解淀粉芽孢杆菌GSBa-1凝乳酶在马苏里拉干酪中的应用

Application of Rennet from Bacillus amyloliquefaciens GSBa-1 in Mozzarella Cheese

对分离自酒曲的1株解淀粉芽孢杆菌GSBa-1发酵所产凝乳酶进行研究,该酶凝乳活力高而蛋白水解活力低,纯酶凝乳活力可达1.46×106 SU/g;使用该凝乳酶和商品凝乳酶制作马苏里拉干酪,并对干酪理化成分、成熟过程中pH值和微生物指标及干酪成熟前后质构特性、游离脂肪酸、可溶性蛋白、风味和干酪性能等指标进行对比分析。结果显示,理化成分上菌株凝乳酶与商品凝乳酶制作的干酪相接近(P<0.05)。干酪在成熟过程中,发酵剂存活数先增加后减少,但其差异不大;菌株凝乳酶制作的干酪pH 4.6可溶性蛋白含量较多,干酪的游离氨基酸总量(76 mg/100 g)也高于商品凝乳酶制作的干酪游离氨基酸总量(55.3 mg/100 g);菌株凝乳酶制作的干酪质构特性优于商品凝乳酶制作的干酪;电镜结果显示,菌株凝乳酶制作的干酪内部网状结构更充实;菌株凝乳酶具有稍强的蛋白水解活力,导致其制作的干酪风味物质种类多于商品凝乳酶制作的干酪,风味物质更加丰富。干酪样品的保形性和拉丝性实验测定结果显示,2种凝乳酶制作的干酪性能差异不大(P>0.05);对2种凝乳酶制作的干酪进行感官评定,其总评分相接近。以上结果表明,解淀粉芽孢杆菌GSBa-1凝乳酶在一定程度上可代替小牛凝乳酶应用于马苏里拉干酪的生产。

The rennet produced by Bacillus amyloliquefaciens GSBa-1, isolated from Jiuqu, a traditional Chinese liquor fermentation starter, was found to possess high milk-clotting activity(up to 1.46 × 106 SU/g) and low proteolytic activity.Mozzarella cheeses were prepared using the purified enzyme, and a commercial rennet was used as a control. During cheese ripening, the physicochemical properties, pH, microbial parameters, texture properties, free fatty acid composition, soluble protein content, flavor properties and other properties were studied. Results showed no significant difference(P < 0.05) in chemical composition was seen between the two cheeses. During cheese ripening, the viable count of Lactococcus lactis increased first and then decreased;however, the difference was not significant. The pH 4.6 soluble protein content and total free amino acid content(76 versus 55.3 mg/100 g) of cheese made with the microbial rennet were higher than those of the control cheese. The cheese prepared using the microbial rennet also had better textural properties than the control.Morphological observation of cheese using scanning electron microscopy showed that the internal network structure of the cheese prepared using the microbial rennet was more compact. Moreover, it contained more volatile flavor compounds due to the relatively strong proteolytic activity of the rennet. There were no significant differences in conformality,stringiness or sensory evaluation between the two cheeses(P > 0.05). All these results showed that the rennet produced by B. amyloliquefaciens GSBa-1 is a promising alternative to calf rennet in processing of Mozzarella cheese.