 CALIFOR);"!A CAXTALOrpS

intervals without entering the car or disturbing the load. Electrical resistance thermometers, connected through leads to a master cable equipped with a metal door plate upon which the car doors could be

FIGURE 5.-A, Sorters working at sorting belt, throwing out culls and grading melons for maturity; B, packers working at bins to which melons are delivered from sorting belts.

dosed, were used for this purpose. A temperaturr indicator box consisting of a modified Wheatstone bridge, !1 sensitive galvunom('ter, and a selector switch was connected to the end of the cable when readings were made. This equipment is shO\,,'Il in figure 6.

12 TECPNIOAL BULL1~TIN 730, U. S. DEPT. O}

13 CALIFORXIA CAXTALOUPS

Melon temperatures during preeooling and in transit: 7

Bottom layer (layer 1). Bunkm' stack (stack 1), center row (row 3 or 4) _ _ _ Midd.le layer (layer 2). {Top layer (layer 3). Quarter-length stack (stack 4 or 5) center row (row IB~ttom layer payer 1).

3 or 4) '1MIddle layer {layer 2). . Top layer (layer 3).

Bottom layer (layer 1).Doorway stack (stack 8), center row (row 3 or 4) ____ Middle layer (layer 2).{Top layer (layer 3).

The sensitive part of the resistance thermometer consists of a coil of nickel alloy wire enclosed in. a pointed metal sheath or cap 2 to 4 inches long, mnking up the "bulb" of the thermometer. The pointed bulb was pushed into a melon at the approximate center of the crate.

In those test cars that were not accompanied by obsel'vers, a record of melon temperatures in transit was obtained by means of recording

FIGURE 7.-Diagram of one-half of carload of cantaloups showing the location of thermometer equipment in transportation tests. During the precooling period the only change hI the location of the equipment was that of the tlH~rmometers used for air temperatures, these being placed so that air-blast and air-return temperatures could be read.

thermometers packed at about the center of test crates. Two thermometers were usually placed in each test shipment to provide duplicate records. In comparative trials the temperatures recorded

20by these thermometers proved to be within 10 to F. of those obtained with resistance thermometers placed in melons at the center of the same crates.

:METHODS OF A:'

14 TECHIHCAL BULLETIN 73(" U. S. DEPT. OF AGfiICUL'TI"fi:E

of peaches, apples, and strawberries from fruit temperatmes obtained in 6 positions in 1 end of the car, namely, top and bottom layers, center row, billIker, quarter-length, and doorway stacks. In averaging these temperatures, the quarter-length stack was given double weight. The average transit temperature of fruit in nonprecooled cars of oranges was computed from the fruit temperatures at the top and bottom quarter-length by Mann and Oooper (13), and in precooled cars the arithmetical means of all of the fruit temperatures obtained were used. Rose and Gorman (1'1) compared the arithmetical means of 10 to 14 fruit temperatmeG 'Jbtained in cars of strawberries with the averages of the top and bottom quarter-length readings in the same cars and concluded, as did Mann and Oooper, that the latter averages could be used to closely approximate the average temperature of the load. Their tests involved averages of both precooled and nonprecooled cars, before precooling, at the end of cooling, ancl after arrival at their destination. Gaylord, Fawcett, and Hienton (6) in obtaining average bottom- and top-layer temperatures of cantaloups in precooli.ng tests, used the mean of 5 readings made in these layers of the quarter-length stacks.

TE~lPERATURE DATA FRO1\[ PR~COOLING STUDIES

In the prl'smt stuuips it was necessary to dett'rmine the average tpmppratme of the load at the beginning and at the ('nd of precooling in order to compute tIle (>iIpctive refrigprution supplied during precooling. For thl' initial tempemtuT(', taken after the car was loaded and just bdore thE' start of precooling, an arithmetical mean of ml.'lon tE'mppmturE's at th(' ninl.' I'Pgular positions in the car wus USE'd.

TABLE 2.-Average temperatures of cantalollps at the end of precooling---0--------.-- .--_. .. ------------:-------:-_____--;-___--:____

_"'[can of , top and Mean of Melin of 1'I'hennom-Cnr 'l'rcatment bottom regular nil posi- i Ner rcadlayers, positions tions, Ings stuck 4 I'

---------------1-----1----------,-----OF. OF. OF. JVumbrr,- Precooled i bours. 40 minutes ..____________ . 59. i 58 I ; 59.0 19Y PreCOOled 4 hours, 28 minutes .. _____________ 74.4 74:2 : 73.4 ; 21AA! Precooled 6 hoUrs. 8 minutes.. __________ .... 55. (i 62.5,57.S j'- 19C(' : Precooled -I honrs, 30 minutes ..... __ ... ____ .. 72.4 7L 7 73. i I 20

This method of dpkrmining an aVl'mge initial temppmture for the load was adoptpd because it soon became pvidcnt during the prl.'cooling tpsts that thp tpmperatures of melons might vary as much as 10 F. from onp cratl'ature of thp load and pmphasiZf'd the possibility of introducing ('1'1'01'8 by wpighting the readings at 1 or 2 positions. For the same reason, th(' final average temperahu'p of tll(> load was determined in a similar mamH'r. In some C!lrs, such as V, Y, and CO. the average temperature of melons in the top and bottom erates in the fourth staek was very close to the mean obtained from the 9 regul~r positions, or from the 19 to 20 melon

http:precooli.ng

15 CALIFORNIA CANTALOUPS

temperatures read ill some cars, as is indicated ill table 2. However, ill other cars, for ('xam.ple, car AA (table 2 and fig. 8), the fourth stack

CAR V ICE

LOADING TIME BUNKER I HOUR 45 MINUTES

PRECOOLED 7 HOURS 40 MINUTES

CAR Y ICE

BUNKER LOADING TIME 3 HOURS 45 MINUTES

PRECOOLED 4 HOURS 28 MINUTES

CAR AA ICE

BUNKER LOADING TIME 3 HOURS 25 MINUTES

PRECOOLED 6 HOURS 8 MINUTES

CAR CC ICE LOADING TIME

BUNKER 7 HOURS 45 MINUTES

PRECOOLED 4 HOURS 30 MINUTES

HALF LONGITUDINAL SECTIONS ALONG CENTER LINE OF CAR

FIGURE S.-Initial and final temperatures of melons in carli precooled with portable fans installed at the top opening of the bulkhead inside the refrigt'rator car. Initial temperatures are in roman figures and final temperatures iII italicized figures.

differed considerably in temperature from the rest of the loud, and it is believed that if that stack alone had been used to judge the temperature of the load considerable eITor would Lave been introduced.

16 TE(,II);lCAL DL'LLI~TIX i-:lO, l'. :-;. IJEPT. OF .\OHl(,lLTlTRJr, quarter-length, and c!oorwllY positions. These records indicated there were no ~great differences bptwppu ~yern.ge transit tempera tures in any of the stacks so long as ('I'iltes lD the same layer were companc1. There was but one ex(,pption, the bottom layer of the stack Ilext to the bunker. Melons in these crates were 2,40 to 4.50 F. colder througbout tlle trnnsit ppriod than melons in crates loachd next to them in the bottom layp/, ()f si-nck 2. It was obvious tbat the tempera wres at tllp bottom b'unker position could be used to represent only the ]2 crntes loaded in this faYol'f1bly cool position, or 12H percent of the bottom layer.

17 CALTFORXJA CAXTALOUPS

.5TACK 6

Row No. 2 .3 ., S

FIGURE 9.-A\-emge melon temperatures in transit. ('ar V, precooled; standard refl'ig

18 TECHNICAL Bl'LLETIK 730, U. S. DEPT. OF AGRICULTURE

METHODS OF WAXING TEST MELONS

The waxes tried consisted principally of cnrnnuba Wll..,( and paraffin in proportions of about 3:1 nnd differed in the type of emulsifying agent used and the concentrntion of the wax materials in the water emulsion. Tests were also made with a solution of wax in a volatile petrolenm soh-ent, applied as a fine mist spray to the melons. This solution of wax and the water emulsions were held at tempftratures of about 110 F. in the equipment used for their appli.cation. Packinghouse equipment for waxing melons is shown in figure 11.

METHODS OF FmnGATING C.\"iTALOUPS 'VITH NITROGEN TRICm,ORIDE

The npplicn.tion of ehlorine in the form of one of the chloramines to citI'm; fruits has been investigated by Klotz (10). Equipment developed for the generation and release of nitrogen trichloride in treating oranges in storage was used in the tests with cantaloups. The packed crates of melons were treated for about 6 hours in a fumigation chnmber or a refrigerator cal'. Gns concentrations Tunging from 4.8 to 9.2 mg. per cubic foot were used in the first test, whereas in later tests concentrations as high as 30 mg. per cubic foot were tried. Equipment for the generation of nitrogen trichloride from chlorine nnd a solution of nmmonium chloride is shO'.vn in figure 12.

~rETHODS OF INSPECTDIG :MELONS ON THE ~fARKET

After the test COTS were unloaded nt destination the test cratt's were taken promptly to tIle laboratory of the Bureau of Plant Industry. There they were held at prevniling room temperatures for 3 doys. As most of the cnrs were unloaded during the night, the first inspection of the melons was mnde the follo\\"ing day. This is referred to as the first day after unloading. At that time all wraps were removed, and snmples consisting of appro)."imlltely one-thinl of the cantaloups per crate were set out for detailed observations with respect to degree of slip, firmness of flesh, skin color, aroma, looseness of seeds, and freedom from mold and decay. Samples representing all test crates of all the cars in any pnrticular tt'st were spread out oyer several large tables and were therefore av-ailable lor simultaneous observations and for ('omparisons between carlots, maturities, varieties, and between those lots treated with wax or gas nnd those not so treated. Observations of the comparatiye appearance of the different lots, although not always shown in the tables of results, were nevertheless used to supp1ement the mOTe detailed records.

AfteT the cantnloups were inspected for external characters they were cut open and observn,tions were made concerning the looseness of seeds, presence of ohjectionahle quantities of liquid in the seed cavity, appeil.rance of the flesh, fluYor, and objectionable firmness or softness of the flesh.

