Kinetics of vitamin A loss in a food system during heat processing : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University

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KINETICS OF VITAM IN A LOS S IN A FOOD SYSTEM DURING HEAT PROCESSING

A thesis presented in partial ful filment of the requir ements for the degree of Doctor of Philosophy in Food T echnology

at Massey Univers ity

Sheelagh Ann Wil kinson

1981

ABSTRAC T

Vi tamin A i s n u triti ona l l y signific a n t a nd is used a s an i nd icator for the per formance of fa t soluble v i tam ins in prod uc ts and process es.

There was a pa uc i ty o f k i netic da ta rela ti ng to i ts los s i n food systems duri ng therma l processing a nd therefore it wa s im port a n t to. d eve l op ki netic mod el s tha t descr ibed destruc tio n ra tes, and their dependence on factors such a s tempera ture and the microenv ironmen t o f the food.

A rea l food sys tem, beef liver, w a s u sed to s tudy the lo ss o f v i tam i n A o n thermal process i ng. Two d i fferen t heati n g method s were emp loyed to ob tain k i netic d a ta - a s teady s tate and an u n s teady s ta te proc ed ure. In the s teady s ta te method, l iver puree w a s hea ted i n gla s s cap il l ary tubes. The order of reac t i on, rate con stants _and their dep en­

dence o n temperature were determ i ned. U s i ng exper imen tal des i gn techniques, the effec ts of com position (fa t, p rotei n a nd moi s ture conten ts, pH and

copper concentr a t i o n) on v i tam i n A lo s s w ere determin ed. The ranges of

compositi ona l var iables were tho_se e x pec ted in manu factured m0�t _products conforming to prac tica l and New Zea land l ega l requiremen ts. The unsteady

state method was emp loyed to see i f the s teady s ta te reac tion kinetic param eter s were val id on scal e-up, and i f s teady s tate resul ts could be

u sed to pred ict v i tamin A lo s ses in commerc i a l thermal process ing opera tion s.

For natura l beef l iver puree, v i tamin A l oss o n s teady s ta te hea ting (103 - 127°C) could b e descr ibed by fir s t ord er k i netic s. The reference ra te con s ta n t, k122, had the va l ue _125.0 x _{10-5 s-1} and the ac tiva tion e nergy wa s 112 + 9 kJmol-1 a t th e 9 5% l ev e l o f confi denc e.

Where fa t, pro tei n and moi s ture con tents were s tu died a t one level of copper and pH to d etermine thei r effec t on vi tamin A l os s, it wa s found

tha t ei ther moi s ture content or f a t content cou l d expl a i n mo s t of the ob served var i a tion . However, moi s ture con ten t was the preferred vari able

to model the effec t of composi tion, a s i t expl ained a grea ter proportion of the va ria tion . Moi s ture con tent inc rea sed the rate of vi tam i n A lo s s

ilS it i ncreased in value from 52 - 72%. The a c tivation energies w0rc v0ry similar fo r the m i x tures, a nd o n l y when the copper l evel was changed did

E chan ge. The change in rate mov ing from 102°C to 122°C wa s l e s s in a r un s where copper was present at h i gh concentrat ions than when it wa s

at a low level . Th i s ind ic ate s that changing cop per concentrat ion probably brough about changes in the mechan i sm o f v it am in A los s.

Under s im i l ar compositional and heat ing cond it ion s to tho se u sed in steady state, p i lot plant cann ing tr i als gave greater v itam in A losses than predicted from the stea dy state data. Part of the di screpancie s wa s due to de stab ili sat ion o f the system which led to some heat tran s fer by convect i on and to fat m i grat i on to the outer parts o f the can. Neither of thes e e ffect s wa s t a ken into account by the pred iction method. The remaining di fference s were �roba bly due to a change in the kinetics b etween the steady state and un steady state exper iment s.

Kinetic parameter s were c a l cu l ated from the unstea dy state data for compar i son with the steady state values . The act ivat i on energies were the

samP. _{hut the} re ference rate con stants were d i fferent. The di fference wn s on ly sli ght with a l iver mixture of 56% moi st ure content but wa s si gni ficant at 69% mo i sture content . Therefore it wa s not pos s ib l e to relate k1 22 _in the steady and un steady state and so the steady state dat a did not scal e up completely.

