Monggana Volume 1 Chapter 1

8/3/2019 Monggana Volume 1 Chapter 1

1/26

CHAPTER I

ASSESSMENT OF THE OIL ENTERING THE MILL

Processing control in the oil mill can becarried out in two v/ays:-a) By weighing the amount of oil produced andcalculating the ratio of that weight, to the' sum o f t h e weight o f o i l produced a n d t h eweight of oil lost in the waste products.This ratio (always lower than'l) will be' termed "efficiency".b) By weighing the amount of oil produced andcalculating the ratio of that weight to theweight of oil received at the factory asraw material and as assessed by analysis(bunch or stripped fruit). This ratio willbe termed "'recovery" .

The first method is accurate and its use isrecommended in the case of a pilot plant. This isbecause all the waste products of processing can be.weighed and are homogeneous enough to be sampledeasily.In industrial practice, this method possessesthe serious disadvantage of ignoring the accidentallosses resulting for instance from faulty plantoperation-The second method, i.e. that based on theanalytical determination of the oil content of theraw material, could laad to useful pointers for.processing control but its implementation is diffi-cult because of the pronounced heterogeneity of theraw material.

A. EfficiencyThe efficiency is given by the followingformula:-

in whichH = Weight of oil produced.HS = Oil lost in steriliser condensate.HR = Oil lost in bunch refuse.Hp = Oil lost in fibre. .HN = Oil lost on nuts.HD = Oil lost in the clarification ofcrude oil.The coefficients a ( / 3 and ^represent theefficiency of the extraction proper ( t } and thatof the purification of the extracted oil (/).The coefficient is affected by another one ( % * )which takes into account the practical industrialefficiency compared with the limit obtainable inthe laboratory.


2/26

Determination of the efficiencyThe method entails the weighing or at least theaccurate estimation of the weight of waste products.After consideration of a number of ways to obtainthese weights, the following system was proposed.It consists in:-

a) Assuming a fixed loss in steriliser condensate.The loss is governed solely ay the sterilisa-tion procedure and the form ,\n which the cropis processed (detached fruits " c r bunches).Generally, once sterilisation procedure isfinalised, no further modification is intro-duced. The amount of oil finding its way intothe condensate is therefore constant. The formin which the crop is processed is practicallyconstant for a given factory except in the caseof/plant receiving progressively less detachedfruit and more and more bunches.aThe loss in steriliser condensate can therefore oeconsidered as a fixed quantity -which is evaluatedonce and for all subject to verification if amodification occurs either in the sterilisationcycle or in the fruit, particularly in the caseof marked changes in the degree of ripeness.b) Assessing the weight of bunch refuse and titratingthe oil content therein. The percentage ratio ofbunch refuse to bunches shows consistency eitherin the course of time or in relation to the typeof bunches. It is therefore generally sufficientto weigh the bunch refuse during a certain periodof time and to carry out a few spot checks duringthe year to determine this ratio with sufficientaccuracy.c) Determining the weight of fibre from the ratio of

fibre to cake and from the weight of nuts. Theratio of fibre or nut to cake is essentiallygoverned by the type of fruit which is processed.It varies between wide limits (vide Chapter VII).In the case of factories dealing with bunches ofone variety only, the variation is not importantand the ratio may be considered as constant.On most estates, however, palms of various originsand ages are encountered. In addition to differ-ences due to the type of fruit, the strippingprocedure also affects the cake composition as aresult of the variable proportion of impurities-mixed with the fruit at that stage.

The determination" of the cake composition is there-fore indispensable. That operation should be doneover the whole processing time either by manualsorting of large samples or by means of a smallscraping knives depulper. The drying of fibredoes not affect the final result since oilcontent is determined on dry basis. It is how-ever important to draw the sample of fibre duringt h e datsrmination o f t h e cake composition.


3/26

- 3 -

d) Weighing the nuts. That operation is performedin a tilting nut -weighing device after separationfrom the fibre. The number of tilts 'of theapparatus is recorded automatically. This makesit possible to know, at the end. of processing,the"weight of nuts derived from a known weightof bunches. Current tilting scales ippears toprovide a sufficiently high accuracy.The oil loss is calculated directly from thatweight and the oil. content of nuts.

e) Weighing the discharged effluents. As for thepreceding weighing, the weight of effluents orsludge originating from the clarification ofcrude oil is determined in a tilting weighingscale. The oil. .loss is calculated directlyfrom that weight and the oil content of sludge.