In nIl the tests a similar inspection was made on the third day after unloading, and in some of them on the second day as well. OccasIonally certain lots were lleld longer. The 3-day holding period during which the melons were under observation approximates the usual length of time during which cantu]oups moye through marketing channels into the hands of the ulth .late ('onsumer.

19 CALlEORNJA CANTALOUP::;

FIGURE ll.--Equipment used for waxing cantaloups: A. Melons entering a tank of wax emulsion; B, drying compartment through which melons pass after emerging from waxing tank; C. waxing equipment for applying spr&,;-type W&-~.

20 TECHXLCAL BULLETIN 730, L. !:i. DEPT. OF AGRICULTURE

STE)I SLIP

As cantaloups approach ma.turity a corklike abscission layer is formed across the stem attachment, seyering the connection of the melon with the stem. "11en this stage is reached, the melons can readily be remoyed from the yine without pullin~ out or tearing off the stem by which they are attached (fig. 2). This IS commonly spoken of as the full-slip st.age of maturity. Less mature calltaloups exhibit a tcuring of the tissues at the st.em attachment \vhen removed from the

FIGURE 12.-Equipment for the generation of nitrogen trichloridp ga!;.

yine (fig. 1). All cantalollps were classified on the basis of the extent to which the total area of the stem scar was exposed without being torn. In order to obtain a single expression for the average condition of slip for the entire 'Sample, yalue!? of 0,25,50,75, and 100,respectively, were assigned to the seyeml classes ranging between no slip and full slip. A weighted average was calculated on the basis of the number of

21 CALI"FORNIA CANTALOUPS

melons in each class. This is referred to as the slip factor. To illustrate its application, the melons of a sample with a slip factor of 62 would ayemge about balfway between half slip and three-quarters slip; those of a sample with a slip factor of 90 would average nearly full slip.

FIR~INESS

The cantaloups were rated bnrd, firm, ripe, or soft, with respecth-e class values of 25, 50, 7.5, and 100. As indicated by the term, cantaloups rated 3.3 bard exhibited practically no "give" when squeezed between the thumb and fingers at the equatorial diameter. They were usually green in color and were entirely unsatisfactory for ea ting. Those designated as firm exhibited a slight give, and those referred to as ripe yielded readily. Cantaloups designated as soft were so far advanced as to be objectionable for retail trade although they might still be edible.

Here again a weighted average wns calculated as the firmness factor. It will be seen from the class values gi\-en aboye that the higher the factor, the riper aud softer were the cantaloups.

SKIN COLOR

In judging the color ()f melons, the netting was disregarded. Three classes of skin color-green, yellow greeH, and yellow-were assigned values of 33,67, and 100, respectively. Thus the higher the skin-color factor, the greater "oas the degree of yellow color.

ARO~[A

Arbitrary standards were adopted for the purpose of evaluating the aroma of cantaloups. Four classes-none, low, medium, Ilnd highwere assignecL values of 25, 50, 75, and 100, respectively.

DETEn~IINATIO':-; OF SOLl.:BLE SOLIDS AND stJGAn

In the market inspections of test melons in 1934 nnd 1935 determiuations of soluble solids were made with n Brix hydrometer. Composite samples of juice were prepared from the edible portion (jf duplicate lots of five cantaloups.

During the last 2 years of the work the refracth-e index of juice from the melons was obtained with an Abbe refractometer, and the sugar concentration wns estimnted from these rendings. Either 5 or 10 cantaloups were used for ench lot tested. In all cases the snmples of juice were obtained from flesh halfway between the seed ca\;ty and the outer rind at a point nn inch or so to one side of the blossom end.

~IOLJ) AND J)ECAY

The mold noted during the market inspections usunlly consisted of ~. a limited growth of Clado.sp07iu'Tn cucumerinum, Ell. and Arlh. Al

though this fungus may cnuse a shallow decay at the stem scnr or elsewhere on the snrface of the melon (22), in enrly stages its presence may constitute only a surface blemish of some\\:hat doubtful commercinl importance. Previous to 1937 the occurrence of only the more ndvanced stages of mold wns recorded. Thus in the mnin tests of 1936, because only scattered lots of melons were found

" affected with mold, its occurrence was considered of insufficient im

22 TECHXICAL BlJLLETIX 730, LT. g. DEPT. OF AGlUCULTURE

portance to present in the summary of inspections for that season. During the tests of 1937, however, all mold was recorded, ~ven though it WIlS chiefly in an early stage at the stem sear.

The decay found was chiefly rhizopus soft rot, caused by Rhizopus nigricans Ehr. and other species of Rhizopus (22). :Much of it ocm{rred at the stem end, although it was not confined to that urea. It ranged from initial to advanced s't>ages. Occasionally cladosporium rot or fusarium rot WllS found, but they occurred so infrequentiy that for aU prnctical purposes the statements made in this bulletin with reference to decay may be considered as referring to rhizopus soft rot.

FLAVOR

Standards established for rating the flavor of the cantaloups were as follows: 50, inedible; 55, poor; 60, low fair; 65, high fair; 70, good; 75 or higher, n:-ry good.

It was soon recognized that the conditions existing in a test where severnl hundred cantaloups were tasted within a period of 2 or 3 hours were not entirely comparable to those e~isting when cantaloups are ordinarily consumed. During the course of the work it was demonstrated that cuntnloups with a fln\'or rating of 60 or 65 when properly chilled and seasoned would ordinllrily be considered to have a verY desirable flavor, whel'ens those \\ith a flayor rating of 70 or 75 would be considered to have an exceptionally fine flavor.

RESULTS AND DISCUSSIO~

PUECOOLING STU])JES

The results obtained in tbe inH'stigations on the handling, precooling, and transportation of cantaloups are discussed under headingR which designate major divisions in the work. Studies on precooling were made in practically ewry test car. Although the information thus obtained is related to the transportation of the melons and their condition and quality on the market and is discussed in connection with these phases of the work, a separate discussion of precooling in itself seems to be justified because of its widespread use in the shipping of cantaloups.

It has long been recognized that, ,,,i.thin certain definite limits, the higher the temperature the faster fmits and vegetables will ripen and soften anti the more rapidly disease micro-organisms will de\'elop to the stage where sE-rious damage is done to the commodity. It follows, then, that the more quickly these products are cooled after harvesting the longer their commercial life should be. This is the aim of precooling. In recent years precooling has also been resorted to as a method of prerefrigerating the carload of produce so that less ice would be needed in transit, thereby permitting shipment under much lower refrigeration tariffs. The usc of precooling for this purpose has not been considerrel in the present investigations.

Although considrrable work has bern reported in recent years on precooling fruits and vegetables, very little of it has dl'alt with can

..

23 CALIFORSIA CASTALOUPS

taloups. Prugh and Goodwin 8 reported that the first carload of can taloups was precooled in the Imperial Valley in 1923. Some experiments were carried on hy commercial agenci{'s in 1924 in which cantaloups were passed through tanks of water coolcd by mechanical refrigeration, but the size and cost of the equipment precluded its commercial adoption. An attempt was also mnde to interest shipP(,l"s in precooling their melons in cold-storage rooms, but b('cause of the

FIGURE l3.-Portable car precoolinp; fan instailed in a refrigerator ear loaded with cantalollps. The fan assembly, made in four parts, consi:::t.g of the fan, the center tapered fan housing in which the fan unit is installed, and two side plates that cover the openings in the bulkhead of the car.

yolume of the daily shipments, which 1"('nch('d 500 cnrloads on peak days, this was Dot practicll ble. Not until the introduction of portable C'quipment, which permitted precooling to be done in the car aft('r it was loaded, was there any widespread intC'rest in precooling cantaloups in the Imperial Valley. 'With equipment of tbis type made a,"ailable during the last 8 or 9 years, the practice of pre(,ooling hus l)(>come general. In 1937 nnd 1938 practically all of the carlot shipments of cantaloups from the district were precookd.

! PRl"GII, A. E., and GOODWlS, W. R. ~IARKETISG I)lPERL", "ALLE!' C.\SnLOt'FE Sl'lOI.\RY or 1fl.17. REASOS. L S. Dept. .\gr. Dur. Agr. Economics and Calil, D~pt. Agr.1-larkct );cwsServicc:. ~ Pr>. )938, 1~limr()graphcd.J

24 TEUHXWAL BULLETIN 730, U. S. DEPT.. OF ,\(JlU(TLTL'Hl~

PRECoOLING EQUIPJIENT USED IN TESTS

The equipment :n most common use for the precooling of cunlaloups consisted of It propeller-type fan mounted in a metnl plate or canvns buIDe that completely coyered the upper bulklwnd opening when insblled in the cnr. One unit was usually installf'd in cnch end of the car. When in operntion, the fan reversed the naturnl circulation of cold nil' from the bunker by forcing it out ovw the top of the load. the nir returning to the bunker tlu'ough the bottom bulkhend openi.ng. The fnns were usually tilted downward so thnt the centers of the streams of air from them struck the top of the lond at nbout quarter-length positions. 'Vhen precooling to the desired temperature had been uc('omplished, the fnns could be quickly removed from the car. FallS of various dimensions, design, numbCl' of blades, and operatillg speeds were in usc, but the one shown ill figure 13 is typical of this equipment. .

Some tests were mnde with l'quipment of 11 type less ('ommonly availnhie, a truck-motmted mechanical refl'igemtiug unit. This equipment consisted of a two-cylind('r verticnl ammonil1 compr('ssor of 7-inch stroke und bon', condenser, forced-air cvnpornti\'e COOI(,I', and two c('ntrifugal fnns, one of which was used to cit'ctrlate air from th(' ('ooling unit through the car and the other to supply nil' to ('001 the wn t('r supply for the condenspr nnd compressot'. Power from the truck motor operntecI the compr('ssor, wnter-pump, and fnns. The truck WfiS drivl'n alongside the refrig('rator car, and the intak(' and discharge duets from the cooling section w('re eOIlIl('ctt'li to tll(' cnr through a false door, as shown in figme 14. Wlwn til(' cen trifugal fan was in operntion, colel nit' WIIS blown into tIl(' Cfit nt the top do'otwny find r('turned to t11(' ('ooling unit fl'om the bottom doorwuy position. The lond was ('o\'er('d with It can ViiS bnffIe pxtC'nding fronl th(' nit' dischnrge duct at the doorway to nbout one-quurter of the distnllce to th{' bunhrs, so that the air wns forced through th(' load b('for(' it r('tuI'll('d to the cooling unit.

