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THE DETERMINATION OF KINETIC PARAMETERS IN HEAT PROCESSING OF BABY FOOD

A thesis presented in partial fulfilment of the r equirements for the degree of Ph.D.

in Biotechnology at Massey University

Kalaya Taimmanenate 1980

. ","lO_l

ABSTRACT

Two methods of heat processing kinetic parameter determination by steady-state and unsteady-state heating procedures were studied.

The unsteady-state procedure was used for colour and viscosi ty where large amounts of samples were required for measurement, and both were used in considering the destruction of ascorbic acid and riboflavin in a baby food .

To ob tain accurate determination of the kinetic parameters,

standard k and Ea, experimental methods had to be developed to measure the quality factors within narrow limits of accuracy.

Determination of the kinetic parameters by unsteady-state procedure involved the development of a computer method for the can temperature distribution calculation, the quality retention calculation, and finally determination of the empirical relationships of the standard parameters,k and Ea,to the residuals (differences between experimental and predicted concentrations) . Temperature distribution in a can was predic ted by a modified computer program based on an analytical solution to obtain a form fitting of the experimental heat penetration curve . From this, the quality retention was calculated by numerical integration.

The standard k and Ea were roughly estimated from the literature either on the studied quality or on a similar quality . Then the ranges of

standard k :and Ea were assigned in an orthogonal composite design and used to calculate the retained quality which then was compared with the experi�

mental result to obtain the absolute residual at each standard k and Ea . The average residual at each processing temperature was used in multiple linear regression to determine the relationships between the standard k and Ea, and the residual. By optimising the empirical equation the best values for the standard k and Ea were determined.

The standard k and Ea for ascorbic acid and riboflavin were also determined by the steady-state procedure. In this, small tubes of the baby food were heated in a constant temperature , oil bath. Nearly identical results ob tained for ascorbic acid by both methods indicated that the method used was feasible and the degradation of ascorbic acid

wa s best described by a f irst order reac t ion . For r ibof lavin , 0

d ifferent r esul ts were found from the two methods but these could be expla ined as the result s o f the low d estruct ion rate of riboflavin on heat ing , the ana lyt ical error and the change in phys ic al cond it ions from cans to tube s . So , use of the steady-state kinetic parameters for qual ity retent ion calculat ion in unsteady-state was conf irmed exper imentally .

For colour and vi sco sity.changes in process ing , the me thod of kine tic parame ter de termina tion in uns teady-s tate heat ing procedure .was used assuming f irs t order kinetics .

It was conclud ed 60-1 3 9 0 c, the kinetic were 0 . 4 2-0 . 44 x 1 0-4 - 1 and 84 - 1 05 kJ mo le ,

in this food syst em for the temperature ranges of react ion rate a t 1 2 9°C and the ac t ivat ion energy

-1 -1 -4 -1

s and 7 7 -8 5 kJ mole ^, 0 . 1 1 -0 . 2 5 x 1 0 s

-4 - 1 - 1 -4

1 . 20 x 1 0 s and 1 22 kJ mole and 1 . 65 x W

- 1 -1

s and 1 5 1 kJ mole for ascorbic acid , riboflav in , colour and viscos ity respec t ively .

ACKNOWLEDGEMENTS

The success of this research was due to the experience and

confidence of my supervisors , Prof essor R . L . Earle and Dr Mary D . Earle , whom I shall always be grateful . Their untiring interes t , patience and encouragement are deeply appreciated .

This work would not have been possible wi thou t the support of Chulalongkorn Univers i ty to whom I am indeb ted . This scholarship would no t have been possible to ob tain wi thou t the help of

Dr Mary D. Earle and the Chemical Technology Depar tment , in

particular , Dr K. Santiyanont , Dr C . Thanyapit tayaku l , Mr V . Premyothin and Dr P . Chi t taporn .

I also wish to express my appreciation to var ious people who assis ted this res earch in many ways . In part icular I would like to thank :

Dr A . C . Cleland for his valuable d iscussions and criticisms and also his willing as sis tance .

