Food emulsions : principles, practices, and techniques

714 Pages·2016·23.171 MB·English

by  McClements, David Julian

T H I R D E D I T I O N
Food Emulsions

PRINCIPLES, PRACTICES, AND TECHNIQUES

T H I R D E D I T I O N
Food Emulsions

PRINCIPLES, PRACTICES, AND TECHNIQUES
David Julian McClements

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Contents
Preface ....................................................................................................................................................xxi
Author ...................................................................................................................................................xxiii
1. Context and Background .................................................................................................................1
1.1 Emulsion Science and Technology in the Food Industry .......................................................1
1.2 General Characteristics of Food Emulsions ...........................................................................2
1.2.1 Definitions .................................................................................................................2
1.2.2 Mechanisms of Emulsion Instability ........................................................................6
1.2.3 Ingredient Partitioning in Emulsions ........................................................................6
1.2.4 Dynamic Nature of Emulsions ..................................................................................7
1.2.5 Complexity of Food Emulsions ................................................................................7
1.3 Emulsion Properties ................................................................................................................8
1.3.1 Dispersed-Phase Volume Fraction ............................................................................8
1.3.2 Particle Size ..............................................................................................................9
1.3.2.1 Collecting Particle Size Data ..................................................................10
1.3.2.2 Presenting Particle Size Data .................................................................10
1.3.2.3 Mean and Standard Deviation ................................................................13
1.3.2.4 Mathematical Models .............................................................................15
1.3.3 Interfacial Properties ...............................................................................................18
1.3.4 Droplet Charge .........................................................................................................18
1.3.5 Droplet Crystallinity ...............................................................................................19
1.3.6 Droplet Interactions ................................................................................................20
1.4 Hierarchy of Emulsion Properties ........................................................................................20
1.5 Understanding Food Emulsion Properties ............................................................................21
1.5.1 Factors Influencing Topics and Directions of Research .........................................22
1.5.2 General Approaches Used to Study Food Emulsions .............................................23
1.6 Overview and Philosophy .....................................................................................................25
References ........................................................................................................................................26
2. Molecular Characteristics .............................................................................................................29
2.1 Introduction ...........................................................................................................................29
2.2 Forces of Nature ....................................................................................................................30
2.3 Origin and Nature of Molecular Interactions .......................................................................30
2.3.1 Covalent Interactions ..............................................................................................30
2.3.2 Electrostatic Interactions .........................................................................................31
2.3.3 Van der Waals Interactions .....................................................................................34
2.3.4 Steric Overlap Interactions .....................................................................................36
2.4 Overall Intermolecular Pair Potential ...................................................................................38
2.4.1 Lennard–Jones Potential: Understanding Bond Strengths and Lengths ................38
2.4.2 Thermal Energy: Judging Bond Strengths..............................................................38
2.4.3 Converting Potential Energies into Forces .............................................................39
vii
viii Contents
2.5 Molecular Structure and Organization Is Determined by a Balance
of Interaction Energies and Entropy Effects .........................................................................39
2.5.1 Forms of Entropy ....................................................................................................40
2.5.2 Physicochemical Basis of Molecular Transitions ....................................................41
2.6 Thermodynamics of Mixing .................................................................................................43
2.6.1 Potential Energy Change on Mixing ......................................................................43
2.6.2 Entropy Change on Mixing ....................................................................................44
2.6.3 Overall Free Energy Change on Mixing ................................................................44
2.6.4 Complications .........................................................................................................46
2.7 Molecular Conformation ......................................................................................................46
2.8 Compound Interactions .........................................................................................................48
2.8.1 Hydrogen Bonds ......................................................................................................48
2.8.2 Hydrophobic Interactions ........................................................................................49
2.9 Computer Modeling of Liquid Properties ............................................................................49
2.9.1 Monte Carlo Techniques .........................................................................................50
2.9.2 Molecular Dynamics Techniques ...........................................................................50
2.10 Measurement of Molecular Characteristics ...........................................................................51
References ........................................................................................................................................52
3. Colloidal Interactions ....................................................................................................................55
3.1 Introduction ...........................................................................................................................55