A third type of ('quipm('nt us('d consisted of 11 stationary blow('[' equipp('(1 with duets, whieh nre conne('tecI to nn op(,IH'd 11l1teh nt end. end of the refrigerator CfiT (fig. 15). TIl(' top bulkhend olwnings W('I'(~ eov('rpd with suitnble bamps so thnt wlH'n tIl(' blow('[' WliS opC'rn.j('(1 airwns ion'eel into one hunkpr down through th(' i(,l', th!'n I1CrosS the ear nncI out the othel' bunkPr. By menns of 11 dnmpPI' and u bypass the direetion of the air flow \VIIS re\T('rSl'(1 enry 30 minutps.

THEORETICAL COSSIDERATIOS OF THE .UIOUST OF HEFHIGERATIO~

REQUIHED FOH I'HECOOLI:-IG

T'H' pr('cooling of eantaloups in 1'pfrig('rntor eHrs illYoh-('s the transfer of IH'ut from the lading and the inside surfnces of till' cnr to 11 "heat nbsorb('I'" or rC'frigerntion SUdllC't'. In the portahle fan C'quipment or tbe stationary blo\\'('r the l'('frigprntion surface WfiS the iee in the bunkers; in the truck-mounted unit, it wns the surface of the finn('d ammonil1 coils. WIH'n the fans or the blow('rs wpre u;wd the somee of refrigpration was the meitage of i('C', wherens in the mp('hllnicnl rdrigerating unit rdrigeration was suppli('d by the vuporizntioll of ammonia in the coils. 'Vith ench of the cooling units the llH'

25 CALI FORXL\. CAXTALO L: PI'i

FI(l1;RE l4.-Precooling carlcads of cantaloup!i with truck-mounted mechanical r('frig('ruting units drhclI by a power take-off frolll the tru..,k engine.

:11 ii5:!-t "--to---l

26 TECHNICAL BULLETIN 730, U, S. DEPT. OF AGRICULTURE

FrG"L'RE 15.-Prccooling unit consisting of 5-horsepower blower and ducts, which are connected to the bunkers of the car. The top openings in the bulkheads are covcred so that air !JIl)wn into the bunker at one end of the car must pass down through the icc-filled bunker and across the car to the bottom ope.ning in the oppogite bunker to reach the return air eluct. Air direction is reversed at regular intervals by means of a bypass and damper.

27 OALIFOHNIA OANTALO UPS

FIELD HEAT

Of most importance in the precooling of cantaloups is th0ir field heat or sensible h0at, os it is sometimes called. It is the umount of heat that they have at uny particular time and is proportional to theil' temperature. It gets its name "field heut" bf'CUllSe it is initially acquITf'Ci in the fi('ld. It is obyiolls thot the amount of sf'nsible heat that must be tak('n from au oLj('ct to cool it to a prNll't('l'mined temperature will depend OIl thn'e factors: The initial tf'mpf'mturc, the finul temperatmc, and thc spl'cific heitt Ol' heat caplwity of the object. The specific heat of any given ll1ttierial is one of its physical chnractf'ristics, but for fruits und vegetubh,s there nre few actual data. Bl'cause of this the specific heats of these products are usually calculated from their water content, using Siebd's (19) formula us adapted from Rose, Wright, and Whiteman (18), S=(1-0.2)fL+0.20, in which S is the unit heat capacity of a substitnce expressed in British thermal units 9 per pound pel' degree Fahrenheit; a is the percentage of water in the substance, and 0.2 is the value ussumed to represent the specific heat of the dry matter in the substan('e. :From the work of Rosa (15) and Chatfield und McLaughlin (3) on the water ('ontent of cantuloups, it is likely that an average value of 90 p0rcent of water for the entire melon would be satisfactory in calculating the specific heat. USirlg this figure, the equution becomes S= (1-0.2) 0.90+0.20 or 8=0.92 for cantaloups of the above-nanwd composition.

The wood of the crates and the inside of the car also con tuin sensible heat that is removNl during precooling. The specific heat of wood was taken as 0.327 from the Smithsonian Physical Tables (20).

YITAL HEAT

The vital heat that is removed in refrigerating living plant organs, such as cantaloups, rrsults from the "ital pro('(>sses going on 1Il thf' tissue, and from these receivl's its name. All living ('('lIs respire, consuming o:xygen uncl liberating cm'bon dioxide and enl'l'gy ill the form of heat in the process. Few actual measurements have I)('('n made of the amount of vitnl heat produced by various fruits and YC'gPtnbles under a standard set of conditions. Howev0r, it is l'easonnbh to assume that the amount of heat libemted will be in proportion to the respiration rate, and so it has become a common practice to cfllculnte the heat of respiration or vitnl heat from the respimtioll rnlt, assuming that the source of heat is the oxidation of a hexost' sugar such as glucose. On this basis the amount of heat (British thennal unit) evolved by a ton o~ produce in 24 hours can be determined hy multiplying the respiration rate (milligrams of ('arbon dioxide 1)('1' kilogram per hour) by the factor 220.

Respiration studies on Powdery Mildew Resistant Cnntnloup K o. 45 melons of the hard-ripe maturity indicated thnt the l"Psppctive rates at 900 ,740 ,500 , and 32 F. during the f-irst 24 hours after picking were approximately 120, 110,20, and 10 mg. of carbon dioxide pel" kilogram per hour. These figures are the average of dpterminations mude in duplicate on three pickings of meioJ:s. A tOIl of (,llIltnloups hf'ld nt 90 0 for 24 hours would liberate 26,400 B. t. u.; at 500 , 4,400 B. t. 11.,

, British thermal unit, the amount of heat required to raise tho temperature of 1 pound of watPr from 63' to&loF.

http:0.90+0.20http:S=(1-0.2)fL+0.20

28 TECHNICAL BULLgTJN 7::10, U. S. DEPT. O:F ,WRICULTURE

ana. at 32, 2,200 B. t. u. These estimations of vital heat are higher than those given by Rose, Wright, and 'Whitemlln (18) for compamble temperatures in the range of 32 to 60, an.:l till' rate of evolution of heat at 90 is considerably lower than that reported by Wharton and Foote 10 fo!" 93. The above values for vital heat should be considered as only approximations since t.he respiration rate, especially at hightemperatures, proved to be varmble.

SUMMARY OF THEORE'l'IC'AL REFRIGEltA'l'10N ltEQUIUEMENl'S

From a consideration of the hpnt removal involvt'd, it is possible to &lTive at a theoretical value for the amount of "pfrigPl"l'ltion required to precool a cnrload of cantaloups. This has been done fo], a carload of 288 crates of cantaloups with an avernge weight of 80 pounds of melons and 5 pounds of wood per crate, an avernge loading temperature of 80 F., and a final temperature of 50 attuiJl('d by precooling the melons for 8 hours with inside flins elI'in'n by 2>~-horsepowpr motors.

Field heat removed: Cantaloups:

'Weight: 288 cratesX80 poullds=23,040 poulldR.

Specific heat: 0.92X23,040=21,197 B. t. u. to lower

temnerature 1F.

Temperature reduction frolll 80 to 50 = 30 F.

Total heat reIllO\'cd: 21,197 X 30"" 685,910 H. t. u.

Crates:

Wei~ht: 288 crates X 5 pounds= 1,440 pOUllC!S.

Specific heat: 0.327Xl,440 c ,171 B. t. u. to lower tem

perature 10 F.

Temperature reduction from 80 to 50 30 F.

Total heat removed: 471 X 30 = 14,130 H. t. u.

Inside surfaces of car, floor raek!OUII(\8 of melOI!!; at au a\'erage

temperature of 65 F. for 8 hourI< (calculatcd from rcspira

tion studies reported abo\'e) .C~ 64,20.5 H. t. u.

Heat froIll other sources: Operation of fall motors:

Two .!~ horsepower llL-Jtor:;.

Estimated that 35 pel'cent of electrical energy is

dissipated as heat, from efficiency specifications for l~horsepower motors (J). 0.35 X 42.4-1 (13. t. u. per horsepower per minute) = 14.85 B. t" u. per minute. For 8 hours the amount is l4.85X480= 7,128 B. t. u.

Heat conducted into car through the insulated surfaces: Conductivity factor of 0.1 B. t. u. pcr square foot per hour for

each degree Fahrenheit temperature difference was used

for 2-inch Celotex iusulation and tongue-and-groove ex

terior and interior. Temperature difference of inside aud

outside surface was taken ai'. 50 F. The insid' surface of

the car was calculated to be 1,171 square feet. Thl' prE-

cooling period involved was 8 hOllrs. The calculation is

then: 1,171 XO.! Y50X8= 46,840 B. t. tl.Total heat removecl ____ _ 768,213 B. t. tl.

The total heat to br removed accordillg to thr above cllleuilltions would require that 5,334 pounds of iee bp mdted, or about 1,000 pounds for each 5.62 F. that the tempemture of the .load was to be lowered. In 19 tests with pOl'tnble fan equipment, summarized in

'" WH.\RTOS, M. F .. and FOOTE. J. :-.r. SI!1PPISr. TE;'T, ,,'(TIl ARIZOS.\ r.\STALOl'PS. I:nh-crsity of Arizona and Arizona Fruit and "egelable Service. 1936. [Mirneo!!raphNl.j

29 CALU'ORNIA CANTALO UPS

table 4, the a.verage temperature reduetion obtained by the meltage of 1,000 pounds of ice was 4.3, a YHlue considerably lower than the one obtained in a t.heoretical calculation of the refrigeration requirement. This would indicate that there are refrigeration losses not included in the calculations. such as leakage of cold air from the car, and also that some of the melons, particularly those in the e:s..-posed top layer, have received more refrigeration than the center mt'lons in the crates where temperatures w('re-taken.