Food Technology Research Centre , Department of Food Technology for financing the exper imental work .

Prof essor R . Richards for provid ing the facili ties and funding the computer expenses .

Mr T . Gracie for his assis tance in experimental work .

Miss S . A . Wilkinson for helpful guidance in setting up s teady- s tate heat ing experiments .

All tas te panelists for taking part in the preliminary work and all those in the Facul ty of Food Science and Biotechno logy for making such a happy working environment .

Also to my typis t , Vivienne Mair , for her efficiency and patience , and Nuch for taking part in the final preparat ion .

Finally to my mother , sis ter and brothers for their cont inual moral support dur ing the s tudy .

Kalaya Taimmanenate Oct ober , 1 9 80

1 . 2 . 2 . 1 2 . 2

CONTENTS

Lis t of Tab les List of Figures INTRODUCTION LITERATURE REVIEW Introduction

Kine tic Theory of the Changes in Food During Heat Processing 2 . 2 . 1 Theory of kine tic reaction rate

2 . 2 . 2 Temperature dependence of the reac t ion rate 2 . 2 . 3 Effect of other variables on the reaction rate

1

3 3 4 4 6 9 2 . 3 Quantitative Es timation of the Changes in Food During Heat

2 . 4

2 . 5 3 .

3 . 1 3 . 2

Process ing

2 . 3 . 1 Analysis of concen trat ion

2 . 3 . 2 Determination of temperature d istribution

2 . 3 . 2 . 1 Determination of thermal lag in steady-s tate heating

--

1 0 1 0 1 0

1 1 2 . 3 . 2 . 2 Experimental heat penetration measurement 1 2 2 . 3 . 2 . 3 Theore tical determinat ion 1 3 2 . 3 . 3 Calcula tion o f kinetic parameters

Changes of Food During Heat Processing 2 . 4 . 1 As corbic acid

2 . 4 . 2 Ribof lavin 2 . 4 . 3 Colour

2 . 4 . 3 . 1 Browning reac tion

2 . 4 . 3 . 2 Pigment / chlorophyll destruc tion 2 . 4 . 3 . 3 Total colour change

2 . 4 . 4 Viscosi ty Conclusion

INVESTIGATION OF TESTING METHODS AND DEVELOPMENT OF PROCESS

Introduction

Inves tigation of Tes ting Me thods 3 . 2 . 1 Ascorb ic acid

3 . 2 . 2 Riboflavin 3 . 2 . 3 Colour 3 . 2 4 Viscos i ty

1 4 1 7 1 8 2 2 2 5 25 28 29 3 2 3 3 3 5

35 36 36 37 3 7 3 8

3 . 3

3.4

3.5 4.

4 . 1 4.2 4.3

4.4

Development of Process

3.3.1 Preparation of baby foods 3 . 3 . 2 Preprocess ing

3 . 3 . 2.1 Thawing 3.3 . 2 . 2 Preheat ing 3 . 3 . 3 Process ing

3.3 . 3 . 1 Temp erature measurement 3.3.3.2 Re tor t opera tion

3 . 3 . 3 . 3 Process ing conditions Adj us tment of Process

3 . 4 . 1 Formula tion

3.4.2 Preprocess ing cond i tions Final Process

TEMPERATURE DISTRIBUTION IN A CAN DURING PROCESSING Introduction

Experimental De termina tion of Temperature Distribution Computer Programs for Temperature Dis tr ibu t ion Calculation 4.3 . 1 Analy tical sqlution method

4.3.2 Numerical .finite dif ference me thod Thermal Property Determinat ion

38 38 40 40 40 41 41 42 4 2 44 44 46 47

51

51 52 54 54 57 60 4 . 5 Comparison be tween Predic ted Temperatures from the Two Computer

Pro grams - Analy tical Solu t ion and Numer ical Fini te Difference ⁶³ 4.6 Comparison of the Predic ted Temperatures from the Analy tical

