Studies on the concentration of apple juice by reverse osmosis : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Food Technology at Massey University

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Copyright is owned by the Author of the thesis. Permission is given for

a copy to be downloaded by an individual for the purpose of research and

private study only. The thesis may not be reproduced elsewhere without

the permission of the Author.

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A th2nin prcsnnted in partial fulfilment

of tl1" requirements for the de~ree

of Mas 1.:) r of Technology in

Food Technol oey at Massey University.

DAN LE VAN 1978

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The Reverse Osmosis (RO) process nnd its food ir,d.u8try Because most of the work published in the li teraturc on the concentration of frui i; jvih!:~ L,y RO wa:::

empirical, it wns decided to select one fruit juice (apple juice) and study the retention of certain comJionents (numely sugurs and acids) whc·n that juice was concentrn Led by RO.

A method wus developed for the an&lysis of sugars and non-volat-ile organic acids in ap1Jl8 jLtice. In this method, acids wert· prc-cipi ta tcd as their le:ud salts from fruit ethanolic extracts, and the sugars in the rema.i.ning supernatant and washinUJ were part:i.cir.a tcu into aqueow; m1;th1,nol. 'l'hese preparations with

ii.

internal ::;ta.ndards were then dried :rnd converted to their

trimethyl:::ilyl de1·ivatives for anaJ yf-;i.:1 by ,~as-liquid chromatography.

The meth(!)d provi<.kd n rupid and :::;j in1,.Lo procedure for tl1u concurren L separation, identification and qwint:i.tativo snaly:::,.·is of suears and non-volatile acids in apple juice.

A pilot-plant scale Abcor '['M5-1tl- RO rr.oclule was used in this stud.y so that the results obtuincd could be applied. to industrial processing. Preliminary CXT,'2l'iments were conducted with dilute sul t solu Lion~~ to en,;u rt' that the membrane performed satisfactorily, and to monitor any chhngcs in the operating

characteristics of the membrane ns the experimental work progre:::::ied. These data provide the common means for comparing different RO

sys terns. The results obtained es i,;_wlished that the membrane performed satisfactorily, and that the membrane characteristics (Permeate flux and% Rejection) responded as expected to changes in the operating parameters of pressure, temperature, flow rate, concentration and operating time. The membrane characteristics did not alter significantly over the time during which the

experiments reported here were carried out.

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A cv.rrcnt theory ( the Kimura-Sourirajan analysis) ,vru:, used in an attempt to p ·edie; t the membrane performance of the RO modu:tc i·:hen the system sodium chloride-water was used as test solution. Tlie Kimura-Sourirajan analysis had previously led to

the development of a set of basic transport equations which, together with the correlations of the RO experimental data, enabled the prediction of membrane performance from a minimum of experimental dat::i.. The application of this analysis to the RO system under study did not establish nny significant correlations between the solute transport parameter (D AM/K~), and feed concentration and operating pressure; neither were the average UJass-transfer coefficient vulues (k) significantly

correlated with feed flow rate. Experimental results obtained suggested a more corr.plex relationship between these parameters, and the narrow range of feed flow rates under which the RO system was able to be operated rwan l. that tho Kimura-Sourirajan analysis could not be used to meaninifully predict the performance of the membrane.

A further attempt wan made to prt~d.ict membrane performance from a knowledge of the 'l'aft number.~ of the sugurs ancl acids

present in the juice. Experiments carried out on model solutions of sugurs and acids prHsent as sincle components or as complex mixtures confirmed the Taft number us li crjterion for predicting the organic rejection of the RO membrane. It was also

established that molecular weight was indjcative of solute rejection, higher molecular weights gave higher rejection by the membrane. Results ol,t:tined further confirmed the fact that the mechanism of solute rejections by RO cellulose acetate

membranes involved both preferential absorption and capillary flow of solutes through the membranes.

Finally, actual apple juice was concentrated by RO and the results obtained on permeate flux and solute rejection confirmed those found previously with model solutions of sugars and acids. It was established that apple juice (initial

concentration 11°Brix) could be concentrated to 35°Brix at 7C

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and 99 atm pressure without any nir;nificant los~, of suears and organi c nei.ds. Experiments were also carried out to as:Jcss the advantage of opr:rat::.r:g :.,t a high0r temperature (20 C), since any increase in flux would b0 desir::tbl(:: from a comnwrcial point of vt.ew. The end-to-end flux or the TM5-14 module was found to te 16.'1-

1 / 1/h r

^a^t ^{20 C c}^ompared ^{to 11.}⁷

1 / n/ lir

^{at 7 C}

when sint;~.e strength apple Juice was concc-:ntr<l ted to ~;5° •,r·i.x under maximum pressure ( 99 a tm), an incrc1a:~(i in flux of ;W%.

