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Flavor Chemistry 820 The Ohio State University

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1 Flavor Chemistry 820 The Ohio State University
Food Science and Technology Instructor : Dr. David B. Min

2 General Objective The objective of this course is to teach students the role of flavor chemistry in food quality. Chemical structures and formation of flavor compounds, organic, bio, and analytical chemistries involved in flavor research, the effects of processing, packaging and storage conditions on the flavor quality and stability of foods, and current research related to flavor are covered.

3 Upon completion of this course, students should be able to:
1. Understand Chemical reactions involved in flavor compounds formation in natural and processed food. 2. Comprehend the effects of food components, processing parameters and storage conditions on flavor quality of foods. 3. Understand principles, techniques and applications of analytical instruments involved in flavor analysis.

4 4. Optimize ingredient concentration, processing
parameters, packing materials and storage conditions for optimum quality and stability. 5. Develop simple research programs of flavor chemistry. 6. Specify the flavor qualities of raw ingredients.

5 Evaluation Midterm Examinations (2) 40% Final Examination 30%
Home Work and Class Participation 30%

6 1. Introduction I. Definition of Flavor
II. Classification of Food Flavor III. Scope of Flavor Chemistry 1.Chemical compounds responsible for food flavor 2.Flavor of foods 3.Reconstitution of flavor compounds 4.Precursors of the flavor compounds 5.Mechanism for the formation of flavor compounds and precursors in foods 6.Relationship between physical properties and its flavor IV. Objectives of Flavor Chemistry

7 2. Isolation and Separation of Flavor Compounds
I. Objective II. Prerequisites III. Apparatus for Isolation 1.Headspace analysis 2.Continuous solvent extraction 3.Steam distillation and continuous solvent extraction IV. Extraction and Concentration V. Preliminary and Final Fractionation VI. Dynamic Headspace analyzer V. Solid Phase Microextraction Analysis

8 3. Flavor Identification by Spectrometric Methods
I. Introduction of Spectrometric Analyses II. Ultra Violet Spectrometry III. Infrared Spectrometry IV. Nuclear Magnetic Resonance Spectrometry V. Mass Spectrometry 1.Furans 2.Pyrroles 3.Thiophenes 4.Pyridines 5.Pyrazines

9 4. Manufacture of Food Flavor
I. Natural or Imitation Flavor II. Problems of Using Natural Flavor III. Disadvantages of Using Imitation Flavor IV. Advantages of Imitation Flavor V Methods in Synthetic Flavor Reconstitution

10 5. Chemistry of Flavor Precursors
I. Flavor Compounds from Carbohydrates and Proteins II. Thermal Degradation of Vitamin B1 III. Lipid Oxidation IV. Flavor Generated from Enzymatic Method, Microbiological Reaction, and Biogenesis

11 6. Dairy Products Flavor Chemistry
I. Milk Flavor 1.Oxidized flavor 2.Rancid flavor 3.Heated flavor 4.Microbiological flavor 5.Absorbed flavor 6.Sunlight flavor II. Cheese Flavor 1.Isolation, separation and identification of cheese flavor 2.Biological pathways of fat in cheese flavor 3.Reaction products of methionine 4.Biochemical pathways of cheese flavor formation from protein 5.2-Butanone and 2-Butanol formation from diacetyl and acetone 6.Biochemical pathways of cheese flavor formation from lactose 7.Lactone formation 8.Mechanisms of methyl ketone formation

12 7. Meat Flavor Chemistry I. Introduction
II. Effect of Psychrotropic Bacteria on the Volatile Compounds of Raw Beef 1.Introduction 2.Volatile compounds of aseptic raw ground beef 3.Effects of psychrotropic bacteria on the volatile compounds of aseptic raw ground beef III. Isolation, Separation, and Identification of Roast Beef Flavor Simulated Meat Flavor Formation

13 8. Interaction of Flavor Compounds with Foods
I. Physical and Chemical Stability of Flavor Compounds of Lipid Food II. Effects and Interactions of Carbohydrates with Flavor Compounds III. Interactions of Proteins with Flavor Compounds

14 9. Packaging and Flavor Compounds Interaction
I. Effects of Packaging Materials on the Flavor Quality of Food II. Sorption of Orange Flavor Compounds by Packaging Materials

15 10. Favor Compounds and Solvent Interaction
I. Commercial Cherry Flavor and Solvent Interaction II. Acetal Formation

16 1. INTRODUCTION I. Definition of Flavor
1. “Flavor is the sensation produced by a material taken in the mouth, perceived principally by the senses of taste and smell, and also by the general pain, tactile, and temperature receptors in the mouth. Flavor also denotes the sum of the characteristics of the material which produces that sensation.” 2. “ Flavor is one of the three main sensory properties which are decisive in the selection, acceptance, and ingestion of a food.”

