Evaluation of Volatile Compounds during the Fermentation Process of Yogurts by Streptococcus thermophilus Based on Odor Activity Value and Heat Map Analysis

Table 1

Content of volatile compounds in yogurt by S. thermophilus at different fermentation times.

RI	Compound names	Content (mg·kg−1)
		0 h	1.5 h	3.0 h	4.5 h	6.0 h
	Aldehydes
955	Benzaldehyde	1.34 ± 0.18^d	1.86 ± 0.31^c	2.03 ± 0.17^c	3.23 ± 0.08^b	3.68 ± 0.26^a
1004	Octanal	1.45 ± 0.13^a	1.65 ± 0.39^a	1.49 ± 0.08^a	0.76 ± 0.26^b	1.28 ± 0.24^a
1045	Benzeneacetaldehyde	nd	nd	1.26 ± 0.28^a	nd	nd
1106	Nonanal	8.54 ± 2.01^a	4.28 ± 0.61^b	3.34 ± 0.31b^c	1.68 ± 0.24^c	3.48 ± 0.12^bc
1206	Decanal	2.35 ± 0.07^a	1.20 ± 0.20^b	1.14 ± 0.13^b	1.28 ± 0.18^b	nd
1216	2,4-Dimethyl-benzaldehyde	6.62 ± 0.34^b	3.41 ± 0.31^c	3.56 ± 0.21^c	3.54 ± 0.54^c	16.49 ± 2.14^a
1263	(E)-2-Decenal	nd	0.64 ± 0.06^a	nd	nd	nd
1308	Undecanal	nd	nd	nd	nd	2.56 ± 0.20^a
1318	(E,E)-2,4-Decadienal	2.22 ± 0.28^a	1.46 ± 0.16^b	1.71 ± 0.12^b	1.78 ± 0.06^b	2.23 ± 0.14^a
1410	Dodecanal	8.75 ± 1.14^a	5.30 ± 0.55^b	6.29 ± 0.79^b	0.92 ± 0.05^c	nd
1614	Tetradecanal	5.38 ± 0.98^bc	4.74 ± 0.37^c	6.34 ± 0.66^ab	4.80 ± 0.39^c	6.83 ± 0.98^a
	Subtotal	36.64 ± 4.25^a	24.54 ± 2.15^b	27.15 ± 2.11^b	17.99 ± 0.45^c	36.54 ± 2.66^a
	Ketones
891	2-Heptanone	54.12 ± 2.90^c	56.57 ± 7.84^c	65.25 ± 6.59^ab	61.17 ± 4.63^ab	71.84 ± 7.59^a
1094	2-Nonanone	64.67 ± 4.98^b	65.34 ± 6.84^b	79.52 ± 3.98^a	60.84 ± 4.12^b	66.71 ± 6.37^b
1130	2-Nonen-4-one	nd	nd	nd	3.05 ± 0.57^a	2.58 ± 0.23^a
1199	2-Decanone	4.52 ± 0.40^a	3.38 ± 0.29^b	3.54 ± 0.35^b	nd	nd
1296	2-Undecanone	88.21 ± 10.22^b	84.38 ± 7.37^b	114.18 ± 12.05^a	38.61 ± 1.16^c	45.79 ± 4.94^c
1399	2-Dodecanone	1.98 ± 0.36^b	2.26 ± 0.37^b	2.78 ± 0.36^a	nd	nd
1498	2-Tridecanone	112.01 ± 14.09^b	108.92 ± 8.41^b	135.40 ± 14.91^a	35.88 ± 2.23^c	45.10 ± 2.02^c
1658	(Z)-Dihydro-5-(2-octeny)-2(3H)-furanone	nd	nd	7.64 ± 0.49^b	6.13 ± 0.68^c	10.33 ± 0.23a
1699	2-Pentadecanone	79.83 ± 8.94^b	90.08 ± 9.04^b	118.29 ± 10.71^a	24.67 ± 2.19^c	17.51 ± 2.69^c
1710	6-Heptyltetrahydro-2H-pyran-2-one	34.58 ± 1.90^b	34.26 ± 2.43^b	35.83 ± 3.35^b	37.20 ± 1.25^b	57.08 ± 0.92^a
	Subtotal	439.92 ± 33.78^b	445.19 ± 41.72^b	562.43 ± 35.72^a	267.55 ± 12.98^c	316.94 ± 24.50^c
	Acids
1008	Hexanoic acid	nd	nd	nd	5.17 ± 0.25^b	30.26 ± 3.54^a
1194	Octanoic acid	nd	0.64 ± 0.07^c	0.81 ± 0.07^c	55.85 ± 5.61^b	149.38 ± 11.51^a
1285	Nonanoic acid	nd	nd	nd	nd	18.36 ± 1.83^a
1377	Decanoic acid	nd	nd	2.68 ± 0.28^b	70.75 ± 4.47^b	782.24 ± 78.33^a
1473	Undecanoic acid	nd	nd	nd	9.88 ± .49^b	15.80 ± 0.40^a
