Impact of solid-state saccharification on the flavor of rice-flavor baijiu.

Rice-flavor baijiu is a traditional Chinese liquor. The flavor profile and volatiles presented with or without the solid-state saccharification (SSS) were investigated to reveal the effects of SSS process on the quality of rice-flavor baijiu. The liquor prepared with SSS had a sweet flavor. It contained significantly higher contents of ß-phenylethyl alcohol, ß-phenylethyl acetate, and ethyl lactate with odor active value of >1. The liquor prepared without SSS had a cheese-like flavor. It was confirmed that the cheese-like flavor derived from butanoic acid was only detected in the liquor prepared without SSS. SSS facilitated the biosynthesis of ß-phenylethyl alcohol and ethyl lactate by supplying a large amount of phenylalanine and lactic acid at the initial stage of fermentation, and it prevented contamination. These results indicated that the SSS process contributed to produce the characteristic flavor compounds of rice-flavor baijiu. PRACTICAL APPLICATION: Solid-state saccharification (SSS) process of rice-flavor baijiu contributes not only in brewing, but also in the production of the characteristic flavor compounds and the repression of the off-flavor derived from the contamination. Therefore, SSS is a critical process to control the flavor of rice-flavor baijiu.

Manufactural impact of the solid-state saccharification process in rice-flavor baijiu production.

Rice-flavor baijiu is a traditional Chinese liquor that is manufactured using a solid-state saccharification process. In the present study, we investigated the role of the process in making of rice-flavor baijiu using chemical and biological quantitative analysis approaches. More than 70% of starch in rice decomposed to glucose after saccharification. In addition, the number of fungal cells, saccharification activity, and lactic acid concentration increased. Rhizopus oryzae was identified as the major fungus proliferating under saccharification based on denaturing gradient gel electrophoresis analysis targeting the internal spacer transcribed region. Lactic acid bacteria were not detected by 16S rRNA gene-based next-generation sequencing analysis during saccharification. Conversely, R. oryzae, isolated from xiaoqu, exhibited a capacity to produce lactic acid. The results imply that the solid-state saccharification is essential not only for saccharification but also for the culture of R. oryzae, which promote saccharification activity and lactic acid production. We also investigated the most appropriate temperature for solid-state saccharification and 35°C was the optimum temperature for R. oryzae cultivation, enzyme production, and saccharification. The results could facilitate the efficient and stable manufacture of rice-flavor baijiu.