Abstract: In this study, head-space solid phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME-GC-MS) ws applied to analyze the main volatile flavor substances of Pixian soybean paste (PSP) sampled at five different fermentation stages from stable fermentation (six months) to the end (five years), and the obtained data were analyzed by principal component analysis (PCA). The results revealed that over 140 volatile flavor substances were detected in all PSP samples, mainly including ethyl acetate (18.39%), 4-ethyl gualacol (10.58%), phenethyl alcohol (7.64%), alcohol (7.16%) and phenylacetaldehyde (6.59%). The relative contents of aldehydes, esters, hydrocarbons and heterocyclic compounds increased with fermentation time, while the relative contents of alcohols, phenols and ketones decreased. The change of volatile aroma compounds was far greater during the early maturation stage than during the late maturation stage and it was very slow after 3 years of post-fermentation and did not significantly change subsequently.

Key words: Pixian soybean paste, volatile compounds, principal component analysis