Monitoring proteolysis and cheese juice composition during ripening of cheddar cheese made from microfiltered milk

Abstract

Cheddar cheeses were made from three types of cheese milks: HTST pasteurized milk (Past), thermized milk (TH) and MF milk, a mixture of skimmilk treated according to the Bactocatch® process and pasteurized cream. Bacterial flora development of MF and TH cheeses during ripening was similar with a high growth of species belonging to the Lb casei group and an increase of Lactococci enumeration. On the contrary, Lc counts in Past cheeses decreased by 3 log. As expected, the mesophilic spore count was much lower in MF cheeses than in the others. Proteolysis of the three categories of cheese was followed by analysis of peptidic fragments contained in cheese water extracts and in internal cheese juice obtained by pressing and by electrophoregrams of non-degraded caseins. TCA 12% soluble nitrogen contents were very similar for all cheeses except for a significant difference, at 6 months of ripening, between Past and MF cheeses. This difference was not found in the data obtained from cheese juices. On the other hand, comparison of cheese water extracts and juices showed that juices had always higher nitrogen content than extracts. β-Casein proteolysis was significantly more pronounced in MF cheeses than in the two other cheese types, maybe, because the plasmin-plasminogene system is activated by filtration treatment. All cheeses were graded in class I but slight better organoleptic qualities were found for MF cheeses (typical Cheddar cheese flavor).