3.2 Colloidal Interactions and Droplet Aggregation...................................................................55
3.3 Van der Waals Interactions ...................................................................................................58
3.3.1 Origin of van der Waals Interactions ......................................................................58
3.3.2 Modeling van der Waals Interactions .....................................................................58
3.3.2.1 Interdroplet Pair Potential ........................................................................58
3.3.2.2 Hamaker Function ....................................................................................59
3.3.3 General Features of van der Waals Interactions .....................................................64
3.4 Electrostatic Interactions ......................................................................................................64
3.4.1 Origins of Electrostatic Interactions .......................................................................64
3.4.2 Modeling Electrostatic Interactions ........................................................................64
3.4.2.1 Interdroplet Pair Potential ........................................................................64
3.4.2.2 Factors Influencing Electrical Characteristics of Surfaces ......................66
3.4.2.3 Influence of Ionic Strength on the Magnitude and Range of Interactions .....68
3.4.2.4 Influence of Ion Bridging on Electrostatic Interactions ...........................69
3.4.3 General Characteristics of Electrostatic Interactions .............................................69
3.5 Steric Interactions .................................................................................................................70
3.5.1 Origin of Steric Interactions ...................................................................................70
3.5.2 Modeling Steric Interactions ...................................................................................71
3.5.2.1 Interdroplet Pair Potential ........................................................................71
3.5.2.2 Mixing Contribution .................................................................................71
3.5.2.3 Elastic Contribution ..................................................................................73
3.5.2.4 Distance Dependence of Steric Interactions.............................................74
3.5.2.5 Optimum Characteristics of Steric Stabilizers .........................................74
3.5.3 General Characteristics of Steric Interactions ........................................................75
3.6 Depletion Interactions ...........................................................................................................76
3.6.1 Origin of Depletion Interactions .............................................................................76
3.6.2 Modeling of Depletion Interactions ........................................................................77
3.6.3 General Characteristics of Depletion Interactions ..................................................80
3.7 Hydrophobic Interactions ......................................................................................................80
3.7.1 Origin of Hydrophobic Interactions ........................................................................80
3.7.2 Modeling Hydrophobic Interactions .......................................................................81
3.7.3 General Characteristics of Hydrophobic Interactions ............................................81
Contents ix
3.8 Hydration Interactions ..........................................................................................................82
3.8.1 Origin of Hydration Interactions ............................................................................82
3.8.2 Modeling Hydration Interactions ............................................................................83
3.8.3 General Characteristics of Hydration Interactions .................................................84
3.9 Thermal Fluctuation Interactions .........................................................................................85
3.9.1 Origin of Thermal Fluctuation Interactions ...........................................................85
3.9.2 Modeling Thermal Fluctuation Interactions ...........................................................85
3.9.3 General Characteristics of Fluctuation Interactions ...............................................86
3.10 Nonequilibrium Effects ........................................................................................................86
3.10.1 Molecular Rearrangements at the Interface ............................................................86
3.10.2 Hydrodynamic Flow of Continuous Phase .............................................................86
3.10.3 Gibbs–Marangoni Effect ........................................................................................87
3.11 Total Interaction Potential.....................................................................................................88
3.11.1 Van der Waals and Steric Interactions ....................................................................88
3.11.2 Van der Waals, Steric, and Electrostatic Interactions .............................................90
3.11.3 Van der Waals, Steric, Electrostatic, and Hydrophobic Interactions ......................92
3.11.4 Van der Waals, Steric, Electrostatic, and Depletion Interactions ...........................93
3.12 Measurement of Colloidal Interactions ................................................................................94
3.13 Prediction of Colloidal Interactions in Food Emulsions ......................................................94
References ........................................................................................................................................95
4. Emulsion Ingredients .....................................................................................................................99
4.1 Introduction ...........................................................................................................................99
4.2 Fats and Oils .......................................................................................................................100
4.2.1 Molecular Structure and Organization ..................................................................101
4.2.2 Bulk Physicochemical Properties .........................................................................102
4.2.3 Fat Crystallization .................................................................................................104
4.2.3.1 Supercooling .........................................................................................105
4.2.3.2 Nucleation .............................................................................................106
4.2.3.3 Crystal Growth .....................................................................................109
4.2.3.4 Crystal Morphology...............................................................................110
4.2.3.5 Polymorphism ........................................................................................110
4.2.3.6 Crystallization of Edible Fats and Oils .................................................111
4.2.3.7 Fat Crystallization in Emulsions ...........................................................112
4.2.4 Chemical Changes .................................................................................................113
4.2.5 Selection of an Appropriate Lipid ..........................................................................114
