Multiple roles of lactic acid bacteria microflora in the formation of marker flavour compounds in traditional chinese paocai

Abstract

Traditional paocai brine (PB), which is continuously propagated by back-slopping and contains multiple species of lactic acid bacteria (LAB), is critical for the flavour of paocai. But the flavour-related compounds of PB-paocai, and the relationships between the LAB communities in PB and the marker volatile organic compounds (VOCs) in paocai remain unclear. A metabolomics-based method was utilized to screen the VOCs marker(s) of PB paocai in situ, and the change of these markers in whole fermentation was monitored to reveal the role of LAB communities in marker compound formation in vitro. A total of 13 compounds were screened as discriminant volatile markers for PB-paocai via gas chromatography-mass spectrometry (GC-MS)-based multimarker profiling. The co-culture of LAB from PB significantly increased the amount of acetic acid by producing it directly, and improved the ethyl acetate and ethyl propanoate yields by interacting with other microbes. However, LAB decreased the amount of sulphides, including methanethiol, carbon disulphide, methyl thiolacetate, dimethyl disulphide and dimethyl trisulphide, in PB-paocai due to inhibiting the growth of other microbes. The major flavour features of traditional paocai originate from LAB. Such volatile markers related to LAB communities may serve to promote starter screening and fermentation optimisation to produce paocai-related foods with better sensory qualities. This study could provide a deeper understanding of the role of LAB in marker flavor compound formation and guidance for the industrial production of Chinese paocai.