TABLE 4.-Su'ltt'lllary 0/ data obtained in cantalonp precooHng te.~ts comLlicled during 1935, 1936, and 1937 seasons

Melon SnIt used ! Tern IA\.cra~etemJ'e::l'

tun's 'f,.mpera1 and ice p{'ra~ : nir Wlll-I melted t ture : perature' (average lurO drop during drop j at fan ,of9 CoolingCar coolin;' per : or top , Equipment use

j 'F": I p

,ie during I', Start: In., Total' er Salt Il'e: melted i cooling __'__\ ..~~___!hour

f OF. IOF. OF. OF. Hr. Min.1 Lb.l-:;-i-o-F-,-1-\--0F-.- -------

A.--.-l 84.4 , 70.6 ,13.8 4.00 1 3 IH' 12.; '0.700 , ~. 4 -Ie. 2 , Centrtfugal fan. B 2____ 1 93.1 I 8fi. Q ~ 7.1 2~24 i 10 ! 0 I 0 I 90.0 KOlle.

C ____ i ~3.0 I 49., '33.3 3.64 I \I 09 11.000 19.300 3. fl 37.0 : IS-inch prnr~'IJer fans.

D._ .. ,' 95.1 ! 6S.7 26.4 4.92I o ~':! 300 6,900, :t ~ I 42. fi \ Dc. E __ .. _' 79.6 : 42.S 36.5 3.45 10 -10 750 9,30(1: 40 37.41' Do.

.4F ____ 82.8 i 55.5 27.:!, 3.81 09 150 ,6.000 I 4. I 45.6 Do. G._ ... 7K2 i 48.8 29.4 3.75 7 50 250 :5. 130 5.7 44.1 H.in,~h prl)~'IJer fans. H ..._ 03.4 46.4 17.0 2.02 8 25 200 0, ()(l{1 I :1.4 I 39. 1 Do.

00J ___ ' 76. -I -Is' (; 27. 9 ~. 30 S 27 292 C,572 4.2, 41.9 Do.L'''_I 864 ,0.6 9.8 1.59 G 10 0 I ........--. 79.0 I Kone. M __ ._, 90.3 61;'3124.0 :139 7 0-1 0 7.500 3.21 5;., IS-in~.h propeU"r fans. K---i 83.4 51. 9 Iat. 51' :1.(11 1, 10 27' 500 ". :I,S :1. 8 41. \I Do. O...--: 9L1 50.3 4(\.8 4.1S I 9 -1.'\ f 0 5IJ2j a7. ~ '1ruckmounted meehani

i 0 Iq_. "_q_-, cal unit.P'_._i83.9 71.9112.0 1.50, 8 00 5.j 81~ lj NODl~.. 0. ____ ' 80.3 ~~.1 ~!.2 ~ ~.z.1: 6 Ofl 250 5, 000 4.2 49.9 IS-incll propeller fans. S ... 78.2 ,_.4 .l,.S: _.,4, \!In 3. \I :1,.0 j'13 III 9.234 Do.

'1', ..._, 84.4 61. 7 22.7 i 3. H7 j 5 ;'2, 100 fl.200 /' 3. 7 50. ;. Do.

G 19\ 0 '16,000 3.4 51. 6 Do.~~y;f ~:3 ~n in 1Ug l~ ~~ I 21g .i:,iQii' ----3:ii- ~g J Noniio. V..... :83.8 58.125.713.35 7 40, ',10 '.360 4.8 46.0 ! IS-inch propcU"r Jans. '!'__ '_, ~~.5 -IR 2 28.3,' 3.54 8 00 I 3'g 6, 2!1~ ! 4. 6 40. 6 Do. 'P.... 78. I -'3.9 14.2 11.10

x. ___ , ,v.3 40.1 35.2 4.10 S 35 I \ --I 37. 1 i 'f~II~::l~UOlt'd mcchalli-Y ... __ : 92.0 74.2 17.8,3.98, 4 2':' 2.'!.l :2,035 ~.~ 44.1 11S-inCh,prOPl'lll'/ (ails. _~A..._ 89.3 57.8; 31.5 ' 5.11 I 6 fJ~ 1S5 5. 1\,1 '.:,'.~ !, 46.3 Dc.BB ____ ' 90.2 66.5; 23. 7 ~. 91 I a 01 125 ,I,O~5 , 45.9! Do. CC ___ 87.0 71.711.,.3 3.40: 4 30 2';0 '3.445 -I. -I : 52. 2 Do.

l I

I In nonprecool~d cars the coolin!, period was the total timp that clap"ed between the initial an'\ final tem perature rpadin~s. when'us in pfPconled C!lr~ it r(>r(ir~ tf) tht\ at'tual tirnf;' that tht~ prl'coolin~ p.Quipm(>nt was operated during the, t"st period.

, Konplerooled car, cooled only by natural cireul .. ttr. .. of air t1nough the Joud and ited bunkers.

COOLING RATES Hi CARS COOLED WITH FANS AND MECHANICAL

REFRIGERATfNG UNITS

"-hen' ail' is the medium USN] for IJ('at ('xchnnge from thf' commodity to th(' refrigerating surface, tIlt' rate of' cooling depends upon several well-recognized factors, the most important of which ure (1) volume, velocity, and distribution of the air, (2) the differenc(> in temperature between the commodity and til(' air used for cooling, (3) the m('thod of packing and stowing as it affects air circulation, and (4) certain properties of the objects to be l~ooled, such as their size, shape, surface as they affect beat transfer, heat capacity, conduc

http:17.8,3.98http:58.125.713.35

30 TECHXICAL Bl'LLETfN 730, u. S. DEPT. OF AGIUCULTGRE

ti,-ity, and mC'tnbolic uctidLy. Under a standard set of conditions in which constant air tempC'rature and vciocity are maintained, cooling rates can be estimated for materials of known thermal properties by means of charts such us those of Gurney and Lurie (7). In the precooli.ng of loaded cars of ctlIltaloups, however, the conditions that afi'('ct cooling rat('s are so variable and so poorly understood that a tll('or('tical estimation of the time required for a ginn temperature reduction was not possible. Precooling tests were therefore conductpcl in it considerable number of cars. The t('mperature data and oth('r l'Pcords that \\'('re obtained have been summarized in table 4.

Among tlle cars precooled with portable inside fans, tlH~ highest cooling 1'lIt('S w('r(' obtmn('d in ctlrs D and AA (4.9 and 5.1 F. per hom, l'rspc,ctively). both of which were fairly warm when precooling was started. Car H, thp cool('st car wh('n loaded, aVI:'l"ilging 63.4, had the ]ow('st cooling- rute of illl the fan-cooled cars, amounting to 2 pC'r hour for an 81,f-hour cooling period. The average cooling rate per hour for the 19 cars coolNI with portable car fUDs WRS 3.58, indicuting that under tbe conditions of these tests a rN]uction of 3.6 per bour ('ould bf' llsed as a guide jn estimating the time requil'ed t{) precool cantaloups.

The prC'('ooling rates with imide fan equipment report(>d here are slig-htly highC'r than tbos(' obtainNI by OverholSN and MosC's (I.n in 1928 bpt compal"E' favorably with the rlltC's obblilled by Gaylord, Fuwcptt, and Hic'nton (6) in J'('(,pnt tests mad{ Oll cantalollps with similn.l pquipnll'llt.

Curs prpcoolpd with trllek-moun(pd nlPchanical rpfrig('l"Ilting unit:: had cooling rntt'~ of 4.18 and 4.10 F. p('r hour 01' 93;_ timl S);"hour p('riod~, l"('sp('('tiVl'l~~. In nonpn'coo]C'd enrs, in which the ail mon'1lH'llt was by natural circulntion only, tIl(> cooling ratE'S ritng-Nl from 1.1 pt'r hOlll' for a lwriod of about 13 hours in ('nr U to 2.24 pE'r hour for a I)(,l"iod of 4 hours 10 minutes in car B.

As E'xampll':" of tbe cooling obtaiJ1Pd with the typC's of equipnwnt us('d, ('ooling ('UlT(,S are shown for th~ top, mid(lie, and bottom laY('J'S in car S cool

31 CALIFon:s-IA. CANTALOUPS

COOLING RATES OF INOIVlDUAL :AlELONS

The preceding discussion gins a general view of the cooling obtain('ct in cantaloup cars. A detailed study of the cooling l"utes of individual melons in crates loaded in the quarter-length stack, ('enter row, was made in car F, cooled with inside fans (fig. 18). These data show clearly that cooling is fast only where the melons are exposed to air

90 fl~~mI:!~E~T:_:205]~~~?:::m~J]{~t~~[~~T]~~~~~~r.l~~t~r~t~t~~~,~~t~:0~~~~~\:I:O[JDNi:S/~0:?:::%:Z1i;?:::0:Z0~,W-~0~~?:::%Z:012m~l\ 1 POUNDS POUNDS ICE-I,400 POUNDS ; , FAN OPERATlON-SA~TING AND ICING RECORD '..

BO l I I ! I ~ ---4! . MELON TEMPERATURES I

~ 70--~--~~-~~~-----+------4-'----~~----------~. w a: ~ 60--~--~------~~--~~----__~M-'-D-DLE LAYER

~ , ! :: w 50 --4-__ AIR FROM I- / PRECOOLING FAN

4o~,_~l~",,=,_......~I'_TO_P_J-_-+ I -------30LlI____________________J-.____~~____.~______~_____J

;r 720 .. 1"1....