1568	Dodecanoic acid	10.92 ± 2.43^c	2.21 ± 0.17^c	6.18 ± 0.79^c	66.71 ± 7.11^b	564.28 ± 58.05^a
1666	Tridecanoic acid	nd	nd	nd	nd	5.97 ± 0.78^a
1765	Tetradecanoic acid	0.98 ± 0.00^c	5.26 ± 0.42^c	20.96 ± 3.87b^c	41.66 ± 3.07^b	300.27 ± 32.23^a
	Subtotal	11.90 ± 2.43^c	8.11 ± 0.29^c	30.64 ± 4.96^c	250.03 ± 20.26^b	1866.56 ± 174.63^a
	Benzene derivatives
852	Ethylbenzene	3.98 ± 0.41^b	5.25 ± 0.52^a	5.44 ± 0.28^a	5.28 ± 0.97^a	5.54 ± 0.21^a
860	p-Xylene	13.19 ± 1.68^a	15.12 ± 0.88^a	13.52 ± 0.49^a	13.63 ± 1.88^a	13.42 ± 0.83^a
884	Styrene	12.71 ± 1.97^a	12.27 ± 1.81^a	11.93 ± 1.25^a	10.19 ± 0.74^a	11.05 ± 0.84^a
1118	1,2,4,5-Tetramethyl-benzene	0.99 ± 0.15^b	2.33 ± 0.11^a	1.98 ± 0.34^a	1.26 ± 0.06^b	1.22 ± 0.18^b
1183	Naphthalene	1.14 ± 0.07^a	0.86 ± 0.08^a	0.71 ± 0.10^c	1.00 ± 0.08^ab	1.14 ± 0.05^a
1289	1-Methyl-naphthalene	3.49 ± 0.15^a	2.00 ± 0.18^b	2.09 ± 0.16^b	2.26 ± 0.18^b	nd
1417	2,3-Dimethyl-naphthalene	1.05 ± 0.04^a	0.65 ± 0.09^b	0.44 ± 0.03^c	0.43 ± 0.08^c	nd
	Subtotal	36.56 ± 3.83^ab	38.48 ± 2.97^a	36.12 ± 2.04^ab	34.05 ± 2.37^ab	32.36 ± 1.95^b
	Hydrocarbons
900	Nonane	539.67 ± 72.04^a	564.57 ± 46.61^a	538.43 ± 58.91^a	550.29 ± 46.52^a	522.47 ± 27.75^a
1000	Decane	1.11 ± 0.15^a	0.58 ± 0.07^b	0.60 ± 0.04^b	nd	nd
1100	Undecane	nd	nd	0.74 ± 0.10^b	1.35 ± 0.09^a	1.34 ± 0.15^a
1197	1-Dodecene	nd	3.39 ± 0.30^b	4.35 ± 0.61^a	0.67 ± 0.13^c	nd
1200	Dodecane	1.35 ± 0.10^a	0.66 ± 0.10^b	0.76 ± 0.07^b	0.66 ± 0.03^b	nd
1300	Tridecane	nd	0.61 ± 0.08^c	0.72 ± 0.09^c	1.21 ± 0.15^b	1.61 ± 0.16^a
1224	4,8-Dimethyl-undecane	1.09 ± 0.16^a	nd	nd	nd	nd
1396	1-Tetradecene	nd	1.04 ± 0.10^b	1.09 ± 0.28^b	2.04 ± 0.10^a	nd
1400	Tetradecane	3.45 ± 0.26^a	1.74 ± 0.20^b	1.49 ± 0.15^b	1.38 ± 0.26^b	nd
1494	1-Pentadecene	nd	nd	nd	nd	6.41 ± 0.48^a
1500	Pentadecane	8.24 ± 0.61^a	nd	nd	nd	nd
1600	Hexadecane	12.68 ± 0.87^a	7.04 ± 0.64^b	6.08 ± 0.48^b	2.01 ± 0.44^d	4.60 ± 0.52^c
1692	1-Heptadecene	nd	nd	nd	7.56 ± 0.51^a	0.70 ± 0.06^b
	Subtotal	567.59 ± 72.94^a	579.64 ± 45.95^a	554.28 ± 60.27^a	567.17 ± 46.77^a	537.12 ± 28.02^a
	Other compounds
917	Diethyl disulfide	nd	2.93 ± 0.27^a	3.11 ± 0.20^a	nd	nd
991	2-Pentyl-furan	2.19 ± 0.38^a	nd	nd	nd	nd
1029	Limonene	3.67 ± 0.69^a	3.32 ± 0.43^a	3.23 ± 0.21^a	1.23 ± 0.26^b	1.26 ± 0.12^b
1515	2,4-Bis(1,1-dimethylethyl)-phenol	46.85 ± 5.33^a	23.11 ± 2.82^b	22.55 ± 1.99^b	19.20 ± 1.22^b	19.99 ± 1.89^b
	Subtotal	52.71 ± 6.06^a	29.36 ± 3.49^b	28.89 ± 2.39^b	20.43 ± 1.47^c	21.26 ± 1.91^c
	Total	1145.32 ± 116.21^b	1125.33 ± 56.95^b	1239.52 ± 102.70^b	1157.22 ± 46.55^b	2810.78 ± 142.56^a