alexandra kathleen lenard smith

166 Pages·2000·7.21 MB·French

THE STABILITY OF WHIPPED CREAM STRUCTURE: THE EFFECT OF HEAT
TREATMENT AND THE ADDITION OF STAEHLIZEREMULSIFIER
A Thesis
Presented to
The Faculty of Graduate Studies
of
University of Guelph
by
ALEXANDRA KATHLEEN LENARD SMITH
In partial filfilment of requirements
for the degree of
Doctor of Philosophy
December, 1999
OAlexandra Smith, 1999
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ABSTRACT
THE ST.4BILITY OF WHIPPED CREAM STRUCTURE: THE EFFECT OF
HEAT TREATMENT AND THE ADDITION OF STABILIZER/EMULSIFIER
Alexandra Smith Advisors:
University of Guelph Dr. ff. D. Goff
1999 Dr. Y. Kakuda
Whipping cream, with 35% butter fat. was high-temperature. short time
pasteurized (7S°C, 16s), and ultra-high temperature sterilized (140UC.Js ), with and
without the addition of stabilizer/emulsifier, to study the effect of these processing
conditions on the stability of foarn structure. Processed creams were whipped to
maximum overrun using a double beater system. Duplicate foams were refrigerated for 24
hours to compare with fresh foams. Low temperature scanning electron microscopy
(LTSEM) was conducted to image foms and establish visual criteria for foam stability
through quantitative stereology. Air bubble size, lamella length and volume fraction of
air in the foam were calculated through cornputer assisted global rneasurement. Fresh
foams were similar but significant differencrs in aged foam morphology were caused by
heat treatment in both the stabilized and unstabilized foams. Results showed more large
bubbles, thicker lamella and a higher volume fraction of' air in aged HTST pasteurized
foams compared to aged foam prepared from UHT sterilized crerun. Rheological
measurement of foam properties was then conducted by dynmic oscillatory testing to
quanti@ visco-elasticity of foms structure to explain differences. Again. fkesh foams
were similar and differences were expressed in aged foams. Aging of stabilized foarns
caused a significmt decrease in G' (storage modulus) and Ga (loss modulus) values
regardless of heat treatment. Differences due to heat treatment were expressed through
tanô (GU/G'b) ecause of a proportionally higher value for G' and greater dependence on
frequency measured in the aged foam prepared from stabilized UHT sterilized creani.
This result is indicative of lower visco-elasticity and less ability to withstand
destabilization processes. Further work concentrated on study of the proteins in the foam
to determine if the more severe heat treatment was affecting structure and therefore, the
contribution of proteins to semm phase viscosity and integrity of bubble interface. It has
been reported that P-lactoglobulin denatures above temperatures of 7O'C and could
account for loss of foam structure. However, electrophoresis (SDS-PAGE) did not show
differences in the quantity of P-lactoglobulin or a-lactalbumin at the milk fat globule
membrane (MFGM). Transmission electron microscopy did show differences in semm
phase morphology with a loss in network structure caused by aging particularly in foam
whipped from stabilized UHT sterilized cream.
I am dedicating this thesis to my sons Andrew and Stuart Smith.
1 would like to thank my fàmily, especially my mother Kay Lemard and my sister
Sara. for their love and support.
The Department of Food Science has made this work possible by allowing me to
baiance work. farnily and study. The faculty and students have been my teac hers
throughout. My CO-advisors.D oug Goff and Yukio Kakuda. have made a signifiant
contribution to the knowledge gained and added to the depth and value of the research.
Iû ppreciate the time and quality of assistance provided by Steve Gismondi who
made the statistics meaningful and fun. Ken Baker provided the basis for the image
malysis in addition to his friendship. Susan Tosh contributed her wealth of information
and invested a considerable amount of tirne to the success of this project. Diane Wood
and Judy Stuart have provided support and friendship.
1 would especially like to thank Brenda Sun. Thank you Brenda for contributing
your humour, your tirne, and your expertise in microscopy which were such a great help.
TABLEOFCONTENTS
TABLE OF CONTENTS
1
LIST OF TABLES v
LIST OF FIGURES vii
LIST OF ABBREVIATIONS ix
GENERAL INTRODUCTION AND STATEMENT OF
OBJECTIVES. ............................................................................................. I
LITERATURE REVIEW ............................................................................ 5
Composition of Whipping Cream .......................................................... 5
2.1.1 Milk Fat Globule Membrane ........................................................ 6
. .
2.1.2 Milk Protein Composttion. ........................................................... 7
2.1.2.1 Casein MiceIIes .............................................................. 8
2.1.2.2 Whey Proteins ............................................................... 9
2.1.3 Milk Fat ....................................................................................... 10
Effect of Processing on Proteins ........................................................... Il
......................................................................
2.2.1 Complex Formation 12
2.2.2 Whey Proteins. ............................................................................. 13
2.3.3 Heat Transtèr and the MFGM ...................................................... 14
The Addition of Stabilizer/EmuIsifier. ................................................... 15
..................
