Flavor chemistry and technology,2. ed

PART I Flavor Chemistry.......................................... 1 Chapter 1 An Overview of Flavor Perception......................................................3 1.1 Flavor Perception .............................................................................................3 1.2 Taste Perception ...............................................................................................3 1.2.1 Anatomy of Taste .................................................................................4 1.2.2 Synopses of Tastes ...............................................................................6 1.3 Chemesthesis..................................................................................................10 1.3.1 Chemesthetic Responses ....................................................................10 1.3.2 Tactile Response.................................................................................12 1.4 Olfaction.........................................................................................................13 1.4.1 Anatomy of Olfaction ........................................................................14 1.4.2 Odor Receptor Functioning ...............................................................14 1.4.3 Signal Encoding .................................................................................15 1.5 Summary ........................................................................................................18 References................................................................................................................18 Chapter 2 Flavor and the Information Age ........................................................23 2.1 Introduction ....................................................................................................23 2.2 History of Flavor Literature...........................................................................23 2.3 Journals...........................................................................................................24 2.4 Professional Societies ....................................................................................25 2.5 Internet ...........................................................................................................27 2.5.1 Internal Communication ....................................................................27 2.5.2 External Communication ...................................................................28 2.5.3 General Information About the Industry ...........................................28 2.5.4 Societies/Organizations ......................................................................28 2.5.5 Internet Searches ................................................................................28 2.5.6 Literature Retrieval ............................................................................29 2.5.7 Locating Materials and Equipment Suppliers ...................................30 2.5.8 Idea Generators/Promotions...............................................................31 2.5.9 Competition........................................................................................31 2.5.10 How to Use the Internet Effectively..................................................31 2.6 Summary ........................................................................................................31 References................................................................................................................31 © 2006 by Taylor & Francis Group, LLC Chapter 3 Flavor Analysis...................................................................................33 3.1 Introduction ....................................................................................................33 3.2 Aroma Compounds ........................................................................................33 3.2.1 Introduction ........................................................................................33 3.2.2 Sample Selection/Preparation ............................................................35 3.2.3 Principles of Aroma Isolation ............................................................36 3.2.3.1 Introduction.........................................................................36 3.2.3.2 Solubility.............................................................................36 3.2.3.3 Sorptive Extraction .............................................................38 3.2.3.4 Volatility..............................................................................39 3.2.4 Methods of Aroma Isolation ..............................................................41 3.2.4.1 Static Headspace.................................................................41 3.2.4.2 Headspace Concentration Methods (Dynamic Headspace).........................................................43 3.2.4.3 Distillation Methods ...........................................................45 3.2.4.4 Solvent Extraction ..............................................................48 3.2.4.5 Sorptive Extraction .............................................................49 3.2.4.6 Concentration for Analysis .................................................51 3.2.4.7 Aroma Isolation Summary .................................................52 3.2.5 Analysis of Aroma Isolates................................................................53 3.2.5.1 Prefractionation...................................................................53 3.2.5.2 Gas Chromatography..........................................................54 3.2.5.3 GC/Olfactometry (GC/O) or GC-MS/Olfactometry (GC-MS/O) .........................................................................54 3.2.5.4 Mass Spectrometry .............................................................56 3.2.6 Specific Analysis ................................................................................58 3.2.6.1 Key Components in Foods .................................................58 3.2.6.2 Aroma Release During Eating ...........................................61 3.2.7 Electronic Noses ................................................................................63 3.3 Taste Compounds (Nonvolatiles)...................................................................64 3.3.1 Introduction ........................................................................................64 