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OF DRIED FRUIT AND VEGETABLES:
A QUANT ITATIVE APPROACH
A THES I S PRESENTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN FOOD TECHNOLOGY
AT MASSEY UNIVERS I TY
CHRIST INE MARIE SAMANIEGO-ESGUERRA 1989
11
ABSTRACT
The quant itat ive approach to she l f l i fe predi ct i on o f foods i s a r e l a t i v e l y new f i e l d o f f o o d t e ch n o l o gy a n d the paucity o f pub l i shed studies in thi s area indi cates a need for further research . The present study was undert aken to deve l op and e v a l u a t e a me t h o do l o g y f o r the s he l f l i fe p r e d i ct i o n o f p a ckaged dried f o o d s u s i n g a qu ant i t at ive approach .
T h e d e v e l o p m e n t o f a t e c h n i q u e f o r t h e s h e l f l i f e p r e d i ct i o n o f pack aged dr i e d f o o d s , sp e c i f i c a l l y onion f l ak e s , s l i ce d green beans , and apr i cot halve s , invo lved t h e m a t h e m a t i c a l m o d e l l i n g o f p r o d u c t a n d p a c k a g e charact e r i st i c s a s funct i on s o f env i r onment a l condit ions , i . e . temperature and humidity .
The WVT R and pe rme ab i l it y c o n s t an t s o f LDP E ( 6 0 �m) , PET ( 1 2 �m) and a l aminate o f both fi lms ( 3 0 � LDPE and 1 2 � P E T ) w e r e d e t e r m i n e d a t d i f f e r e n t t e mp e r a t u r e s a n d humidi t i e s . A general mode l was devel oped whi ch
sat i s fact o r i l y p redicted permeances o f the three fi lms as a funct i on o f external re l at ive humidity and temper ature .
The moi sture s o rpt ion i s otherms o f the three p roduct s we re det e rmined at 2 0 , 3 0 , and 4 0 o C . The GAB mode l adequat ely de s c ribed the i s otherms u s ing a di rect non l inear regre s s i on ana l y s i s .
The k inet i c s o f the det e r i o r at ive react i on s l im i t i ng the s he l f l i fe o f the thre e dried products and their accept able l imi t s we r e determined . S t o r age t r i al s wer e conducted on the three p roduct s unde r di f ferent re l at ive humidity ( 3 2 % t o 5 9 % RH f o r dr i e d o n i o n f l ake s and g r e e n bean s ; 5 9% to
8 1% RH fo r dr i ed ap ri cot ) and temperature ( 2 0 0 C t o 4 0 oC ) condition s .
Nonen zymi c browni ng in onion flakes and chl orophy l l a l o s s i n g r e e n b e a n s w e r e b e t t e r d e s c r ib e d b y a z e r o - o r de r r e a c t i o n m o de l . T h i o l s u l ph i n a t e l o s s i n o n i on f l ake s , nonen z ymic browning in apricot , and S02 l o s s in both green b e an s and ap r i cot s we re bett e r de s cr ibed by a fi r s t - o rder r e act i o n m o de l . F o r on i on f l ake s and g r e e n b e an s , the rates of react i ons were found t o increase with an increase in the wate r act ivity of the product s . Empirical e quat ions were der ived de s cribing the r e l ationship between the rates of react i on s and wat e r act ivity . The Arrhe n i u s equat ion s at i s f a ct o r i l y de s c r ib e d t h e r e l at i on s hip between rate const ant s and t emperature .
N o n e n z ym i c b r o wn i ng and s u l phur d i o x i de l o s s i n d r i e d apricots e xhibited a t rend wherein the rate increased with w a t e r a c t i v i t y u n t i l a m a x imum w a s r e a c h e d a n d t h e n de cre a s e d with a further i n c rease i n water act ivity . The r e a ct i on s f o l l owed the Ar rhen i u s e qu at i o n a t a l l three wate r act ivity levels .
Mathemat i c a l models o f qua l ity det er iorat i on i n the dried foods we re devel oped based on the theoret ical and emp i r ical e qu a t i on s obt a i ned on t he kinet i c s o f t he de t e r i o rat ive react i ons a s funct ions o f storage t ime , wat e r act ivity and t empe rature . There was c l o se agreement between the actual a n d p r e d i ct e d s he l f l ive s of the unpackaged dried fo ods s t o r e d under v a r i ab l e t e mperature and r e l a t ive humidity condit i on s .
