1976_Brokensha_Evaluation of the Press

8/3/2019 1976_Brokensha_Evaluation of the Press

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212 Proceedings of' The South Afvican Sugar Technologists' Association -June 1976

EVALUATION OF THE PRESS METHOD FOR CANE ANALYSISUNDER SOUTH AFRICAN CONDITIONS

By M. A. BROKENSHA and S. KINGSugar Industry Central Board

andJ. P. LAMUSSE

Sugar Milling Research InstituteAbstract

Cane analysis by an inferential method using the press isdescribed. Experiments conducted to assess the method haverevealed certain limitations, more particularly the results ob-tained when there is a significant level of soil present in thecane samples. Variety, and whether the cane is trashed orburnt, also have influence on results.Introduction

Small hydraulic presses have been in use in many labora toriesto extract juice samples from cane. T he first systematic attem ptto use a hydraulic press for routine cane analysis appears tohave been made by Tanimo tos in Hawaii when he comparedthe press and pol ratio methods.Jam ois5 in G uadeloupe carried out considerable experiment-ation on the use of the hydraulic press in conjunction with acore sampler for cane analysis to be used for cane paymentpurposes. Work along the same lines was carried out in R eunionby Caza12 and Boyer de la Giro dayl and finally by Hoarau31who showed that the ratio of sucrose % absolute juice to

sucrose % extracted juice was equal to the ratio of juiceextraction t o sucrose extraction.Hoarau's work and his definition of the relationship betweenjuice extraction and sucrose extraction improved the accuracyof cane analysis by the press method and led to its acceptanceas the official method of cane analysis for payment purposesin Reunion and other countries. This led to an inferentialmethod of analysis which only involved massing the presscake and analysis of the exp ressed juice.The work carried out in Reunion has shown that fibre %cane, degree of cane preparation, pressure and time of appli-cation had a definite effect on the results obtained by the pressmethod. The effect of other variables such as cane variety,trash a nd soil was not reported a nd i t was considered necessaryto have some information on their effect on cane analysis usingthe press. The Sugar Milling Research Institute acquired aPinette Emidecau hydraulic press operating at 25 MPa to testthe method under South African conditions where there isprobably a larger variation in cane quality than in Reunion.After initial tests at the Sugar Milling Research Institute,the press was transferred to th e Tong aat sugar mill where theSugar Industry Central Board (SICB) carried out analyseswhich encompassed the following aspects:(a) Determ ination of pol, brix an d fibre % cane by theanalysis of both the extracted (press) juice and thebagasse (press cake) for pol and brix as well as the

analysis of the press cake for moisture content.(b) Investigation, using the above data, into the relation-ships necessary for obtaining pol, brix a nd fibre % canesolely from the press juice pol and brix data and themass of the press cake, for all samples analysed as wellas for the cane varieties encountered.

(c) Comparison of the cane analysis data obta ined via theprocedure described in (a) with that obtained via thedirect analysis of cane procedure as described in theManual of Cane Sampling and Analysis for South AfricanSugar Fac tor ie ~ .~(d) Investigation into the effect of soil and trash in cane.(e) Investigation into the extent to which variations in

degree of cane preparation affect results obtained bythe press method of cane analysis.Description of the inferential method of press analysis

A known mass of shredded cane is subjected to pressing inthe hydraulic press- he time of pressing and pressure app liedbeing specified. The press juice is collected and analysed forpol and brix per cent. The bagasse residue (press cake) isremoved from the press and m assed. From this data fibre, poland brix per cent cane are calculated as follows:Fibre % cane

Numerous analyses are carried out to establish a relationshipbetween mass of press cake and fibre per cent cane. In eachanalysis the cane mass a s well as the press cake mass are notedand the press cake analysed for moisture and brix from whichfibre per cent is inferred. Fibre per cent cane is then calcu-lated as follows: Fibre % press cake x press cake % caneFibre % cane =100

Thereafter the cake mass and fibre % cane are related vialinear regression analysis resulting in a general equation ofthe typeF c = a + b M . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .where a and b are constants and M = cake mass. (1)

