高分子蛋白和蛋白酶A对纯生啤酒泡沫稳定性的影响

Effects of High-molecular Protein and Proteinase A on the Foam Stability of Pure Draft Beer

利用考马斯亮蓝法、荧光底物法分别跟踪检测啤酒酿造和贮存过程中高分子蛋白含量及蛋白酶A活力变化，研究影响纯生啤酒泡沫稳定性的关键因素。结果表明，各发酵罐因发酵阶段工艺参数的不同，导致高分子蛋白含量及蛋白酶A活力变化趋势存在明显差异。发酵阶段高分子蛋白含量缓慢降低，由入罐麦汁时的350～407.6 mg/L降到成品酒时的180.1～243.1 mg/L；蛋白酶A活力在回收酵母前增加，后达到最高值，其范围是18.27～30.13 U/mL，回收酵母后蛋白酶A活力下降，最终在成品酒中的蛋白酶A活力检测值为发酵过程中最高值的19.06%～36.4%。通过对成品纯生啤酒中高分子蛋白含量、蛋白酶A活力的跟踪，分析各自对泡持性的作用发现，高分子蛋白含量与泡持性（r=0.794，P＜0.01）显著正相关；蛋白酶A活力与泡持性及高分子蛋白含量之间没有显著相关性。

In this study, the key factors influencing the foam stability of pure draft beer were investigated. The content of high-molecular protein and the activity of proteinase A were detected by Coomassie brilliant blue method and fluorescence-based assay in both beer brewing and beer storage process, respectively. The results showed that, different fermenting parameters in each fermenting vessels resulted in significant difference in the change of high-molecular protein content and proteinase A activity. During the fermenting stage, high-molecular protein content decreased slowly from 350~407.6 mg/L in wort to 180.1~243.1 mg/L in product beer, and proteinase A activity strengthened slowly prior to yeast harvest-ing and reached the highest levels of 18.27~30.13 U/mL, after yeast harvesting, proteinase A activity reduced and finally its activity in product beer was only 19.06%~36.4%of the previous highest value. Through the tracing of high-molecular protein content and proteinase A activity in product pure draft beer and the analysis of their effects on beer foam stability, it was found that there was significant positive relations between high-molecular protein content and foam stability （r=0.794, P＆lt;0.01）, however, there was no significant relations between proteinase A activity and foam stability/high-molecular protein content.