Download P4 2 Flavor enzymatic - e

Flavor-forming processes - enzymatic
OBJECTIVES
1. Formation of aroma compounds via enzymatic mechanism;
2. Transformation of carbohydrates, lipids and amino acids;
3. Transformation of other compounds.
Flavor-forming processes - enzymatic
1. Carbohydrates
Lactic acid fermentation
Homofermentative LAB – used in dairy starter culture applications
(Lactobacillus delbruckii subspecies bulgaricus, Lb. acidophilus; Streptococcus
salivarius subsp. thermophilus, Lb. helveticus).
Heterofermentative LAB – ferment glucose with lactic acid, ethanol/acetic acid
and carbon dioxide as by products; used for some fermented milk products
(Lactobacillus brevis, Lb. fermentum, Lb. plantarum, Lb. casei).
2
Flavor-forming processes - enzymatic
3
1. Carbohydrates – pyruvic acid and pyruvayes
HO
OH
lactic acid
O
CH 3
HO
H3 C
H 2N
O
ethanol
CH3
O
acetoin
alanine
HO
CH3
acetyllactate
HO
O
O
O
CH 3
H 3C
O
diacetyl
H3 C
acetaldehyde
CH3
piruvic acid
O
acetic acid
HO
butyric acid
HO
Ac-CoA
O
O
O-
H 2C
HO
O
C
HO
malic acid
O
P
phosphoenolpyruvate
O
O-
butanol
acetone
Flavor-forming processes - enzymatic
1. Carbohydrates – pyruvic acid
4
Flavor-forming processes - enzymatic
Pyruvic acid – important
intermediate in carbohydrate degradation
5
diacetyl
acetoin
Flavor-forming processes - enzymatic
6
malty
flavor
Flavor-forming processes - enzymatic
2. Amino acids and proteins
Formation of lactones – from glutamic acid
7
Flavor-forming processes - enzymatic
2. Amino acids and proteins
Oxidative deamination - leucine
Found in banana oil
(could be obtained synthetically)
other use – obtaining of esters
8
Flavor-forming processes - enzymatic
2. Amino acids and proteins
Skatole (o-cresol) formation
(Emmental cheese, tortillas, taco)
9
Skatole degradation - formation
of o-amino acetophenone
(aroma defect in tortillas, taco)
Flavor-forming processes - enzymatic
3. Lipids
Formation of influential volatile flavor compounds from milk fat
Obtained through enzymatic cleavage of acylglycerols
10
Flavor-forming processes - enzymatic
3. Lipids
Esters biochemical synthesis from fatty acids
11
Flavor-forming processes - enzymatic
3. Lipids – occurrence and smell of lactones
13
Flavor-forming processes - enzymatic
4. Other aroma substances – sulfur-containing
I – methional
II – methionol
III – 3-(methylthio)
propyl acetate
found in wines
14
Flavor-forming processes - enzymatic
4. Other aroma substances –
sulfur-containing
Some thiazoles in
foods
15
Flavor-forming processes - enzymatic
4. Other aroma substances – tertiary thiols
17
Flavor-forming processes - enzymatic
18
4. Other aroma substances
allicin
alliin
alliinase
allyl-methyl sulfide
Propanethial S-oxide
Flavor-forming processes - enzymatic
4. Other aroma substances - pyrazines
N
OCH 3
CH 3
N
CH 3
Formation of pyrazines – by Pseudomonas perolans and
Pseudomonas taetrolens
As byproducts (off flavor in eggs, milk, fishes)
20
Flavor-forming processes - enzymatic
4. Other aroma substances
dimethyl disulfide (in beers) – precursor is methionine
Amines formation (precursors – amino acids)
21