Flavor Chemistry 820
The Ohio State University
Food Science and Technology
Instructor : Dr. David B. Min
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.
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. 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.
Evaluation
Midterm Examinations (2)
Final Examination
Home Work and Class Participation
40%
30%
30%
1. Introduction
I.
II.
III.
IV.
Definition of Flavor
Classification of Food Flavor
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
Objectives of Flavor Chemistry
2. Isolation and Separation of Flavor
Compounds
I.
II.
III.
Objective
Prerequisites
Apparatus for Isolation
1.Headspace analysis
2.Continuous solvent extraction
3.Steam distillation and continuous
solvent extraction
IV.
V.
VI.
V.
Extraction and Concentration
Preliminary and Final Fractionation
Dynamic Headspace analyzer
Solid Phase Microextraction Analysis
3. Flavor Identification by Spectrometric
Methods
I.
II.
III.
IV.
V.
Introduction of Spectrometric Analyses
Ultra Violet Spectrometry
Infrared Spectrometry
Nuclear Magnetic Resonance Spectrometry
Mass Spectrometry
1.Furans
2.Pyrroles
3.Thiophenes
4.Pyridines
5.Pyrazines
4. Manufacture of Food Flavor
I.
II.
III.
IV.
V.
Natural or Imitation Flavor
Problems of Using Natural Flavor
Disadvantages of Using Imitation Flavor
Advantages of Imitation Flavor
Methods in Synthetic Flavor Reconstitution
5. Chemistry of Flavor Precursors
I.
II.
III.
IV.
Flavor Compounds from Carbohydrates and
Proteins
Thermal Degradation of Vitamin B1
Lipid Oxidation
Flavor Generated from Enzymatic Method,
Microbiological Reaction, and Biogenesis
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
7. Meat Flavor Chemistry
I.
II.
Introduction
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
8. Interaction of Flavor Compounds with Foods
I.
II.
III.
Physical and Chemical Stability of Flavor
Compounds of Lipid Food
Effects and Interactions of Carbohydrates with
Flavor Compounds
Interactions of Proteins with Flavor Compounds
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
10. Favor Compounds and Solvent Interaction
I.
II.
Commercial Cherry Flavor and Solvent Interaction
Acetal Formation
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.”
Stimulus
Senses
Sensory Response
Taste
Food
Flavor
Odor
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.
Almond: Benzoaldehyde
CHO
Green pepper: 2-Methoxy-3-isobutyl-pyrazine
N
N
OCH3
CH2CH
CH3
CH3
Vanilla: 4-Hydroxy-3-methoxy-benzolaldehyde
CHO
OCH3
OH
Cucumber: 2-Trans-6-cis-nonadienal
H
CH 2
CH
CH 3
2 C C
H
H
CHO
C C
CH 2
H
Reversion Rancid Flavor of Soybean Oil:
2-Pentylfuran and 2-Pentenylfuran
O
(CH 2)4 CH 3
2. Flavor of Foods
1) Desirable flavor
orange juice
potato chip
roast beef
2) Undesirable flavor (off-flavor)
oxidized
stale
rancid
warmed-over
3. Precursors of Flavor Compounds
Linoleate
2-pentylfuran
1) Non-enzymatic reaction
Precursor of beef flavor can be isolated as a white fluffy powder.
White fluffy powder
Oil
broil stew
Amino acid + Sugar
Maillard reaction
Water
beef broth
2) Enzymatic reaction
Processed banana
no fresh banana flavor
enzyme extracted from banana peel
Fresh banana flavor
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)
2
1
S
H3 C
S
3
5
S
CH 3
4
3, 5-Dimethyl-1,2,4-trithiolane
Model Studies
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.
5. Relationship between Physical Properties of
Compound and Flavor
B.P.(0C)
Solubility in
H2O g/100 ml
Sense of smell
(ppm)
n-propanol
n-butanol
n-hexanal
61.0
75.7
131.0
20.0
4.0
0.5
0.17
0.07
0.03
CH3-S-CH3
37.5
insoluble
0.012
Odor Threshold (ppm) in Water
2-t-pentenal
2-t-hexanal
2-t-heptanal
2-t-octenal
2-t-nonenal
2-t-decenal
2-t-undecenal
2.3
10.0
14.0
7.0
3.2
33.8
150.0
The series has an increase b.p. and decreased solubility in H2O
Effect of Medium on the
Vapor Compositions of Flavor Compounds
Headspace Analysis
Compound
(200ppm)
acetone
2-butanone
2-pentanone
2-hexanone
2-heptanone
Water
(peak area)
10
14
22
29
24
Corn oil
(peak area)
47
11
5.7
2.7
0.7
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 offflavors 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.
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.
OH
CH 3
C
CH3
CH
CH 2
CH2
C
CH
CH2
CH3
Ceylon tea contains cis-hexenol, India tea doesn’t contain cishexenol
II. Classification of Food Flavors
Flavor Class
Fruit flavor
Subdivision
Representative Example
citrus-type flavors (terpeny)
grapefruit, orange
berry-type flavors (non-terpeny) apple, raspberry, banana
Vegetable flavors
lettuce, celery
Spice flavors
aromatic
lachrymogenic
hot
cinnamon, peppermint
onion, garlic
pepper, ginger
Beverage flavors
unfermented flavors
fermented flavors
compounded flavors
juices, milk
wine, beer, tea
soft drinks
Flavor Class
Meat flavors
Fat flavors
Cooked flavors
Processed flavors
Stench flavors
Subdivision
mammal flavors
sea food flavors
Representative Example
lean beef
fish, clams
olive oil, coconut fat, pork
at, butter fat
broth
beef bouillon
vegetable
legume, potatoes
fruit
marmalade
smoky flavors
ham
broiled, fried flavors
processed meat products
roasted, toasted, baked flavors coffee, snack foods,
processed cereals
cheese