Understanding the Impact of Colloidal Calcium Phosphate on the pH Variation in Cheddar Cheese During Early Stages of Aging

The Cheddar cheese industry has recently observed variation in the pH of their cheese during the early stage of storage. This variation may be due to the addition of the faster acid producing thermophilic starter culture Streptococcus thermophilus which was recently introduced into the Cheddar cheese making process. This starter culture may impact the calcium buffering properties of the cheese due to more retention of the insoluble calcium (INSOL Ca) within the cheese. To investigate this problem, we studied how insoluble calcium affects cheeses with pH ranging from 4.8 to 6.6 and found that INSOL Ca was positively correlated with the protein content and pH of the cheese. After gaining an understanding of the interactions between pH, INSOL Ca, and protein, a modified acid-base titration method, which involved standardization of the samples based on protein content was tested on curd samples taken through cheese production with varying sample preservation methods (fresh, refrigerated, air-blast frozen, and frozen with liquid nitrogen). The protein acid-based titration method produced reliable results. There was no statistical difference in the amount of INSOL Ca between the fresh, air-blast frozen, and samples frozen with liquid nitrogen. Liquid nitrogen frozen samples were used to test cheese made with different amounts of thermophilic and mesophilic culture blends. The pH and INSOL Ca were tracked over a 6-week period. The cheese made with more thermophilic starter culture had a higher pH and amount of INSOL Ca making the addition of the S. thermophilus a possible cause for the increase pH seen in the Cheddar cheese industry.