Search for potential molecular indices for the fermentation progress of soy sauce through dynamic changes of volatile compounds

- Changes of volatiles during soy sauce fermentation were revealed by HS-SPME GC-MS.
- The potential indices for the fermentation progress were searched by PCA analysis.
- 2-methoxy-4-vinylphenol and phenylethyl alcohol were suggested as potential indices.

To date, the fermentation progress and maturity of soy sauce are mainly judged by olfactory and individual experiences, which are subjective and lack quality control. In this study, dynamic changes of volatile compounds during soy sauce fermentation were profiled to search for molecular indices of fermentation progression. In total, 119 volatile compounds were identified and quantified by headspace solid-phase microextraction gas chromatography-mass spectrometry. Principal component analysis (PCA) revealed the compounds that contributed most to the distinction of various stages of fermentation progression; the list included 2-methoxy-4-vinylphenol, phenylethyl alcohol, phenylacetaldehyde, and benzaldehyde. The degradation of 2-methoxy-4-vinylphenol and the generation of phenylethyl alcohol could remarkably discriminate between the discrete stages of soy sauce fermentation. It therefore suggests that their group was a refined and potential index to indicate the progression of the soy sauce fermentation. This work furthers our understanding of the molecular changes occurring during soy sauce fermentation and improves its quality control and process management.