1'h<" rilot pLmt data thus obt&i.n0d for the RO module were .:.i.ppl:i.cd to a study of the reasj !Jili ty of using

no

us a pre-concentration stei, prior to ,1v1.Lporation.

compriain:: of 296 modules (mE-mbrane are,, :-508

An HO plant

m2) with a permeate

'>

flux of 20. 7 1/m' hr was found Lo be: J"c[,si.ble for concent:rc1ting the juic1· from 11°Brix to 20°Brix in 7.5 hours.

'l'hc economy of :;uch ;, proc-G:;s 1-.aG also assessed, und compared wi th that obtained by us:i.n1~

,t

^t^ri^pl^e ⁰^f'f^c^ct^AT'V ^plate

evapo1·a lOJ'•

iv.

A comparison of the concent1~tion costs ($ /to1me of water removed) of tJ,e two sys toms re:vc;,l..:d that HO w.::tG more than twic.;,.J as expensive than evaporc.tion ($122 comparecl to $51) fol'.' 900 operationAl hours pr-r ycn.r, tlius cun1·irn1ing rc:.iul b-: l'.rom the r,ubli . .;hed literature, which also sue-t~estcd th1d. the cu~, L of IW was compe Li tive with pla to evaporation when operated year rour,cl (6,300 hours/ year). The results found in this study indicated that the annual operating costs for RO ($142,200) were almost twi ce as high as the equivalent for plate evaporation ($71 ,500). An well, the capital investment for RO was substantially higher than that for the equivalent plate evaporator ($700,000 compared to $282,300), thus makine RO very unattractive for short seasonal operation.

Thus i t is concluded that the use of RO as a preconcentration technique in apple juice processing will never be realised unless capi tal costs are reduced considerably and operating hours are

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incr0ascd substnnti.alJy. On the basis of this study, it is not financially economical for thl Apple and Pear Board in Hastings

to consider RO for the p:rcconcentration of apple juice when the capacity of their present cvapontor is no longer adequateo

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ACKNOWLF.DGEMENTS

I wish to thank the following people:

My supervisor, Mr. G.L. Robertson, for his valuable assistance and encou.cagement throughout the course of this study, and without whose help this thesis would never have been completed.

Mr. M. Gyde of the Apple and Pear Board Ltd., Hastings, for providing the apple juice used in this study.

Dr. G.M. Wallace, Mr. M.J. Reeves, Dr. I.W. Boag, Mr. B. Imison and Mr. F.B. Walter, for helpful discussions on some aspects of the work.

Messrs. 'l'.M. Gracie, G. Burton anJ Miss S. Quin, for technical assistance.

Khanh, Long and Sharon for thei:r encouragement.

'

Mrs. M.M. Garden and Mrs. M. Booker for typing this thesis.

This study was supported by a Brooker Ru:Jearch Award, a Faculty grant, and a Colombo Plan Award. The reverse osmosis module was purchased in part from a University Grants Committee grant-in-aid awarded to Mr. G.L. Robertson.

' ...

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"WOng. khong kho vi ngan song ^,..

n.gai nui ^I•

• ^e^song"

T1ng ^Ba toi

., _;

each nui,

~

ngu 1>i

va

'

,

_'

ma kho vi long '

/ ,. I

Me qua co

Dan Le Van September, 1978

nguii

vi.

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CHAPTER

3

"Membrane ch.s.racteristics and

prediction of membrane performance" 49 Section I "Membrane characteristics" 50

1. Mechanism of Reverse Osmosis 50

2. Concentration polarisation 51

3.

Description and oper:ition of the TM5-14

module 51

4. Experiments with dilute salt solutions 55

5. Results 58

6. Discussion 65

7.

Conclusion 66

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viii.

Section II "Predictivn of membrane performance using

the Kimura-Sourirajan analysis" G8

1 • Introduction

2. Experimental procedure 3. ^Results

4.

^Di^scw_,::;^j_ôn 5. ^Cônclusîon

Section III "Use of Taft numbers to predict membrane performance"

1. Introduction 2. Ex~erimental 3. Hc:mlts 4. Discussion

5.