I n o rder t o predi ct the she l f l i fe o f the d r i e d product s p a ckaged in polymeric f i lms , a computer iterat ive t e chn ique
·w a s deve l op e d wh i ch c omb ined the mode l s de s c r ibing the p e rmeabi l i t y charact e r i st i cs of the pack a g i n g f i lms , the s o r p t i o n p r o p e r t i e s o f t h e p r o du c t , t h e k i n e t i c s o f
iv d e t e r i o r a t i o n i n t he p r o du c t s a n d t h e m a s s t r a n s p o rt equat io n . By s o lvi ng the se equ at ion s numerica l l y with the a i d o f a c ompu t e r , mo i sture gain , qua l i t y l o s s and she l f l i fe o f t h e p r o duct s were s at i s fact o r i ly p redi cted unde r various st o rage condit i ons .
ACKNOWLEDGEMENTS
I w i s h t o t h a n k my s u p e r v i s o r , P r o f e s s o r G o r d o n L . Rob e r t s o n , fo r a l l the h e l p , t ime and e n c o u r ag em e nt he provide d during the cou r s e o f thi s work . Appreciat i on is a l s o e xt ended to Dr I an B o ag fo r h i s a s s i s t an c e in the stat i s t i cal and mathemat ical aspect s o f the study .
I am g r at e fu l t o D r R o b e rt H o l l a nd f o r r e v i e w i n g the chapt e r on perme ab i l ity ; t o Mr G . Radford, Mrs M . C . Bewley, M r M . C o n l o n a n d M r H . van T i l f o r t h e i r t e c h n i c a l a s s i st ance ; and t o Uni l ever ( N . Z . ) Ltd . for p roviding the dr ied vegetables .
This work would not have been p o s s ible without funding from t h e New Z e a l and and P h i l ippine gove rnment s , t o whom I am i n debt e d . I a l s o w i s h t o thank D r Al i c i a Lu s t re and my company the Food Deve l opment Centre for the i r support .
F i na l l y , t o Mark , my family and friends for the i r cont inual moral support , I sha l l a lways be very grate fu l .
TABLE OF CONTENTS
ABS TRACT
ACKNOWLEDGEMENTS L I S T OF TABLES L I S T OF F I GURES CHAP TERS
1 . I NTRODUCT ION
2 . MO I S TURE SORP T I ON I SOTHERMS OF DRIED F OOD S
Vl
PAGE
ii v ix xv
1
2 . 1 Introduct ion 8
2 . 2 Literature Review 9
2 . 2 . 1 Sorpt ion I s otherm Model s 1 1 2 . 2 . 2 E f fe ct o f T emperature 15 2 . 2 . 3 Mo i sture S o rpt i on I sotherms of D r i e d 1 7
Onion , Green Beans , and Apr i cot
2 . 3 Methodol ogy 1 8
2 . 3 . 1 Background 1 8
2 . 3 . 2 Materials 1 9
2 . 3 . 3 Re l i abi l it y o f the Method 2 1
2 . 3 . 4 S ample P reparat ion 2 1
2 . 4 Experiment al 2 2
2 . 5 Re sult s and D i s cus s ion 2 4
2 . 5 . 1 General Observat ions 2 4
2 . 5 . 2 S o rpt ion I s otherm Equat ion 3 4 2 . 5 . 3 F i t o f the GAB Mode l 4 3
2 . 6 Conclusion 4 8
3 . WATER VAPOUR PERMEAB I L I TY OF PACKAGING F I LMS 3 . 1 Introduct ion
3 . 2 Literature Revi ew
3 . 2 . 1 E f fe ct o f Rel at ive Humidity 3 . 2 . 2 E f fe ct o f Temperature
5 1 5 2 5 5 5 6
3 . 2 . 3 E f fect o f P inholes 57
3 . 2 . 4 Other Fact o r s 5 8
3 . 3 Methodology 5 9
3 . 3 . 1 Background 5 9
3 . 3 . 2 P rocedure 5 9
