Abstract: Gas chromatography-olfactometry-mass spectrometry (GC-O-MS) and electronic nose (E-nose) were used to study the changes in the aroma compounds in Pixian broad-bean Paste during its production process. The changes in aroma compounds were analyzed from the raw material to the starter-making, fermentation at constant temperature, and post-fermentation stages. The formation mechanism of characteristic aroma substances was explored, and correlation analysis was carried out on the aroma substances at different stages. The results showed that the number of volatile substances increased initially and then decreased during the fermentation process. Benzaldehyde was mainly converted from benzyl alcohol; furfural was mainly derived from the degradation of sugars; soamyl alcohol was produced by leucine conversion; 4-ethylphenol and 4-ethyl-2-methoxyphenol were mainly derived from fermented hot pepper; 2,3,5,6-tetramethylpyrazine was derived from board beans; phenylethanol and phenylacetaldehyde were mainly derived from microbial metabolism. Moreover, the degradation of methionine may be responsible for 3-methionyl propanal. The starter-making stage contributed minimally to the aroma, which accumulated mostly during the constant-temperature fermentation stage. Fermented hot pepper made a large contribution to the aroma at the early stage of fermentation but resulted in reduced aroma concentration at the late stage. During the first six months of post-fermentation, the concentration of aroma compounds changed slowly, but dramatically from month 6 to 12; however, it gradually reduced after 1 year. The correlation analysis showed that the aroma substances at the early stage of fermentation were significantly different from those at the late stage.

Key words: Pixian broad-bean paste, aroma compounds, gas chromatography-olfactory-mass spectrometry, formation mechanism