As fast methods of analysis are available (seerelevant paragraph), the oil losses can bechecked daily by this system. The quantityof oil produced can also be accuratelyassessed daily by means of a tilting scale,the recommended method permits therefore tocalculate daily the mill efficiency.An outline of ^tilting weighing scale is givenon the following page (figures 1 & 2).B. RecoveryIts determination involves:-

i) The weighing of the raw materialentering the factory.ii) The determination of the averageoil content thereof.

iii) The weighing or the volume assess-ment of the oil produced.The weight of the raw material can be knownwith less than 0.1$ error but the determination ofthe average oil content may be seriously erroneous"since it is carried out on a small aliquot. Thedetermination of the oil content of the raw materialinvolves sampling and analysis operations.\In this paragraph only sampling will be con-sidered. The analyses themselves present 'littledifficulties. .They can be carried out using con-ventional methods. An attempt has howev er been madeto evolv e analytical procedures particularly suitablefor application to the palm fruits or the waste pro-ducts of processing.


4/26

Tilting weighingdevice (withfeed manifold)

Tilting weighingdevice for palmoil

Figure 2


5/26

Sampling #In the case of processing of bunches, the amountof oil entering the factory can be assessed from theweight of frash bunches or from the weight of sterilised

fruits (as collected from, the strippar).a) StgrilisQd fruit

The second method is, "a priori", more attrac-tive because of the higher homogeneity of the steri-lised fruit compared with that of the bunches. Itiapliss however the weighing of a material notparticularly suited for that operation. It wastriad in the pilot plant and it has been possible toestablish that with homogeneou s batches of fruitwithout impurities the oil content is determinedwith an error of less than 1% if the sample is madeup of the following number of fruits:-

1 3 x P material 2,500 fruitsT x T material 4,000 fruitsP . G - . material -- 5,700 fruitsMixed material 5,700 fruitsOn account cf the pronounced variability ofthe material, the determination of the percentageof trash (x) of the fruits requires the analysisof 8,500 x 500 g samples to obtain an accuracy ofl y i s or of 340 x 500 g for an accuracy of 57- Hew-ever, by using 5 kg samples, the percentage oftrash in sterilised fruits can be evaluated witha 5% error if 52 samples of fruit are examined.The variations in oil content of the trashare smaller than those of the trash content offruit. The determination, with an accuracy of10$, of the oil content of trash requires thesoxhlet extraction cf 27 samples (the av erage oilcontent is 20% on dry matter in trash).Although the above remarks still permit toenvisage the determination cf the cil content ofsterilised fruit, the method v v a s definitelydiscarded when it was observed that after stripp-ing the sterilised fruit sustains an importantloss of weight. (vide Chapter II, Effect ofSterilisation).After 10 minutes storage the apparent, increase in oil content of the fruit is approxi-mately 2 % . It can reach 4 to 5^ after one hour.Variations of such magnitude constitutetoo serious an obstacle to the accurate deter-mination of the oil content of sterilised fruit.

# Unless mentioned to the contrary the numberof bunches or fruit to be sampled isgiven for P = 0.05.(x) Vide appendix 2.


6/26

b ) Fresh bunchesThe analysis of fresh bunches involves:-

- the determination of the ratio offruit to bunch.- the determination of the ratio ofoil to fruit.

The ratio of fruit to bunchThis is generally established by choppingthe spikelets from the bunch then cutting thefruit from its socket. The method is extremely

time consuming and can only be used if a limitednumber of determinations are to be carried out.A worker can only deal with a few bunches perday.To speed up the work, the bunch or thespikelets are sometime allowed to remain in aheap for a day or two. The removal of the fruitis then carried out. The resulting desiccationof the fruit and the stalk is detrimental to theaccuracy of the analysis (v:ie the analysis offruit).In order to achieve easy fruit strippingwithout the need for maturation storage ofbunches or spikelets, the use of steam at'atmospheric pressure was tried. It has beenobserved that under these conditions, a periodof 20 minutes steaming practically does notaffect The weight of the fruits or spikeletsand releases all the fruits from the sockets.A trained worker using suitable equipment canin this manner strip 20 bunches per hour. Ithas been established that it is necessary to

strip 1,200 bunches drawn from homogeneousbatches to achieve an accuracy of 1% in thedetermination of the ratio of fruit to bunch.- Ratio of oil to fruit