3 . 3 . 3 Calculat ions 6 2
3 . 3 . 4 Materials 62
3 . 4 Experiment al 6 2
3 . 5 Re sult s and D i s cu s s i on 6 5
3 . 5 . 1 WVTR and P e rmeance 6 5
3 . 5 . 2 Development o f the Perme ab ility Model 7 9
3 . 6 Conclus ion 8 2
4 . KINE T I C S OF DETERIORAT IVE REACT I ONS IN DRIED FOOD S
4 . 1 I ntroduct ion 8 4
4 . 2 Literature Review 8 4
4 . 2 . 1 Background 8 4
4 . 2 . 2 Fact ors Affect ing the Kinet ics o f 8 6 React i on s
4 . 2 . 3 Mode s o f Deteri orat ion 93
4 . 3 Materials and Methods 9 9
4 . 3 . 1 Moi sture Content 9 9
4 . 3 . 2 Onion 1 0 0
4 . 3 . 2 . 1 Material 1 0 0
4 . 3 . 2 . 2 Thiolsulphinate Determinat ion 1 0 0 4 . 3 . 2 . 3 Browning Measurement 1 0 4
4 . 3 . 3 Green Beans 1 0 5
4 . 3 . 3 . 1 Material 1 0 5
4 . 3 . 3 . 2 Chlorophyll Determinat i on 1 0 6 4 . 3 . 3 . 3 Sulphur Diox ide Determinat ion 1 0 8
4 . 3 . 4 Apr i cot 1 1 1
4 . 3 . 4 . 1 Material 1 1 1
4 . 3 . 4 . 2 Browning Measurement 1 1 1 4 . 3 . 4 . 3 Sensory Evaluat ion 1 1 5 4 . 3 . 4 . 4 Sulphur Dioxide Determinat i on 1 1 6
4 . 4 Experiment al 1 1 7
4 . 5 Re sult s and D i scu s s ion 1 2 1
vi i i
4 . 5 . 1 Onion 1 2 1
4 . 5 . 1 . 1 Nonenz ymic Browning 1 2 1 4 . 5 . 1 . 2 Thiolsulphinate Loss 1 3 3 4 . 5 . 1 . 3 Shelf L i fe o f the Dried On i on 1 3 9
Flake s 4 . 5 . 2 Green Beans
4 . 5 . 2 . 1 Chlorophyll Loss 4 . 5 . 2 . 2 Sulphur Dioxide Loss 4 . 5 . 3 Apr i cot
4 . 5 . 3 . 1 Nonenzymic Browning 4 . 5 . 3 . 2 Sulphur D i oxide Loss 4 . 6 Conclu s i on
5 . DEVELOPMENT AND EVALUAT I ON OF SHELF LIFE PRED ICTION MODELS
1 4 2 1 4 2 1 5 1 1 5 5 1 5 6 1 65 1 7 1
5 . 1 Introduct i on 1 7 3
5 . 2 Exper iment al 1 7 5
5 . 2 . 1 Calculat i on and P rogram Development 1 7 5
5 . 2 . 2 Storage T r i als 1 7 5
5 . 3 Development o f Models for Qualit y 1 7 6 D eteriorat i on in Dried F oods
5 . 4 P redi ct i on of Mo i sture Trans fer and Shelf L i fe of P ackaged Dried F oods 5 . 5 Conclu s i on
6 . SUMMARY AND CONCLUS IONS
BIBLI OGRAPHY APPEND I CES
1 9 1 2 1 5 2 1 6 2 2 0 2 4 5
L I S T OF TABLES
TABLE PAGE
2 . 1 Water act ivity o f the saturated s a l t 2 0 s o lutions at di f ferent temperatures .
2 . 2 Equ i l ibrium moi sture content s o f dri ed onion 2 5 at di f ferent wat er act ivit ies and t empe ratures . 2 . 3 Equ i l ibrium moi sture content s o f dr i ed green 2 6
beans at di f ferent aws and temperatures .
2 . 4 Equ i l ibrium moi sture content s o f dr i ed apr i cot 2 7 at di fferent aws and temperature s .
2 . 5 Re sul t s o f the trans formed, polynomial 37 regre s s ion analyis .
2 . 6 Re sults o f the we ighted, non l inear, three 3 8 parameter GAB equat ion .
2 . 7 Estimate s o f the s i x parameters for the 3 9 nonl inear GAB equat ion .
2 . 8 Calculated i sotherm constant s based on the 4 0 nonl inear, s ix parameter GAB equat i ons .
2 . 9 Re sults o f the BET analysis . 4 2 2 . 1 0 Exper iment a l and calculated mean mo isture _4 4
content va lues for dried onion .