ACKNOWLEDGEMENTS

I wi s h to thank my superv i sors Or Ma ry D . Earl e and

Or A . C . C l el a nd for a l l the he lp, t i me a nd e ncouragement, wh i ch they provi ded dur i ng the cour se of th i s work .

App re c i at i on i s a l so extended to Mr T.O.R. Haggett for h i s a s s i s tance i n the i n i ti al s tages of the chem i ca l a s say ;

M rs M . C . Bewl ey for hel p i n orga n i s i ng chem i cal s and equ i pment ; Profe s sor E.L. R i cha rds for provi d ing the fac i l ities a n d rev i ewi ng the ma nuscr i p t ; a n d to my typ i st M i s s V i v ie nne Ma i r .

Th i s work wou l d not have been pos s i b l e wi thout fu ndi ng from the De partment of Sc ient i fi c and Indust ri a l Resea rch

(

^{Resea rch}

Con tra c t UV/4/ 29 ) , to whom I am i ndebted. I a l so wi s h to thank Gl obus G roup ( NZ ) Ltd for the persona l fi nanc i a l support g i ven i n

the latter stages o f th i s study.

F i na l l y , to my fami l y and fr i ends for thei r con t i nua l mora l su pport . ^I s ha l l a l ways be very gra tefu l .

TABLE OF CONTENTS

PAGE

ABSTRACT ; ;

ACKNOW LEDGEMEN TS LIST OF FIGURES LIST OF TABLES

iv ix xi

1.

2.

3.

INT RODUCTION LITERATURE REVIEW

1 3

2. 1 Vitami n A 3

2.2 Factors Affecting Stability of Vitamins During 4 Heat Pro cessing

2.3 Sta bi lity of Vitami n A During Processing 6

2 . 4 Rea ctio n Ki netics 15

2.5 Determinatio n of Kinetic Mode ls 17

2.6 Co nclusio ns and Research Objectives 18

METHOD S 20

3. 1 Vitami n A Determination 20

3. 1. 1 Literature Review on Vitami n A

Determination 1 n Foods 20

3. 1. 2 Reagents 23

3. 1.3 Sta ndardizatio n 25

3. 1.4 Method for Determining Tr ans -Retino l

in Beef Liver Puree 25

3. 1.5 Accuracy of Assay 27

3.2 Pro ximate Ana lysis of Liver 3. 2.1 pH Determi nation

3.2.2 Redox Potential Determination

3.2.3 Moisture Determi natio n 3.2.4 Crude Fat Determinatio n 3.2. 5 P rotei n Determin atio n 3.2.6 Copper Determi natio n 3.3 Reagents for Samp l e Adjustment

29 29

29

29 29 29 2 9 30

co ntinued . ..

Content s - cont i n ued

PAGE

3 . 3 . 1 pH Adjus ters 30

3 .3 . 2 Copper Ions 30

3 . 3 . 3 Fat 30

3 .3 . 4 P ro te i n Sou rce 30

3.3 . 5 Water 30

3.4 Heat i ng Met h ods 31

3 . 4 .1 Steady State Heat i ng Theory 31 3 . 4 . 2 U nsteady State Heat i ng Theory 33

3.4 .3 Steady State Heat i ng Met hod 33

3 .4 .4 U n st eady State Heati ng Method 36

4. CHA RACTERISATION OF THE K I NET ICS OF VITAMIN A LOSS

ON STEADY STATE HEATING OF _{LIVER 3e}

4 . 1 Introduc ti on 38

4 . 2 Experi menta l ₃₉

4.2. 1 Samp l e Prepara ti on ₃₉

4 . 2 . 2 Thermal Process i ng Cond i t i ons 39

4.3 Resu l ts and Di scus s i on 40

4 . 3 . 1 Temp erature- T i me Prof i l es of Heated Tubes 40 4 . 3 . 2 Extent of React i on Dur i ng "Come-Up" T i me 4 2 4 .3 .3 E s t i mati on o f Parameters C ha racteri s i ng

Therma l Loss of V i tami n ^A 43

4. 4 Conc l u s i on s 4 9

5 . EFFECT OF P ROXIMATE COMPOS IT ION ON THE LOSS OF VITAM I N A

DURING STEADY STATE HEA T I NG 50

50 5 1 51 5 .1 I ntroduct i on

5 . 2 Exper i menta l

5.2.1 Sample Preparat i on

5.2 . 2 Des i gn of Extreme Verti ces M i xture Experiment 5 2

5. 3 Res u l t s and D i s cu s s i on 5 6

5 .3 . 1 E st i mat i on of Parameters C haracter is i ng Thermal Los s o f Trans - Ret i no l in Beef L i ver

M i xt ures 56

5. 3. 2 E ffict of Sys tem.Compos i tion on React i on Rate 6 2

cont i n ued ...