The determination of this ratio requirestwo operations: the assessment of the per-centage of pulp and the oil content of thatpulp.- Single bunch analysis

The object of the experimental work wasto establish what weight or - w h a t number X 5 ffruits should be drawn from a bunch to obtainan estimate of the proportion of pulp with agiven accuracy.


7/26

The statistical analysis of 36 samples offruits per bunch (1/3 external fruits, 1/3 middlefruits, 1/3 inner fruits) drawn from a number ofDura .and Tartars "bunches of various sizas showedthat approximately 3 to 6 % of the weight Qf fruitsmust "be taken in order to attain a relative errorof 1$ on the determination of the ratio of pulpto fruit.Table 1 gives the relevant dat a for Dura"bunche s ' -

Table 1Number of fruits to " b e drawn from a "bunch todetermine the percentage ratio of pericarp " t ofruit 7/ith an accuracy of 1$

i'Bunch" i Bunch ! Bunchi 1 ! 2 . ! J_'Number of fruits

$ of the total weight iof fruits75 106 ; 166

5 o$ i 5 6$ ; 6. 4$

Bunch j Bunch Aver age4 j 5 i 6200 i 90 127

i . 16.6$ I 5.1$ i 5.9$In the case of fruit from Tenera bunches issuedfrom T x T crossings, the ratio of pulp to fruit can

be determined with an accuracy of 1% using samples ofhalf the size indicated above.Vanderweyen and Alias (l) have established thatin a sample consisting of 50 fruits of average weigh"?,the percentage of pulp is ascertained with an accur-acy of 2.5$ to 4.5 . The determination of pulp onfruits of average weight is perfectly justified forsingle bunch analyses performed in a research station.It is impractical for industrial analyses carried outin control laboratories.The determination of the moisture content ofpulp requires a larger number of fruits because ofthe higher v ariability of that characteristic. Afew results are given in Table 2.

Table 2Number of fruits to be drawn from a bunch todetermine the percentage ratio of water topericarp with an accuracyof 1$

Number of fruits 350 ; 300 11,069il,342j 150% of the total weight | jof fruit i26.9$ il5-S$|41.1$;43. 3$ ; 8.6$

o n c h i Bunch iBuncn i au n c n Average ;638

27.2$


8/26

In the case of Tenera bunches, the sample mustalso amount to about 25$ of the total fruit to achievean accuracy of 1%.Finally, to determine the cil c'ontent of fruitof a bunch, whether Dura or Tenera, with ! , " - > accuracy,'it is necessary to analyse from 15 " c o ICOfo of itsfruit;. That kind accuracy is seldom required. Itshows however the considerable heterogeneity of thebunches. If a 5% relative error is deemed acceptable,it is necessary to take approximately 2.3^ of the fruit.That degree of accuracy is sufficient in certain cas'asbut it is of no interest if the object is to assess theextraction efficiency which must have an accuracy ofapproximately ~ L % .As a palliative against the hsterogensity of bunchesthe possibility of building up samples from spikeletsinstead of from fruits was envisaged. The idea beingthat a spikelet of 5 fruits might be more representa-tive of the bunch than just 5 fruits -oaken at randomfrom it. The analysis carried out on a number ofbunches showed that for an equal number of fruits,the error is larger for the spikelets than for thefruits.