Pol % caneWith the fibre % cane available via equation (1) it is but ashort step to calculate the absolute juice per cent cane. Thenext step necessary is to determine a relationship between polper cent abso lute juice and pol per cen t press juice. With thisrelationship established it is then possible to calculate the polper cent cane.Use is again made of the analytical data obtained in theprevious section to calculate the ratio of pol % absolu te juiceto pol % press juice (C factor) for each test. These calculationswill show that the ratio is not a constant but, as shown byHoarau, varies inversely with fibre % cane -i t will also varywith cane preparation and pressure but these two variablesare standardised. Thus the relationship between C and fibre% cane must first be established so a s to allow the ready deter-mina tion of the C factor fo r any fibre level encountered. Linea rregression analysis is used to relate C factor to fibre % canevia an equation of the type


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edings of The South African Sugar Technologists' Association -June 1976 213C = a - b F c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

= Fibre % cane. (2)Thus given the mass of the press cake and pol % press juice,% cane is first determined via equa tion (1); theC factor determ ined by equ ation (2) and p ol %

C x Pol p j x (100 - Fc)Po l % cane = . . . . . ,.. .100 (3)Po l % absolute juicewhere C =Po l % press juicePol p j = Pol % press juiceF c = Fibre % cane.% cane

The same procedure as used for the pol % cane determina-C factor- eing the ra tio of brix % absolute juicebrix % press juice - s established. Thereup on brix % cane

C x Brix p j x (100 - c)Brix % cane = . . . . . , . . . .100 (4)Brix % absolute juicewhere C1 = Brix % press juiceBrix p j = Brix % press juice

Fc = Fibre % cane.Apparatus

The hydraulic press used was a 45-ton Pinette Emidecau0 B 102. The maximum specific load on the materialkg/cm 2 for a gauge pressure of 25 MPa. All othe r

f Cane Sampling and Analysis for South African Sugar

Experimentalons for relating press cake mass to jibre % cane,% cane to the C and C1actors

A sample of mill-prepared cane (i.e. sample taken from the

this sample of shredded cane, 1 000 g were massed andload of 268 kg/cm2 was applied for 4 minutes. The press- ol was

For the latter determ ination samples

The press cake was removed from the press and massed. Oftract from the cold digestion was analysed for

1000 g a nd 300 g.In all 104 samples were analysed in this way.

Investigation into the eflect of soil and trashA set of seven samples was analysed to determine more fullythe effect of soil and trash. Sufficient whole stick cane fromwhich all trash and tops had been removed was cut into 5 cmbillets and then sh redded to provide three sub-samples. T o onesub-sample soil was added to constitute 5% by mass whilst toanother dry trash was added to constitute 1 0% by mass. Allthree samples were given a further shredding before being

subjected to the press procedure as described above; pressjuice and cake also being analysed as described before.Investigation to determine the eflect of variations in canepreparation

A set of ten samples was analysed to determine the effect ofpreparation of the cane. In this case, from a sample of mill-prepared cane, one sub-sam ple was pressed "as is", one sub-sample was shredded for o ne second before being pressed a nda further sub-sample was shredded for five seconds beforepressing. Analysis of press juice and cake was as-describedabove. A furthe r p ortion of the five-second shredded cane wasanalysed by direct analysis of cane procedures as describedin the Manual of Cane Sampling and Analysis for Sou th AfricanSugar Factories. In conjunction with the above analyses, thepreparation index was determined on the three differentpreparation levels.

Results and DiscussionAs mentioned earlier 104 samples were analysed in ord er todetermine the relationships necessary for obtaining pol, brixand fibre % cane from the press cake mass and press juiceanalysis. In each case the press juice was analysed for pol a ndbrix, the mass of the cake determined as well a s pol, brix andmoisture % cake using direct analysis of cane procedu res. Fromthese analyses the pol, brix and fibre % cane were computedas well as the equations necessary for obtaining this informa-

tion solely from the press cake. In parallel with each of theabove cane samples a second sample was analysed for pol,brix and fibre % cane via the SICB direct analyses of caneprocedure. A verage results of the press juice a nd c ake analysesas well as the comparison of the two sets of pol, brix andfibre % cane data are shown in Appendix A.Press cake m ass versus jibre % cane .

Regression equations relating press cake mass to fibre %cane (via fibre % press cake) were comp uted in respect of thetotal n umb er of tests as well as for. he tw o major cane varietiesencountered, i.e. NCo 376 and N55/805 -the former beingseparated into trashed and burnt cane categories. Results areshown in Table 1 and plotted in Figure 1.

101240 260 280 300 320 340 360 380 400Mass of! cake (g)

F IGURE I Mass of cake vs fibre % cane.