3.3.1.1 Taste Compounds................................................................64 3.3.1.2 Other Nonvolatile Components of Foods...........................65 3.3.2 The Analysis of Taste Substances......................................................65 3.3.2.1 Sweeteners ..........................................................................65 3.3.2.2 Salt ......................................................................................66 3.3.2.3 Acidulants ...........................................................................66 3.3.2.4 Umami.................................................................................66 3.3.2.5 Bitter Substances ................................................................66 References................................................................................................................67 Chapter 4 Flavor Formation in Fruits and Vegetables .......................................73 4.1 Introduction ....................................................................................................73 4.2 Biogenesis of Fruit Aroma.............................................................................74 © 2006 by Taylor & Francis Group, LLC 4.2.1 Aroma Compounds from Fatty Acid Metabolism.............................74 4.2.2 Aroma Compounds from Amino Acid Metabolism..........................77 4.2.3 Aroma Compounds Formed from Carbohydrate Metabolism ..........80 4.3 Biogenesis of Vegetable Aroma.....................................................................83 4.3.1 The Role of Lipids in Vegetable Aroma Formation..........................85 4.3.2 Aroma Compound Formation from Cysteine Sulfoxide Derivatives..........................................................................................86 4.3.3 Glucosinolates as Aroma Precursors in Vegetables...........................88 4.3.4 Additional Pathway for Vegetable Flavor Formation........................88 4.4 Glycosidically Bound Aroma Compounds....................................................88 4.4.1 Glycoside Structure............................................................................91 4.4.2 Freeing of Glycosidically Bound Flavor Compounds ......................91 4.5 Location of Flavor in Plant............................................................................92 4.6 Influence of Genetics, Nutrition, Environment, Maturity, and Storage on Development of Flavor .............................................................................92 4.6.1 Plant Products ....................................................................................93 4.6.1.1 Genetics...............................................................................93 4.6.1.2 Environmental and Cultural Effects on Flavor Development on the Plant ..................................................93 4.6.1.3 Influence of Maturity and Postharvest Storage on Flavor Development off the Plant ......................................94 4.7 Animal Products.............................................................................................97 4.8 Conclusions ....................................................................................................97 References................................................................................................................98 Chapter 5 Changes in Food Flavor Due to Processing ....................................103 5.1 Introduction ..................................................................................................103 5.2 The Maillard Reaction .................................................................................103 5.2.1 General Overview of the Maillard Reaction ...................................103 5.2.2 Pathways for Flavor Formation via the Maillard Reaction.............104 5.2.3 Factors Influencing the Maillard Reaction ......................................105 5.2.3.1 Heating Time/Temperature ...............................................106 5.2.3.2 Influence of System Composition ....................................108 5.2.3.3 Influence of Water Activity ..............................................109 5.2.3.4 Influence of pH.................................................................109 5.2.3.5 Influence of Buffer/Salts...................................................110 5.2.3.6 Influence of Oxidation/Reduction State ...........................110 5.2.4 Kinetics of the Maillard Reaction and Flavor.................................111 5.2.4.1 Pyrazines ...........................................................................111 5.2.4.2 Oxygen-Containing Heterocyclic Compounds.................112 5.2.4.3 Sulfur-Containing Compounds.........................................113 5.2.4.4 Miscellaneous Compounds...............................................113 5.2.4.5 Summary...........................................................................114 5.2.5 Flavor Formation via the Maillard Reaction ...................................114 © 2006 by Taylor & Francis Group, LLC 5.2.5.1 Carbonyl Compounds .......................................................115 5.2.5.2 Nitrogen-Containing Heterocyclic Compounds ...............115 5.2.5.3 Oxygen-Containing Heterocyclic Compounds.................117 5.2.5.4 Sulfur-Containing Heterocyclic Compounds ...................118 5.2.5.5 Oxygen-Containing Compounds ......................................119 5.3 Flavors from Lipids......................................................................................119 5.3.1 Deep Fat Fried Flavor ......................................................................119 5.3.2 Lactones ...........................................................................................121 5.3.3 Secondary Reactions ........................................................................121 5.4 Flavors Formed via Fermentation................................................................123 5.4.1 Esters ................................................................................................123 5.4.2 Acids.................................................................................................124 5.4.3 Carbonyls..........................................................................................125 5.4.4 Alcohols ...........................................................................................127 5.4.5 