- Analysis of a batch of bunchesj

Practically in the industry the need for singlebunch analysis does not arise. The problem is todetermine the oil content of a batch of bunches.To that end, a study has been made of the numberof fruits that it is necessary to draw from eachbunch in order to arrive at a predetermined degree ofaccuracy..The number of fruits to be taken depends on themanner in v/hich the sample is drawn. For instance,10 fruits drawn at random lead to the same relative

error as 3 selected respectively from outer, middleand inner fruits.Moreover, increasing the sample to 9 and 24fruits per bunch, still distributed as 1/3 each fromouter, middle and inner layers respectively does notdecrease the relative error appreciably. The factthat 10 fruits drawn at random - a r e just as represen-tative of a bunch as 3 selected from outer, middleand inner layers respectively was established onlywhen the research was about to be completed. Con-sequently, all experiments aimed at ascertaining the

number of bunches to be sampled from a batch werecarried out with the, . - 3 fruits per bunch samplingtechnique.


9/26

The number of bunches required to achieve apredetermined degree of accuracy is given by thegeneral formula:-N = A ()2

whereN = number of bunchesA = a constant which has beendetermined in each case .x = The required rela tiv e error(in percentage)

Table 3 gives the value of "A" as determinedfor the various compone nts of the Dura and Tenerabunches subjected to test.Table 3

Value of "A"

RatioParticulars

o f pericarp t o fruit ;Ratio of moisture to wetpericarpRatioRatio

of oil to fruitof fruit to bunch

Dura iBun he s ;26.5 i

13.0 ;28.23-1 :

TeneraBunches3 - 69 - 1

12.312.6

The following remarks may be ma de regarding thedata of the above table:-The heterogeneity of the fruit is morepronounced for Dura than for Tenera.On the contrary, Dura bunches are morehomogeneous than Tenera's in respectof the fruit to bunch ratio.

c) Loose fruitThe sampling has shown that the analysis of approxi-mately 1% of the fruits in batches of ?.(J. crop leads to

a relative error of 1$ on the oil content. In practice,no more than 0.01$ if the fruit is subjected - to analysis:Factories dealing with loose fruit assess the oil_,_con-tent on fruit with" an error of 5 to 1C$ (20$ oil - 1%under suitable conditions). The abo ve results wereobtained on batches of fruit derived from completelystripped bunches: that is containing the whole of theinner fruits, parthenocarpic fruits, etc... Normally,the batches of fruit bought from the local farmers aremore homogeneous because the inner fruits are notincluded.


10/26

- 10 -

The method, of sampling described above shouldtherefore lead to a more accurate determinationof the oil to fruit ratio. The impurities con-tent of loose fruit subjected to test was fairlyconstant, approximately ' ! . % (sand, calyx leavesetc....)- Th e sampling of estate loose fruitwas not studied.

2. ANALYTICAL PROCEDURE ?CR THE PHUIT AM) THE 7/ASTEPRODUCTS OF PROCESSING "A. Desiccation of the fruit and of the freshbunches

This point was studied with a view toestablishing if the stripping made possible byageing of the bunches modified the ratio offruits to bunch. A few results are given inTable 4 which shows the loss in weight of freshlystripped fruit (cut from the spikelets) and ofbunches as a function of time.

Table 4Effect of time of storage on the loss of weight(in percentage units)

Hours ofstorage011

1520256890

. _Prxiits

Dura Tenera0 00.1 0.2

BunchesDura0

0.7 I - ! 0.9-

2.14.86.0

1.7- 2 J L2.55.77.1

-1.92.36.1

Tsnerai " 1c0.2-1.72.12.46.07.5

The desiccation of bunches appears faster thanthat of fruits. Prom a large number of testscarried out over several months by Vanderweyen &Alias (2) it appears that the loss in weight ofTenera and Dura loose fruits amounts respectivelyto 3-45$ and 2.79$ after 1 day and to 6.23?' and5.08$ after two days. The loss recorded for" theTenera material is statistically higher than thatfor Dura's (P = 0'. 1) over a period of 4 days, butthe relative rate of evaporation of the pulpmoisture is higher for Dura.