^Conclus^ion

CHAPTER tJ "Reverse Osmosis of lifiphl juice"

1. Introduction 2. Experim,mtcll 3. R,.~ul ts tJ. Discussion 5. Conclusion

68 C8

81 91

~)3

94

102 106 109

111

112

11)

11 3

115 121 L?2

CHAPTER 5 ¹¹Êconomic^(:valua^L"i.ûnôf^ReverseÔ~miosî::;" ¹²³

1. Introduction 124

2. Current evaporation ~l.'r .. t em 1.:',1

3.

4.

Proposed Revl' rse Osmo:,is ::ys tem , 1 ''5

Si~o of RO plant requir0d 128

5.

^D^esign^of^module conf_i_, ^{~ 1}^{·, 1}tion 1 32 6. ^Costing ^01' ^f0a:jib.L1· 11,c)rlulu configuration 135

7. ^Cos^t ^of^e^quiva^lent evaporutor 137

8. DiscU8SiOn 150

APPENDIX I APPENDIX II

APPENDIX III APPENDIX IV BIBLIOGRAPHY

Sample calculation of 'A'

Data for the syf;tem (NaCl-H₂o) at 25 C Sample calculation of

(DAM/K 5)

Sample calculation of 'k'

143 144 145 147 148

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FivurP

2 3

G 7 8

9 10

1 1 12

13

LIST OF' Pl cUln:~;

0!'1cnosi :_,

Rc .. versc Osmosis Ln.c Lo.::.v 1ircc!uction

Glc sc p.'.:Lra tion of TMS ethers of GS apple SU/;&rs on SE- J2 column

Glc :i:)attern or oreunic ·1c·i.,l~; in

cc

^,;:J

·

uppl".:3 Glc: p~l L Lc⁰rn of 01·ganic acid .. : in GS &.Pl lu:J

Calibr:..ttion curves of .JU[~<t r stand:n·ds Cali brli tion cu1·ves or ac ~et ::-t:indards Glc 1•attu1·n of sucar stnr,clurds

l•'lou dja~rc.1rn fur tlt, H, ,,er...;1..; J.._.wo:;js pilot f,!·,nt.

Effr et. ,)f 011, 1·:.iting J)l'l:; •• uc·L· on lllvP:b1·urie

pe rl'orm.:...nce

EiTc et of co11c, ntraLion or1 r,11Jn,1Jrane 1,vr·\ rw:a1ce 14 Ef'i'cct of rc·c· i 1·cula tiuu '--· ~·1 1..'n mcmbran1,

p1.;

,·r ·c,n ..

allc,~

1 5 16 17

18

Effr1ct of op, ra tin1: t iwc, on membrane performance Effect or tc,u,pera Lur1· on mcrnlli·anc performance Reverse osmosis !J!'OC•~ss uncler steady state conditions

Effect of op< ratinc pressure on the pure wntcr p~rweability ~onstant A

19 Effect of feed conclntrations on the solute transport parurueter

20 Effect of feed flow rate uri fct-Jd conct:ntratlon on the average mass trc1nnfor coefficient fo1·

th& syslcm so1U urn d1loricle-water

.,,

.) ..)

8

33

4 1

GO (, 1

(,2

Gj

64

69

88

89

90

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x.

21 Permeate flux versus concentration at P

=

99 atm 119

22 End-to-end flux versus ⁰Brix for :--in,n;lc strencLh

apple juice at P = 99 utm 120

23 Flow rate vernus pressure drop fo1· TM5-14 and

TM5-20 tubular RO modules 127

24 Number of modules required us ~1 function of

final juice concentration :ind !tours of operation. 131 25 Flow path through fe:.1siblc

no

^modul^e ^configuration

design. 131

26 Dewaterinc; costs for plate evaporator and reverse OSlilOSiS at 1,800 opcr;1 Lio11al hours per year 1 !:-1 27 Dewatering costs for pJate evaporator and reverse

osruosis l:it 6,300 o Jl' .ea t.i.onul boun1 per yeHr. ¹⁴¹

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Table I

II

III IV

V

VI

VII

VIII IX

X

XI

XII

XIII

XIV

xv

XVI

XVII

LIST OF TAPLES

Cllar·n:-tc rj sties of hyperfil trn tj on and ullrafiltr~tion

Some advantages of Reverse Osmo:;is over truditional methods in food processing

Typical osmotic pressures for different foods Relative retention time of TMS du1•iv&tiv1;s of sugu.rs on SE-52

Relation retention time of 'rMS dervivatives of non-vola tlle orr.;anic acitis on Sf~-52