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\214 Proceedings of The South African Sugar Technologists' Association - une 1976It is seen from Fig. 1 that there is similarity between thecurves found for the trashed and bu rnt categories for NC o 376but that the curve for N55/805 is dissimilar from those foundfor NCo 376. It has been found from a study of the press cakemass and fibre % press cake data that for NCo 376 the ratioof fibre % cake to press cake mass is constant while there isa distinct negative correlation in the case of the N55/805variety, i.e. the fibre % press cake decreases with increase in

press cake mass. In other w ords there is an increase in thejuice to fibre ratio with increase in cake mass. A satisfactoryexplanation for this has still to be found.Because of the variations in slope for the various canecategories there do appear to be limitations 'in the prac ticalapplication of the press method.

Pol % press juice and pol % absolute juiceRegression equations relating the ratio of pol % absolutejuice to pol % press juice (C factor) with fibre % cane werecomputed in respect of the various cane categories, and areindicated in Table 2 and plotted in Figure 2.

The relationship between C and fibre % cane is inverse andthis can be ascribed to two factors, i.e, the relationship pol %absolute juice to pol % undiluted juice and the relationshippol % undiluted juice to pol % press juice. Thus C can beexpressed as follows :Pol % absolute juice Pol % undiluted juiceC = XPol % undiluted juice Pol % press juice

The finer the cane preparation and the higher the pressureapplied the more nearly will the second factor approach unityand C therefore tend toward the relationship pol % absolutejuice to pol % undiluted juice.In the absence of fibre it is clear that C should be equal tounity, yet in Table 2 the intercept for all equations (exceptvariety N55/805) is greater than unity. An exp lanation for theintercept found being greater than unity is that the relation-ship between C and fibre % cane is non-linear, and that infitting a linear relationship in the fibre range encountered inthe experiments there is an over-determination of the slope

towards zero fibre. The relationship between the ra tio of po l %absolute juice to pol % undiluted juice and fibre % cane isclearly non-linear and it is unlikely that the ratio of pol %undiluted juice to pol % press juice increases with fibre %cane. Hence the deduction of a non-linear relationship.Fo r the twenty N55/805 results there is effectively no corre-lation between C factor and fibre % cane and this matterrequires further investigation. A very real problem in the caseof N55/805 and to a lesser extent for NCo 376 has been thelimited fibre range encountered in the tests and it is felt thatthis has contributed to the low correlations.As in the case of the relationship between press cake and

l o 1'1 1 2 1'3 1'4 1'5 ' 1'6 1'7 18 fibre O /, cane there are variations in the slope for various caneFibre % caneFIGURE 2 Fibre % cane vs. C factor.

catego;ies and again this does appear to impose a limitationon the practical implementation of the press method.TABLE 1

T = Trashed caneB = Burnt cane SD = Standard DeviationFc = Fibre % cane

VarietyAll samples . . .NCo 376T . . .NC o 376 B . . .N55/805 T . . .

M = Mass press caken = number of tests

Fibre % cane( f s D >15,45

( z t 1,64115,82( 5 1,86114,26( 5 1,72115,67(& 039)

n104511422

TABLE 2

Regression equationFc = 1,48 + 0,0420MFC = - 0,37 + 0,0477MFc = 1,70 + 0,0415M

T = Trashed caneB = Burnt cane

VarietyAll samples . . .NCO376 T . . .N C o 3 7 6 B . . .

SD = Standard DeviationFc = Fibre % cane

Corr.Coefficient0,920,940,94

Pol % absolute juiceC = Pol % press juicen = number of tests

Standard error ofregression esimatef ,63f ,61f 3

Fc = 6,42 + 0,0270M f 0 3 2

Standard error ofregression estimatef ,011f ,010& 0,010

n1045114

f ,012I 22N55/805 T . . .Fibre % cane(k D)

15,45(f 1,64115,82( 5 ,86114,26(= t ,72115,67(f ,891

Regression equationC = 1,0508 - ,006543 FcC = 1,0456 - 0,006181 FCC = 1,0822 - ,008601 FC

Corr.Coefficient- ,69- ,75- ,82

C = 0,9865 - 0,002499 Fc - ,18


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Proceedings of The South A fiican Sugar Technologists' Association -June 1976TABLE 3

T = Trashed caneB = Burnt cane

SD = Standard DeviationFc = Fibre % cane

Standard error ofregression estimate& 0,018

0,020f ,017f ,013

Bx % absolute juiceC'= Bx % press juicen = number of tests

Corr.Coefficient- ,35- ,44- ,40- ,07

TABLE 4

I Fibre % cane( k SD115,45(& 1,64115,82( k 1,86114,26

(A 1,72115,67(3 ,891

VarietyAll samples . . .NC0376 T . . .NC o 376 B . . .N55/805 T . . .