2 . 1 1 Experiment a l and calculated mean moisture 4 5 content values for dried green beans .
2 . 1 2 Experiment a l and calculated mean moi sture 4 6 content values for dried apri cot .
3 . 1 a S aturated s alt so lutions and the i r 6 4 corresponding RH at di fferent temperatures .
3 . 1b As sumed internal re l ative humidit i e s fo r 6 4 PET film .
3 . 2 Change i n abs orbance o f the detector f i lm 6 6 a s a funct i on o f time .
3 . 3 Re sults o f the regress ion equat ions for WVT R 6 8 as a funct i on of �p .
3 . 4 WVTR at const ant external RH . 7 0
3 . 5 Regre s s ion equ at ions for In WVTR ver sus T - 1 . 7 1
3 . 6 Water vapour permeance . 7 4
3 . 7 Water vapour permeab i l ity constant s . 7 4 3 . 8 S ummary o f pub l i shed results o f permeab i l ity 7 5
constant s .
3 . 9 Re sult s o f the Arrhen ius equat ion s for 7 7 p e rmeance .
3 . 1 0 Re sult s o f the regre s s ion equat ions 8 1 de scribing In ( P / X ) o as a funct i on o f
external RH .
3 . 1 1 Re sult s o f the regre s s i on equat i o n s de scribing 8 1 Ep a s a funct i on o f RH .
3 . 1 2 Est imates o f the parameter cons t ant s o f the 8 2 permeabi l it y mode l .
4 . 1 Thiol sulphinat e cont ent o f dried onions . 1 0 3 4 . 2 Opt ical index o f dr ied onion . 1 0 5 4 . 3 Chl orophy l l content o f dried green bean s . 1 0 8 4 . 4 Sulphur di oxide cont ent o f dr ied green beans . 1 1 1 4 . 5 Browning mea su rement s for dried apri cot . 1 1 3 4 . 6 Browning measurement s o f apricot s amp l e s o f 1 1 4
varying browning intensities .
4 . 7 Su lphur dioxide content of dried apricot . 1 1 7 4 . 8 The salts used in p reparing the s aturated 1 1 8
salt s lurries and their corre sponding re l ative humidit i e s .
4�9 Re sults o f the regre s s i on analys i s for 1 2 4 browning in onion flakes based on a zero- o rder
react ion mode l .
4 . 1 0 Re sults o f the regre s s ion analys i s for 1 2 4 browning i n onion fl akes based o n a first-
o rder react i on mode l .
4 . 1 1 Errors in calcu l ated rate constants caused 1 2 7 by analyt i c a l error s .
4 . 1 2 Equat i on s de s cribing the re l at i onship between 1 2 9 rate const ant ( k ) and aw for browning in
dried on ion flake s .
x
4 . 1 3 Result s o f the Arrhenius equat i o n s and QI 0 1 3 1 values for b rowning in dr ied onion flake s .
4 . 1 4 Results o f the regre ss ion analys i s for 1 3 5 thi o l sulphinate l o s s in onion flakes based
on a z e r o - o rder reaction mode l .
4 . 1 5 Re sult s o f the regres s i on analys i s for 1 3 5 thi o l su lphinate l o s s in onion fl akes based
on a first - o rder react i on model .
4 . 1 6 Equat ions de s cribing the re l at i onship between 1 3 7 k an aw f o r thiolsulphinat e l o s s in dried
oni on flake s .
4 . 1 7 Result s o f the Arrhenius equat i ons and Q I 0 1 3 9 values for thi o l su lphinate l o s s in dried
onion flakes .
4 . 1 8 Shelf li fe o f dr ied onion flake s based on 1 4 0 browning and thi o l sulphinate lo s s .
4 . 1 9 Re sult s o f the regre s s ion analy s i s for 1 4 4 chl orophyll £ lo s s in green beans ba sed
on a z e r o-order react ion model .
4 . 2 0 Re sul t s o f the regres s i on ana l y s i s for 1 4 4 chlorophy l l £ l o s s in green beans on a
first - order react ion model .
4 . 2 1 Result s o f the regre s s ion ana l y s i s for 1 4 5 chlorophyll Q lo s s in green b e ans based
on a z e r o- o rder react ion mode l .
4 . 2 2 Result s o f the regre s s ion ana l y s i s for 1 4 5 chlorophyll b lo s s in green beans based
on a f i r st - order react ion mode l .