~g 600 -+ 1 ~: I -r

l ; ------1

32 TECH~lCAL neLLETIN i30, l'. S. DEPT. or ,\CmeULTURE

by measuring the ice level in the bunkers at the start and the finish of cooling, keeping a record of the ice used to replenish the bunkers during the cooling periods. In tests with mechanical refrigera,ting units, records were obtained of the suction and discharge pressures

AND BLOWER OPERATING

r I ]---+--+--~--+ -._1_. 1 !- __..L_ , ! ' MELON TEMPERATURES

i ! J! ,

..--+--=~""';:'-.:-,.--- ---r'''' --. -+--,---- -..--r---~.--

.. I ' ..;.- MIDDLE LAVER t I

i I 60 w

II:: :>

0.. 20.., >

30 ;--~-----------.--.

4 5 p r.: JUNE 12

FIGURE 17.-Air and melon tC'JIljJcmture.,; ill car X prc(!ooi('d with a truck-moullted mechunical rC'frigeratiJ,g ullit, JUlie ]2, 19;~7.

MELON TEMPERATURES (OF) AIR TEMPERATURES COF)AT END OF 7 HOURS 40 MINUTES AT END OF 7 HOURS 40 MINUTES

WHEN LOADED

SS.7"

COOLING

469 0

ROW TEMPEiVlTURE 5

DROP 41 so __

ROW 3 WHEN

LOADED

87.4'

COOLING

41. 3

TEMPERATURE DROP

46.1 SI. 5' 54. ~ 0 ~7 3"

B 7.3 0 62.5 0 248' 85.2" 50.5 347

B8. 2 0 503 37.9 69.0 46.4 42.6

S7.9 66.7 21 2 0

S3.6 63.6"

B3. 2 53,0"

B I. S' SS.6 54.6 19. I S03 62.7 46 So 2 I 1"

FIGCRE lB.-Cross section of ccnter 1'0\\' of fifth stuck of crates showing melon and air temperatures and temperature TI.'dllctiOll8 in various positions ill the stack in car F jJrccooll.'d with portable fans, salt, and ice.

of the refrigerant during operation and the speed of operation, so that the refrigeration output of the compressor could be estimated.

The temperature reductions obtained by the meltllge of 1,000 pounds of ice (table 4) differed considerably from car to car, as Wfi~

33 CALIFORXIA CAXTALOUPS

t.o be e:\."J>ected in view of the wide range of conditions under which the tests were conducted. They ranged from 2.4 F. per 1,000 pounds of ice ill car A, cooled with air circulated through a duct exposed to the sun, which would fayor refrigeration loss, to as high as 5.8 in car BB, cooled with propeller fans. The latter yalue approximates the theoretical amount of cooling that should be obtained and is therefore probably too high, possibly beeause of errors in measuring ice meltllge. The n,yerage amount of cooling obtained by the meltage of 1,000 pounds of ice in the fan-cooled cars was 4.3.

The temperature reductions obtained in tests ,dth truck-mounted, mechflnieul refrigerating units of 4.18 and 4.10 F. per hour indicated thnt the l"l'frigeration supplied by the precooling unit was about equiya-

FIGCRE 19.-Drip meter used to measure ice meltage during precooling. When a definite weight of liquid accumulates in one compartment of the container, it tilts, spilling the water from this compartmcnt, strikes a counter which records the number of trips, and raises the other compartment into recehingposition.

lent to that obtained by the meltage of 1,000 pounds of ice per hour Vlith portable fUllS. Cpon this basis the efecti\"e refrigeratioll obtained from the two-cylinder compressor, each cylinder ha \"ing i-inch stroke and bore, would be 12 tons per day, although the theoretical rating would be about 23 tons under operation of 250 revolutions per minute with 30-pound suction pressure and 240-poundhead pressure.

The amount of ice needed in cars precooled with portable fnns, or the length of time the mechanical refrigerating unit would haye to be operated to precool a carload of caJltafoups, can be ascertained from the foregoing consideration of cooling efficiencies. It is not uncommon for carloads of cantaloups loaded in the afternoon or evening of

218524--40----5

34 TECHNICAL BULLETIN 730, U. S. DEPT. OJ,' ,\GlUCVLTURE

warm days in the Imperial Vnlley to average 90 F. or higher (cars B, D, 1\[, 0, Y, and BB, table 4). To cool these londs to 50 would require a tempera ture reduction of 40, which would cnIl for the meltage of about 9,300 pounds of ice. The mechnnically operated units used in the tests would have to be operated for about 9}~ hours. (See car 0 in which the precooling period with this equipmeut for similar temperature reduction was 9% hours.) The bunkers in most refrigerator cars in use in the Imperial Valley hold 10,600 pounds of ice, but only about 8,000 pounds is effective in precooling, as the iee level is progressiYely lowered to such an extent that eyentually little cooling surface remains. Because of tllls fact it is eyident that carloads of cantaloups at 90 or higher will need re-icing during precooling if they are to l'eceiYe sufficient refrigemtion to be cooled to 50 or lower. Equipment for re..;icing during preeooling Is shown in figure 20.

Picking 111elons before the sun warms them and loading UWnl into the refrigerator car as soon as possible is not only good prartir(' in handling a product as perishable as melons but will also reduce til(' amount of ice neNlecl for precooling. A 15 cooler loading tempNuture, not uncommon in cars loaded in the moming as compared "'iih those loaded in the late afternoon, may SHVe 1!f tons of ice and 3 hours in the time required for precooling, resulting in u net Sit\-iug of about 2Jf cents per crate.

ICE-~IELTAGE R \.TES nIDUNG I.OADlNG AND PHECOOLING

The rate at which ice is melted in ill{' bunker il'; of interest. b('cause it provides a measure of the rate ut which heat is being r('mov('(1 from the load and the inside surfuce of the car. By l11cuns of drip metPrs (fig. ] 9) ice-meltuge rn,tes during loading lind pr('('oo]ing \\,('1'e dpt

35 CALIFORNIA CANTALOUPS

In car W salt was added in a different way from that followed in cars Nand S. A heavy application, 125 pounds, was made at the start of precooling and then a light one of only 62}~ pounds was made

~. r

FJG1:'HE 20.-He-iciug eautaloup cars at the loading track during precooling: A, With ice tongs, Tope, and chute; B, with mechanical hoist.

some 5J~ hours later. The first salting resulted in an exceedingly high meltnge rute of oyer 1,080 pounds per hour, but it lusted only hulf ;'tn hOllr bpciHlsP the salt wus dissolvpd and wnshed from tllp iec during the period of Jl(,UYY meltuge. The melons in cnr ,,~ had n t('mp('rnture

36 TECHXICAL BULLETIN 730, U. S. DEPT. O:F AGRICULTURE

of 76.5 F. at the start of cooling as compnred with 7~0 for those in car S; yet, despite the lower temperuture in the former cnr, the air blast u,veraged 45.6 tllere us compured with 37 in car S. A compnrison of the meltage rates indicates thnt this wns to be expected, for in car S, ns n result of more frequent nnd henvy sulti1lg of the icc, a higber ice-meltage rate was muintuined over n longer time.

From u, study of the murked effC'ct of su.lting the ice on meItag(' mtes and the short durn.tion of the lllcrpased mte, on(' must conclude that for ma:.\.-llnum meltage rat('s suIt should be added nt the start of precooling und more frequently th('reafter than was the practice in the hundling of any of th(' curs under observntion. "lIen salt is added to ice. tenipemttlres of less than 32 F. are produced in the film of brine surrounding the ice particles. A mixture of 2 percent of salt nnd 98 percent ice, which would be equivalent to nbout 200 pounds of salt per bunker. would have n. temperature of 30; 5 percent of salt would I!h-e '27; and 10 perC'ent, of Rult" :Wo. .A,dually in til(' application of s:1l1 to thC' i('e in rC'frigNutor-cur hllnkt'rs during PI'('('ooling,

W GAR W ~ 900 f .~ - f ----- t

If

;;:: 600 f ::;; , I W 300 LO.OING '" -,- .L.,L -:-f':-'--'.c:-,--;..----i.~.;..d U /FINISHEO 125 POUNDS;. ALT !FANS ON

~,0 o 2 3 4 5 6 7 8 9 10 HOURS

FWUlm 21.-lcc-mcltage rates in cars of cantaloups during loading and precooling.

the suIt is mixed with ice in the top of the bunker, resulting in a high conrentrn,tion and low temperature there, with correspondingly less ('frect d('eper in the bunker.

It if', evident from all examination of the ice-meltage rates thut for shOlt ppriods the hent rpm oval is ,'ery mpid in curs precooled ,...-ith inside fans, ice, and salt. III car 'Y an ice-meltuge rate from one bunker of over 1,080 pounds per hour was maintained for 30 minutes, which for the entire car would be equivalent to 2,160 pounds per hour. For a peI'h~d of about g}~ hours an average ice-meltage rate of 1,176 pounds per hour was recorded for cur S.

HEco,un;:\I),\T1o:"S FOH SALTI:"!: THE ICE f)l1HI~G "IIE

37 CALIFORXIA CAXTALOUPS

by noting the tempem,ture of the air blnst and the mte nt which ice is melting from the bunkers. Enough snIt should be used nt the st!lIt of prec-ooling so thnt the nir blnst from the fnn will drop in tempemture rn,pidly, renching 45 F. or less within hnlf nn hour nfter the fnns lire stnrted. In cur S, 'with melons nt 78 wh{'n londed, 50 pounds of snIt n,dded to ench bunker wns enough to CHUS(' sucll n drqp, but in u' wnrmer car 75 or 100 pounds would probnblv be needed. The icc should be resulted ut, frequent intervnls, using- n, totnl of 300 to 500 pounds of suIt per cnr. If the nil' tempernture does not continue to drop during the first severn I hours of cUDling, or begins to rise during the In tter pnrt of the precooling p('riod, it is nn indication thn t the ice should be resulted. .An nil' blr.st of 30 to 32 CUll be used snfely, ns t,he nvernge freezing point of the rind of cantnlollps is 28.4 (18).

Towurd the end of the precooling period when the ice leyel in the bunker is low, it is oft.ell neceSSill'~- to ndd snit to lower the temperntmc of the ice surf:1('es left to eompensn te for the luek of refrigera ting surfuel'. ruder such conditions, suit should be added in small quantities nt the rate of nbout 2 pPl'ePIlt of the iee left, so tlwt subfreezing telllperatmes will not, be produepd in the bottom Illyers of llleions lifter the preeooling fnns arc stopped lind rapid nir eireulution censp!>.