1 Cane (press juice + cake) I Cane (theoretical)

Regression equationC1= 1,050 - 0,00412 FcC1= 1,070 - 0,00509 FCC1 = 1,048 - 0,00433 FCC1 = 0,995 - 0,00101 Fc

n104511422

Clean . . . . . . ..Soil (5 %) . . . . . .Trash (10%j . . . . . .

Clean . . .soil (5%) . . .Trash (10%) . .

Brix % press juice and brix % absolute juiceLow correlations were found between the ratio of brix %absolute juice to brix % press juice (C1 factor) and fibre %cane. These are listed in Table 3 above.

Press juice

..loi l (5 %)Trash (10 %j 18,02This relationship is discussed further in the next section.

Press cake

Pol16,071 5 , ~14,45

0,924 0,962

Influence of extraneous materialAverage results of a limited number of tests (7) to determinethe influence of soil and trash a re presented above in T able 4.Individual results are shown in Appendix B.

Purity89,989,988,2

Pol19,OO18,9719,07

Sufficient soil and trash (dry leaves) were added to sub-samples of shredded clean (trash-free) cane to constitute 5 %of soil and 1 0 % of trash in. he respective sample. (All canesamples, i.e. clean, with soil and with trash, were subsequentlyre-shredded before analysis.)

--Brix21,1321,ll21,61

Mass250 g277 g395 g

Brix18,1317,4117,05

The soil added to the cane was analysed for moisture andwater solubility with the following results:Soil type % Moisture % Water solubilityFernwood 0,3 1 o

Fibre44,6055,0745,73

The dry leaves used for the trash addition were analysed formoisture content only with the following result:Trash type % MoistureDry leaves 12,O

Purity79,878,573,3

Pol7,316,087,38

Moist.70,5967,3564,93

With the above analytical data as well as that for the cleancane samp les it was possible to calculate theoretical results forthose samples to which soil and trash had been added andcompare them with actual.The average C factors and C1 factors were calculated fromthe analytical data and are also shown. Individual samplefactors are reflected in Appendix B.Some of the points to no te from a study of the data in Table 4are the following :(a) The press cake m oisture for the sample with soil issubstantially lower than the mo isture recorded by eithe rof the other two samples (clean cane and cane withtrash).(b ) The moisture % press cake for the sample with trashis also lower than the clean cane sample, but to a muchsmaller degree than the sample with soil.(c) The extent to which soil is washed out of the press cakeinto the press juice must be quantified.(d) The fibre % cane figure recorded for the sample withtrash is persistently lower than the theoretical fibre %

cane.( e ) Th e C an d C factors for the cane sample containingsoil are higher than those for the clean cane sampledespite the former sa mple being associated with a fibre% cane considerab ly in excess of the latter sam ple.

Brix9,167,7510,07

Fibre11,2815,241 8,02

Moist.46,2237,2044.15

Purity88,688,s84,8

Pol16,0715,2714,46

Brix18,1317,2316,32

Moist.70,5967,0564,73

Fibre11,2815,7218,95

Purity88,688,688,6


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216 FProceedings of The South Afvican Sugar Technologists' Association -June 1976(f) The cane sample with trash has a C1 actor only mar-ginally lower than the clean cane samples despite afibre difference of nearly 7 units.These points are discussed below.

Variations in moisture % press cake levels and the relevancethis has to Jibre % cane determinationFur ther tests were conducted to confirm the trends indicated

in Table 4. I n these additional analyses the same quantities ofsoil and trash were added as before but only the mass andmoisture con tent of the press cake were determined. The aver-age moisture figures for all samples including those used forthe Table 4 data are given below in Table 5.TABLE 5

Moisture % press cake

It is seen that for soil there is confirmation of the trendindicated in Table 4 bu t in the case of trash there is seeminglylittle or no effect on the press cake moisture. However theresults for the samples with trash must be treated with cautionsince in the second run of 5 comparisons all the trash samplemoistures were higher than those of the clean cane samples,which is a reversal of the trend found in the first run of 7comparisons. Thus although the overall result indicates thatthe addition of trash has virtually no effect on the press cakemoisture this aspect requires further work before a definiteconclusion can be drawn in this regard.Returning to the sample containing soil, a twofold reasonis put forward for the low moisture of the press cake:

(a) The soil added to the cane sample contained virtuallyn o moisture, i.e. either as surface, absorbed or bondedas brix-free water.(b) The juice to insoluble matter ratio is lower in the presscake with soil than in the clean cane press cake. Lessjuice is retained in the cake per unit of soil than isretained per unit of vegetable fibre.

