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MANUFACTURE
A dissertation presented in partial fulfillment of the requirements for the degree of Master of Technology
at Massey University.
ZHENG ZHAO
1989
I
i
ABSTRACT
Blending experiments and storage trials were carried out to assess the feasibility of manufacturing infant formula through dry blending of high fat whey powder (HFWP) with whole milk powder (WMP) or a base powder (BP) made from skim milk, sucrose and corn oil.
An indication of cohesiveness of the components of the blends was obtained by measuring compressibility using an Instron testing machine. Compressibility decreased in the following order: BP, WMP, HFWP, lactose and ascorbic acid. Particle size determination using a laser sizer indicated that the particle size increased in the above sequence.
Scanning electron microscopy revealed no evidence of an ordered mixture for either whey powder with milk powder or the powders mixed with ascorbic acid. The mixtures did not exhibit complete randomness and segregation. They are thus termed 'pseudorandom mixtures' .
HFWP was blended with WMP or BP to achieve a target ratio 50:50 in both an experimental ribbon blender and a pilot ribbon blender. Using Response Surface Methodology, load ratio and mixing time but not rotation speed were found to have significant effects on the homogeneity with the experimental ribbon blender. At load ratio 0.4, the time for reaching a certain homogeneity was shorter than that at load ratio 0.8. The cohesiveness of BP impaired its mixing.
A mixing index based on a satisfactory sample standard deviation has an acceptable value of 1. Both powder ratio scores and ascorbic acid level could be mixed below a MI of 1.5 but above 1. As to
protein, fat, carbohydrate, the mixtures reached the acceptable MI.
The secondary nutritional requirements such as the ratio of whey protein to casein and the ratio of unsaturated fatty acid to saturated fatty acid were above 1 when the powder ratio Mis were higher than 1.
After mixing WMP and HFWP for 10 minutes differences of sensory quality could not be detected by the taste panelists even though the MI was still above 1.
Unblended and blended samples of WMP and HFWP were tested through a 180 day storage trial at 20°c, 30°c and 40°c. There was no significant difference between unblended and blended samples on the criteria of TBA, PV, HMF, oxidised flavour and caramel flavour at the 5%
probability level.
Using the Arrhenius approach, at 20°c, the shelf lives of unblended and blended samples were estimated as 1628 days and 1090 days respectively, with an oxidised flavour limit of 3.5 out of 7 points.
The shelf lives were 480 days and 466 days based on a PV limit of 2 milliequivalents
o
2 per kg fat.Dry blending is a feasible technique for manufacturing infant formula, with acceptable homogeneity of the main components of the blended samples and with normal storage stability. The cohesiveness of the components and the design of blender are important factors in improving homogeneity. Further trials are recommended in both experimental and commercial plants.
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ACKNOWLEDGEMENT
I wish to thank my supervisor Mr Rod Bennett for all his help and encouragement during the course of this work.
My appreciation is extended to:
Dr Gordon Robertson for his suggestion on storage trial.
Dr Mary Earle for her suggestion on experimental design.
Miss Barrett Susan for organising the sensory evaluation and the staff of Food Technology Department and Food Research Center, Massey University who were the members of sensory panels.
Mr D. H. Hopcroft, Biotechnology Division, DSIR, Palmerston North, for his work on scanning electron microscopy.
Miss Wendy Cawdron, Milk Powder Section, DRI, for the her work on particle size determination.
Mr Scott Morris, Whey Product Division, NZDB, for organising the experimental material.
My acknowledgement is also extended to New Zealand Dairy Board and the Chinese Government who made it possible for me to study in this country.
