Levels of three natural milk antimicrobial proteins during the manufacture of Cheddar cheese

Variations in cheese quality are explained by many factors. Among them, some influence the microbiota of cheeses such as native milk antimicrobial proteins. This project aimed to determine the concentration and activity of lactoferrin (LF), lactoperoxidase (LP) and lysozyme (LZ) during cheesemaking. Each antimicrobial protein was analyzed by two methods. An enzyme-linked immunosorbent assay (ELISA) technique was utilized to analyze each antimicrobial protein. In addition, LP was measured by spectrometry and LZ by fluorescence. Despite the lack of correlation between the results obtained by ELISA and the other methods, the measurement of LF, LP and LZ in raw milk and thermized milk showed no significant differences. The ELISA methods were selected to determine the retention of LF, LP and LZ in fresh cheese made from thermized milk. A total of 12 independent assays of cheddar cheese made commercially by a Canadian Dairy processor and at a pilot plant were evaluated. The concentration and activity of the three antimicrobial proteins were higher in cheese than in milk by an average factor of 3.5. These results allow a better understanding of the transition of the antimicrobial proteins present in milk when making cheese and to potentially, be able to control their concentration.