Moisture %

It is clear that under these conditions, i.e. in the presenceof soil, the ratio of press cake mass to fibre % cane variessignificantly from that for clean cane or cane with trash andhence any simple formu la which merely relates press cake massto fibre % cane as a fixed ratio or near to a fixed ratio doesnot hold for all conditions.

Cleancane42,7244,48

Returning to the data in Table 4 it is seen that a formulaFibre % Cane = 0,0455 x Mass cake satisfies the averagesituation for both the clean cane and cane with trash samplesbut under-determines the fibre % cane fo r the sample with soilby 2,64 units (refer to Table 6).

Diff.5,78

Cane + extraneousmatter36,94 (soil)44,30 (trash)

TABLE 6

SD& 2,85

SE0,59

SampleClean . .

0,18

n23

Soil 1 .Trash . .

& 3,14 , + 0,91 I2

Since there is no simple and rapid method for determiningthe am oun t of soil in order to correct for its presence, it appearsthat the method for determining fibre % cane by the applica-tion of a ratio to the cake mass is limited to situations whereall cane delivered to the mill has 'little or no soil present.Where this latter condition does not obtain it is necessary to goa step further than the mere determination of cake mass andalso to determine the moisture % press cake for all samples.With this additional information it is possible to determine afibre % cane using the method accord ing to Tanimoto . Essen-tially this procedure assumes that the total moisture in thepress cake belongs to the residual juice and that the residualjuice has a brix concentration equal to that of the extractedor press juice- his implies no brix-free water. Any differencebetween press and residual juice brix will also introduce anerror although this is likely to be small with finely-preparedcane.

Masscake(g)

Using the data in Table 4 the fibre % cane as determinedby the S ICB indirect method is compared in Table 7 with theTanim oto fibre. The fibre derived by the application of a con -stant factor to the press cake mass is also included forcomparison.

Fibre % caneDerived(Fc = 0,0455M) Analysed 1 Diff

TABLE 7

M = Mass cake7lean .SoilTrash . .

Because of the assumption of no brix-free water the Tanim otofibre % cane is under-determined and it will be necessary tocorrect this by means of a factor relating all the individualfibre determinations to a m aster fibre % cane as obtained viathe summation of the fibre present in final bagasse and mixedjuice. However there is still the problem that the percentageerror via the Tanimoto method is not uniform, indicationsbeing that it is the greatest for clean cane.Removal of soil in the press cake by the press juice

Th e press juices obtained fr om clean cane and fo r the sam ecane but to which soil had been added to constitute 5% of thetotal mass were each analysed in toto for insoluble solid con-tent according to the method published by Prince.' Twentysuch comparisons were carried out, and in all the same soil,i.e. Fernwood sand, was used. The increase in insoluble solidsconten t found in the press juice obtained from the cane samplewith soil was attributed to loss of soil from the press cake.Results are given in Table 8.

Fibre % cane

TABLE 8Insoluble solids % press juice

methodICB11,2815,2418,02

c = 0455.)11,3812,6017,97

Tanimotomethod10,4514,6417,25

Di ff0,23

Insoluble sqlids %press julce

n20

SD& 0,lO

Cane +soil0,48

SE& 0,02

Cleancane0,25


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Proceedings of The South African Sugar Technologists' Association - une 1976Based on a cane sample mass of 1 000 g and a n average presscake ma ss of 315 g the mass of press juice by difference isgiven as 685 g. On this mass, an increase in insoluble solidsconte nt of 0,23 units % will account for a redu ction in fibre %cane by 0,158 units. This loss is not excessive or of particularsignificance but more work is required for different soil types.