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TABLE OF CONTENTS
ABSTRACT
ACKNOWLEDGEMENT TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES LIST OF PHOTOGRAPHS
CHAPTER 1: INTRODUCTION
CHAPTER 2: LITERATURE REVIEW
2.1 Cohesiveness of food powders 2.2 Determination of cohesiveness 2.3 The types of mixtures
2.4 Assessment of homogeneity of mixture 2.5 Mixing practice
2.6 Stability of milk powder and whey powder
CHAPTER 3: MATERIALS AND METHODS FOR CHEMICAL TESTING AND SENSORY EVALUATION
3.1 Introduction 3.2 Materials 3.3 Methods
3.3.1 Determination of powder ratio index 3.3.1.1 Background
PAGE i i i i
iv
X
xiii xvi
1
3 5 6 8 9 11
13
13 13 14 14 14
CHAPTER 4:
3.3.1.2 3.3.1.3 3.3.1.4 3.3.1.5
Preparation of samples Calcium testing method Amido Black binding method Comparison of calcium testing method with Amido Black method 3.3.2 Determination of ascorbic acid
3.3.2.1 3.3.2.2 3.3.2.3
Background Procedure
Reliability of the method 3.3.3 Determination of 2-Thiobarbituric Acid
(TBA) Value 3.3.3.1 3.3.3.2 3.3.3.3
Background Procedure
Reliability of the method 3.3.4 Determination of peroxide value
3.3.4.1 3.3.4.2 3.3.4.3
Background Procedure
Reliability of the method 3.3.5 Determination of 5-hydromethylfurfral
3.3.5.1 3.3.5.2 3.3.5.3
Background Procedure
Reliability of the method 3.3.6 Miscellaneous
3.3 7 Sensory evaluation 3.3.7.1
3.3.7.2
Background
Experimental conditions and procedure
SOME PHYSICAL PROPERTIES OF HIGH FAT WHEY POWDER,
V
15 15 17 18
18 18 19 19
20 20 20 21 21 21 22 23 23 23 24 24 26 27 27
28
CHAPTER 5:
WHOLE MILK POWDER AND BASE POWDER 4.1 Introduction
4.2 Compressibilities of the powders 4.2.1 Introduction
4.2.2 Experimental 4.2.2.1 Material 4.2.2.2 Procedure 4.2.2.3 Data Analysis 4.2.3 Results and discussion
4.3 Sorption isotherms of high fat whey powder, whole milk powder and base powder
4.3.1 Introduction 4.3.2 Experimental
4.3.2.1 Material 4.3.2.2 Procedure 4.3.3 Results and discussion
4.4 Scanning electron microscopy of the powders 4.4.1 Introduction
4.4.2 Experimental
4.4.3 Results and discussion 4.5 General discussion
CHARACTERIZATION OF EXPERIMENTAL BLENDER 5.1 Introduction
5.2 Experimental design 5.3 Experimental
5.3.1 Blending
5.3.2 Testing of the homogenei ty
30 30 30 30 31 31 31 31 32
35 35 36 36 36 37
41 41 41 42 43
47 47 48 49 49 49
CHAPTER 6:
CHAPTER 7:
5.3.3 Data analysis 5.4 Results and discussion
5.4.1 Selection of rotating mode 5.4.2 Analysis of co-rotating data 5.5 Conclusion
STUDY ON MIXING RATE 6.1 Introduction
6.2 Experimental design 6.3 Experimental
6.3.1 Blending 6.3.2 Testing
6.4 Results and discussion
6.4.1 Mixing rate equations
6.4.2 Effects of load ratio on homogeneity and mixing rate
6.4.3 Effects of cohesiveness on homogeneity and mixing rate
6.4.4 Fluctuations of homogeneity after the minimum MI points
vii 49 50 51 51 54 56 56 56 57 57 57 57 62
63
64
64 6.4.5 Effects of the profile of the blender 65 6.4.6 Sensory quality variance due to powder 66
ratio 6.6 Conclusion
STUDY ON PILOT BLENDER TRIAL 7.1 Introduction
7.2 Experimental
7.2.1 Description of the blender
67
68 68 68 68
7.2.2 Experimental procedure 7.3 Results and discussion
7.3.1 Sampling effects on homogeneity 7.3.2 Validity of first order equation 7.3.3 Optimum zone of a mixing run 7.3.4 Mixing index and nutrition
specification
7.3.5 Mixing microcomponents with bulk powders
7.4 Conclusion
CHAPTER 8: STUDY ON STORAGE TRIAL 8.1 Introduction
8.2 8.3
8.4
Experimental design Experimental
8.3.1 Sample preparation 8.3.2 Chemical testing 8.3.3 Sensory evaluation 8.3.4 Data analysis Results and Discussion
