Inhibitory activity against plasmin, trypsin, and elastase in rennet whey and in cheese fortified with whey protein

The inhibitory activity against trypsin, elastase, and plasmin was determined in samples of Danbo 45+ that were manufactured from milk pasteurized at 72, 80, and 90 degrees C for 15, 30, and 60 s; the corresponding rennet wheys; and Havarti 45+ manufactured from milk concentrated 1.8-fold, 2.7-fold, and 4.6-fold by ultrafiltration. A sensitive colorimetric assay demonstrated that the incorporation of thermally denatured whey proteins into the cheese curd by pasteurization resulted in a decreased proteinase inhibitory activity against trypsin and elastase in Danbo 45+ and against trypsin, elastase, and plasmin in the corresponding rennet wheys. However, incorporation of native whey proteins into Havarti 45+ by ultrafiltration of the cheese milk resulted in an increased inhibitory activity against trypsin and elastase in the cheeses. Cheese manufactured from milk concentrated 1.8-fold, 2.7-fold, or 4.6-fold displayed trypsin inhibitory activity that was 1.8, 2.9, and 5.1 times, respectively, that of the reference cheese. Similarly, the elastase inhibitory activity in the cheeses increased 2.2, 3.2, and 7.8 times. The increased inhibitory activity in cheese fortified with native whey protein likely contributes to the decreased proteolysis and altered ripening characteristics of the resulting cheeses, and, further, the method can be adapted to detection of other inhibitors if sufficiently sensitive substrates are available.