Influence of soil and trash on the C nd C1 actorsIn T able 4 average C and C1 factors are show n for the threecategories of cane quality, i.e. clean cane, cane with 5 % soiland cane with 10% of dry leaves. It is seen that relative tothe factors recorded fo r the clean cane sample, the sample withsoil has C and C1 factors that are too high for the fibre %cane figures concerned. Furthe rmor e the C1 factor fo r the can esample with trash also appears to be too high.In the case of the cane samples with soil the elevation infactor level can be explained by the fact that the soil containedno brix-free water. As a consequence the pol % absolute juice(and pol % cane) will be higher for the sample with soil thanfor a sample of the same fibre % cane content but in whichall of the fibre is vegetable fibre capable of containing brix-free

water. This is illustrated in the example below which assumesthat vegetable fibre in the cane contains 25 % brix-free water.Sample . Samplewithout soil with soilPo l .% undiluted juice. . . . 18,71 18,71Vegetable fibre % cane . . . 15,24 10,78Soil %cane . . . . . . - 4,46: Fibre % cane . . . . . 15,24 15,24

Sample without soil18,71 x (100 - 1,25 x 15,24)Pol % absolute juice = (100 - 15,24)- 17,87Pol % press juice = 19,OO17,87 18,71: C factor - - -8,71 19,OO- 0,941Sample with soil18,71 x (100 - 1,25 x'10,78 +4,46)Po l % absolu te juice = (100 - 15,24)- 18,12Pol % press juice = 19,OO18,12 18,7 1: C factor - - --18,71 19,OO- 0,954The above has therefore show n that the presence of soil canresult in significant variation in C factor level from that re-corded for cane of the same fibre % level but in which soil isabsent. Similar reasoning to the foregoing can be used toexplain the elevated C factor for the cane sample with soil.

In so far as the cane sample with trash is concerned it isseen (Table 4) that despite the large fibre % cane differencefrom the clean cane sample, there is very little difference in C1factor levels. A possible explanation is that the brix presentin the trash is extracted with greater difficulty than the brixpresent in the rest of the cane. Consequently for the samplewith trash the press juice brix will be lower than the undilutedjuice brix to a greater extent than would obtain (if at all) forclean cane. Therefore the ratio of brix % undiluted juice tobrix % press juice (and in turn the C1 factor) will be higherfor the sample with trash than for the corresponding cleancane sample with the same fibre % cane level.

However there is another possible explanation and this maybe linked to the influence of suspended matter on the refracto-metric brix determination. Particularly in the case of thesamples with trash, the filtrates appeared cloud y and the pres-ence of suspended matter may have introduced a high percent-age error at the low levels of brix- pproximately 1 unit-encountered in the analysis of the press cake.Thus further work is necessary to determine whether theelevation of the C factor in the presence of trash is due to

poorer extraction of trash brix or due t o limitations of presentanalytical methods. Indication that it may be due to the latteris given by a study of the data in Appendix A in which pol,brix and fibre % cane were determined in 104 samples viatwo avenues, i.e. :(a) analysis of press juice and press cake for pol and brix(press cake analysis via cold digestion) with the presscake being further analysed for fibre (indirect meth od);(b) analysis of a duplicate cane sample by the standardSICB procedure.It is seen from the comparison that there is a definite biasin the brix determination with that determined via procedure(a) above being the higher- ending support to the contention

that there could well be over-determination of the press cakebrix.Whatever the reason for the trash elevating the C1 level itis clear that this has contributed to the poor correlations foundbetween C1 and fibre % cane. Any soil present in cane sampleswill also upset the correlations both for C and C1.

The eflect of cane preparationAverage results of 10 tests, each consisting of a comparisonof the press results on mill-prepared cane, mill-prepared caneplus an additional one-second shredding and finally mill-prepared cane plus five seconds shredding, are given below.As anticipated the press cake mass for the sample with mill

preparation alone is higher than that of the cane subjected toa further five seconds shredding. The rise of press juice poland brix with increased cane preparation must be viewed inthe light of parallel increase in the cane pol and brix data -the cane d ata being obtained via com plete analysis of the presscake and the press juice. There clearly has been moisture loss(i ) Mill preparation . . . .(ii) Mill + 1 sec. shredding . . .

(iii) Mill + 5 secs. shredding . . .Mean Diff.(i)-(iii) . . . . . . .Standard ~jeviation. . . . . .StandardError . . . . . . .

