TABLE 1 .

Volatile compounds detected in kefir by GC-MS

Compound	LRIa	Ref LRIb	Odor descriptor(s)	Source
Carboxylic acids
Acetic acid	692	629	Vinegar, peppers, green, fruity, floral, sour	Carbohydrate metabolism
Hexanoic acid	968	983	Sweaty, cheesy, sharp, goaty, bad breath, acidic	Lipid metabolism
Octanoic acid	1,163	1,160	Cheesy, rancid, pungent, sweat, soapy, goaty	Lipid metabolism
Nonanoic acid	1,254	1,276	Fatty, soapy, waxy, green, goat	Lipid metabolism
n-Decanoic acid	1,355	1,379	Soapy, waxy, stale, buttery, fruity, grassy, cheesy, milky	Lipid metabolism
Alcohols
2-Methyl-1-butanol	733	755	Penetrating, alcohol, wine-like, plastic	Amino acid metabolism
2-Ethyl-1-hexanol	1,025	1,031	Animal, cardboard	Lipid metabolism
Ethanol	468	426	Dry, dust	Carbohydrate metabolism
2-Butanol	601	596	Fruity	Carbohydrate metabolism
2-Methyl-1-propanol	621	647	Malty	Amino acid metabolism
3-Methyl-butanol	730	768	Fresh cheese, breathtaking, alcoholic, fruity, grainy, solvent-like, floral, malty	Amino acid metabolism
Phenylethyl alcohol	1,119	1,112	Unclean, rose, violet-like, honey, floral, spicy	Amino acid metabolism
1-Pentanol	730	768	Fruity, alcoholic, green, balsamic, fusel oil, woody	Lipid metabolism
Aldehydes
3-Methyl-butanal	649	654	Malty, cheesy, green, dark chocolate, cocoa	Amino acid metabolism
2-Methyl-butanal	658	662	Malty, dark chocolate, almond, cocoa, coffee	Amino acid metabolism
Octanal	1,002	1,004	Green, fatty, soapy, fruity, orange peel	Lipid metabolism
Nonanal	1,103	1,106	Green, citrus, fatty, floral	Lipid metabolism
Pentanal	694	697	Pungent, almond-like, chemical, malty, apple, green	Lipid metabolism
Hexanal	798	801	Green, slightly fruity, lemon, herbal, grassy, tallow	Lipid metabolism
Heptanal	900	901	Slightly fruity (balsam), fatty, oily, green, woody	Lipid metabolism
Esters
Ethyl acetate	609	614	Solvent, pineapple, fruity, apples	Carbohydrate metabolism
Ethyl butanoate	802	800	Ripe fruit, buttery, green, apple, pineapple, banana, sweet	Carbohydrate metabolism
Ethyl hexanoate	995	1,002	Fruity, malty, young cheese, moldy, apple, green, orange, pineapple, banana	Carbohydrate metabolism
Ethyl octanoate	1,190	1,198	Fruity, apple, green, fatty, orange, winey, pineapple, apricot	Carbohydrate metabolism
Ethyl decanoate	1,388	1,396	Fruity, grape, cognac	Carbohydrate metabolism
3-Methyl-1-butanol, acetate	874	879	Fruity, banana, candy, sweet, apple peel	Unknown
Ketones
2,3-Butanedione	589	596	Buttery, strong	Carbohydrate metabolism
2,3-Pentanedione	694	693	Creamy, cheesy, oily, sweet buttery, caramellic	Carbohydrate metabolism
2,3-Hexanedione	781	788	Sweet, creamy, caramellic, buttery	Carbohydrate metabolism
2-Heptanone	887	891	Blue cheese, spicy, Roquefort	Lipid metabolism
2-Undecanone	1,288	1,294	Floral, fruity, green, musty, tallow	Lipid metabolism
2-Pentanone	679	687	Orange peel, sweet, fruity	Lipid metabolism
2-Nonanone	1,088	1,094	Malty, fruity, hot milk, smoked cheese	Lipid metabolism
Acetone	494	496	Earthy, fruity, wood pulp, hay	Lipid metabolism
2-Butanone	598	593	Buttery, sour milk, etheric	Carbohydrate metabolism
Sulfur compounds
Dimethyl sulfone	920	926	Sulfurous, hot milk, burned	Amino acid metabolism
Carbon disulfide	537	568	Sweet, ethereal	Amino acid metabolism

^aLRI, linear retention index.

^bReference LRI.