Physicochemical Properties and Consumer Acceptance of Yak Mozzarella Cheese Produced by Culture Acidification and Direct Acidification

The rate of acidification (pH = 6.1) at an appropriate degree is responsible for supplying suitable aroma components and functional properties to cheese. This study aimed to evaluate variations in physicochemical, functional properties, and consumer acceptance in yak mozzarella cheese produced using different starter cultures or lactic acid during ripening. The results showed that consumers preferred ripened yak M cheese, made with mesophilic multi-strain starter, which received the highest scores for aroma (6.8) and flavor (5.9). The average levels of most major volatile organic compounds were relatively higher in ripened M cheese. Furthermore, the degree of proteolysis increased continuously during the 42 d ripening period. The contents of pH 4.6-soluble nitrogen and 12% trichloroacetic acid-soluble nitrogen in cheeses produced with starter cultures reached 11% and 8%, significantly higher than those of directly acidified L cheese. Specifically, greater protein degradation corresponded to lower hardness and stretchability, hardness of T and M cheeses decreased from 226.67 ± 2.23 g and 232.87 ± 3.66 g to 202.36 ± 2.63 g and 197.09 ± 2.33 g, respectively, while their stretchability declined from 52.1 ± 1.6 cm and 49.3 ± 1.7 cm to 34.5 ± 1.2 cm and 37.6 ± 2.4 cm. However, yield and moisture content of T and M cheeses were significantly lower than those of L cheese. Overall, this study provides valuable insights for optimizing the production and quality of yak mozzarella cheese.