Nitrogenous fractions during the manufacture of whey protein concentrates from Feta cheese whey

摘要

Samples taken from different manufacturing stages of Feta cheese whey protein concentrates (WPCs), with 65 and 35% total protein content, were analyzed by chemical methods and by reversed-phase HPLC and by size-exclusion chromatography. Mean total protein content of Feta cheese whey was 1.37%. 22% of total nitrogen (TN) was non-protein N (NPN) and 12% was pro-teose-peptone N (PPN). The mean native N (NN), NPN and PPN percentages of WPC 65 and 35%, were 63 and 71%, 10 and 14%, 0.08 and 0.08%, respectively. According to reversed-phase HPLC data, the percentages of β-Lg and α-La and their ratio were high; 56.5 and 59% of native proteins of whey and of WPC powders, respectively, were β-Lg. The respective α-La percentages were 13.1 and 14.1% and the respective caseino-macropeptide (CMP) percentages were 12.9 and 15.3%. Apart from ultrafiltration, the most critical stage for nitrogenous fraction composition was the evaporation process before spray drying.