Evolution of proteolysis during the ripening of traditional Feta cheese

Four cheesemaking trials were conducted in three different traditional Feta cheese plants. The characteristics of the cheesemaking process had to do with: the heat treatment of the cheese milk, the use of yoghourt as a starter, the use of traditional rennet from kids and lambs abomasa, and the packaging in wooden barrels without brine addition. At 60 d (minimum ripening period according to Greek Codex Alimentarius), the percentage of water soluble nitrogen (WSN) varied from 15.88% to 19.58% of total nitrogen (TN) and 73.4%-79.9% of the WSN was nitrogen soluble in 12% TCA. At the same age, 13.3-23.6% of WSN was nitrogen soluble in 5% PTA. The quantitative and qualitative changes of the middle area of the RP-HPLC profiles (A(220)) indicated the evolution of nitrogenous fractions during the ripening and the effect of each cheese plant technology on them. Most of the qualitative and quantitative changes occured during the pre-ripening period (18 d). In general, the rate of proteolysis was similar to that of the industrially made Feta. However, the percentages of low-molecular weight fractions were higher.