Bacterial communities and volatile organic compounds in traditional fermented salt-free bamboo shoots

Abstract

Fermented bamboo shoot is a traditional salt-free fermented vegetable product, which has been widely used as cooking ingredient in southern China. This paper intends to evaluate the changes of bacterial diversity and volatile organic compounds (VOCs) in bamboo shoots during fermentation. FT-IR spectra confirmed the significant original difference in transmittance between fresh and fermented bamboo shoots. Four VOCs in fresh bamboo shoots, namely α-gurjunene, p-cresol, methoxyphenyloxime, hexanal, were retained after fermentation. At the same time, new VOCs, namely β-cedrene, ethyl caprylate, 1-nonanal, 4-methylanisole, (z)-2-heptenal, acetic acid, valeraldehyde, 1-hexanol, ethyl palmitate were produced. Among them, the concentration of p-cresol was the highest among all VOCs. At the phylum level, proteobacteria was the dominant bacterial biota in fresh bamboo shoots (GC-0 group). Firmicutes became the dominant bacterial biota in fermented samples. At the genus level, bacterial groups in fresh bamboo shoots were dominated by Oxyphotobacteria (unclassified) and Lactobacillus. With the progress of fermentation, Lactobacillus increased continuously and finally became the dominant bacterial biota. Weissella appeared in the early stage of fermentation, but began to decline to less than 0.1% in the later stage. Lactobacillus became increasingly abundant during fermentation, and there was a significant positive correlation between Lactobacillus and valeraldehyde, 1-hexanol, ethyl palmitate, propyl acetate, 2-methoxy-4-methylphenol. These results suggest that the aroma quality of fermented bamboo shoots may be seriously affected by the bacterial biota in traditional fermented bamboo shoots. To sum up, this study provides a comprehensive and in-depth correlation between bacterial community and VOCs in fermented bamboo shoots.