11/26

to The loss in weight of bunches amounts to 1.7d j f after 1 day and 3 - 1 - 3.4$ after two days.Vanderweyen i Alias ascribe the loss of -.'/eightof the bunch chiefly to the desiccation of the stall*and that of the fruit tc loss of moisture through thearea of attachment to the bunch and hot through theexocarp. They suggest to allow for a 1 to 2> correc-tion for bunches stored for 1 or 2 days before analysisor, bettar still, if the weight of bunches as harvestedia known to add the loss of weight to the weight of thebunch stalk.This can be arranged on research stations but not

on commercial estates where it is not possible eitherto weigh the bunches immediately after harvesting oreven to know with any degree of certainty how manyhours have elapsed between harvesting and analysis orprocessing.3. Desiccation of the pulp

In the standard analysis of the fruit of theoil palm, the fresh pulp is peeled off and weighed.Does this depulping entail a certain amount ofdesiccation liable to induce an increase in oilcontent? The loss of weight of fresh pulp immediatelyafter depulping was assessed. Depulping was performed-as quickly as possible. The time elapsing between thebeginning of the operation and the first weighing was 2 minutes. Figure 3 gives the loss of weight againsttime.

Figure 3Effect of time on the desiccation o: :ulp

0.70' ' I0.50

0.50s

0.40l

0.300.200.10

0

Loss of weight(in #)

Time2581015243041516175

Loss ofweight (f)0.020.050.090.120.190.290.360.480.600.710.86

10 20 30 40 50 60 70Time in minutes


12/26

- 12 -

It may be observed, that up to 75 ninutes, thedesiccation is dirsctly proportional to time andthat a normal time of d e pulping, 15 to 20 mjnutes,does not practically affect the oil content. Thedepulping operation entails very low losses ofweight if it is carried out with suitable care.It appears from ten of thousands of analyses thatthe difference between the initial weight and thesum of the weights of nuts and pulp averages 0.4$.About 1 to 2 % of the analyses show a depulping lossof more than i f o (for a sample of 100 to 150 g offruit). This is in fact a loss of matter ratherthan the effect of desiccation. As a general rulethe results of such analyses are discarded in controllaboratories.

Recently, an investigation into the determina-tion of the oil content of pulp .(34) has shown thatthe loss of weight due to depulping and pounding wasapproximately 1%. It seems that 95$ of the loss isdue to pounding which is not used in the BelgianCongo. The extraction being carried out on pulp aspeeled off from the fruit.Determination of the oil contenta) Combined determination of o i l - , moisture andnon-oily solids (N.O.S.)

The standard analytical procedure for theassessment of fatty matter requires drying ofthe pulp o^ the fibre before solvent extraction.The drying is generally carried out in an ovenand is truly the most time consuming step ofthe analysis. It usually requires 12 to 14 hours.The possibility of substituting azeotropic dis-. tillation to drying. ha.s been .envisaged by severalresearch workers but, to our knowledge, noapparatus suitable for the fruit of the palm orthe waste products of processing has yet beenevolved.

The proposed apparatus is a Kumagawaextractor (high temperature Soxhlet extraction)in which the solvent is, before percolation,separated from the water by a separator of theDean & Stark or the Sundin type depending onwhether the solvent used is heavier or lighterwater.Moreover, the method of oil extraction,from the effluents was evolved by a firm belonging to the Cooperative (5). The descriptionand the specifications of the equipment aregiven in Appendix.The method can be used for the combineddetermination of moisture, oil and IT. 0.5. ofthe pulp of the fruit , t h e - cake , the bunchrefuse .and the mill effluents.


13/26

- 13 -

The time required ' fo r " the analysis varieswith the solvent "used. It is shorter for toluene.(or xylsne) than with -richlcrethylene. Thelatter offers the advantage of being uninflammable.The completa analysis with toluene as solvent,that is the weighings, the extraction and dryingtalces 2-3C hours for pulp and 1.3C hours for fibreon buiich refuse.

te) Determination of oil by measurement of the refrac-tive indexIn the' preceding meth od, the solvent is usuallydistilled off and the residue is dried to constantweight. In order to eliminate the drying step, the

possibility has been investigated of titrating oildirectly in the solvent through measurement of therefractive index'of the solution.*Mention is made in technical pub lications(6,7) of several procedures for the determination .Of oil in various organic media based on the varia-tions of the refractive index according tc o i l -content.

The following factors which affect therefractive index were studied:-i) The oil concentration,

ii) The temperature of the solution.iii) The ?.F.A. content.iv) The nature of the oil.