8.4.1 Storage stabilities assessed by chemical testing
8.4.1.1 TBA values 8.4.1.2 PV values 8. 4 .1. 3 HMF
8.4.2 Storage stabilities of the podwer assessed by sensory evaluation
8.4.3 Kinetics of TBA, PV, HMF and sensory
68 68 71 71 72
74
74 76
77 77 79 79 79 80 80 80 81
81 81 91 92
93
scores
8.4.3.1 TBA and PV 8.4.3.2 HMF
8.4.3.3 Sensory score
8.4.3.4 Prediction of shelf life 8.5 Conclusion
CHAPTER 9: SUMMARY AND CONCLUSION
BIBLIOGRAPHY APPENDIXES
ix 96 96
104 105 107 112
114
117 12 6
TABLE 3.1
3.2 3.3
3.4 3.5
3.6
3.7
3.8 3.9 3.10 3.11
4.1
4.2
4.3
LIST OF TABLES
Chemical composition of high fat whey powder, whole milk powder and base powder.
The ratio of milk and whey in standard samples Coefficients of regression equations for ratio
indexes (calcium testing method) Calcium content of whole milk powder
Coefficients of regression equations for ratio indexes (Amido black method)
Absorbance of reconstituted whole milk powder tested by Amido Black.
Ascorbic acid content of the mixture of whole milk powder and high fat whey powder
TBA value of whole milk powder PV value of whole milk powder HMF value of whole milk powder
Chemical methods for analysis of milk powders and high fat whey powder
Arithmetic average diameters, bulk densities and compressibilities of high fat whey powder, whole milk powder, base powder, ascorbic acid and lactose B.E.T. parameters of high fat whey powder, whole milk powder and base powder
G.A.B. parameters of high fat whey powder, whole milk
PAGE 14
15 16
16
17
18
20 21 23 24
26
34
38
4. 4
5.1
5.2
5.3
5.4
5.5
6.1
6.2
6.3
6.4
6.5 7.1
7.2
powder and base powder
Variations of particle sizes of high fat whey powder, whole milk powder, base powder lactose, and ascorbic acid
23 Factorial experimental design and results of counter-rotating block
23 Factorial experimental design and results of co-rotating block
Coefficients and t values of the regression equation (5 .1)
Coefficients and t values of the regression equation (5. 2)
Predicted mixing indexes from PSA
Ratio and ascorbic acid mixing indexes of the mixture of whole milk powder with high fat whey powder
Ratio and ascorbic acid mixing indexes of the mixture of base powder with high fat whey powder
Coefficients of mixing rate equations (whole time range)
Coefficients of mixing rate equations (reduced time range)
Variance of powder ratio and sensory scores Ratio and ascorbic acid mixing indexes in pilot blender trail
Coefficients of mixing rate equations
xi 38
44
50
50
52
53 54
60
60
62
63 67
69 65
7.3
7.4 8.1 8.2 8.3 8.4 8.5 8.6
8.7 8.8 8.9 8.10 8.11 8.12
8.13 8.14 8.15 8.16
(whole time range)
Coefficients of mixing rate equations (reduced time range)
Composition indexes of the pooled samples Chemistry testing results
Mean scores of sensory evaluation
F ratios of chemistry testing results by twoway ANOVA F ratios of individual scores of sensory evaluation F ratios of mean scores of sensory evaluation
Correlation coefficients between sensory evaluation scores and chemistry testing results
TBA reaction rate constants based on regression PV reaction rate constants based on regression HMF reaction rate constants based on regression Arrhenius equation constants of TBA, PV and HMF Linear equation constants of TBA, PV and HMF
72
72 75 86 90 90 94 95
96 99 99 100 103 103 Effects of analytical precision of the method on the
estimation of the rate constant for chemical reactions 104 Sensory score change rate constants