It hus b('en contended by some operntors thnt the application of suIt to ice durhlg precooling results in considernble loss of refrigeration through the lowered temperature of the brine leaving the bunker, ns compnred with that from unsuited ice. It \f'iIS found thn t actunlly the brine running from heavily snItI'd bunk('rs WilS only nbout 4 or 5 F. cold('r thiln ice wntp}" drnining f!"Om nOJlsnlted bunkl'rs, nnll thnt brine tl'm peru tUl'(,S lowpr thn n :32 w('re not ('ncoun t('l'pd wh('n the fnns \\'('r(' operuting. even when 200 pounds of SilIt. wns nppliNI to ench bunk('l' within n 2-hour period. The loss of rl'frigerntion bN'Huse of n 5 colder run-oJI' from the bunkers would be t'quivnI('nt to nn ic(' meltage of 277 pounds in n pr('('ooling job l"Nluiring 8,000 pounds of ice. To of!'s('t this small incr('ns(' in ice r

38 TEOHXICAL BULLETIX 7ao, (T. S. DEPT. 0]:' AGRTCl'LTURE

RECO~BIENDATIONS FOR ESTIMATING THE A~IOUNT OF PHECOOLING

A(,CO:lIPLISH ED

There are several means by which an eRtimate clln be made of the extent to which cooling has been accomplished during the precooling period. The quantity of ice that has been melted provides a good measure of the refrigeration supplied in cars cooled with fans, ice, and salt. A.s mentioned in the discussion of the refrigeration uspd for precooling (p. 33), for eyery 1,000 pounds of ice melted in the cars, an average reduction in temperature of 4.3 F. was obtained in the melons throughout the ear. On this basis, about 0,300 pounds of ice would be IH'ecied to cool a carload of cantaloups from 90 to n finnl temperaturp of :')0. By tnking the tempemture of tIl(' nwlolls as thp? aTC' pnckpd 01' londed, thl' initial temperntun' of till' CIII' Cllli 1)(> aR(,pl'tniIwd IIl1d pnough iC'p thNl mdtI'd to nRSlll'p the final tpmpprn.tuIp dpsil'pd. '1'hp bllnkprs of most rl'fl'igpmtor eflrR Ila.,"p an iC'p cllpneity of nbOll t 10.000 to ] 0,600 pounds, nbOl1t 8,000 pounds of whieh is pfl'pcti\'p for pr('('ooling bdOl'p thp icp level is below the bottom bulklwud opening. .From this it is obyioliS that n'-icing during precooling is IH:'cessnlT if melons flS wnrm ns 90 nre to be cooled to 50.

In CHl'S cooled with a I1wchnnicul refrigerating unit the refrigemtion obtnined wns equiYfllent to the meltnge of 1,000 pounds of ice per hour. To do the sume amount of cooling as outlined nbove, thesE' units would hnyp to operute about 9]~ hours.

Another bnsis for estimating the amount of precouling accomplighed is the time required. From the t('sts made with inside fan equipment, an a\"ernge mte of 3.0 F. pel' hour wns obtnined in ear,; precooled sufficiently to lower the melol1 temperu.tures to 55 01' less. For ('Ill'S cool wh('n londed or thoge not snitI'd, this rate would be too hif!h, Hlld for warm CIll'S 01' those in whieh the iec wns heflyily snitI'd during precooling 01' which \\,('I'e precooled only n few hOllI'S, it would be too low. Using this rnte, it clln b(' estimated that in 8 hoUl's n cilrlond of me~ons could be cooled from 80 to a. final temperature ,)f 51.

An nttempt was made in the precooling studies to find fill acce:;sible position in the cnr at which to judge tbe tempernture of most of the lond n.t the end of precooling. Thc practice of using indi,"idullimeions placed on the top of the lond 01' 011 the floor rneks lends to unjustifit'd conclusions, for til('se "test" melons wel'e found to be I:~o to 19 .B"'. cooler thn n the ayerngp of the lond nt the end of cooling, nnd 1""(>[1 greater difl'el'ences were ob5elTed curlier in the precooling p('riod. In cars pI'ceooled with ingicle fnns thnt blow nil' from tht, top bulkhend opening out 0\"('1' the 10nd. the fnns b('ing tilted so thllt the nil' stl'enm is direeted at the quarter-l('ngth position t thf~ t('mpel'lItll1'ps of melons in the center of th(' C!'Htes in the top Inyel', d(~()l'wny Muck, center I'OW were fnirly close to the nyernge of nil temperaturps tllkplI in the ('Ill'. This \VIIS tmp in 1111 cnl's in ~ \'(,IlI'S' studies fwd in most of those in the t bird yenr's stlld iI'S. It II PP~':1 ni, th(,l'pfol'('. tJuH tNIl pel':! t u res taken nt this position c!tn usually be relied upon for guidullee in IHpcooling.

TE.\II'EHATURES IS UEFHIGERATOH C\J{S Di THANSIT

The stlldies on tI'nnsit tempernturp were confined prirnnrily to (I) a compflrison of t\tr temp(,l'aturps rnnintnin('d in ,'nriou;; parts of the lond ill curs rpeeiying IlO precooling with those .in compilnion Cilrs

39 CALIFORXL-\ CAXTALOFPS

precooled to various degrees, and (2) a determina tion of the transit temperntures required for the successful delh-ery of clmtaloups to eastern markets. The work was planned to ans,,-er the question of what precooling accemplislH's in terms of loweled traIlsit temperatures and prolonged market life of the melons.

EAHLlER TR \NSPORTATION INVESTIGATIONS WITH CANTALOlJJ>S

McKay, Fischer, and Nelson (12), in experiments carried 011 in 1915 to 1917, gave particulnr attention to the effect of packing and loading methods, Cfir construction, nnd the use of snIt with ice to increase refrigerutiQ~l in trllllsit. ~lany of the recommendntions for the improvement of equipment nnd handling methods thut were made us 11 resllit Qf tllese earl~er iuvestigntions hnve been adopted and put intQ prnctice. FQr example, it wus suggested that better refrigeration would be obtaincd b}- ~egregatillg crutes of one size und louding them in one end of the cur. This is now the gelll'rlll prnctice. It wns found thut curs 10ilded with cmtes {QUI' lnyers high did not cool ns satisfactorily as those londed Qnly three lnyers high, the CQmmon method of louding cnntaloups ut the present time. Cantnloups IQnded in Cilrs eqllipped with sitlthd fulse floors (flQor racks), insulnted bulkheads, and baskettype bunkers that provided un nil' spuce of 2 inches on nIl sides of the ice were refrigerated more effectively than melQns in c9-rs without these improvements. These aids to better air circulution. have nIl become standard equipment in most refrigerutQr cnrs.

The nddition of snit to the ice in the bunkers of CflTS equipped with the nbo\'l'-nnmed improvements resulted in lower~ temperutures in trnnsit nnd consequently fewer soft melons thun wus the cuse in cars without snlt. It 'lhould be borne in mind that these t('sts were mude with non precooled londs, long before precooling equipment wus genern}\v Ilyuilnble. McKay, Fischer, und Nelson (12) recommended thnt llS m'lIch ns 10 percent of suIt be applied immedintely.nfter louding wus completed if the temperature of the melons wus SOo F. or higher. This was consi.deru.bly more sult thun is used nt the present time.

Since these early investigations were reported, little has been published on the transportation Qf CnIifQrnin cantnloups. A report ()f n preliminary na.ture was ronde on a test conducted in 1921 (21), in which the enrlier results on the disndvontnges of wrnpping cnntulQups \..-ere confirmed und the possibility Qf shipping riper melons was estn blished.

nEFRIGEHATION SEHVICES IN USE FOR CA~TALOUPS

The refrigerntion of eilntnloups in trilllsit invoh-es II cQntinuation of the process of removin~ hen t discussed undcr the refrigem tion required for precooling (p. 28). III non precooled or poorly cooled Cllrs a considernble quantity of ~ield hent will be removed en route to destination. Vital heltt, which is being libernted continuollsly by melon respiration, and the heut thut lenks into the refrigemtQr car durillg the trip to the eastern mnrket alSQ odd tQ the nmount of refrigeration required. A detailed discllssion of the ice-meltnge unci refrigemtiVll requirement is presented Inter under un appropriate bending (p. 53). The rate at which cuntaloups ure cooled is much slowN in trnnsil than dllring precooling, o.veraging about one-tltird. The reuson for this is that with the equipment now in use, Ilir circulntion by grnvity

l+>e.?

~ i:'j o ~ \.o'! ..... (")

~ t;J r:: r' r' t:j H .... ~

-1

o"" c. (I'

t;; i:'j

~ o ":l

;.. o ~ oc: ~ C. ::::l i:'j

Flllun.,; 22.-..1, Conveyor londed with ice fur cantnloup car,;, Rrnwlcy, CuliLi B, icing crews sliding cakes of iec from cOllveyor to bunkers of refrigerator cars.

41 CALIFORNIA. CANTALOUPS

alone is depended on to trunsfer heat through thermal convection from the loaded part of the car to the ice during the trunsit period. ,Varm nil' in the car rises to the space above the load and finds its way into the bunker through the top opening in the bulkhead. As the air comes in contact with i(;e in the bunker it cools, becomes heavier, sinks to the bottom of the bunker, and returns to the loaded space through the opening in the bottom of the bulkhead. The cool air passes toward the center of the car under the floor racks, some of it rising between the rows of crates, removing heat from the melons as it does so, and rising as it is warmed. It is obvious that there will be a difference between air tempern,tures at the bottom and those at the top of the load in cars cooled by natural circulation. Also, it can be readily seen that air circulation will be faster in warm cars than in cool cars, for in the former there will be a greater difference in the temperature and resultant density of the nil' issuing from the bottom of the bunker and that returning to it nt the top 0pclIing. Suiting the icc should likcwise nccelernte nil' movement, for it brings about largcr lliffercnces ill air temperaturcs inside the cur.