C ontent s - c onti nued

6.

5.3.3 _Effect of System Compo s i t i on on Act i vat i on Energy

5.3.4 Effect of System Compos i tion on Frequency

Factor 5 . 4 Concl usions

EFFECT OF COPPER AND pH ON THE LOSS OF VITAMIN A IN DIFFERENT BEEF LIVER MIXTURES DU RING STEADY STATE HEATING

6.1 Introduct i on 6.2 Experimental

6.2 .1 Sample Preparati on

6.2.2 Des ign of 2 3 Factor i a l Exper i ment 6. 3 Results and Di scussion

6 .3 . 1 Es timation of Parameters Character i s i ng

Thermal Loss of Tra ns- Retinol in Beef Li ver P uree as a Function of Copper, pH and

Composition

6. 3.2 E ffect of C opper, p H and Compos ition on Reaction Rate

6. 3. 3 Effect of C opper, pH and Composition on Activation Energy

6.3. 4 _Effect of Copper, pH and Composit i on on Frequency Factor

6.4 Concl u si on s

7 . EFFECT OF UNSTEA DY STATE HEATING ON VITAMIN A L OSS BEEF LIVER MIXTURES

IN

7.1 Introduction 7.2 E xperiment al

7.2.1 Sample Preparation

7.2.2 Design of 23 Facto ria l Experiment 7. 2. 3 Thermal Diffusi vity D etermi nation 7.3 Simulation

7.3.1 F i n it e Differenc e Model 7.3.2 Kin etic Calculation

cont i nued ...

PAGE

64

65 66

68 68 69 69 69 72

72 7 6 82

83 84

8 5 8 5 8 6 86 86 88 90 92 94

Co ntents - continued PAGE

7.4 Result s a nd Di scus sion 9 6

7 .4 .1 C ompari son of Pred icted and Exper imental Time -

Temperature P rofi l es 96

8.

7 .4. 2 Compar i son of Pred icted a nd Experime ntal Vitamin A Rete ntio n s

7. 4 . 3 K i ne tic Parameter Determi na t i on for Uns teady Stat e Heat i ng of L ow and High Moi sture Conte nt Liver

7 .5 Conclusions

DISCUSSION AND CONCLUSIONS BIBLIOGRAPHY

APPE NDIX

A. 1 Publ i shed Pa per Summarising the Findings in Section 4 A.2 Computer List i ng for Temperat ure- Time Profile and Exte nt

of Reaction i n Gla s s Vial Pr ogram

A. 3 Concentra t i on of Tr ans-Ret i no l i n Natur a l Beef Li ver Puree B efore and After Thermal Processing

B.1 Co nc entration of Trans -Reti nol i n Beef Liver Mixtures Befor e a nd After Therma l Proc e s s i ng (M i xture De sign ) C . 1 Concentr ati on o f Trans -Reti nol i n Beef L i ver Mixtures

Before a nd After Thermal Pr oce s sing ( 23 Factorial Desig n) 0.1 Computer Li sting f or Temperature - Tim e Profile s and

V i tam i n A Reten t i on Program for Uns teady Sta te Hea t i ng

99

106 1 1 2 1 14 1 17

1 30 1 3 3 134 1 36

1 39 14 1

LIST OF FIGURES

FIGURE

3.1 Heat ing a ppa ratus for steady state heat ing

4.1 Temperatu re-t i me p rofi l es for heat ing and coo l ing v i a l s during steady state proces s ing

4 . 2 Calcul ated temperature-t i me p rof i l e dur i ng "come-up" t i m e

PAGE 35 41

for 1 2 2.1°C heat i ng p rocess 4 1

4.3 Degradat i on rates for vitam i n A i n beef l i ver puree on heat ing, showing the natu ra l l ogarithm of the concent ra -

t i o n rat i o as a funct i on of t im e for va ri ous temperatu res 44 4 . 4 P robabil ity p l ot of calculated percent "res i duals" f or

vitam i n A

4 . 5 Arrhenius plot for loss of v itami n A i n beef l i ver pu ree, showi ng t he natu ra l l ogarithm of the f i rst order rate constant as a funct i on of the i nverse of absolute temper­