Terpenes............................................................................................128 5.4.6 Lactones ...........................................................................................129 5.4.7 Pyrazines ..........................................................................................129 5.4.8 Sulfur Compounds ...........................................................................130 5.4.9 Conclusions ......................................................................................130 References..............................................................................................................132 Chapter 6 Flavor Release from Foods..............................................................139 6.1 Introduction ..................................................................................................139 6.2 Lipid/Flavor Interactions..............................................................................140 6.2.1 Effect of Fat: Flavor Interactions on Aroma ...................................141 6.2.1.1 Equilibrium Conditions ....................................................141 6.2.1.2 Dynamic Conditions .........................................................143 6.2.2 Effect of Fat: Flavor Interactions on Taste......................................144 6.3 Carbohydrate: Flavor Interactions ...............................................................145 6.3.1 Simple Sugars: Aroma Interactions .................................................145 6.3.2 High Potency Sweeteners: Aroma Interactions ...............................146 6.3.3 Complex Carbohydrate (Polysaccharide): Aroma Interactions.......148 6.3.3.1 Chemical Interactions .......................................................149 6.3.3.2 Resistance to Mass Transfer.............................................151 6.3.4 Carbohydrate: Taste Interactions .....................................................152 6.4 Protein: Flavor Interactions..........................................................................153 6.4.1 Protein: Aroma Interactions .............................................................153 6.4.1.1 Chemical Interactions .......................................................153 6.4.1.2 Resistance to Mass Transfer.............................................155 6.4.2 Protein Hydrolysate: Aroma Interactions ........................................155 6.4.3 Protein: Taste Interactions................................................................155 6.5 Minor Food Components: Aroma Interactions............................................155 6.5.1 Melanoidin: Flavor Interaction ........................................................156 6.5.2 Hydrogen Ion Effects (pH effects) ..................................................156 © 2006 by Taylor & Francis Group, LLC 6.6 Summary ......................................................................................................157 References..............................................................................................................157 Chapter 7 Off-Flavors and Taints in Foods ......................................................161 7.1 Introduction ..................................................................................................161 7.2 Sensory Aspects of Off-Flavor Testing........................................................161 7.3 Taints in Foods.............................................................................................163 7.3.1 Airborne Sources..............................................................................164 7.3.2 Waterborne Sources .........................................................................166 7.3.3 Disinfectants, Pesticides, and Detergents ........................................167 7.3.4 Packaging Sources ...........................................................................168 7.4 Off-Flavors Due to Genetics or Diet ...........................................................174 7.4.1 Genetics............................................................................................174 7.4.2 Diet ...................................................................................................174 7.5 Off-Flavors Due to Chemical Changes in the Food ...................................176 7.5.1 Lipid Oxidation ................................................................................176 7.5.2 Nonenzymatic Browning .................................................................183 7.5.3 Photo-Induced Off-Flavors ..............................................................184 7.5.4 Enzymatic Flavor Changes ..............................................................185 7.6 Microbial Off-Flavors ..................................................................................189 7.7 Summary ......................................................................................................192 References..............................................................................................................193 PART II Flavor Technology................................... 201 Chapter 8 Flavoring Materials ..........................................................................203 8.1 Introduction ..................................................................................................203 8.1.1 Definitions ........................................................................................203 8.1.1.1 Flavoring ...........................................................................203 8.1.1.2 Natural Flavoring..............................................................203 8.1.1.3 Artificial Flavoring ...........................................................204 8.2 Natural Flavoring Materials (Plant Sources)...............................................204 8.2.1 Herbs and Spices..............................................................................205 8.2.1.1 Definitions and Markets ...................................................205 8.2.1.2 Historical Associations .....................................................206 8.2.1.3 Classification of Herbs and Spices...................................209 8.2.1.4 Flavor Character of Herbs ................................................211 8.2.1.5 Preparation of Herbs for Market ......................................212 8.2.1.6 Introduction to Spices.......................................................213 8.2.2 