2.4 The Effect of Heat Treatment on Whipping Charactenstics 16
2.4.1 Development of Foam Structure. ................................................. 16
2.4.2 The Stability of Emulsions and Foams ......................................... 19
. . .
2.4.3 De-stabilmtion Processes ............................................................ 23
7.44 Stability of Whipped cream .........................................................
2.4.5 Measurement of Foam Stability ...................................................
METHO DS ...................................................................................................
Heat Treatment of Whipping Cream. .....................................................
Laser Light Scatterhg. ............................................................................
Electrophoresis (SDS.PAGE) ................................................................
Rheology of Whipped Cream .................................................................
Electron Microscopy of Whipped Cream ...............................................
3 .5.l Low Temperature Scanning Electron Microscopy (LTSEM). .....
3.5.2 Freeze Substitution and Low Temperature Embedding for
.........................................
Transmission Electron Microscopy
Quantitative Stereology ................... .... ...................................................
WHIPPED CREAM STRUCTURE MEASURED BY
QUANTITATIVE STEREOLOGY. ........................................................
4.1 INTRODUCTION. ..............................................................................
4.2 MATEMALS AND METHODS. ..................... ...............................
,.,
4.2.1 Cream Preparation ......................................................................... 64
4.2.2 Low Temperature Scanning Electron Microscopy (LTSEM). ...... 65
................... . ..........................................................
4.2.3 Stereology 66
4.3 FWSULTS AND DISCUSSION. .......................................................... 69
4.3.1 Effect of Heat Treament and Stabilizer on whipping time and
Overrun Percent. ............................................................................
4.3.2 Microstructure of Foams. .............................................................. 70
. .
4 *. .~ Q uantitative St ereology ................................................................. 73
J
4.4 CONCLUSION ...... ..,. . ....................................................................... 86
5 MICROSTRUCTURE AND RHEOLOGICAL PROPERTIES OF
WHIPPED CREAM AFFECTED BY HEAT TREATMENT AND
ADDITION OF STABILIZER TO THE CMAM... ................................ 87
5.1 INTRODUCTION ................................................................................ 87
......................................................
5.2 MATERIALS AND METHODS 91
5 .2.1 Crearn Processing. ......................................................................... 91
5-22 Light Scattering. ............................................................................ 92
5.2.3 Low Temperature Scanning Electron Microscopy (LTSEM) ....... 92
5.2.4 Rheology ........................................................................................ 93
5.3 RESULTS AND DISCUSSION. ......................,,.................................... 95
5.4 CONCLUSION. ...................................................................................... IL0
6 CHANGES IN PROTEIN AND FAT STRUCTURES IN WHIPPED
CREAM CAUSED BY HEAT TREATMENT AND THE ADDITION
OF STABILIZER TO T m C REAM ......................................................... 111
.................................................................................
6.1 INTRODUCTION 111
iii
METHODS. ...........................................................................................
6.2.1 Cream Processing. .........................................................................
6.2.2 SDS-PAGE ....................................................................................
6.2.3 Freeze Substitution of Foams for TEM .........................................
RESULTS AND DISCUSSION ...........................................................
CONCLUSION. ................. ........... ........................................................
CENERGL CONCLUSIO N.S.. .*......*, ......**............**....*...**........*........
REFERENCES. ............................................................................................
APPENDICES ...............................................................................................
LIST OF TABLES
. . . .
Table 2.1 Composition of whipping cream. .........................................................
Table 3.1 Processing system parameters to achieve heat treatment conditions ...
Table 3.2 Properties of cryogens for LTSEM and TEM ......................................
Table 4.1 Whipped crearn treatments prepared for analysis and nurnber of
bub bles counted ....... .. .. .. .. .. . .. .. .. . . ....... . . .. . . . . .. . .. . .. . .... .. . . .. . . . . . . .. . . . . . . . . . . .. . ..
Table 4.2 Whipping times and ovemm percentage for crearn treatments
whipped to maximum o v e m. ............................................................
Significance of whipped cream treatrnent coninsts defined by the
mean air bubble size and mean lamella length ....................................
Table 4.4 Significance of treatrnent contrasts defined by the air bubbles as a
percent of the volume ................................... ........... ... .. . . .. . ...... ............
,
Table 5.1 Whipped cream treatments prepared for analysis. ...............................
Tabie 5.2 Means and significance (Pi0.0 1) of fat globule surface-volume
measurement. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 5.3 Lest squares means and significant difference of whipping time (s)
and ovemm % for HTST and UHT whipped cream treatmenis ..........
Table 5.4 Significance of the effect of heat treatment and addition of stabilizer
to whipping cream comparing fiesh and aged foams through G'
...........................................*......................................
(elastic modulus)
Table 5.5 Significance of the effect of heat treatment and addition of stabilizer
to whipping cream comparing fiesh and aged foams through logG"
(viscous modulus) ................................---..-......--.................................*