Abstract: 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.

Key words: milk clotting enzyme, Mozzarella cheese, proteolysis, texture, flavor