4.7

Solu tion Program and the Exper imen tal Temperatures 4 . 6 . 1 Comparison of temperatures in the heating 4 . 6 . 2 Comparison of temperatures in the cooling 4.6 . 3 Comparison of temperatures in the overall Mod ification of the Analy tical Solu tion Program

4.7.1 The beginning of the cooling 4.7 . 2 The later cooling s tage 4 . 7 . 3 Conclusion

s tage

phase phase process

4.8 Comparison of the Exper imental Temperatures and the Predic ted 68 68 71 75 75 75 79 80

Temperatures from the Mod if ied Analy tical Solu tion Program ⁸²

4.9 Conclusion ⁸⁶

5 . DETERMINATION OF KINETIC PARAMETERS BY UNSTEADY-STATE PROCEDURE 88

5 . 1 5 . 2 5 . 3

5 . 4

Introduction

Experimental Analysis of Quali ty Retention Quali ty Re tention Calculat ion

5 . 3 . 1 Theory of quali ty retention calculat ion

88 88 89 89 5 . 3 . 2 Computer program for quali ty retention calculat ion 9 2 5 . 3 . 3 Size o f time increment and dimens ion increment 9 3 Determination of Kine tic Parame ters

5 . 4 . 1 The des ign 5 . 4 . 2 The analysis

95 96 96 5 . 5 Determinat ion of Kine tic Parameters for Ascorbic Acid 1 00 5 . 5 . 1 Determination of the range of k1 29oc and Ea 1 00 5 . 5 . 2 A model for ascorbic acid for d e termination of kinetic

parame ters 1 0 1

5 . 6 De termination o f Kine tic Parame ters for Riboflavin 105 5 . 7 Determination of Kine tic Parame ters for Colour 1 10 5 . 8 Determination of Kine tic Parame ters for Viscosi ty 1 1 1

5 . 9 Conclus ion 1 1 4

6 .

6 . 1 6 . 2

6 . 3 6 . 4 6 . 5

6 . 6

KINETIC PARAMETER DETERMINATION BY STEADY-STATE PROCEDURE

Introduc tion Experimentation

6 . 2 . 1 Sample preparation

6 . 2 . 2 Thermal process ing sys tem

6 . 2 . 3 Determination of ascorb ic acid and riboflavin Des truct ion of Ascorb ic Acid and Riboflavin on Heating Determina tion of the Order of Reaction

Kinetic Parameters Determination

6 . 5 . 1 Calculat ion of kine tic parame ters for f irs t order reaction

6 . 5 . 2 Calculat ion of kine tic parame ters for second order reaction

6 . 5 . 3 Determina tion of kinetic parame ters for as corb ic acid 6 . 5 . 4 De termination of kinetic parame ters for riboflavin Comparison of Kinetic Parame ters Determined by S t eady- S tate and Uns teady-S tate Procedures

1 1 7

1 1 7 1 1 7 1 1 7 1 1 8 1 1 9 1 1 9 1 2 1 1 26

1 26

1 2 7 1 29 1 3 3

1 38

6 . 7 7 .

7 . 1 7 . 2

7 . 3 7 . 4

7 . 5 8 .

3 . 1 3 . 2 3 . 3 4 . 1 4 . 2 4 . 3 4 . 4

4 . 5

6 . 6 . 1 As corb ic acid 6 . 6 . 2 Ribo flavin Conclusion

DISCUSSION

Temperature Predict ion in the Can

Use of Steady-State Kine tics Data to Pred i c t Quali ty Changes in Uns teady-Sta te Heat Proces sing

Kine tic Analysis Us ing Uns teady-State Heating Procedure Kine tic Parame ters for As corb ic Acid, Riboflavin, Colour and Viscos i ty in Heat Process ing of Baby Food

Applicat ion to Processing

CONCLUSION REFERENCES APPENDICES

Analysis of Ascorbic Acid and Riboflavin Analytical Me thod

x, y and Y of Control and Heated Samples Analy tical Solution Program

Numerical Finite Dif ference Me thod Program Thermal Dif fusivi ty De termination Results

