Cheesemaking: why only some milk coagulates with rennet

Cheese production relies on the coagulation of milk proteins into a gel matrix after the addition of rennet. Milk that does not coagulate (NC) under optimal conditions affects the manufacturing process, requiring a longer processing time and lowering the cheese yield — which, in turn, has an economic impact.

In an article appearing in the Journal of Dairy Science, scientists from Lund University studied the protein composition of milk samples with different coagulation properties to learn more about why only some milk coagulates with rennet.

The authors of the study analysed protein composition in NC and coagulating milk samples from 616 Swedish Red cows. They reported that the relative concentrations, genetic variants and post-translational modifications of the proteins all contribute to whether rennet could induce coagulation in each sample. The NC milk had higher relative concentrations of α-lactalbumin and ß-casein and lower relative concentrations of ß-lactoglobulin and κ-casein when compared with coagulating milk.

“The non-coagulating characteristics of milk relate to protein composition and genetic variants of the milk proteins,” said first author Kajsa Nilsson, PhD. “Roughly 18% of Swedish Red cows produce noncoagulating milk, which is a high prevalence. Cheese-producing dairies would benefit from eliminating the NC milk from their processes, and breeding could reduce or remove this milk trait.”

These results can be used to further understand the mechanisms behind NC milk, develop breeding strategies to reduce this milk trait, and limit use of NC milk for cheese processing.

Image credit: ©stock.adobe.com/au/Milen