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The aim was to discover the effect of high gravity brewing on yeast protease activity during fermentation, on the loss of hydrophobic polypeptides from wort during fermentation, and on the foam stability of stored beer. The hydrophobic polypeptide content of low (10° Plato) gravity worts showed a steady decline throughout fermentation, but for the 20° Plato wort there was a rapid decline over the first 8 days of fermentation, followed by little change over the remaining period. The decrease in hydrophobic polypeptides was greater in the high gravity fermentation. Proteinase A increased during fermentations with the highest levels being present at the end of fermentations. High gravity fermentations exhibited levels of yeast protease that from the 3rd to 11th day of fermentation were at least twice the values of the low gravity fermentations. The high gravity brewed beer contained significantly higher levels of proteinase A activity than the low gravity brewed beer. The inclusion of FERMCAP™, an antifoam, in high gravity wort did not affect either the hydrophobic polypeptide levels or foam stability of the resultant beer. This suggests that proteinase A, rather than fermenter foaming, must be the major contributor to the lack of foam stability of high gravity brewed beer. Head retention measurements conducted on the high and low gravity brewed bottled beers, over a five month period, demonstrated a steady decline in foam stability for both beers. The declines in head retention did not occur in high and low gravity beers that had been pasteurised. 相似文献
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用As1.398中性蛋白酶水解大豆分离蛋白,采用四因素三水平中心组合设计优化大豆分离蛋白酶水解条件,应用SAS分析软件对实验数据进行处理。得以最佳酶水解条件为:温度40.2℃,pH7.2,酶与底物浓度比0.87%(W/W)。底物浓度8.86%(W/W),水解时间3 h;在此条件下水解度预测值为11.28%,实际测定水解度值为11.24%。 相似文献
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本文报道了从花生地土壤分离到一株分泌中性蛋白酶的枯草芽孢杆菌,经纯铜蒸汽激光诱变,选育到一株高产菌株HD401,产酶提高幅度高达72.7%。诱变过程说明,菌体存活率和正变率以及激光波长、孢子体生理状态有一定的相关性。B.S.HD401经多次传代,产酶性状稳定,通过正交试验对培养基进行优化,在2升罐中酶活达8520u/ml。 相似文献
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ABSTRACT: Virgibacillus sp. SK37 exhibited high extracellular proteolytic activity in skim milk broth containing 10% NaCl. Optimum conditions of the crude proteinase were at pH 8.0 and 65 °C. The proteinase was strongly inhibited by phenylmethanesulfonyl fluoride (PMSF) and preferably hydrolyzed Suc-Ala-Ala-Pro-Phe-AMC, suggesting the serine proteinase with a subtilisin-like characteristic. Proteolytic activity increased with NaCl concentration up to 20%. Ca2+ activated the enzyme activity but reduced enzyme stability at 65 °C. Several proteinases with dominant molecular mass (MW) of 81, 67, 63, 50, 38, and 18 kDa were detected on native-polyacrylamide gel electrophoresis (native-PAGE) activity staining in the absence and presence of 25% NaCl. These results demonstrated that Virgibacillus sp. SK37 produced salt-activated extracellular proteinases. Virgibacillus sp. SK37 could be a promising strain for starter culture development used in fish sauce fermentation. 相似文献
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蛋白酶对大豆分离蛋白的降解模式研究 总被引:1,自引:0,他引:1
采用十二烷基酸钠聚丙烯酰胺凝胶电泳(SDS-PAGE)方法,分析了几种商品蛋白酶(包括枯草杆菌蛋白酶、胰蛋白酶、胰凝乳蛋白酶、木瓜蛋白酶和细菌碱性蛋白酶)对大豆分离蛋白(SPI)的降解模式。结果表明,大豆球蛋白酸性亚基的Ax多肽链最容易被水解,所有的酶对其均有作用,而碱性亚基和大豆伴球蛋白的B亚基最难被水解。木瓜蛋白酶对大豆分离蛋白的水解最迅速、彻底,由于大豆蛋白中含有胰蛋白酶抑制因子,胰蛋白酶和胰凝乳蛋白酶对大豆蛋白水解能力较差。 相似文献
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