ature

5.1 Extrem e vertices des i gn for beef l i ver m ixtu res of d ifferent fat, protein and mo i stu re contents

5.2 Degra dat i on rates for vitamin A in beef l i ver mixtu res at 122.0 °C, s howi ng the natura l l oga rithm of the concen­

trat i on rat i o as a funct i on of t ime

5 . 3 Degradat i on rates for vitam i n A i n beef l i ver m ixtures at 102.1?c, s howing the natura l l oga rithm of the concent rat i on

rat i o as a funct i on of t i me

5.4 Degradat i on rates for vitamin A i n beef l i ver mixtures at 112.0 °C, showing the natural logarithm of the concentrat i on

rat i o as a funct i on of t i me

5.5 Arrhenius pl ot for l oss of v itamin A in beef l i ver mixtu res on heat ing, showing t he natu ral l ogarithm of the f i rst

4 5

4 8 54

5 7

58

58

order rate c onsta nt as a funct i on of the i nverse of abso lute

temperature (average Ea) 60

5.6 P l ot of a ppa rent fi rst order rate constants for vitam in A l oss as a funct i on of compos it i ona l factors at va r i ou s temperatures

c ont i nued ...

63

List of Figu res - continued

FIGURE PAGE

6.1 Degradation rates for vitamin A i n b eef liver pu ree mixtu res at differi ng pH and copper concent rations,

showi ng the natural l ogari thm o f the concentra tion ra tio

as a function of time at 102°C 73

6. 2 Degra dation rates for vitami n A i n beef li ver puree mixtures at differing pH and copper concent rations,

showing the natural l ogari thm of the concentration ratio

as a function of time at 122°C 74

7.1 Compa rison of experimental cent re temperatures and

predicted cent re t empe ratures for a low moistu re mixture

at a retort temperature of 11 2°C ( run 1) 98 7. 2 Compa rison of experimenta l cent re temperatures and

predicted cent re temperatures for a high moisture mixtu re

at a ret ort temperature of 11 2°C ( run c) 98 7.3 Processed l ow moisture content beef li ver showing the meat

ma trix and the exudate ( run 1) 100

7.4 Process ed high mo istu re content b eef l i ver showing the meat matrix and the exudate ( run c)

7.5 A cent ral com posite d esign to fit a sec ond order response surfac e

100

108

LIST OF TAB LES

TAB LE PAGE

2.1 Effect of H eat P rocess i ng on U nsuppl emented Foodstuffs 7 2 . 2 Effect of Heat P rocess i ng on Fort if i ed Foodstuffs 9 2 .3 Fa ctors Affect i ng V itami n A Sta b i l ity 1 2 3 . 1 Cl ass if i cat i on of Methods to D etermi ne V itami n A (Ret i no l )

Propos ed by Parrish (1977 )

4.1 Temperatu re-Time Comb i nat i ons for Therma l Process i ng of Beef L iv er Pu ree

4. 2 Lengt h of 11Come-Up11 Ti mes i n Heated Tu bes

4.3 Extent of V itami n A Loss i n S i xty Seconds 11Come-Up11 T i me i n Heated Tubes

4 . 4 Fi rst Order Rea ct i on Rate Consta nts for Trans-R et i nol i n Natura l Beef L iver Pu ree

5 . 1 Compos i t i on of Mixtu res i n Extreme Vert i ces Des i g n 5 . 2 Prox i mate Ana lys is of Mixtures i n t he Mod if i e d Ext reme

Vert i ces D es i gn

5 . 3 Temperatu re- Time Combi nat i ons for Therma l Process i ng of

39 40

4 2

46 53

55

the Extreme Vert i ces M i xture Des i gn 55

5 . 4 Appa rent F irst Order R ate Consta nts for Trans -Ret i no l i n

5 . 5

5 . 6 6.1

6.2 6 .3

Beef L iver Pu ree as a Fu nct i on of C ompos it ion

Est i mate d Value of the Ea a nd A Pa rameters of the Arrhen ius Equat i on for the Thermal Loss of T rans -Ret i no l i n Beef

56

L i ver Mi xtu res Over the Temperature Ra nge 102- 12 2°C 59 Est i mates of A for Eac h Des i g n Po i nt Us i ng an Av erage E a

(11 2 kJmo l-1 ) 61

23 Factori a l Des i gn Fo r Beef L iver Mixtures at D iffere nt

pH and C o pper Levels 70

P rox imate Analys is of 23 Facto ria l Des ign M ix tures 70 Temperatu re-Time C ombi nat i ons for Therma l P rocess i ng of

23 Factor i a l Mixtures 71

cont i nued .. .

