TABLE 2.

Volatile compounds detected in the fermented grains and their factor loadings obtained by PCA

Group and no.	Aroma compounds	Factor loading
		Loading 1	Loading 2
Group IIb
1	Ethyl tetradecanoate	0.97	0.15
2	Acetic acid	0.97	0.08
3	Ethyl hexadecanoate	0.96	0.18
4	Octanoic acid	0.95	0.00
5	Isoamyl lactate	0.95	0.03
6	Ethyl 3-phenylpropionate	0.94	0.13
7	Ethyl 9-hexadecenoate	0.94	0.22
8	Phenylethanol	0.94	0.31
9	2-Methoxy-4-methylphenol	0.93	−0.13
10	Pentadecanoic acid ethyl ester	0.93	−0.04
11	1-Octen-3-ol	0.93	−0.14
12	n-Decanoic acid	0.93	−0.19
13	2,3-Butanediol	0.93	0.03
14	Ethyl phenylacetate	0.92	0.07
15	Isopentyl acetate	0.91	0.01
16	3-Methylpentanoic acid	0.91	−0.09
17	2-Furanmethanol	0.91	0.07
18	2-Phenylethyl acetate	0.88	0.35
19	Hexanoic acid	0.88	−0.06
20	Ethyl caprate	0.84	0.47
21	Ethyl hexanoate	0.84	0.28
22	Furfural	0.84	−0.13
23	Ethyl acetate	0.83	0.42
24	Ethyl lactate	0.79	0.16
25	Ethyl octanoate	0.74	0.41
26	Isoamyl alcohol	0.73	0.06
27	Geranyl acetone	0.71	0.31
28	Ethyl isobutyrate	0.52	−0.36
Group Ia
29	3-Hydroxy-butanoic acid ethyl ester	−0.41	−0.26
30	Propanoic acid	−0.40	−0.26
31	1-Nonanol	−0.39	0.34
32	5-Heptyldihydro-2-(3H)-furanone	−0.36	−0.23
33	Isooctanol	−0.36	−0.23
34	4-Ethyl guaiacol	−0.23	−0.18
35	Ethyl butyrate	−0.22	−0.03
36	Ethyl propanoate	−0.21	−0.02
37	Butanoic acid	−0.18	−0.18
38	1-Nonen-3-ol	−0.16	−0.17
39	4-Dodecanolide	−0.14	0.08
40	Nonanoic acid	−0.09	−0.33
41	Isobutyl acetate	−0.04	−0.07
42	2-Heptanol	−0.02	−0.13
43	5-Methyl-2-hexanol	0.04	−0.27
44	Dodecanoic acid	0.04	−0.27
45	Butanedioic acid diethyl ester	0.10	−0.10
46	Ethyl heptanoate	0.06	−0.07
47	2,6-Dimethyl-4-heptanol	0.06	−0.07
Group IIIc
48	4-Vinylguaiacol	0.18	0.92
49	1-Octanol	0.04	0.89
50	1-Pentanol	0.24	0.88
51	Ethyl dodecanoate	0.09	0.86
52	2-Propenyl phenylacetate	0.21	0.84
53	3-Hydroxy-2-butanone	−0.08	0.79
54	γ-Nonalactone	0.24	0.79
55	2-Methyl-1-propanol	0.16	0.73
56	Ethyl nonanoate	−0.09	0.67
57	2-Methyl-1-butanol	0.36	0.55
58	Hexanal	−0.03	0.35

^aGroup I contained 19 aroma compounds. These compounds were characteristic of the samples collected during the early stages of the four batches.

^bGroup II consisted of aroma compounds which had high loadings in the positive section of PC1. These compounds were present at high concentrations in the samples A20 and B20.

^cGroup III consisted of aroma compounds which had high loadings in the positive section of PC2. These compounds were present at high concentrations in the samples C20 and D20.