Salt reduction-driven biogenic amine accumulation in broad bean paste: Insights into physicochemical properties, key enzyme activity, and microbial community dynamics

Abstract

The mechanisms governing biogenic amine (BA) production and the excessive accumulation of BAs in response to reduced salt content during broad bean paste (BBP) fermentation remain inadequately elucidated. This study conducted a comparative analysis of BBP fermentation under low- (LS, 6 %), medium- (MS, 9 %), and high-salt (HS, 12 %) conditions, emphasizing the dynamic changes in physicochemical properties, key enzyme activity, and microbial community dynamics, as well as their correlations with BA formation. The findings revealed that salt reduction accelerated the fermentation process, with LS samples exhibiting the most pronounced variations in pH, total acidity, and amino acid nitrogen. By the end of fermentation, these values reached 4.17, 0.64 g/100g, and 0.84 g/100g, respectively, whereas HS samples exhibited minimal changes, with final values of 4.90, 0.29 g/100g, and 0.67 g/100g. Additionally, LS samples displayed heightened protein hydrolysis activity, as evidenced by the highest acid protease activity (1.84 U/g vs. 1.47 U/g in HS) and protein degradation rates (44.45 % vs. 24.70 % in HS), resulting in a 1.55-fold greater accumulation of free amino acids at the end of fermentation (2.59 g/100g vs. 1.67 g/100g in HS). Moreover, the elevated amino acid decarboxylase activity in LS samples promoted substantial BA accumulation, with total BA content reaching 1346.81 mg/kg, compared to 854.69 mg/kg in MS and 764.22 mg/kg in HS samples. Mammaliicoccus, Tetragenococcus, and Staphylococcus were the dominant genera in the HS and MS samples, whereas Mammaliicoccus, Weissella, and Bacillus were predominant in the LS samples. Correlation analysis identified significant associations between pH reduction, protein hydrolysis, and BA formation patterns under different salt concentrations (P < 0.05). Differential analysis further indicated that the intensified pH decline and accelerated protein hydrolysis induced by salt reduction were primary contributors to the excessive accumulation of phenylethylamine, histamine, spermidine, and spermine, while the upregulation of amino acid decarboxylase activity specifically accounted for the elevated tyramine levels in reduced-salt samples. Microbial analysis indicated that Weissella, Bacillus, Companilactobacillus, and Pichia were key microbial factors involved in or promoting BA formation under reduced-salt conditions. These findings provide novel insights into the mechanisms underlying BA formation under varying salt concentrations and offer a scientific basis for improving the safety and quality of reduced-salt BBP.