Study on the rules and influencing factors of yeast proteinase A secretory under industrial scale brewing

The secretory regularity of proteinase A from yeast was investigated in industrial scale fermentation.The factors such as yeast generation and storage conditions were studied to achieve their influencing extent of yeast proteinase A excretory, and the change of proteinase A activity, foam protein and head retention of draft beer with different initial proteinase A level during storage were tested in this study. The results showed that the activity of proteinase A would increase during fermentation, and the tendency was pronounced for fermenting worts while the generation of yeasts was increased. In addition, with the increase of storage period, the concentration of proteinase A excreted from yeast cells also increased. When the activity of proteinase A by yeast was below 0.015U/m L and the initial proteinase A activity in final product was less than 15×10-5U/m L, the foam stability of draft beer would be better than others after 4 months.