K factors for crystalline sui:ars and ;_,cids as their TMS derivativos

Recovery of sugars by direct injection from var .ious amow1 ls input

Recovery of acids by djrect injection

Individu;il rr•covery by analy tieal procedure from 4 synth<..:l.ic mixtures at a

w

1 :Ws = 1.0 Total suear recovery by unc.dyticul p1·ocedurc from mixtures A,B,C and D ut a

w

₁:Ws - 1.0 Recovery analysis of mjxlures of acids at a

w

₁^:Ws """ 1.0 hy lead salt w._.thod

Quantitative determination or :;u·;urs in Granny Smith apples by glc

Q.uanti ta live determination of oreanic acids in Granny Smith apples

Characteristics of the TM5-14 module

Typical performance of the AS-197 membrane Material balance for the RO module run with fresh water. T = 25 C

Effect of operating pressure on membrane p~rformance - RR= 5 1/min; T = 25 C

4

6

11

35

37

40 43 44 44

45

4H

48

55

58 58

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XVIII

XIX

XX:

XXI

XXII

XXIII

XXIV

XXV

XXVI

XXVII

XXVIII

XXIX

XXX

XXXI

XXXII

XXXIII

Effect of concentration on membrane performance - RR= 8 1/min; P = 75 atm; T = 25 C

F.l'fne:t of recircuJr.tion rA.te on membrane perforrnunce - P

=

60 atm; 'l'

=

25 C

Effect of opera ting time on membn,me performe.nce - RR= 5 1/mj.n; C

=

⁰^.^5%NaCl; P

=

⁷⁷atm untl T

=

2, C

Effect of feed temperature on membrane performance - R

=

⁵^1/min; ^P⁼ ⁷⁷^atm^;

'1' ""2~ C

Effect of pressure on the pure water perrneabili ty corn; Lan L A

Effect of chaneinG feed flow rates and feed concentrations on pe1·me&tc· flow and permeate concenL1·ation - P

=

'y1.4 .-ltm

Effect of ch,:1.nging feed flow 1·ates and feed concentrations on permc:u Lt' ('low cl!ld per1tt( a Le, c:oncen Lra ti.011 - P 92. '.j a till

Effect of feed conce11 Lr:_d,ion on the solute tranoport pt.1·,Lffi() Ler -

:r -

'>·I .IJ ~-1. Ln1

Effec L of feed coucentration on (DA]\/K ) P

=

9?.5 atw

Effect of feed concentration on the mass transfer coeffjci011-L l: - P = 5•1./J aLm

Effect of fceJ concentration on the mass tru1wfer coefficicnL k - P = 92.5 atm

Relative retention ttme and K factors of TMS derivatives of sugars and ncids (food grade) on SE-52 column

Reverse osmosis of glucose, FR= 5 1/min;

P = 77 atm

Reverse osmosis of fructose, FR= 5 1/min;

P = 77 atw

Reverse osmosis of suerose, FR= 5 1/min;

P = 77 atm

Reverse osmosis of mixture of sugars, FR= 5 1/min;

58

59

83

s,

BG 87

106

107

P = 77 atm 107

xii.

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Table XXXIV

XXXVI

XXXVII

XXXVIII XXXIX

XL

XLI

XLII

XLIII

XLIV

XLV

XLVI

XLVII

XLVIII

Reverse osmosis of malic acid, FR= 5 1/min; P

=

⁷⁷ atm

Reverse osmosis of citric acid, FR= 5 1/min;

108

P

=

77 atm ,108

Reverse osmosis of mixture of acids, FR= 5 1/min; P

=

77 atm

Reverse osmosis of' mixture of sugars and acids, FR= 5 1/min; P

=

77 atm

Characteristics of' the apple juice studied Permeate flow and rejection characteristics of single strength apple juice

Permeate flow and rejection characteristics of diluted apple juice concentrate

Sugars and acids of permeate and concentrate obtained from concentrating single strength apple juice

Sugars and acids of' permeute and concentrate obtained from concentratln~ diluted apple juice concentrate

Concentrution of single strene;th 11p:r,le juice; P

=

99 atm

Concentration of dilute apple juice concentrate;

P =

99

atm

Effect of cooling temperature on concentration of single strength apple juice; P = 99 atm Material balances for preconcentration by RO from 11°Brix to various concentrations in 7.5 hours

Cost estimates for the RO concentration of

136,000 1 of apple juice from 11°Brix to 20°Brix in 7.5 hours

Cost estimates for the evaporating concentration of 68,000 1 of apple juice from 11°Brix to 72°

Brix in 7.5 hours.

109

109 115

115

11 6

116

117

i 17

118

130

136

138