Derivatives of Spices........................................................................216 8.2.2.1 Essential Oils (Distillation) ..............................................216 8.2.2.2 Oleoresins (Solvent Extraction) .......................................220 © 2006 by Taylor & Francis Group, LLC 8.2.2.3 Expressed “Essential” Oils (Citrus Oils) .........................224 8.2.2.4 Mint Oils...........................................................................230 8.2.2.5 Fruit, Fruit Juices, and Concentrates................................236 8.2.2.6 Vanilla ...............................................................................241 8.2.2.7 Cocoa, Coffee, and Tea Flavorings ..................................249 8.2.2.8 Aromatic Vegetables .........................................................253 References..............................................................................................................256 Chapter 9 Flavoring Materials Made by Processing ........................................261 9.1 Introduction ..................................................................................................261 9.2 Natural Products Made by Roasting: Cocoa/Chocolate..............................261 9.2.1 Production of Cocoa Powder...........................................................262 9.2.2 The Dutch Process ...........................................................................262 9.2.3 Chocolate..........................................................................................262 9.3 Process Flavors: Meat-Like Flavors ............................................................263 9.3.1 The Evolution of Process Meat-Like Flavorings ............................264 9.3.2 The Creation of Process Flavorings ................................................265 9.3.2.1 Reaction System Composition .........................................265 9.3.2.2 Reaction Conditions..........................................................271 9.3.2.3 Final Flavor.......................................................................272 9.3.3 Hydrolyzed Vegetable Proteins (HVP) ............................................273 9.3.4 Autolyzed Yeast Extracts (AYE)......................................................273 9.4 Enzymatically Derived Flavorings...............................................................274 9.4.1 Introduction ......................................................................................274 9.4.2 Properties of Enzyme Catalyzed Reactions ....................................275 9.4.3 Enzyme Modified Butter/Butter Oil ................................................278 9.4.4 Enzyme-Modified Cheese (EMC) ...................................................279 9.4.4.1 Enzymes Used ..................................................................280 9.4.4.2 General Processes Employed ...........................................281 9.4.5 Further Processed EM Dairy Products ............................................282 9.5 Flavors Made by Fermentation....................................................................283 9.5.1 Yeasts................................................................................................283 9.5.2 Vinegar/Acetic Acid .........................................................................283 9.5.3 Dried Inactive Yeast Powder............................................................285 9.6 Flavors Made by Pyrolysis: Smoke Flavors................................................285 9.6.1 The Smoking of Foods ....................................................................285 9.6.2 Natural Liquid Smoke Flavorings ...................................................286 9.6.3 Pyroligneous Acid ............................................................................286 9.6.4 Smoke Condensates .........................................................................286 9.7 Biotechnology to Produce Flavoring Materials...........................................287 9.7.1 Introduction ......................................................................................287 9.7.2 Production of Natural Flavoring Materials by Enzymatic Action ...287 9.7.2.1 Ester Formation ................................................................288 9.7.2.2 Resolution of Racemic Mixtures......................................290 © 2006 by Taylor & Francis Group, LLC 9.7.3 Production of Natural Flavoring Materials by Microbial Action .............................................................................................290 9.7.3.1 Fermentation to Produce Flavoring Materials...............291 9.7.3.2 Bioconversions Via Microorganisms .............................293 9.7.3.3 Resolution of Racemic Mixtures...................................293 9.7.4 Economics of Biotechnology .........................................................294 References..............................................................................................................294 Chapter 10 Artificial Flavoring Materials ..........................................................299 10.1 Artificial Flavorings .....................................................................................299 10.2 Synthetic Flavoring Materials......................................................................299 10.2.1 Introduction ......................................................................................299 10.2.2 Consumer Attitudes Toward Synthetic Chemicals ..........................300 10.3 Classification of Aroma Compounds by Molecular Structure ....................300 10.4 Sensory Threshold Values............................................................................303 10.5 Sensory Characters of Odor Compounds ....................................................305 10.5.1 Hydrocarbons..................................................................................306 10.5.2 Carboxylic Acids ............................................................................307 10.5.3 Acetals ............................................................................................307 10.5.4 Alcohols..........................................................................................308 10.5.5 Carbonyls........................................................................................308 10.5.5.1 Aldehydes.......................................................................309 10.5.5.2 