Table 2.

Volatile compounds identified in nutty chocolate-like aroma generated by C. glutamicum from enzymatic soybean meal hydrolysate supplemented (NF-A) and unsupplemented (NF) with amino acids.

Peak No	Components		Time of fermentation								Description
		KIa	3 days		5 days		7 days		9 days
			NF	NF-A	NF	NF-A	NF	NF-A	NF	NF-A
1	2-Methylbutanal	639	0.06a ± 0.01	0.02a ± 0.00	0.09a ± 0.01	0.02a ± 0.00	0.82b ± 0.10	0.12b ± 0.02	1.40c ± 0.18	0.53c ± 0.07	Malty chocolate1
2	3-Methylbutanal	682	0.14a ± 0.02	0.07a ± 0.01	0.19a ± 0.12	0.09a ± 0.01	0.27b ± 0.03	0.10a ± 0.01	1.82c ± 0.23	0.83b ± 0.11	Malty chocolate1
3	Acetoine	714	0.55a ± 0.07	0.42a ± 0.05	0.44b ± 0.06	0.31b ± 0.04	0.25c ± 0.03	0.11c ± 0.01	–	–	Butter2
4	2-Methylpyrazine	834	–	–	–	0.03b ± 0.00	–	0.12 ± 0.02	0.01a ± 0.00	0.17d ± 0.02	Earthy nutty3
5	2,5-Dimethylpyrazine	918	–	0.02a ± 0.00	0.02a ± 0.00	0.51b ± 0.06	0.04a ± 0.00	0.78c ± 0.10	0.06a ± 0.01	0.55b ± 0.07	Chocolate nutty3
6	2,6-Dimethylpyrazine	923	–	–	–	–	0.03a ± 0.00	0.08b ± 0.01	0.01a ± 0.00	0.03c ± 0.00	Nutty herbal3
7	2,3-Dimethylpyrazine	933	–	–	–	–	0.01a ± 0.00	0.07b ± 0.01	0.05a ± 0.01	0.08b ± 0.01	Nutty3
8	Trimethylpyrazine	1030	–	0.07a ± 0.006	0.03b ± 0.00	0.16b ± 0.02	0.07c ± 0.01	0.26c ± 0.03	0.11d ± 0.01	0.17b ± 0.02	Chocolate nutty3
9	Tetramethylpyrazine	1098	–	–	–	0.03a ± 0.00	–	1.80b ± 0.23	3.70b ± 0.47	3.23c ± 0.41	Roasted nutty4
	Total yield		0.75 ± 0.01	0.60 ± 0.08	0.77 ± 0.10	1.15 ± 0.15	1.49 ± 0.19	3.44 ± 0.44	7.16 ± 0.91	5.59 ± 0.71

Values are the average of triplicate analysis (mg/L fermented cultures) ±SD.

Mean values in the same row for each culture followed by different superscript lower case letters are significantly different at P < 0.05.

^aRetention indices.

¹Rodriguez-Campos et al. [41].

²Forster et al. [35].

³Bonvechi [42].

⁴Afoakwa et al. [7].