Chemical, Microbiological, and Functional Characterization of Kefir Produced from Cow’s Milk and Soy Milk

Table 5

Amino acids in unfermented and fermented cow’s milk and soy milk with kefir grains.

Amino acids (mg 100 mL^−1)	Unfermented cow’s milk	Fermented cow’s milk (cow’s milk kefir)	Unfermented soy milk	Fermented soy milk (soy milk kefir)
Asp	0.42 ± 0.31^a	0.03 ± 0.01^a	1.66 ± 0.01^b	2.72 ± 0.16^c
Thr	0.16 ± 0.02^a	1.30 ± 0.33^b	0.20 ± 0.02^a	0.39 ± 0.03^a
Ser	0.14 ± 0.01^a	0.48 ± 0.17^a	0.30 ± 0.02^a	0.54 ± 0.04^a
AspNH2	ND	ND	2.16 ± 0.04^a	1.46 ± 0.07^b
Glu	5.90 ± 0.01^a	6.21 ± 0.57^a	8.81 ± 0.03^a	16.62 ± 2.26^b
GluNH2	0.25 ± 0.01^a	ND	ND	ND
Gly	0.73 ± 0.04^a	0.63 ± 0.03^a	1.72 ± 0.03^b	2.79 ± 0.10^c
Ala	0.40 ± 0.02^a	1.04 ± 0.13^a	2.10 ± 0.05^b	3.42 ± 0.22^c
Val^∗	0.22 ± 0.03^a	1.01 ± 0.11^b	0.46 ± 0.01^a	0.09 ± 0.02^a
Cys	Traces	ND	ND	ND
Met	0.02 ± 0. 00^a	0.09 ± 0.01^a	0.30 ± 0.02^b	0.07 ± 0.04^a
Ile	0.08 ± 0.00^a	0.88 ± 0.16^b	0.39 ± 0.02^a	0.10 ± 0.01^a
Leu	0.12 ± 0.01^a	1.04 ± 0.01^b	0.53 ± 0.05^c	0.06 ± 0.02^a
Tyr	0.12 ± 0.01^a	0.53 ± 0.10^a	0.25 ± 0.03^a	1.17 ± 0.11^b
Phe	0.05 ± 0.01^a	0.52 ± 0.01^b	0.57 ± 0.04^b	0.48 ± 0.05^b
Trp	ND	ND	ND	ND
Lys	0.35 ± 0.04^a	0.67 ± 0.01^a	0.77 ± 0.03^a	2.76 ± 0.17^b
His	0.07 ± 0.01^a	1.07 ± 0.09^b	0.61 ± 0.01^c	2.08 ± 0.05^d
Arg	0.38 ± 0.02^a	0.10 ± 0.12^a	12.13 ± 0.11^b	ND^a
Pro	0.30 ± 0.02^a	5.31 ± 0.41^b	0.49 ± 0.01^a	1.43 ± 0.07^c
Total	9.72 ± 0.18	20.92 ± 2.43	33.44 ± 0.17	36.20 ± 3.41
Tau	2.59 ± 0.08^a	3.42 ± 0.04^b	ND^c	0.19 ± 0.04^d
gABA	ND	ND	ND	ND

ND: not detected. Essential amino acids. Essential amino acid for children. Seven consecutive fermentations were carried out; samples on days 1, 4, and 7 were taken; and amino acids were determined. The values shown are the mean ± standard deviation of these three measurements. Different lowercase letters in the rows indicate that the values are significantly different.