Characterization of volatile compounds of Pixian Douban fermented in closed system of gradient steady-state temperature field.

As an essential flavor condiment in Sichuan cuisine, Pixian Douban (PXDB) is usually produced by open fermentation process in strip pools or ceramic vats. In this study, an experiment of PXDB fermentation was conducted for 90 days in a closed system of gradient steady-state temperature field (GSTF). To investigate the characterization of volatile compounds of PXDB in the closed system, the volatiles in three kinds of samples including samples of GSTF (SGT), samples of constant temperature (SCT), and samples of traditional fermentation (STF) were analyzed. The results showed that 75, 67, and 68 volatile compounds were detected in SGT, SCT, and STF, respectively. Compared with the traditional fermentation, the process in the closed system of GSTF was conducive to produce more kinds of esters and alcohols. A total of 22 major aroma active compounds were identified in three samples by combination analyses of gas chromatography-olfactometry (GC-O) and odor activity value (OAV). The appearance, smell, texture, and taste of the three different samples had shown different changes, but the sensory characteristics of the SGT were more similar to those of the STF by quantitative descriptive analysis (QDA) and principal component analysis (PCA). This study indicated that the closed system of GSTF could be applied in PXDB fermentation to obtain higher quality products, which brought a bright prospect of replacing the traditional fermentation process to realize the controllable industrialized production of PXDB.