The effect of moisture content needs not beconsidered since the solution of oil in xyiene isalways dehydrated by a zeotrcpic distillation prior'to testing.The time of ebullition of the solution of oil in xyiene does not affect the refractive index.i) Effect of concentration and tempe rature

The results regarding the effect of .concentration and temperature plotted onFigure 4 were obtained for a 5-76> : F.F.A.'-oil.The refractive index of the solution^: of oil in xyiene fellows a linear relation-ship until 6 C 5 t . After that point, the line- deflects slightly into a curve. The follow-ing equation gives the concentration of oilfor 100 ml of solution according to therefractive index.


14/26

- 14 -

C = NY - at - NsA - btwhere% = refractive index fxylene at OOC.Ns = refractive index of thesolution.t = temperature.A, a and b = constants which havebeen established.

Figure 4Refractive index

\r \ x x x\\\\

Oil10 20 30 40 50 60 70 80 90 100Variation of the refractive index accordingto the oil concentration and the temperatureof the solution


15/26

- 15 -

ii) Effect of acidityThis has "been studied on oil acidifiedby addition of palm oil fatty acids. The

refractive index of artificially acidifiedoil is not, of course, identical to that ofa spontaneously acidified oil which, containsa higher proportion of mono and diglycerides.Although the refractive index of fatty acidswas found, .to "be. 1.439-8 at 600Q .against1.4585 at 40C for most oils, the differencein refractive index between oil of normalacidity (between 1 and 6$) is of the samemagnitude as the testing error, that is0.0002. It may be ignored. The variationin refractive index resulting from variationsin P.P.A. is negligible if the average indexis determined daily on the oil produced atthe mill.

iii) Effect of the nature of the oil.Twelve samples.of oil extracted fromfruits of various origin and from differentparts of the bunch were found to have anD40C index ranging from 1.4583 to 1.4590

(average 1.4584).In that case again, the recordeddifferences may be assimilated to thetesting error. It may therefore be postu-lated that the refractive index is indepen-dent of the nature and the origin of theoil. The oil concentration can be deter-mined with an accuracy of 1.5$', comparedwith the solvent evaporation method. Theprocedure avoids the evaporation of thesolvent after extraction and the frequent

ovsrhaating suiting Z The determinationproper is very fast but aelicate volumeadjustments are required. ^therefrom.The method was successfully used atMongana but it is not recommended for alaboratory where supervision of personnel

is not permanent.' Checking .is easy. Itsimply involves the evaporation of thesolvent from the 100. ml of solution fromwhich one drop has been drawn for therefractometer reading. Zylene wasselected in prefer.ence to benzene ortoluene on account of its lower vapourpressure.


16/26

- 16 -

The table "below gives a few comparativeresults obtained by weighing of the oil and byrefractometry.Table 4

Origin \ Oil as : Oilof | determined by : determine.d .i the o il refract cine try ; by weighing i! Fruitsi Fruits

!j Fruitsj Fruits; Fruits! j1 Fruits|Fruits|Fruitsi ;; Crude o il :; Crude oil iFibre i

: Fibre ii Fruits1 ; Fruits

21.60 g26.60 g30.40 g20 .50 g ;28.80 g42.10 g18.20 g22.90 g21-30 g30.30 g32.40 g31-60 g25.40 g i26.80 g

21.20 g I25-20 g29-60 g i19-75 g '.27-30 g ;41.20 g19-10 g 123-40 g -21.60 g29OO g32.55 g :31-30 g !25.30 g ;26.70 g

Assessment of the oil content of pmoisture content through its

It is known that F.M. Dyke of the Research Depart-ment of HCB (Huile-rie-s du Congo 3elge) stablished morethan 30 years ago tha~ in fresh fruit the sum of oiland moisture of pulp is practically constant and equalto 84$.fruitIt had been observed that in the case of loosederived from bunches stored long enough to makemanual stripping possible, the total oil + moisturefell - t o 82.5( 0.25) except for fruit with very lowpulp content (30$) for which the sum remained below&0$. The oil content was therefore described by thefollowing equation:-

whereY = 82.5 - X

Y is the oil contentX _ i s the moisture content of pulp.