In the trnnsportution of can taloups from California to Now York, the refrigeration 8"rvice most commonly used is that known as standard refrigeration. Practically all cars are preiced, that is, supplied ",ith ice a few hours before being delivered for loading. After loading is finished and precooling completed in those cars receiving precooling, the cars are switched to the nmlrest icing station and the bnnkers are replenished (fig. 22). Many shippers avail themselves of a service provided by the railroads for the salting of the ice in the bunkers. The amount of snlt applied is usually 2 or 3 percent of the weight of ice needed to fill the bunkers at thefiL'st and second icing stations. At the second icing station the bunkers are replenished and the nnal salting of the ice takes place if the car is shipped under salting instructions for the first and second icing stations only. Under standard refrigeration, the bunkers are filled to capacity at each of the regular icing stations en route, at all points where cars can be held on track, a,nd at final destination until delivery is taken by the consignee. On one of the routes over which cantaloups are commonly shipped the cars are re-iced 11 times from EI Centro, Calif., to New York, N. Y., at intervals of ahout 20 to 24 hours. Late in the cantaloup season, when the melons are less firm and outside temperatures are extremely high, some cars are shipped under standard refrigeration with salt added at every icing station in the amount of 5 percent of the ice required to replenish the bunkers.

In recent years, with the advent of more thorough precooling, some cars have been shipped to midwestern markets with the bunkers filled with ice initiaUy and Te-iced once en route. The number of curs moving under this service during the 1937 season is estimated to have been less than 10 percent of the total movement.

EFFECT OF PRECOOLING ON lIlELON TE~IPERATURES IN TUANSIT

Precooling has been defined recently by Fisher (4) as" the compul'ati-:-ely rapid reduction of the temperature ?f a. c0n;tmodity. before shIpment to or below that temperature whICh It mIght ultImately attain during transit under conventional refrigeration practices." According tr. this definition, the temperature record of the commodity

i

42 TECHNICAL BULLETIN 7HO, U. f;. DBPT. 01portation period. TIl(' melons in ca,r M were precooled to an nVel'flp'

CALIFOItNIA CAN'rALO UPS

!~___lf-' FOURTH STACK. THIRD Row __-+__-,-1__-I-... \1 85 I ~80~_~;__-+f___~'~___Q~U_A_R_T_E~.R~L~_H~G,T_H__-+____~____,-__~

... : I I ~ I, ~C"'RIL i

jl

~70~--~~--+----+----4---~t-----:-----r----t----+----1

2 \1 \1 j I I I ~601-----':~'!~:-=::+---+-.--+----+\--I---i!,--+--.:-i'---J ~ \ 1 i iWtRf1 50~---4;~~r~~O~~~~I~--4-----r---~----~----~---+!----~C"'RN~~~~1"'O I

CA~N_'c-45 ---- .i c"Rf::3;~7C"RN

I ! EIGHTH STACK, THIRD Row

DOORWAV

60

FiG-I CA

44 TEGHXICAL BULLETI~ 730, U. S. DEPT. 01

45 OALH'ORNIA CANTALOUP:-;

In thc top layer this temW'ruture was about 45, \\"l1('1'cIIS ill the middle layer it was about 40.

BOTTO:lI LA YERS

The bottom layers of all cars cooled rapidly after loading, whethC'r prpcooled or not (fig. 25). It is cvident from these records that the bottom layer was refrigeruted well ellough by air ein'ulatiol1 from the ice bunkers so that precooling was of little benefit to it.

COllPARISON OF AIR TEMPERATURES IN I>HECOOLED AND

NONPHECOOLED CAHS

~>tir temperatul'('s tahn in trunsit at the top nIld bottom bulklvad opt'llings and at th(, doorway bl'[H'uth til(' floor rncks in tpst curs L, ~1, N, und 0 an' shown in compurison with outsidt' air tempemtuJ'('s in figure 26. The transportation tl'St was conduetpd during a fWI'ioel of wurm weather not uneommon in the Imperial Valley aIld Arizonu during the cflntuloup shipping Season. A maximum temperatul'(' of 114 was reached the second day, with temp('ratures exceeding 1000 F. for 4 successive days.

The temperature of the air at the top of the load wus higher ill the llonprecooled car L and poorly cooled cur~:[ than was the templ'rature in well-cooled cars Nand O. 11S WUS to be l'xpected. These diffprPllces in air temperatures lasted for 41~ dnys un til the loud was cooled ill the wnrlll curs L and ~1.

Thl' telllpl'ra ture of the air en tl'ring til(' loaded paJ't of UJ(' rur through th(' bottom bulkhi;'ud op

46 TECHNICAL BULLETIN 730, U. S. DEPT. OF AGRICULTURE

- I 1 T I 80

!SAt L F'II.ST STACH. THIRD Row

\ G ..RM I NeXT To BUNHell.\ V:-" 1 .I I 1\'70 . , I , 1\ 11\

GO I I

I ; I I , I

I\ " \1

t'~ I l

so7.rt I !

1 c..,,-~ f\\1 4o I I f I i I90 40

I CA'!...,O CA" MI ,.I\~\ ~ I I CA.. L."/I I .~~lIO

FOURTH STACH. THIR.D Row1\ \f \ . QVART1l LNGTH \\

1 i

ICARt\ \\ ! 1 "

II~CARMI I I , I

! I !

I I~~ I I

t C.AR O. CAIl..L.-CA" N- F':::::::

I\ ~'!O C..;('M C'::N c ....q y ! I MW' E,r;,HTH STACK. THIRD Row

< 1 90 , Ooo~w....Y I

t

I ICA.. L.- i.,

80 '"

, II I i 1 ."\~~ IC..~N\ 70 "'-I

! I

. ! I .

, L~OINO\fu I I i IJ

--- TIlAN81T PEII'OD _60 i --------- PIII6COOLIN. p~",oo

I~ ! I ! I.so I

CA.. ~~l I c",..,1 L,- I 40 , ! ~C"R.M

-=r= T -T 9 10

FIGURE 25.-Bottom-layer melon temp{'rutures ill trunsit from Imperial Valley, Calif., to Xew York, N. Y., in cantaloup cars, J'une 20 to 28, J936. Car L, not precooled, and cars Nand 0, precooled; shipped uIIder standard refrigeration, with 2 percent of salt added at first two re-icings. Car M, precooled, shipped under standard refrigeration; 3 percent of salt added at first two re-icings.

47 CALIl!'OnNIA CANTALOUPS

"0r-~r,-~"---+--~----~--+---4-__~__~__~

~40r-~~1r---~---r----r----r--. '

30 CAli 0 (iN SLU"H Ic.c)

70 :', eARN -,--ZO- AIR 7it:"'''~IfATU.~. t-l---+'---+-----120 , UND~" Fi..oolO RACK AT 000'..,.,..., II

r:" , ~ ~ 60

~

30L--'~--~~-3.--L~4~~-'S~~~--L--7~-L-'8'-~-'9'-~-~~~ DAV. 0, T..6r

FIGURE 26.--Air temperatures in transit from Imperial Valley, Calif., to New York, N. Y., in cautaloup cars, June 20 to 28,1936. Car L, not precooled, and cars X and 0 precooled; shipped under staudard refrigeration i 2 percent of !!alt added at first two re-icin/!s. Car 1\1, precooled; shipped under standard refrigeratioll; 3 percent of salt added at first two re-icings.

48 'fECHXICAL nl'"LLETIK 730, U. S. DEPT. OF AGRICeLTrRE

the various temperature zones is given in to hIe 5. In car 0, wellprecooled, it is evident (fi~. 30) that nwlons throughout the load had transit temperatures lower than 45.

HALF" LONGITUDINAL ,sECTION

LEGF:ND

IlJuow.f.5.1 FlGlJRE 2i.-..\xerage llll'loll and air temperatures in transit. Car L, non pre

cooled: shipped under standard refrigeration; 2 percent of i'aJt added at Brawley, Calif., and Yuma, Ariz.; ,June 20 to 28, 193G. Thermometers loeated in rellter of erate:". along l'entpJ" line of car.

AIIil Tc....,.pc~.. rIJAZI! ~ 412-

HALF" L ONGITUOINAL JECTION

LEGEND

~i~ e1:;~~ IlJ'rLO_~s-1 FIGCUE 28.-A\'erage meloll and air telJlperatures ill transit. ('ar l\I, precooled;

shipped uucicr standard refrigeration j 3 percent of salt added at El Centro, Calif., and Yuma, Ariz.; ,June 20 to 28, J98G, Thermometers located in center of cratei', alollg l'(,lIter Jiue of car.

In car X, with the ('xc('ption of the top layer, 01' 29 p('l'cent of the load, whieh was sli~htly above 45 F., the ml'lons WC'I'(' as eool in transit as tbos(' in car 0 and could be l'xpected to arrin' in similar condition.

49 CALIFonXIA CAXTALOUPS

The transit temperatures in cor ),1, prl'cooled to an aYl'roge tl'mpE:'l"ature of only 66 F., show a wide yariution from bottom to top lavers. The bottom lay(r ond most of thl' middlE:' Iaye I' close to the blInker

A TCM... lfilflY't.I4cz"S,..6

f No.- '___-7 'I)

'-I

4".~

HALF LONGITUDINAL SECTION

FIGURE 29.-Averagc melon ami air tcmperatures ill tram;it. Car X, precooled; shipped ullder stalldard refrig~'ratiOI1; 2 jJ('n'l'llt of salt added at EI C'(,lItro, Calif., ami Yuma, Ariz.; Jline 20 to 2!l, I!l:3fi. Thermometers loeah'd ill ('~'II tl~r of e rate:; , ulollg cent('r line of cur.

'.0Z

iL ~~ Allft 7i.+""'... 'VIllrCz,.47t1!J"

~ J

~

~~

~~ ()"

~ { )

4 ........... .:Jr ... c,< No, -~I 'l Icc

!% ~

BVNI(61l

.... 4 .. 7i1l~81 LAY.~ .... '" v.V.