Constants of Arrhenius equations of sensory scores Constants of linear equations of sensory scores Storage lives estimated with criteria of TBA, PV and Sensory scores
106 106 107
108
xiii LIST OF FIGURES
FIGURE PAGE
4.1 Compressibilities of high fat whey powder, whole milk powder, base powder, lactose and ascorbic acid 4.2 Sorption isotherms of the powders
6.1 Mixing indexes of ratio and ascorbic acid of WMP mix at load ratio 0.4
6.2 Mixing indexes of ratio and ascorbic acid of WMP mix at load ratio 0.8
6.3 Mixing indexes of ratio and ascorbic acid of BP mix at load ratio 0.4
6.4 Mixing indexes of ratio and ascorbic acid of BP mix at load ratio 0.8
7.1 Mixing indexes of ratio and ascorbic acid of BP mix in pilot blender (sampled from discharge)
7.2 Mixing indexes of ratio and ascorbic acid of BP mix in pilot blender (sampled from the inside)
7.3 Mixing indexes of ratio and ascorbic acid of BP mix in pilot blender (pooled sample)
7.4 Optimum zone of mixing high fat whey powder and base powder
8.1 Changes of TBA values in whole milk powder at 20°c, 30°c and 40°c
8.2 Changes of TBA values in high fat whey powder at 20°c, 30°c and 40°c
8.3 Changes of TBA values in the blended samples at 20°c,
33 37
58
58
59
59
70
70 70
74
83
83
30°c and 40°c
8.4 Changes in PV of whole milk powder at 20°c, 30°c and 40°c
8.5 Changes in PV of high fat whey powder at 20°c, 30°c and 40°c
8. 6 Changes in PV of the blended sample at 20°c, 30°c and 40°c
8.7 Changes of HMF in whole milk powder at 20°c, 30°c and 40°c
8.8 Changes of HMF in high fat whey powder at 20°c, 30°c and 40°c
8. 9
8.10
8 .11
8.12
8 .13
8.14
8.15
Changes of HMF in the blended sample at 20°c, 30°c (o) and 40°c
Changes of sensory mean score of oxidised flavour in the blended samples at 20°c, 30°c and 40°c
Changes of sensory mean score of oxidized flavour in the unblended samples at 20°c, 30°c and 40°c
Changes of sensory mean score of caramel flavour in the blended samples at 20°c, 30°c and 40°c Changes of sensory mean score of caramel flavour in the unblended samples at 20°c (x), 30°c and 40°c Schema of the prediction of the shelf lives through kinetic approch
Shelf lives as a function of temperature of whole
83
84
84
84
85
85
85
88
88
89
89
97
milk powder and high fat whey powder estimated by TBA 109 8.16 Shelf lives as a function of temperature of the blended
samples and unblended samples estimated by TBA 109
8.17
8.18
8.19
Shelf lives as a function of temperature of whole milk powder and high fat whey powder estimated by PV
Shelf lives as a function of temperature of the blended samples and the unblended samples estimated by PV Shelf lives as a function of temperature of the blended samples and the unblended samples estimated by oxidised flavour score
xv
110
110
111
LIST OF PHOTOGRAPHS
PLATE FOLLOWING PAGE
1
2 3 4 5
6 7 8
Scanning electron micrograph of high fat whey powder lOOx Scanning electron micrograph of high fat whey powder 500x Scanning electron micrograph of whole milk powder lOOx Scanning electron micrograph of whole milk powder 500x Scanning electron micrograph of base powder lOOx
Scanning electron micrograph of base powder 500x Scanning electron micrograph of ascorbic acid lOOx Scanning electron micrograph of lactose lOOx
9 Scanning electron micrograph of the mixture of high fat whey powder, whole milk powder, lactose and ascorbic acid lOOx
10 Scanning electron micrograph of the mixture of high
11 12
fat whey powder, base powder, lactose and ascorbic acid lOOx
Photograph of experimental ribbon blender Photograph of pilot ribbon blender
41 41 41 41 41 41 41 41
41
41 48 68
