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 2 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).

Flavor-forming processes - enzymatic 3 1. Carbohydrates – pyruvic acid and pyruvayes

Flavor-forming processes - enzymatic 4 1. Carbohydrates – pyruvic acid

Flavor-forming processes - enzymatic 5 diacetyl Pyruvic acid – important intermediate in carbo- hydrate degradation acetoin

Flavor-forming processes - enzymatic 6 malty flavor

Flavor-forming processes - enzymatic 7 2. Amino acids and proteins Formation of lactones – from glutamic acid

Flavor-forming processes - enzymatic 8 2. Amino acids and proteins Oxidative deamination - leucine Found in banana oil (could be obtained synthetically) other use – obtaining of esters

Flavor-forming processes - enzymatic 9 Skatole degradation - formation of o-amino acetophenone (aroma defect in tortillas, taco) 2. Amino acids and proteins Skatole (o-cresol) formation (Emmental cheese, tortillas, taco)

Flavor-forming processes - enzymatic 10 3. Lipids Formation of influential volatile flavor compounds from milk fat Obtained through enzymatic cleavage of acylglycerols

Flavor-forming processes - enzymatic 11 3. Lipids Esters biochemical synthesis from fatty acids

Flavor-forming processes - enzymatic 13 3. Lipids – occurrence and smell of lactones

Flavor-forming processes - enzymatic 14 4. Other aroma substances – sulfur-containing I – methional II – methionol III – 3-(methylthio) propyl acetate found in wines

Flavor-forming processes - enzymatic 15 4. Other aroma substances – sulfur-containing Some thiazoles in foods

Flavor-forming processes - enzymatic 17 4. Other aroma substances – tertiary thiols

Flavor-forming processes - enzymatic 18 4. Other aroma substances allicin alliin alliinase allyl-methyl sulfide Propanethial S-oxide

Flavor-forming processes - enzymatic 20 4. Other aroma substances - pyrazines Formation of pyrazines – by Pseudomonas perolans and Pseudomonas taetrolens As byproducts (off flavor in eggs, milk, fishes)

Flavor-forming processes - enzymatic 21 4. Other aroma substances dimethyl disulfide (in beers) – precursor is methionine Amines formation (precursors – amino acids)