""4 .$CGOooI'D 43... I..A""~ 42~" ~ t/. 41"- Fut.. r

4Zo5LcOQI('d;

shipped under ;;tulldard refrigeratioll; 2 percent of ,.;alt added at 1::1 Centro, Calif., and Yuma, Ariz.; ,IUIlC 20 to 28, 1936. Thermometers located ill cent(>rof crates, alollg ceuter line of car.

had tronsit trmpemhll'ps low('r than Mio fj'. Till' rpmnind!'r of t iiI' middle layer and most of the top Illyc'r l"('fH'ps(>lIting 4() 1)(,1"(,(,.IIt of til(l load fell in the 45 to 50 zone as compared with 29 percent of ('ur X that fell in this zone.

50 TEGHXlCAL BlILLJ.;TJ.X 730, U. ~. UI~JYJ.'. OF AURlGl'LTlTHB

TABJ,E 5.-Division of the load of nonprecooled and precooled cars of cantaloups 'into average transit temperature zOlles

! Portlcn Portion: Portion . I I' Ir loud " of lond I oC loadCar ShipP JI~ uuthod hl'll)w at .150 to. abo\'(~

15 F. ' 51)0 F. I 50 }'.

L I",N'nnl'reCOnll'(i. s(anliard n.c,' i~'rIltion. 2 l:':~-,.n~t~::;'~ ~~S;'::;,I" Perrf1l1 l-;':;!-;':II~I

s~eond rt'-iciIl~S. :t.'-; ~'Y 33 1\1 Precool('d to 6(jO F. ll\~(lrag:l'j stundnrd Tl'frigt'Tation, 3 IJt,'rt,'\'ut of

salt, at first lind second n-icings ., , , . , ~t; ~6 I; N Pn'cooled to 52 F. 8\Irngr. stJUltinrti ,eCriglrutinn. 2 pln~nt of

snit at first and Sl't"Ond re-icings ... , , i\ ~>9 0 o Pll'eooled to .;00 F. 8"l?ragt', standard rl'frigl'ration, 2 IWrttmt nf

, saiL at filst and second rl~icillgs ,., lOO : 0 , 0

It is estimatl'd thut in nonpr('('ooled car L. 38 pprcl'lIt of the mC'lons had transit tl'mp('ratur'('s of 1('8s than 45 F., as compul'(d with 100 percl'nt in this zonl' in weIl-cooiPd CHI' O. This portion of the load consistC'd of till' bottom layC'l', l'xcluding tiJ(' doorway stack, and the middle laYl'r of stacks 1 and 2 (bunkC'r and IH'Xt to bUllker stacks). The temperu.ture zone of 45 to 50 included most of thC' middle lay(r or 29 percent of th(' load. In the high(st tC'mp!'rutun' zone (abow 50) 33 pC'rcent of nonpl'pcoolNI cllr L was includ('(1, ns compar('d with 8 percent in partly ('ooIrd ('ur ~J and nOTH' in pn'('ooINI curs N and O.

l:~JFOR.~IITY OJ" TEMPEH,\TIJHES J:X THA:xsrl"

The mean transit temppru.tures at nlrious positions in cars L, ~l, N, and 0 haw beC'n comparl'd to ddprminl' tite pff('('t of prl'cooling on the uniformity of tl'mp('ratl1l'l'S throughout till'load. Th(' t('mpl'r ature rangl'S, l'xcluding tht' bottom bunk!'r position. as it r('presC'nts a vC'ry small purt of the load, a/"(' summllrizN\ in table 6.

The uveragl' minimum t('mlwratul'C's W(>I'(' about th(' same for Illl cars, so actually thl' C'JfC'd of prl'('ooling was to lowl'r thC' transit temperaturC' of the warm portion of til(' load, bringillg it dosl'r to til(' minimum temperatun'. In Illl ('aI's the awragc" maximum trallsit tC'mperature was in tll(' top laycr. doorway stack. Tb(' ay('rage minimum temp('mture (excluding the bottom bunkl'r) WllS in the bottom lnyer, doorwny, 01" qUllrtl'r-I('ngth stll('\;:S.

REFRIGERATIOl'" nEQt:IHED IH}lUl'"G THE TIlAl\'SJT PEIlIOD

The amount of r(frigN'atioll or jet' meltagl' that will lw /]{'(ded to r('frigeratl' u. cllrload of cantaloups during transit from the Implrinl Vulll'v to l'astC'rn markds cnn be dpterminC'd by u consid('ratioll of the heat ioad to be extmd(d. Of first importallce is thp fipld hpllt to be removed. Also of importnnc(' is thC' :t"l'moval of ,-.it II I hC'1l t from r('spiration, and a third sour('e of Iwat contributing to till' total h('at load is til(' oulsid(' atmosphere to which the refl'ig(,l'Utor car is cxpos('d en route to market.

51 CALIFORNIA CANTALOUPS

TABLE 6.-Extremes -in average Irall.~it temperatures at various positions, and temperahlTe ranges in nOIl]Jrecooied and 7Jrecooled cars 0/ carllaloups in transit from the Imperial ralley, Coli/omia, 10 Kew }'ork, N. Y., .hme 1936

IExtreml'S In I0u.r ShiJ\J1lng nwrhod a \'rl age 1 Rangef temperaturoot--___ --'_0_._-OF. ! OF.

L XOllprf!cooled. standard Icfrig.'ration, 2 P

52 TECHNICAL nLlI~r...E'rIN no, U. S. mu:vr. m' A(mICUI.{rulU~

TABLE 7.-S1I1nmary of temperahlres and 'icing ancZ salting records of test cars of c(lllta/oups shipped 'under 8tandard refrigerai'ion, with salt added at first and second re-icings, fromlhe imperial Falley, California, to New York, N. Y.

--,-;;::;'1 I ~ ,- ~;. g ]~ L I2'E- Ice melle8.1 ' 25.7 41.4 16.7 I 4:!\ I S,3r", , 15,673 21,03:1 2113 W 7S.9: 43.1 do ... 7f'.0 ,4~.2 28.3 40.(; I' 7.d. :\5.9: 0,200: 13,,\57 19,6.'7 612 X3 78.9 :'7.5 do,.! 7;'.3.40.1 332 3fl,2 ..9 i ~Ui.l! 0' 12.Q76 12,076 234 Y 178.9 45.2 C" dO----i 92.0 174.2117.8\40.8\ :tl.4l.'il.2! 3.6.15: 15,415 i 19,050 492

I :M.,an Inside air temperatures w~re obtained by B\'eraginl' the air tcmperatuTl'S at the top and bottom bulkh\'lId opcn!ngs.

i ~(ln[lreC(JOl\'d r...quirt~d (or n'lIlo\'u.( o( t1f'ld hf1ut WfL~ SlJJull"

TABI".; 9.' Rsli'lllfl/f' of vi/lIl ht'lltlibe1ll1ed by tlll.'/ons in car M during BdllY trmlsit pI'I'/lld

." ___ u'_""_~'_""-""""', \'(tal VIt,,1 heat heat

londin!; (days) ,:/g~l ;per curhours' lund 1

'ltinlt~ 11((('1"

,-- - ......... ------ '----- ----t"~---

I 0I 0 f'. .\fU. R.I. ". B.t.u. F. Mg. B.l.tl. iRt.u. 2~8r 3il 40.6 16.0 3, .>;20. 40, .'i.'lI')1 "."",._" ~ ...... i 71.1 9.... 0 !!l. {J'iQ 2 . 41l.2 22.0 4,1>10 {).1.757 ~::::::::::::::! 40.1 15.4 3.3S8' 39.0.10

::1 4:1.4 1~.1l :1,91:.0 45,619 8... 3\1. I 15.!? 3,:lH ;{Ij.ii2:1 1 12.1 17.0 :!,740 4~,0S5 ,---'----------....... fi I ,1I.1l Hl.4 :1.1;08 41.f>f>l ~l'otal 5.'>2,4911

l I "~-X""~j":~'~~._ : 47, ~iO ,...-.--

53 CALI FOHNIA CAN'rALOU PH

HEAT TRANSMITTED INTO THE CAR .'UOlI 'l'HE OUTSIDE

The heat that enters the car by conduction through the walls, ceiling, and floor can be calculated from the difference in temperature between the inside and outside surfaces of the car and from the conductivity factor for the materials used in the conHtruction of the car.. This has been done for cars L, 1'1, N, and 0 for the precooling and transit period and the results are presented as ice-meltage equivalents in table 8. A conductivity coefficient of 0.1 B. t. u. per square foot per hour for each degree of temperature difl'erence was used for the car walls, ceiling, and floor. It should be noted that these calculations are at best only rough estimates, for the actual surface temperatures of the refrigerator car, inside und out, probably differed considerably froUl the meitn air temperatures inside and outside the car. However, it is estimated f!'Olll these clllculutiOIlS thnt the amollnt of heat entering the cur during illl 8-day period would require iI.bout us much refrigeration as the removal of the field heat, and thus would constitute one-third to olle-half of the total cllleuluted heat loud.

'rOTA!, RE.HIGERA'r!OX HEQI'!I(ElIENT

'l'he toUt! Ilmollnt of ice melted as determined bv mellsurement was greater than the cak'ulated amount. There are probably seyeral fuctors that account fur this difference: (1) 1\/felon temperatures after precooling were taken in the center or warm part of the c.rates. This would tend to show less heat removal than was actually uccomplished during precooling and in transit. (2) Heat conduc.ted into the car was undoubtedly greater than wus indicated.

From th(' rl'cords of jCl' nwltag(' fOI' cars L, ~[, and .N shown in tnblP 7 it is l'yid('nt thnt in iel'-cooled cars during the WiU'm tnlllsportlttion t

54 TECHNICAL BULLETIN 730, U. S. DEPT. OF AGRICULTURE

RELATION OF PRECOOLING AND TRANSIT TEl\IPERATURES TO THE CONDITION AND QUALITY OF CANTALOUPS AFTER ARRIVAL IN EASTERN MARKETS

Considerable attention ha