L ist of Tab l es - cont inued

TABLE PAGE

6 .4 Appa rent F i rst Order React i on Rate Constants for Trans­

Ret inol in Beef L i ver Puree as a Funct i on of C opper, pH and C ompos it i on

6.5 Experim ent a l ly Determ ined Act i vat i on Energ i es for Trans­

Retinol in Beef L i ver Puree as a Funct i on of Copper, p H and Compos it i on

6 .6 Experi mental ly Determ ined Frequency Factors for T rans­

Ret inol Loss in B eef Li ver Puree as a Funct i on of Copper, p H and C ompos it i on

6 .7 Est imated Cont rasts

(

by Yates Ana l ys is

)

of k102 for V itamin A L oss in Beef L i ver Mixtu res Fo l l owing a 23 Factori a l Experiment

6 .8 Est imated Contrasts

(

by Yates Ana lys is) of k1 22 of V itam in A Loss in Beef L i ver Mixtu res Fo l l owing a 23 Factoria l Experiment

6 .9 Est imated Cont rasts

(

by Yates Ana lys is

)

of the Rate Constant for V it am in A Loss i n Beef L i ver M i xtu res Fol l owing a 24 Factori a l Experiment

6 .10 Est imat ed Contrasts

(

by Yates Ana l ys is

)

of Ea for V itam i

n

A Loss in Beef L i ver Puree Fol l owing a 23 Factor i a l

7 2

7 5

76

7 7

78

80

Experiment 82

7.1 Layout for 23 F actori al Des ign for Unsteady State Heating of Beef Liver Mixtu res

7. 2 P rox i mate Ana lys is of 23 Fact

o

r i a l Des ign Mixtu res for

87

Unsteady State 88

7 .3 Therma l D iffus i v it i es for Beef L i ver Mixtures at Vari ous Temperatu res

7 .4 Processi ng Cond i t i ons for 23 Factori a l Unsteady State Experi ment

7 . 5 Vitamin A Va lues and Experi men ta l and Pred ic ted Retent i ons for Each Des i gn Point

c ont inu ed . . .

96 101 102

L i s t o f Tab l es - con t i nued

TAB L E PAGE

7 . 6 Estimated C ontrasts {by Yates Ana l ys i s ) of % V i tami n A Retent i on i n Beef L i ver Mi x tures Fo l l owi ng a 23

Factori a l Experi men t

7 . 7 Ac tua l a n d Pred i c ted V i tami n A Retenti ons for the Des i gn

104

Po i nts i f Heati ng wa s Pu r e Conduc t i on or Pure Conv ec t i on ¹⁰⁶ 7 . 8 Centra l Compos i te Des i g n for Low and H i gh Moi s ture Content

L i ver M i x tures 109

7 . 9 Reten t i o n Re s i dua ls for Low Mo i stu re Con tent Ru n s 11 0 7 . 10 Retent i o n Res i d ua l s fo r H i g h Moi s ture Content Runs ^{1 10} 7 . 1 1 Ki neti c Pa rameters for Two D i fferent Beef L i ver M i xtures 1 1 1 A . 1 Concen tra t i on of Trans - Reti nol After Hea t i ng for Vari ous

Times {Na tu ra l Beef L i v er )

B.l Conc entra t i on of Tra ns - R eti nol After H eati n g for Va r i ou s

134

Time s at 102 . 1°C (Mi xture De si gn ) 1 36

8. 2 Concen tra t i on of Trans - Reti nol After Hea t i ng for Va r i ou s

T i mes a t 1 1 2 .0°C (M i xtu re Des i gn ) 137 S. 3 Concentrat i on of.Tra ns - Reti nol After Heati ng for Va r i ou s

Ti m es a t 1 2 2.0°C ( M i x tu r e D es i g n ) 1 38

C . 1 Concentra ti on of Tra ns - R eti nol After H ea ti ng for Var i ou s

Times a t 102°C (23 Fac tori a l ) . 139

C . 2 Concentra t i on of Trans -Reti nol A fter Hea ti ng for Va ri ou s

Times a t 1 22°C ( 23 Fac tori a l ) ¹⁴⁰