4 . 2 3 Result s o f the regre s s i on anal y s i s for 1 4 6 tot a l chorophy l l los s in green beans based
on a z e r o - order react ion mode l .
4 . 2 4 Re sult s o f the regre s s i on ana l y s i s for 14 6 total chlorophyll los s in green beans based
on a f i r s t-order react i on mode l .
4 . 2 5 Equat i on s de scribing the relat ion ship between 1 4 8 k and aw for chlorophyll a l o s s in dried
green beans .
·4 . 2 6 Re sult s o f the Arrhenius equ at ion and Q I 0 1 5 0
value s for chlorophyll a l o s s in dried green beans .
4 . 2 7 Re sults o f the regre s s ion ana ly s i s for 15 3 S02 l o s s i n green beans based on a zero-
o rde r react i on mode l .
4 . 2 8 Re sults o f the regress ion ana ly s i s for 1 5 3 S02 l o s s i n green beans based o n a first-
o rder react ion mode l .
4 . 2 9 Equ at ions de s cribing the re l at i onship between 15 1 k and aw for S02 l o s s in dried green beans .
4 . 3 0 Result s o f the Arrhen ius equ at i o n and Q1 0 1 5 5 values for S 02 l o s s in dried green beans .
4 . 3 1 Re sults o f the regre s s ion ana ly s i s for 15 8 browning i n dried apr i cot based on a z ero-
order react i on mode l .
4 . 3 2 Re sult s o f the regres s ion analy s i s for 1 5 8 browning i n dried apricot based on a first-
o rder react i on mode l .
4 . 3 3 Equat ions de scrib ing the re l at i onship between 1 6 0 k and aw for browning in dr ied apr i cot .
4 . 3 4 Results o f the Arrhenius equat i ons and Q10 1 6 4 values for browning in dried apricot .
4 . 3 5 Results o f the regres sion ana l y s i s for S02 1 6 6 l o s s in dried apr i cot based on a zero-
o rder react ion mode l .
4 . 3 6 Re sults o f the regress ion ana l ys i s for S 02 1 6 6 l o s s i n dried apricot based o n a f i rst -o rder
react i on model .
4 . 3 7 Equat i on s de scr ibing the relation ship between 1 6 9 k and aw for S02 l o s s in dri e d apr i cot .
4 . 3 8 Re sults o f the Arrhenius equ at i on s and Q10 1 6 9 values fo r S02 l o s s in dried apricot s .
5 . 1 Re sults o f the nonl inear regres s i on analys i s 1 8 3 o f the deteriorat ion mode l for nonenzymic
brown ing in onion flake s .
5 . 2 Re s u l t s o f the nonl inear regres s i on ana ly s i s 18 3 o f the deteriorat i on mode l for thiol sulphinate l o s s i n onion flake s .
5 . 3 Re sult s o f the nonl inear regres s i on analys i s 18 4 for chlo rophy l l a loss in onion f lake s .
xii
5 . 4 Result s o f the nonl inear regre s s ion analys i s 1 8 4 for the dete riorat i on mode l for browning
in dried apr i cot s .
5 . 5 Actual and p redicted she l f l i fe o f dried onion 1 8 9 fl akes b ased on browning .
5 . 6 Actual and predicted she l f l i fe o f dried onion 1 8 9 f l akes based on thiol sulphinate l o s s .
5 . 7 Actual and predicted she l f l i fe o f dried green 1 9 0 bean s based on chlo rophy l l a l o ss .
5 . 8 Actual and predi cted she l f l i fe o f dried 1 9 0 apricot halves based on browning .
5 . 9 Actual and predi cted results for dried onion 1 9 8 flakes packaged in LDPE and st ored at
3 0 0C / 7 5 %RH .
5 . 1 0 Actual and predicted result s for dried onion 1 9 9 flakes packaged in laminate f i lm and stored
at 3 0 0C / 7 5 %RH .
5 . 1 1 Actual and predicted results for dried onion 2 0 0 flakes packaged in LDPE film and stored at
4 0 0C / 9 0 %RH .
5 . 1 2 Actual and predicted result s for dried onion 2 0 1 packaged in l aminate film and stored at
4 0 0C / 9 0 %RH .
