Separation and Identification Volatile Compounds of

1
Dairy Products Flavor
2
Milk Flavor

• Oxidized Flavor
• Rancid Flavor
• Heated Flavor
• Microbiological Flavor
• Absorbed Flavor
• Sunlight Flavor

3
Oxidized Flavor
Cardboard Due to some lactones (Butter
flavor) Metallic Vinyl methyl ketone Oily
Oct-1-ene-3-one (Mushroom flavor) Tallowy
Trans-2, trans-6-nonadienal Autooxidation of
phospholipids are considered as responsible for
the oxidized flavor
4
Phospholipid
Lecithin (phosphatidyl choline)

O
H
C O C R
2
O
R C O CH
CH
O
3

H
C O P O CH
CH
N
CH
2
2
2
3
CH
O_
3
Choline
Phosphatidic Acid
5
Autooxidation of Phospholipids

• Iodine value of oil in oxidized milk is not
  changed, Iodine value of phospholipids in
  oxidized milk is decreased.
• Sweet cream butter-milk high in phospholipids is
  more susceptible to oxidized flavor.
• Butter oil, free of phospholipids is less
  susceptible to oxidized flavor.

6
Preventive Method

• Avoid cupric iron and ferric ion
• Elimination of oxygen pack under vacuum or
  nitrogen
• Avoid light
• Better quality milk, less bacteria, more
  susceptible to oxidized flavor.
• The bacteria can either using up the available
  oxygen or generate antioxidant compounds.

7
Rancid Flavor
Hydrolysis of triglycerides by lipase. The
lipase are present in the aqueous phase of the
milk at the time of secretion. Any process which
alter the membrane, such as homogenization,
agitation, and warming and cooling will
accelerate the rancidity.
8
Heated Flavor
General information Pasteurization induces
heated flavor. Now people are used to
pasteurization and consider heated flavor as
normal milk flavor. Cooked flavor is the
off-flavor induced by temperature above 75 oC
beyond the pasteurization. Too much heat will
develop caramelized flavor.
9
Flavor Compounds Formation by Maillard Reaction
Reducing Sugars and ?-amino acids
N-glycosylamine or N-fructosylamine
1-Amino-1-deoxy-2-ketose (Amadori intermediate)
or 2-Amino-2-deoxy-1-aldose (Heynes intermediate)
Reductones and Dehydroreductones
H2S NH3
Strecker degradation
Amino Acids
Retroaldol Reaction
Furans Thiophenes Pyrroles
Hydroxyacetone Hydroxyacetylaldehyde Acetoin Acet
ylaldehyde
Glyoxal Pyruvaldehyde Glycerolaldehyde
Strecker Aldehydes ?-aminoketone
(Methional, NH3, H2S)
Heterocyclizaion
Pyrazines Pyridines Oxazoles
Thiazoles Pyrroles
10
Cooked and Caramelized Flavor Origin

• Cooked flavor H2S (Strecker degradation of
  cysteine)
• b. Caramelized flavor

CH2-CHO
CH2-CH-COOH
NH2
Strecker degradation of amino acid
O
Pyruvic acid or dehydrororeductone
CH3-C-COOH
CH2-CHO
CH3-C-COOH

NH2
(Strecker aldehyde)
11
Microbiological Flavor
1) General Molds, yeast, bacteria can all grow
in milk and affect flavor. 2) Origin a.
Psychrophilic bacteria Bitter, fruity, stale,
putrid flavor b. Moldy flavor
12
3-Methyl-butanal from Leucine
H3C
CH-CH2-CH-COOH
H3C
N
H2
leucine
maltigens
S. latics var.
H3C
NH3
CH-CH2-CHO
H3C
Tomato Flavor
Threshold 0.5 ppm
13
Absorbed Flavor
Feed flavor Weed flavor Barney flavor 1) Nose
or mouth lung blood
udder cell milk 2) Digestive
tract blood udder cell
milk
14
Sunlight Flavor
Sunlight will induce oxidized flavor and sunlight
flavor and hay-like flavor. Oxidized
flavor Sunlight flavor burnt and / or
cabbage
15
Riboflavin Effect on Sunlight Flavor

• Riboflavin is a catalyst for production of the
  sunlight flavor.
• Milk protein and riboflavin sunlight
  sunlight flavor
• 2) Riboflavin increase in milk will increase the
  sunlight flavor
• 3) Riboflavin removal prevent the sunlight flavor

