关键词: 凝乳酶, 马苏里拉干酪, 理化性质, 风味

Abstract: 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.

Key words: rennet, Mozzarella cheese, physicochemical properties, flavor