Abstract: Two stepwise fermentation modes of low salt and low temperature followed by high salt and high temperature for the production of Pixian broad bean paste were established in this study. In mode 1, salinity, temperature and fermentation time were set as 6%, 12 ℃ and 12 days for the early stage; 6%, 37 ℃ and 4 days for the middle stage; 15%, 37 ℃ and 14 days for the late stage, respectively. The conditions for mode 2 were the same as those for mode 1 except that the salinity was 9% at the early and middle stages of fermentation. The traditional high temperature fermentation was set as the control group. The changes of mold count, total bacterial count and physicochemical indexes were detected during the fermentation process. Meanwhile, the biogenic amines and volatile components of broad bean paste mash samples at the end of fermentation were analyzed. The results showed the mold count and total bacterial count kept stable at first, and then decreased rapidly in the two stepwise fermentation modes. In the control group, the mold count kept decreasing during fermentation, while the total number of bacteria decreased at the beginning and then increased slowly to reach a plateau. At the end of fermentation, the contents of total acid, amino acid nitrogen and biogenic amine in the mode 1, mode 2 and control groups were 0.96%, 0.92% and 0.87%; 0.76%, 0.83% and 0.66%; and 122.93, 126.50 and 176.12 mg/kg, respectively. In addition, the types and contents of volatile compounds in modes 1 and 2 were higher than those in the control group. The total content of volatile compounds especially esters was the highest in mode 1. Sensory evaluation showed that the sensory quality of mode 1 was the best, followed by mode 2, while the control group was the worst. The comprehensive analysis showed that the quality of broad bean paste mashes produced by the stepwise fermentation modes was better than that of the control group, especially mode 1.

Key words: Pixian broad bean paste mash; stepwise fermentation; microorganism; quality