Dis tribution of Residuals for Determining Ac curacy of the Analy ti'cal Solution for Calcula ting Temperatures

Mod i fied Analyti cal Solution Program

4 . 6 Comparison o f Experimental Tempera tures and Predic ted

1 38 1 39 142

144 1 44

145 145

146 1 4 8

149 1 50

1 75 1 76 1 80 1 8 1 1 86 1 89

190 1 9 3

Temperatures from the Mod i fied Analytical Solut ion Program 199 4 . 7 Me thod of Quali ty Re tent ion Calcula tion for Micro-organisms

and As corbic Acid

4 . 8 An Example of Le thali ty Calculation

4 . 9 Dis tribution o f Res iduals for Determining Accuracy o f the Mod i f ied Analy ti cal Solution Program for Calcula ting Temperatures

5 . 1 Analyt ical Results

5 . 2 Quali ty Re ten tion Calculation Prog�am

201 203

205 207 2 1 1

5 . 3 5 . 4 5 . 5

An Examp le of Kine tic Parame ters Calculation

Est imation of k 1 29oC for the Design for Ascorbic Acid

Determination of k 1 29 oc and Ea for Ribof lavin , Colour Y , and Viscos i ty Using Equivalent Process ing Time

6 . 1 Quali ty Re tention Calculation Program Based on Second Order Kine tics

2 1 7 2 24

226 2 30

LIST OF TABLES

2 . 1 Reac tion Ra te Cons tants and Ac tivation Energies for Ascorb ic Acid

2 . 2 Reac tion Rate Cons tants for Riboflavin

2 . 3 React ion Rate Cons tants and Ac tivation Energ ies for Non-Enzymic Browning Reac t ion

2 . 4 Reaction Rate Cons tants and Ac tivat ion Ene rgies for Chlorophyll Des truc tion

2 . 5 React ion Ra te Cons tants and Activat i'on Energies for Colour Change

3 . 1 Dis tance from the Centre to the Measured Points 4 . 1 Experimental Run Number and Proces sing Cond i tions

4 . 2 Comparison of the Calculated Tempera tures a t the Centre of the Can

4 . 3 Diffusivities o f Baby Food a t Variuos Tempera tures 4 . 4 Comparison of Temperatures Predicted by the Analy ti cal

Solution and the Numeri cal Fini te Dif f erence Programs 5 . 1 The Mean Ini t ial and Final Quali ty on Hea t Process ing

5 . 2 Effect of Size of Increment on Quali ty Re ten tion Calcula tion

5 . 3 Level of the k 1 29oC and the Ea in the Or thogonal Compos i te Des ign for As corbic Acid

5 . 4 Or thogonal Compos i te Des ign f or Ribo flavin

5 . 5 Average Absolu te Res iduals and their Standard Deviations Resulting from Dif ferent Levels of k 129 oC and Ea

6 . 1 Hea ting Temperatures and Times for Steady-State Hea ting Me thod

6 . 2 Concentration o f Ascorbic Acid and Riboflavin Be fore and Af ter Heating

6 . 3 Correlation Coe f f i c ien ts of Regression Analysis of

Concentrat ion of As corbic Acid and Riboflavin wi th Time of Heating

2 1 24

27

30

3 1 43 5 3

5 7 6 2

64 90 93

103 106

107

1 1 9

1 20

1 23

6 . 4 Kine tic Reaction Rate Cons tants at Various Temperatures for Ascorbic Acid

6 . 5 Ac tivation Energy , Frequency Factor and Kine tic Reaction Rate at 1 2 9°C for As corb ic Acid

6 . 6 Kinetic Reaction Rate Cons tants at Various Temperatures for Riboflavin

6 . 7 Activation Energy , Frequency Fac tor and Kine tic Reaction Rate at 1 29 °C for Ribof lavin

6 . 8 Second Order Kine tic Reaction Rate Cons tants at Various

6 . 9

Temperatures for Riboflavin

Ac tivation Energy , Frequency Factor , Kinetic Reaction Rate at 1 2 9°C for Second Order Kine tics for Riboflavin