17 Stimulus Senses Sensory Response
Taste Food Flavor Odor

18 II. Scope of Flavor Chemistry
1. Chemical compounds responsible for food flavor 1) Even distribution: Brandy 2) Star compound: A star compound can not be identical to the total true flavor but is close and can not produce the true flavor without the star compound.

19 Almond: Benzoaldehyde

20 Green pepper: 2-Methoxy-3-isobutyl-pyrazine

21 Vanilla: 4-Hydroxy-3-methoxy-benzolaldehyde

22 Cucumber: 2-Trans-6-cis-nonadienal

23 Reversion Rancid Flavor of Soybean Oil: 2-Pentylfuran and 2-Pentenylfuran

24 2. Flavor of Foods 1) Desirable flavor orange juice potato chip
roast beef 2) Undesirable flavor (off-flavor) oxidized stale rancid warmed-over

25 3. Precursors of Flavor Compounds
Linoleate 2-pentylfuran

26 1) Non-enzymatic reaction
Precursor of beef flavor can be isolated as a white fluffy powder. White fluffy powder Oil Water broil stew beef broth Amino acid + Sugar Maillard reaction

27 2) Enzymatic reaction Processed banana no fresh banana flavor enzyme extracted from banana peel Fresh banana flavor

28 4. Mechanisms for Flavor Compounds Formation and Precursors in Foods
1) Volatile flavors developed in most food plants mainly at the ripening stage - the result of plant metabolism through enzymatic reaction. 2) Raw meat must be heated before it develops any organoleptically acceptable flavor. meat flavor (boiled beef) 3, 5-Dimethyl-1,2,4-trithiolane

29 Model Studies

30 Apply the knowledge we gained from the mechanism and precursor studies to processed food.
a. Enhance the desirable food flavor. b. Elimination of the undesirable food flavor. c. Application of heated model system to processed foods.

31 5. Relationship between Physical Properties of Compound and Flavor
B.P.(0C) Solubility in Sense of smell H2O g/100 ml (ppm) n-propanol n-butanol n-hexanal CH3-S-CH insoluble

32 Odor Threshold (ppm) in Water
2-t-pentenal 2.3 2-t-hexanal 10.0 2-t-heptanal 14.0 2-t-octenal 7.0 2-t-nonenal 3.2 2-t-decenal 33.8 2-t-undecenal The series has an increase b.p. and decreased solubility in H2O

33 Effect of Medium on the Vapor Compositions of Flavor Compounds
Headspace Analysis Compound Water Corn oil (200ppm) (peak area) (peak area) acetone 2-butanone 2-pentanone 2-hexanone 2-heptanone

34 IV. Objectives of Flavor Chemistry
1. To understand the chemical composition of natural flavors and the mechanism of their formation. 2. To retard or prevent the development of the off- flavors in foods. Reversion rancid flavor in soybean oil: hexenal, 2-pentyl furan 3. To restore the fresh flavor to a processed food 4. To improve the flavor of food by the addition of synthetic flavor. 5. To produce new foods with special flavor such as potato chip flavor.

35 6. To improve flavor by the acceleration of reactions which
produce desirable flavor compound (onion flavor: pH 5~7). 7. To assist geneticist to breed food raw material with improved flavor compounds or flavor precursors. 8. To specify raw material and to control quality of food products. The price of tea can be correlated with GLC peak of linalool. Ceylon tea contains cis-hexenol, India tea doesn’t contain cis- hexenol



38 II. Classification of Food Flavors
Flavor Class Subdivision Representative Example Fruit flavor citrus-type flavors (terpeny) grapefruit, orange berry-type flavors (non-terpeny) apple, raspberry, banana Vegetable flavors lettuce, celery Spice flavors aromatic cinnamon, peppermint lachrymogenic onion, garlic hot pepper, ginger Beverage flavors unfermented flavors juices, milk fermented flavors wine, beer, tea compounded flavors soft drinks

39 Flavor Class Subdivision Representative Example
Meat flavors mammal flavors lean beef sea food flavors fish, clams Fat flavors olive oil, coconut fat, pork at, butter fat Cooked flavors broth beef bouillon vegetable legume, potatoes fruit marmalade Processed flavors smoky flavors ham broiled, fried flavors processed meat products roasted, toasted, baked flavors coffee, snack foods, processed cereals Stench flavors cheese

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