17/26

- 17 -

As a result of this observation a table wasprepared giving the sum of oil and moisture contentof fresh pulp over a wide range of moisture content.The tabl-e- could., e used. to determine the oil contentof fresh pulp in the following manner: The moisture^en-tent as determined by analysis, was deducted.fromthe corresponding sum of oil and moisture. The methodhas been adopted by all important mills of the Belgian

Vanderweyen and Alias (3 ) confirmed the correla-tion. From 136 'analyses they derived the followingregression equation:-y = 37.33 - 1.08 X

from which they computed a table showing the oilcontent of pulp according to moisture content (seeTable 6). These authors do not specify the timeelapsed between harvesting and analysis. It must beassumed however that the time is short sines the workwas. arried out. on a research station. There was adiscrepancy of a few percentage units between theresults of Dyke and those of Vanderweyen, which weassumed originated from a more important desiccationof the fruit in the case of Dyke's work than in thecase of

We wanted to check whether the latter ' s resultswere applicable'to fruit stripped by the local farmer,as. it is delivered to mills dealing with loose fruit,that - i s - ithout information or control over the age of _the fruit.To that end, 150 analyses wers carried out o n -loose' frui't "delivered, on the average, 4. days afterharvesting of the bunches. The results confirm theINEAC data. The slope coefficient is smaller than 3#-

Table 5 gives the average result of 10 analyses listedin order of increasing moisture content.


18/26

- 18 -

Table 5Analysis of fresh pericarpFruits plucked routinely "b y the small holders

| % Moisture/fresh pulp2 4 . 4 726.8630.0031-5732.583 3 - 2 037-713 4 - 5 735.6236.233 7 . 2 438.0840.50| . 46.8751.80i

Average:35.55

7 Oil/freshpulp60.9058.9555.0852.0852 .1851.3551.324 9 - 5 250.3348.5047.3947.8344.3637.6731-59

4 9 - 2 7

% Oil +moisture8 5 - 3 785.8185.0883.6084.7684.5585.0384.0985.9584.7384.6385-9184.868 4 . 5 433.39

84.82

f o Oil/drypulp80.6080.1278.3776.0677.4076.8777.4675.6978.1576.0475.5577.127 4 - 5 370.4365.39

76.01

% Oil/freshpulp(calculated)60.8158.3055/0053.5552.2951.6451.1150.2049.1048.4647.4046.5243-9837.2932.11

49.17It is therefore confirmed that the IITEAC' tablecan be used for loose fruit as received in processing

mills. We assume that the discrepancy recordedbetween the above figures and those of Dyke is due tothe fact that desiccation is now less pronounced thanit was 30 years ago. Transport conditions hav eimproved considerably and the time elapsed betweenharvesting and delivery to the mill certainly exceededtaBK the present average of 4 days (Numerous marketswere open only weekly or even fortnightly).


19/26

- 19 -

We give below (Table 6) the table establishedby Vandarweyen for the analysis of fresh pulptogether with the data collected at Mongana.Table 6

i! % Moisture/ jPulp252 6 -272829 !3 0- |313 23 3 -3 4-35-3 637

! 3 83 94041424344

: 454647484950

AnalSun of ?turs ancf reshMongana

83. 385-38 5 . 28 5 - 285.285.185.085.08 4 . 98 4 . 984.084.884.784.784. 684.684.584.584.484.48 4 . 384.384.384 .284.18 4 . 0

.ysis of mois-L oil toT3UlT3

I N E A C85 .485.3

- 85.285.185.185-184.9S4. -88 4 . 78 4 . 734.534.58 4 . 484.384.33 4 . 284.184.083-983-983.883.78 3 . 683o83. 53 3 . 4

fresh ta% Oitofresh

Mcngana60.359-358.257.256.155.15 4 . 053-051-95 0 . 94 9 - 84 8 . 847.74 6 . 74 5 - 644.64 3 - 54 2 . 541.440.43 9 - 33 8 . 33 7 . 33 6 . 235-13 4 - 0

ult)

1M u l D :

INEAC6C.459-3 ;5 6 . 257-156.155-053-95 2 . 651.75 0 . 74 9 - 64 8 . 5.47.44 6 . 34 5 - 344.243-142.0

< r\ f^i*y,y3 9 - 93 8 . 33 7 . 73 6 . 33 5 - 53 4 . 5

. 3 3 - 4

% c^~v -gaJt ^

Montana80.480.179. 779.47 9 . 078.17 3 . 377 .97 7 . 577.176.676.275.77 5 . 37 4 . 77 4 . 373-773-37 2 . 672.1

