Influence of calcium and phosphorus, residual lactose, and salt-to-moisture ratio on Cheddar cheese characteristics

The objective of this study was to study the influence of calcium (Ca) and phosphorus (P), residual lactose, and salt-to-moisture ratio (S/M) on lactose fermentation, proteolysis, buffering properties, and changes in Cheddar cheese pH. Three replications of 8 Cheddar cheeses with two levels of Ca and P (0.67 and 0.47% vs. 0.53 and 0.39%, respectively), lactose at pressing (2.4 vs. 0.78%) and S/M (6.4 vs. 4.8%) were manufactured by modifying the cheese making parameters. The manufactured cheeses were ripened for 48 wk at 6-8°C, and were analyzed for changes in residual sugars and organic acids, proteolysis, and changes in cheese pH during ripening. Our results indicate that the largest decrease in lactose and the largest increase in organic acids in cheeses occurred between salting and day 1 of ripening. Higher concentration of organic acids was produced in low S/M treatments as compared to high S/M treatments (p < 0.05). Cheeses with low Ca and P, low lactose, and low S/M treatments exhibited higher levels of proteolysis (p < 0.05) as compared to their corresponding treatments. These differences in proteolysis were attributed to variations in protein conformation and differences in residual chymosin in the cheeses. Cheddar cheese ripening also involves changes in cheese pH, the mechanism behind which is not well-understood. A mathematical model was developed to characterize the chemical species and chemical equilibria that are responsible for the pH buffering properties of cheese. The model indicates that pH buffering in the pH range from 4.5 to 5.5 is predominantly due to colloidal Ca phosphate (CCP), and the protonation equilibrium involving the side chains of protein-bound glutamate. Correspondingly, our experiments demonstrate that while conversion of lactose to lactic acid decrease cheese pH, colloidal calcium phosphate (CCP) buffers the changes in cheese pH during ripening. We demonstrated that Fourier Transform Infrared spectroscopy (FTIR) can be used to measure organic P, bound Ca, and for prediction of the buffering capacity of cheese. In conclusion, a controlled approach to cheese manufacturing should involve control on Ca and P, residual lactose, and S/M, and their online monitoring using spectroscopic or other suitable techniques.