甲醇芽孢杆菌凝乳酶对马苏里拉干酪加工特性的影响

为了探究甲醇芽孢杆菌（Bacillus methanolicus）凝乳酶在马苏里拉干酪加工中的应用，分别以使用甲醇芽孢杆菌凝乳酶、混合酶制剂（含质量分数10%甲醇芽孢杆菌凝乳酶和90%商品凝乳酶）制作的马苏里拉干酪作为实验组，以商品凝乳酶干酪作为对照组，测定不同组别干酪成熟期间的蛋白水解特性、质构、风味和微观结构变化，研究甲醇芽孢杆菌凝乳酶对马苏里拉干酪加工特性的影响。结果表明，实验组干酪在成熟过程中pH值（4.6～5.3）、微生物数量（8.80～9.68（lg（CFU/g）））与对照组无显著差异（P＞0.05）；实验组干酪水分质量分数（混合酶干酪为（43.21±1.17）%、甲醇芽孢杆菌凝乳酶干酪为（46.15±0.94）%）均显著高于对照组（（41.08±1.04）%），得率（混合酶干酪为（9.27±0.17）%、甲醇芽孢杆菌凝乳酶干酪为（9.46±0.16）%）也显著高于对照组（（8.98±0.13）%）（P＜0.05）；且实验组干酪的蛋白水解特性（pH 4.6时可溶性蛋白、酪蛋白水解程度和游离氨基酸质量分数）以及风味物质种类和相对含量等指标也优于对照组干酪。但是实验组中甲醇芽孢杆菌凝乳酶干酪保形性相对欠佳，感官评定得分偏低，混合酶干酪与对照组质构及感官基本得分一致，因此甲醇芽孢杆菌凝乳酶可以作为商品酶的部分代替品应用于干酪的生产中。

Effect of Milk Clotting Enzyme from Bacillus methanolicus on the Processing Properties of Mozzarella Cheese

In order to explore the application of milk clotting enzyme (MCE) from Bacillus methanolicus in Mozzarella cheese making, single B. methanolicus MCE and an enzyme mixture of 10% B. methanolicus MCE and 90% commercial rennet were used separately in the preparation of Mozzarella cheese, while that made with commercial rennet was used as the control. The proteolytic properties, texture, flavor and microstructure of the cheeses were determined during the ripening process. Results showed that there was no significant difference in pH (4.6–5.3) or microbial count (8.80–9.68 (lg(CFU/g))) between the three groups (P > 0.05). The moisture contents and cheese yields of the experimental groups ((43.21 ± 1.17)% and ((9.27 ± 0.17)% for single B. methanolicus MCE, and (46.15 ± 0.94)% and (9.46 ± 0.16)% for the enzyme mixture, respectively) were both significantly higher than those of the control group ((41.08 ± 1.04)% moisture content and (8.98 ± 0.13)% cheese yield) (P < 0.05). Moreover, the experimental cheeses were also better than the control in terms of the proteolytic properties (the content of pH 4.6 soluble protein, the degree of casein hydrolysis and the content of free amino acids) and the types and contents of flavor substances. However, the cheese made with single B. methanolicus MCE had relatively poor shape-preserving property together with low sensory score. The cheese made with the enzyme mixture was comparable to the control in terms of texture and sensory scores, indicating that MCE from B. methanolicus could be used as a partial substitute for commercial rennet in cheese production.