16
Storage Effect on Milk Volatile Compounds under
Light
D
D
D
17
Mass Spectra of Peak D and Dimethyl Disulfide
Gas Chromatographic Peak D
Authentic Dimethyl Disulfide
18
Effect of Ascorbic Acid on Dimethyl Disulfide in
Milk
19
Mechanism of Dimethyl Disulfide Formation from
Methionine by Singlet Oxygen
COOH
OO
COOH

N
H
C
H
C
H
C
H
S
C
H

1
O
N
H
C
H
C
H
C
H
S
C
H
2
2
3
2
2
2
2
2
3
O
COOH
OOH
COOH

N
H
C
H
C
H
C
H
S
C
H
O
H
N
H
C
H
C
H
C
H
S
C
H
2
2
3
2
2
3
COOH
COOH
O
N
H
C
H
C
H
C
H
O

S
C
H
N
H
C
H
C
H
C
H
S
C
H
2
2
3
2
2
3
C
H
S
S
C
H
S
C
H
2
3
3
3
20
Cheese Flavor
21
Cheese Flavor Isolation, Separation and
Identification
Dynamic headspace analyzer, gas chromatographer,
and mass spectrometer arrangement
22
Cheese Flavor Isolation, Separation and
Identification
Dynamic headspace analyzer, gas chromatographer,
and mass spectrometer arrangement
23
Reproducibility of Gas Chromatogram of Cheddar
Cheese Volatile Compounds after One Week Storage
24
Volatile Compounds of Cheddar Cheese during
Storage
25
Volatile Compounds of Swiss Chesse during Storage
26
Changes of Volatile Compounds of Cheddar and
Swiss Cheeses during Ripening
27
Biochemical Pathways of Fats in Cheese Flavor
Formation
Fat
Amides Aldehydes Primary Alcohols Methyl Kotones
Fatty acids
Secondary Alcohols
Esters Lactones
28
Reaction Products of Methionine
CH
SCH
CH
CH(NH
)COOH CH
SSCH
3
2
2
2
3
3
Methionine Dimethyl
disulphide
Strecker degradation
CH
SCH
CH
CHO CH
SH CH
CHCHO
3
2
2
3
2
Methional
Methanethiol Acrolein
H2O
H2O
HCOOH

CH
SCH
CH

Ethylmethyl sulphide
3
2
3
CH
SH CH
CH
HCOOH
3
2
2
Methanethiol Ethylene Formic Acid
29
Biochemical Pathways of Cheese Flavor Formation
from Protein
Products Caseins ( trace of whey)
Peptides
Amines a-keto acids Acids Phenols H2S NH3
Amino acids
Alcohols
30
Formation of 2-Butanone and 2-Butanol from
Diacetyl and Acetone
Reduction
CH3COCOCH3
CH3CHOHCOCH3

Acetoin
Diacetyl
Isomerization
Reduction
CH3COHCOHCH3
CH3COCH2CH3
2,3-Butyleneglycol
2-Butanone
Reduction
CH3CHOHCH2CH3
2-Butanol
31
Diacetyl Formation in Butter from Lactose
Lactose
Oxalacetic acid
Citric acid
S. Lactis
COOH
COOH
- Acetate
CO
CH2
CH3
CH2
HO-C-COOH
H-COH
COOH
CH2
COOH
COOH
Lactic acid
OH
OH
(odorless )
H
C
C
C
C
H
3
O
H
3
H
H
-CO
2
2,3-butylane glycol
CH3
CO
COOH
H
Pyruvic acid
Aldol condensation
C
H
O
O
OH
3
-CO
2
H
C
O
H
C
C
-CO
Acetoin
H
C
C
C
C
H
3
2
3
3
COOH
H
CH3
O
Acetyl lactic acid
CO
O
O
H
H
C
C
C
C
H
3
3
Acetaldehyde
Diacetyl
32
Biochemical Pathways of Cheese Flavor Formation
from Lactose
Lactose
Pyruvic Acid
Lactic Acid Diacetyl Acetaldehyde CO2
Ethanol Acetic Acid
33
Lactone Formation
O
H2C
C
O
R
O
C
HC
O
R
1
O
O
H2C
(CH2)4
CH3
(CH2)3
CH
C
OH

H2O
DG
O
O
HO
(CH2)4
CH3
(CH2)3
CH
C
OH
-
H2O
O
(CH2)4
CH3
(CH2)3
CH
C
O
34
Mechanism of Methylketone Formation
O
H2C
C
O
R
O
C
HC
O
R
1
O
O
H2C
(CH2)4
CH3
CH2
CH
C
OH

H2O
DG
O
O
HO
(CH2)4
CH3
CH2
CH
C
OH
-
CO2
O
C
H3C
(CH2)n
CH3