Abstract: Post-fermentation of Pixian broad-bean paste was conducted for 90 days at a constant temperature in a semi-closed system designed by the authors, and this was compared with the tradition natural post-fermentation process. The contents of total acid, amino nitrogen, reducing sugar, free amino acids and moisture and chromaticity at the end of traditional natural fermentation were 1.13%, 0.27%, 2.81%, 19.68 mg/g, 48.80%, and 0.784 while those at the end of constant temperature fermentation were 0.78%, 0.20%, 2.12%, 16.11 mg/g, 60.21% and 1.025, respectively. The results showed that the fermentation of Pixian broad-bean paste proceeded normally in the semi-closed system and the product was in accordance with the quality criteria. All quality parameters evaluated changed more greatly during the traditional fermentation process and more violent physical and biochemical reactions took place. The spatiotemporal distribution of temperature and change in moisture content had a great influence on the fermentation process. Both fermentation processes had their own advantages, and the constant-temperature fermentation process should be optimized by referring to the important conditions for traditional natural fermentation.

Key words: Pixian broad-bean paste, fermentation, constant temperature, comparison and analysis