6 . 10 Comparison of Ea and k 129oc for Ascorbic Acid Determined by Steady- and Uns teady-State Procedures

6 . 1 1 Comparison of Ea and k 1 29oC for Ribof lavin Determined by Steady- and Uns teady-State Procedures

6 . 1 2 Average Res iduals at Various k 1 2 9oc and Ea for Riboflavin in Uns teady-State Heating in Can

1 �

1 30

1 34

1 34

1 36

1 36

1 38

1 39

1 4 1

3 . 1 3 . 2

4 . 1

4 . 2

LIST OF FIGURES

Thermocouple Arrrangement in a Can

Time , Temperature and Viscos i ty Relationships During Preprocessing of Baby Food

Comparison of Predicted Temperatures from the Computer Programs at ( r/a , x/h) of (0 . 0 , 0 . 0)

Comparison of Predic ted Temperatures from the Computer Programs at ( r/a , x/b) of ( 2 / 3 , 2 / 3)

4 . 3 Distribution of Residuals for Comparison of the Analy tical Solution and the Numerical Finite Difference Me thod f or ^· Run no . 6

4 . 4 Comparison of Experimental Temperatures and Predic ted

Temp eratures from the Analytical Solution Computer Program for Run no . 6

4 . 5 Comparison of Experimental Temperatures and Predic ted

Temp eratures from the Analyt ical Solution Computer Program for 43

48

65

66

67

69

Run no . 7 70

4 . 6 Heat Pene tration Curves for Dif ferent Can Contents and Different

4 . 7 4 . 8

Head spaces

Diagram Showing Different Parts in Heat Processing Variance versus Thermal Dif fusivity

4 . 9 Comparison o f Experimental Temperatures and Predic ted

Temperatures from the Modi fied Analy tical Computer Program for Run no . 6

4 . 10 Comparison o f Experimental Temperatures and Predicted

Temperatures from the Modif ied Analytical Computer Program for Run no . 7

5 . 1 5 . 2

Flow Char t for Quali ty Re tention Calculation Program

An Or thogonal Central Composite Design to Fit a Second Order Response Surface

7 3 7 6 7 8

8 3

84 94

9 7

5 . 3 Firs t Design for Ascorbic Acid with Calculated Average Absolute Res iduals and their Standard Deviations

5 . 4 Orthogonal Design for Ascorbic Acid with Calculated Average Res iduals and their Standard Deviations

5 . 5 Second Orthogonal Composite Des ign for Riboflavin with Average Absolute Residuals and their S tandard Deviations 5 . 6 First Orthogonal Composite De sign for Colour, Y,with Average

Abs olute Res iduals and their Standard Deviations

5 . 7 Second Orthogonal Composite Design for'colour, Y, wi th Average Absolute Res iduals and their Standard Deviat ions 5 . 8 Firs t Orthogonal Compos i te Design f or Visc osity with Average

Absolute Res iduals and their Standard Deviations 5 . 9 Second Orthogonal Composite Des ign for Viscosity with

Average Absolute Residuals and their Standard Deviat ions 6 . 1 Degradation Rate for Ascorbic Acid in Baby Food on Heating

Described by Firs t Order Kinetics

6 . 2 Degradation Rate for Ribof lavin in Baby Food on Heating Described by Firs t Order Kinetics

6 . 3 Degradation Rate for Rib oflavin in Baby Food on Heating Described by Second Order Kinetics

6 . 4 Arrhenius Plot for Degradation of Ascorbic Acid and Ribof lavin in Baby Food on Heating

6 . 5 6 . 6

Probability Plot of Calculated % Residual for Ascorbic Acid Probability Plot of Calculated % Res idual for Riboflavin 6 . 7 Arrhenius Plot for Degradation of Ribof lavin in Baby Food on

Heating Described by Second Order Kinetics

102

104

108

1 1 0

1 1 2

1 1 3

1 15

1 24

1 25

125

1 3 1 1 3 2 1 35

1 3 7