CaneFibre % cane(Fc = 1,48 $ 0,042M)153915,5515,170,42f ,56f ,18

Masscake(g)33633532610

f 2,6f 4,O

Pol %12,2012,2812,31- , l lf ,22i ,07

Press juiceBrix %

14,6814,7814,87- ,19f ,28f 9

Pol %15,1415,2315,30- ,16k 0 2 1* ,07

Fibre %14,7514,9815,09- ,34

& 0 3 2zk 0,16

Brix %17,4417,5817,82- ,38f ,19i ,06


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Proceedings of The South Afiican Sugar Technologists' Association - une 1976 219APPENDIX B

Analysis of cane samples with and without extraneous m atter. Fo r the soil and trash (dry leaf) samples sufficient of each were added to sub-samples ofshredded clean (trash-free) cane t o constitute 5 and 10 per cent respectively of the sub-sample mass.

(I) Clean. .(1) Soil . .(I) Trash. .( 2 ) C l e a n . .(2) Soil . .( 2 ) T r a s h . .( 3 ) C l e a n . .(3) Soil . .( 3 ) T r a s h . ,( 4 ) C l e a n . .( 4 ) S o i l . .(4) Trash. .(5) Clean. .(5) Soil . ,(5) Trash. .( 6 ) C l e a n . .( 6 ) S o i l . .(6) Trash. .(7) Clean. .(7) Soil . .(7) Trash. .AverageClean. .S o i l . .Trash. .

Press

(1) . . . .(2) . . . .(3) . . . .(4) . . . .( 5 ) . . . .(6 ) . . . .(7) . . . .Mean . . .

Po l19,3519,2819,4019,3919,4419,6319,9019,8119,8018,4218,3218,3019,1719,1419,3919,7619,7319,7117,Ol17,0517,2319,OO18,9719,07

cake

C1 factorsfactors

Iress juiceBrix Purity

21,01 91,s20,94 92,l-71,37 90,s

Clean0,9610,9590,9500,9470,9460,9500,9590,953

Trash0,9530,9670,9650,9730,9650,9610,9530,962

Clean0,9650,9760,9620,9680,9580,9670,9740,967

21,3121,3421,8821,6121,5522,0320,46209020,8021,6121,6122,1222,1522,0922,6519,7319,822 0 921,1321,1121,61

Soil0,9760,9730,9690,9720,9790,9760,9650,973

Purity91,491,287,O89,s89,O86,l90,991,O87,388,l88,784,987,686,s83,787,787,s82,984,985,281,388,688,584,s

91,O91,l89,792,l91,989,990,O89,s88,O88,788,687,789,289,387,O86,286,O84,s89,989,988,2

Soil0,9660,9510,9590,9600,9560,9560,9560,958

Trash0,9140,9280,9380,9380,9210,9150,9170,924

Brix18,0417,4116,7218,4117,7617,4818,5517,8017,4717,8316,9116,7418,3217,8517,4419,0318,2317,8716,7615,9215,6518,1317,4117,05

Mass-------53278391246281396244266389240260345263288412246270412

,260295419250,3276,9394,9

Brix9,088,269,499,518,6010,769,097,4210,329 3 47,OO9,039,098,5710,769,497,8211,088,316,599,069,167,7510,07

Po l8,047,026,997,526,538,057,526,188,137,135,566,437,326,307,737,305,767,846,34$256,46

' 7,316,087,38

Press caneMoist.70,6567,7665,3870,1267,7465,1270,7067,4464,6872,1668,3666,0170,1666,4964,2569,8266,3564,2370,4667,3164,8370,5967,3564,93

Fibre----1,3114,8317,9011,4714,5017,4010,7514,8017,8510,Ol14,7317,2511,5215,6618,3111,1515,4217,9012,7816,7719,5211,2815,2418,02

Moist.46,1838,4844,6846,8039,8045,1846,9436,9143,6848,7736,5340,9247,1237,0544,7945,1635,0545,5842,5536,5644,3146,2237,2044,15

Fibre44,7053,2545,7743,6351,5943,9343,9755,7345,8941,6456,5650,Ol43,7954,3844,4545,3557,1343,4549,1456,8546,5944,6055,0745,73

~ ~ ~ ~urity ( Po l88,s85,O73,779,175,974,s82,783,378,s74,779,471,280,573,s71,s76,973,770,s76,379,771,279,s78,s73,3

----6,4915,8714,5516,4715,8115,0516,8716,1915,2615,7015,OO14,2116,0515,4414,5916,6815,9514,8114,2313,5712,7216,0715,4014,45

1976_Brokensha_Evaluation of the Press

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