Ketones...........................................................................309 10.5.6 Esters ..............................................................................................309 10.5.7 Ethers ..............................................................................................310 10.5.8 Heterocyclic Compounds ...............................................................310 10.5.9 Lactones..........................................................................................311 10.5.10 Nitrogen-Containing Compounds ..................................................311 10.5.10.1 Amines ...........................................................................311 10.5.10.2 Amides ...........................................................................311 10.5.10.3 Imines.............................................................................312 10.5.10.4 Amino Acids ..................................................................312 10.5.10.5 Isothiocyanates...............................................................312 10.5.11 Phenols............................................................................................312 10.5.12 Sulfur-Containing Compounds.......................................................312 10.6 Nomenclature of Organic Chemicals ..........................................................313 References..............................................................................................................313 Chapter 11 Flavor Potentiators ...........................................................................317 11.1 Introduction ..................................................................................................317 11.2 Chemical Properties of L-Amino acids and 5 ′ -Nucleotides .......................318 11.2.1 Structures ........................................................................................318 11.2.2 Stability...........................................................................................319 © 2006 by Taylor & Francis Group, LLC 11.3 Sensory Properties of MSG and 5 ′ -Nucleotides .........................................320 11.3.1 Influence of MSG and 5 ′ -Nucleotides on Taste ..............................320 11.3.2 Influence of MSG and 5 ′ -Nucleotides on Aroma ...........................321 11.3.3 Synergism Between MSG and the 5 ′ -Nucleotides..........................322 11.4 Traditional Flavor Potentiators in Foods .....................................................322 11.4.1 MSG and 5 ′ -Nucleotides in Foods ..................................................322 11.4.1.1 Yeast Extracts ...................................................................323 11.4.1.2 Hydrolyzed Vegetable Proteins (HVP).............................324 11.4.2 MSG and 5 ′ -Nucleotides Added to Foods.......................................325 11.4.3 Sources of MSG and 5 ′ -Nucleotides ...............................................326 11.4.4 Table Salt as a Flavor Potentiator....................................................329 11.5 Toxicity of MSG and 5 ′ -Nucleotides ..........................................................329 11.5.1 Monosodium Glutamate...................................................................329 11.5.2 5 ′ -Nucleotides ..................................................................................330 11.6 Other Potentiators ........................................................................................330 11.6.1 Beefy Meaty Peptide........................................................................330 11.6.2 Umami Tasting Glutamate Conjugates ............................................331 11.6.3 Alapyridaine .....................................................................................331 11.6.4 Sweetness Potentiators.....................................................................332 11.6.4.1 Maltol and Ethyl Maltol ...................................................332 11.6.4.2 Cyclic Enolones ................................................................332 11.6.5 Other Potentiators ............................................................................332 References..............................................................................................................332 Chapter 12 Flavorists and Flavor Creation.........................................................337 12.1 Introduction ..................................................................................................337 12.2 The Flavorist ................................................................................................337 12.2.1 Selection of Individuals to Become Flavorists................................337 12.2.2 Training of Flavorists.......................................................................338 12.3 Working Environment ..................................................................................338 12.4 Flavor Creation.............................................................................................340 12.4.1 Imitation Flavorings .........................................................................340 12.4.2 Blending of Seasonings (Culinary Products) ..................................345 12.5 Sensory Assessment .....................................................................................346 12.5.1 Sample Evaluation ...........................................................................347 12.6 Conclusions ..................................................................................................348 References..............................................................................................................348 Chapter 13 Flavor Production.............................................................................351 13.1 Introduction ..................................................................................................351 13.2 Liquid Flavorings .........................................................................................351 13.3 Emulsions .....................................................................................................352 13.3.1 Beverage Emulsions.........................................................................353 13.3.2 Baker’s Emulsions............................................................................360 © 2006 by Taylor & Francis Group, LLC 13.4 Dry Flavorings ........