4.2.5.1 Nutritional Profile ..................................................................................114
4.2.5.2 Flavor Profile .........................................................................................114
4.2.5.3 Crystallization Behavior ........................................................................114
4.2.5.4 Oxidative Stability .................................................................................115
4.2.5.5 Bulk Physicochemical Properties ..........................................................115
4.2.5.6 Oil Quality .............................................................................................115
4.3 Water ....................................................................................................................................115
4.3.1 Molecular Structure and Organization ..................................................................116
4.3.2 Bulk Physicochemical Properties ..........................................................................117
4.3.3 Influence of Solutes on the Organization of Water Molecules ..............................117
4.3.3.1 Interaction of Water with Ionic Solutes .................................................118
4.3.3.2 Interaction of Water with Polar Solutes .................................................121
4.3.3.3 Interaction of Water with Nonpolar Solutes: The
Hydrophobic Effect ..............................................................................122
4.3.4 Influence of Solutes on the Physicochemical Properties of Solutions ..................124
4.3.5 Selection of an Appropriate Aqueous Phase .........................................................124
x Contents
4.4 Emulsifiers ..........................................................................................................................125
4.4.1 Surfactants ............................................................................................................125
4.4.1.1 Molecular Characteristics .....................................................................125
4.4.1.2 Physicochemical Properties ..................................................................127
4.4.1.3 Surfactant Classification Schemes .........................................................133
4.4.1.4 Common Food-Grade Surfactants .......................................................140
4.4.2 Amphiphilic Biopolymers ......................................................................................142
4.4.2.1 Molecular Characteristics ......................................................................142
4.4.2.2 Interfacial Activity and Emulsion Stabilization ....................................143
4.4.2.3 Biopolymer-Based Food Emulsifiers .....................................................145
4.4.2.4 Protein–Polysaccharide Complexes ......................................................149
4.4.3 Selection of an Appropriate Emulsifier .................................................................149
4.5 Texture Modifiers .................................................................................................................151
4.5.1 Thickening Agents .................................................................................................151
4.5.1.1 Effective Volume of Biopolymers in Aqueous Solutions ......................151
4.5.1.2 Relationship between Biopolymer Molecular Structure and
Effective Volume in Solution .................................................................152
4.5.1.3 Viscosity Enhancement by Biopolymers in Solution ............................153
4.5.1.4 Shear-Thinning in Biopolymer Solutions .............................................154
4.5.2 Gelling Agents ......................................................................................................156
4.5.3 Commonly Used Texture Modifiers .....................................................................160
4.5.3.1 Polysaccharides .....................................................................................161
4.5.3.2 Proteins .................................................................................................166
4.5.3.3 Biopolymer Blends ................................................................................167
4.5.4 Selection of an Appropriate Texture Modifier .......................................................169
4.6 Other Food Additives ...........................................................................................................170
4.6.1 pH Control ..............................................................................................................170
4.6.2 Minerals .................................................................................................................170
4.6.3 Chelating Agents ....................................................................................................171
4.6.4 Antioxidants ...........................................................................................................171
4.6.5 Antimicrobial Agents .............................................................................................172
4.6.6 Flavors ....................................................................................................................173
4.6.7 Colorants ................................................................................................................173
4.6.8 Weighting Agents ...................................................................................................174
4.6.9 Fat Replacers ..........................................................................................................174
4.7 Factors Influencing Ingredient Selection .............................................................................175
References .......................................................................................................................................176
5. Interfacial Properties and Their Characterization ...................................................................185
5.1 Introduction ..........................................................................................................................185
5.2 General Characteristics of Interfaces ..................................................................................186
5.2.1 Interfaces Separating Two Pure Liquids ................................................................186
5.2.2 Interfaces in the Presence of Solutes .....................................................................188
5.3 Adsorption of Solutes to Interfaces ....................................................................................192
5.3.1 Definition of Surface Excess Concentration .........................................................192
5.3.1.1 Gas–Liquid Interface in the Absence of Solutes ..................................192
5.3.1.2 Gas–Liquid Interface in the Presence of Solutes .................................193
5.3.1.3 Liquid–Liquid Interfaces ......................................................................193
5.3.2 Relationship between Adsorbed and Bulk Solute Concentrations .......................194
5.3.3 Stipulating Interfacial Properties of Surface-Active Solutes ................................196
5.3.4 Adsorption Kinetics ..............................................................................................197
5.3.4.1 Movement of Molecules to the Vicinity of an Interface ......................197
5.3.4.2 Attachment of Emulsifier Molecules to Interface ................................199