Abstract: Commercial rennet, 70% commercial rennet + 30% milk-clotting enzyme (GSBa-1 MCE) from Bacillus?amyloliquefaciens GSBa-1 and GSBa-1 MCE were used for making Cheddar cheeses A, B and C, respectively. Changes in physicochemical parameters, proteolysis and bioactivity of cheese during 12 weeks of ripening were studied. Microrheological results?showed that GSBa-1 MCE had good milk coagulation ability similar to that of commercial rennet. Compared to cheese A, cheese C exhibited significantly lower pH, higher moisture content, and the content of Lactococcus lactis in cheese C decreased significantly from 9.77 (lg(CFU/g)) to 5.08 (lg(CFU/g)); its proteolytic activity, pH 4.6 soluble nitrogen and 12% trichloroacetic acid (TCA) soluble nitrogen content were higher. During cheese ripening, cheese C showed significantly higher calcium- and zinc-chelating ability and stronger antioxidant capacity in terms of 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation radical scavenging ability. The metal chelating ability and antioxidant capacity of cheese B were in the middle. Antidiabetic effect in terms of α-amylase and α-glucosidase inhibition showed no significant difference among the three cheeses. Therefore, GSBa-1 MCA can be use as a partial substitute for commercial rennet for making Cheddar cheese owing to its ability to control proteolysis during ripening, improve the functionality of cheese, and maintain a good quality of cheese.

Key words: Cheddar cheese; milk-clotting enzyme of GSBa-1; proteolysis; bioactivity