5 . 1 3 Actual and predicted value s for dried green 2 0 2 beans packaged i n LDPE f i lm and stored at
3 0 0C / 7 5 %RH .
5 . 1 4 Actu a l and predicted values for dried green 2 0 3 beans packaged i n l aminate f i lm and stored at
3 0 oC / 7 5%RH .
5 . 1 5 Actu a l and predicted values for dried green 2 0 4 beans packaged in LDPE fi lm and st ored at
4 0 oC / 9 0 %RH .
5 . 1 6 Actual and predicted values for dried green 2 0 5 bean s packaged i n l aminate f i lm and st ored
at 4 0 oC / 9 0 %RH .
5 . 1 7 P redicted result s for browni ng in dri ed 2 1 0 oni on f l akes stored at 2 0 oC/55 %RH .
5 . 1 8 Actual and predicted she l f l ive s for dr ied 2 1 3 onion f l akes based on nonenzymi c brown ing .
xiv 5 . 1 9 Actual and predi cted she l f l ives for green 213
beans based on chl orophyl l a l o s s .
LIST OF FIGURES
F I GURE PAGE
2 . 1 S chemat i c s orpt ion isotherms with typical 1 0 marking po int s .
2 . 2 Schemat i c di agram o f the proximity 1 9 equ i l ibrat ion ce l l .
2 . 3 Mo i sture so rpt ion i sotherms o f dried onion . 2 9 2 . 4 Mo i sture sorpt ion i s otherms o f dri ed green 3 0
be an s .
2 . 5 Mo i sture sorpt ion i s otherms o f dr ied apr i cot . 3 1 2 . 6 Re s idua l plots for the weighted regre s s ion 4 9
ana l y s i s o f the GAB equat ions .
3 . 1 D iagram o f the microce l l u s ed for the 6 1 det e rminat i on o f the WVTR o f packaging fi lms .
3 . 2 Re l at i onship between WVTR and vapour pres sure 6 7 di f fe rence (�p ) for LDPE .
3 . 3 Re l at i onship between WVTR and �p for P E T . 67 3 . 4 Re l at i onship between WVTR and �p for 67
l aminate fi lm .
3 . 5 P l ot o f ln WVTR against T - 1 for LDPE f i lm . 7 2 3 . 6 P l ot o f l n WVTR against T - 1 for PET f i lm . 7 2 3 . 7 P l ot o f l n WVTR against T - 1 for laminate f i lm . 7 2 3 . 8 P l ot o f ln P I X against T - 1 for LDPE f i lm . 7 6 3 .. 9 P l ot o f ln P IX against T - 1 for PET f i lm . 7 6 3 . 1 0 P l ot o f ln P I X against T- 1 for l aminate f i lm . 7 6 4 . 1 D iagramat ic representat ion o f the i n fluence 9 0
o f wate r act ivity o n chemi cal , enz ymat i c and microb i o l ogical changes .
4 . 2 S emi-micro apparatus for S02 determinat i on 1 0 9 by aerat ion- oxidat i on .
4 . 3 The container set -up used in the st o r age 1 1 9 t rial s .
xvi 4 . 4 Increase in mo i sture content o f dried onion 12 2
fl ake s .
4 . 5 Change i n co lour o f dried oni on f l akes 12 3 packa
g
ed in LDPE film during storageat 4 0 C / 9 0 %RH .
4 . 6 Change in c o l our o f dried green beans 12 3 packaged in
4 0 0C / 9 0 %RH . LDPE film during sto rage at 4 . 7 Nonenzymic browning in onion f l akes during
stor age at 2 0 0C . 12 6
4 . 8 Nonenzymic browning in onion f l akes during
storage at 3 0 0C . 12 6
4 . 9 Nonenzymi c brown ing in oni on f l akes during
storage at 4 0 0C . 12 6
4 . 10 Re l at i onship between rate const ant ( k ) and 12 8 aw for browning in oni on flake s .
4 . 11 Arrhenius re l at i onship between k and T 12 8 for browning in oni on flakes .
4 . 12 Re l at i on ship between Ea and aw for browning 13 4 i n onion fl akes .
4 . 13 Thi o l sulphinate l o s s
s t o r age a t 2 0 0C . in onion flakes during 13 6 4 . 14 Thi o lsulphinate l o s s
sto rage a t 3 0 0C . in onion flakes during 13 6 4 . 15 Thio l su lphinate l o s s i n oni on fl ake s during 13 6
s t o rage at 4 0 0C .
