TABLE 1.

Concentrations of volatile aroma compounds found after 72 h of water kefir fermentation^a

Volatile aroma compound	Concn after 72 h (mg liter−1)	KI	Id	Threshold valuec (mg liter−1)	Aroma descriptord
2-Methyl-1-propanol	11.62 ± 0.05	1,097	MS/RF	40	Spirituous, fuel
Isoamyl alcohol	44.13 ± 0.82	1,222	MS/RF	30	Harsh, nail polish remover
Ethyl acetate	13.40 ± 0.58	831	MS/RF	7.5	Fruity
				>150	Varnish, nail polish remover
Isoamyl acetate	0.11 ± 0.01	1,141	MS/RF	0.03	Sweet, fruity, banana, pear
Ethyl hexanoate	0.37 ± 0.01	1,250	MS/RF	0.014	Fruity, apple, banana, violets
Ethyl octanoate	3.44 ± 0.61	1,450	MS/RF	0.005	Fruity, pineapple, pear
Ethyl decanoate	1.40 ± 0.18	1,659	MS/RF	0.2	Floral
Ethyl butanoate	DNQb	1,043	MS	0.02	Floral, fruity
Ethyl 2-methyl-butanoate	DNQb	1,058	MS	0.001	Fruity, strawberry, pineapple

^aThe Kovats index (KI) and the method of identification (Id) are given for every compound. Identification was via the mass spectrum (MS) and by comparison with the retention time of the reference compound (RF).

^bDetected but not quantified.

^cSee references 57 and 58.

^dSee references 56, 59, 60, and 61.