! 71.470 .9

1 70.469. 668.86 6 . 0

5il;omisISEAC80.580.179-779-37 9 . 0 178.6 i78.1T~> , C 'i l . D ]77.2 .7 6 . 876.375.875.27 4 . 774.37 3 - 773-17 2 . 471.871.27 0 . 569-869-068.3.1 SiO / . O

66.8 ;

Case of the sterilised fruitIt was deemed necessary to ascertain whether aregression equation between the oil content and themoisture content of pulp of sterilised fruit could beestablished as it was for fresh fruit.


20/26

- 20 -

To that end 300 samples of sterilised fruitwere subjected ~o analysis. The 300 results aregiven in Table 7 in 15 groups of 15 each.Table 7

Analysis of sterilised pulp1 i v l o i attire/

1 6 - 5 818.4-51 9 - 6 420.7021.4522.6823.8524.8125.95

' 27.2728.8329.8231.7533-0139.42_____ ,25.67

( o) Each res

Oil/Fresh "oul'D65.4464.0063.2762,6761.6860.5559-9859.7856.8456.6455.3954.0351-90'50.854 5 - 2 2____57.88

suit is the avei

Sum of oil ;and moisture ;32.0282.45 J32.9183-3783 .138 3 . 2 38 3 - 3 284 .593 2 . 7 93 3 - 9 184.223 3 . 3 5 |3 3 . 5 58 3 . 8 6 !3 4 . 6 2 8 3 - 5 5

'a*ce of 20 anal.ys

Oil/Dry T2uiD78.4478.4878.7379-0378.5378.3273.7779.5176.7677-8877.8376.0476.0475-9174.65_ _ _ _ _ _ _77.38

es.

Although, a relationship may be observed, as inthe case of fresh fruit, between the oil and moisturecontents of the pulp, important deviations occuraround 25% moisture. At that level, oil on dry pulpfalls by almost 3$ for a difference of slightly morethan ~ L % in the moisture content of pulp.

If we compare the results obtained on fresh andsterilised fruit, we observe that sterilisation notonly induces a certain amount of desiccation but alsoincreases the oil content on dry matter.Three hypotheses can be formulated to acco'unt

for the increase in .oil/dry matters from 76$ forfresh pulp to 1$% for sterilised pulp. (Thedifferenceexists for 2/3 of the results, discarding those atboth ends of the range).


21/26

- 21 -

- The oil content en dry matterloose fruit purchased from the localfarmer is different iron that boughtin the form of bunches. A largeproportion of the fruit with highoil/dry basis might not be deliveredby the local farmer.

The absolute oil content increasesduring sterilisation.- Part of the N.O.S., that is part of theextracted dry pulp is solubilised andwashed away thus increasing the ratio

of oil to dry matter.In all probability the second hypothesis shouldbe rejected whilst the other two should be retained.The local farmer, tends in fact, to keep the largefruits,those with low moisture content and highmoisture + oil content, for his personal consumption.The loss also may occur of loose fruits which arerelatively drier (8) and richer in oil on dry matter.Moreover, it may be observed that a certainamount of dry matter finds its way into the conden-

sate resulting from sterilisation. It is difficultto ascertain which part of this loss comes from thebunch stalk and which originates from the fruit.CONCLUSIONS

The calculation of the percentage recovery in amill implies necessarily the determination of theamount of oil entering the factory. That determina-tion requires the analysis cf the bunches or theloose fruit. The analysis of bunches provides theoil content with an accuracy of 1% only if mere than3,000 bunches of a batch of standard homogeneity aresubjected to test. That degree of uniformity pro-bably prevails in some sectrrs, such as blocks ordivisions of one estate during a certain period oftime. The number of bunches that must be drawndaily for the computation of the monthly recovery isabout 100. The relative error must not exceed 1%, .failing which the calculated percentage recoveryloses its usefulness and, particularly, the facultyof detecting any abnormal loss occurring duringprocessing.

. - . -

Documents

Monggana Volume 1 Chapter 1