Variation of aroma profile in fermentation process of Wuliangye baobaoqu starter

Changes of volatile compounds and sensory properties in the fermentation process of Wuliangye baobaoqu starter (WBS) were determined by sensory analysis, gas chromatography-olfactometry (GC/O) and GC quantitative analyses. The sensory properties of WBS changed from the sour, fruity, bready notes at the temperature-rise phase (3-day and 7-day) to the nutty and moldy notes at the temperature-fall phase (18-day, 21-day and 27-day). Acetic acid, methional, ethyl acetate, phenylethyl alcohol, ethyl 2-phenylacetate, 4-vinylguaiacol were potential aroma active compounds based on their Osme values. Results of GC quantitative analyses showed that the acids had the highest concentration. The concentration of (E)-2-hexenal, ethyl acetate, isoamyl alcohol, phenylethyl alcohol, 2-n-pentylfuran, acetic acid and lactic acid increased with the fermentation time, presented the highest level in the temperature-rise phase and decreased after this period. The concentration of (E,E)-2,4-hexadienal, 2,6-dimethylpyrazine, trimethylpyrazine, tetramethylpyrazine presented the highest level at the temperature-fall phase. Ethyl 3-methylbutanoate, (E,E)-2,4-hexadienal, (E,E)-2,4-nonadienal, acetic acid and butanoic acid had high odor active values. Results of principal component analysis showed that acetic acid, hexanal, (E)-2-hexenal, lactic acid, isoamyl alcohol, 1-hexanol and 1-octen-3-ol were critical volatile chemicals to distinguish different WBS samples.