4 . 1 6 Re l at i on ship between k and,aw for
thiol su lphinate l o s s i n onlon f l akes . 13 8 4 . 17 Arrhenius relat ionship between k and T f o r 13 8
thio l sulphinate l o s s i n onion flakes .
4 . 18 Shel f l i fe plot s for dried onion flake s . 141 4 . 19 P l ot of the reciproca l of she l f l i fe 141
at 2 0 0C based on browning and thio l sulphinate l o s s .
4 . 2 0 P lot o f the reciprocal o f she l f l i fe at 14 1 3 0 0C based on browning and thi olsu lphinate
l o s s .
4 . 21 Chl o rophy l l a l o s s in dried green beans during sto rage at 2 0 0C .
4 . 2 2 Chl o r ophy l l a loss in dried green beans dur i ng storage at .3 0 0C .
4 . 2 3 Chl o r ophy l l a l o s s in dried green beans during storage at 4 0°C .
4 . 2 4 Re l at i onship between k and aw for
chl o r ophy l l � loss in dri ed greeen bean s . 4 . 2 5 Arrhenius p lot for chlorophyll a l o s s
in dr ied green bean s .
4 . 2 6 S ulphur di o xide l o s s in dried green beans dur i ng storage at 2 0 0C .
4 . 2 7 S ulphur dioxide l o s s in dried green bean s dur i ng s t orage at 3 0 0C .
4 . 2 8 S u l phur dioxide l o s s in dried green beans during storage at 4 0 °C .
14 7
14 7
14 7
14 9
14 9
15 2
15 2
15 2
4 . 2 9 Re l at i on ship between k and aw for S 02 l o s s 15 4 in dried green bean s .
4 . 3 0 Arrhenius p l ot for S02 loss in dried green 1 5 4 b e ans .
4 . 31 Change in colour o f dried apricot halves 15 7 packaged in LDPE f i lm during storage at
3 0 0C / 7 5%RH .
4 . 3 2 Change in colour o f dried apri cot halve s 15 7
4 . 3 3
4 . 3 4
4 . 3 5
4 . 3 6 4 . 3 7
packaged in LDPE fi lm during storage at 4 0 0C / 9 0 %RH .
Nonenzymic browning in dried apri cot s dur ing storage at 2 0 0C .
Nonenz ymi c browning in dried apr i cot s during storage at 3 0 °C . .
Nonenz ymic brown ing in dried apri cot s during st o rage at 4 0°C .
Re l at i on ship between k and aw
in dried apr icot . for browning
Arrhenius p l ot f o r browning in dried apr i cot s .
15 9 15 9 15 9
161
161 4 . 3 8 Sulphur dioxide l o s s in dried apri cot s during 1 6 7
storage a t 2 0 °C .
xvi i i
4 . 3 9 Sulphur dioxide l o s s in dried apricot s dur i ng
storage at 3 0°C . 1 6 7
4 . 4 0 S ulphur di oxide l o s s i n dried apricot s dur ing
storage at 4 0°C . 167
4 . 4 1 Re l at i on ship between
in dried apricot s . k and aw for S02 l o s s 1 6 8 4 . 4 2 Arrhenius plot for S02 l o s s in dried apricot s . 1 6 8 5 . 1 Compar i s on o f the actual and predicted values 1 8 5
for nonenz ymic browning i n onion flake s .
5 . 2 Compar i s on o f the actual and predicted values 1 8 6 for t h i o l sulphinate l o s s in oni on flakes .
5 . 3 Compar i s on o f the actual and predicted values 187 for chlo rophy l l a l o s s in green bean s .
5 . 4 Compari son o f the actual and predicted values 1 8 8 for browning in apr i c ot s .
5 . 5 F l ow di agram o f computer iterat ion . 1 9 4 5 . 6 Samp l e o f the computer program output . 1 97 5 . 7 Corrected and uncorrected moi sture cont ent s 2 0 7
for onion flake s packaged i n LDPE fi lm .
5 . 8 Corrected and uncorrected mo i sture cont ent s 2 0 7 for onion flakes packaged in l aminate f i lm .
5 . 9 Mo i sture content s for green beans packaged 2 0 8 in LDPE film during storage .
5 . 10 Mo i sture content s for green beans packaged 2 0 8 in l aminate film during storage .
