Effects of extracellular proteases and its inhibitors on the gel characteristics of soy protein induced by lactic acid bacteria

The purpose of this study was to analyse the relationship between extracellular protease activity and gel characteristics of soybean protein gel induced by lactic acid bacteria (LAB), the influence of protease inhibition on the gel characteristics was discussed through SDS-PAGE, rheological properties and microstructure. The results showed that the pH value of Lactobacillus casei decreased slowly, but the gel could be formed at 2 h, maybe its higher extracellular protease activity improved the gel characteristics. The addition of ethylenediaminetetraacetic acid (10 mmol L-1) reduced the gel quality, when the protease activity was inhibited, the gel quality would decrease, even if there were macromolecular crosslinkers in the system. This study showed that extracellular protease had an important influence on gel characteristics and provided a theoretical basis for the application of protease producing LAB in fermentation-induced soybean gel foods.