Influence of different processing methods on anti-trypsin activity in bovine colostrum

Colostrum is important for supplying the bovine neonate with nutrients, bioactive substances, and immunoglobulins to acquire passive immunity. Trypsin inhibitory activity represents a general characteristic of the first bovine colostrum. It is assumed that the anti-trypsin activity serves to protect bioactive molecules in the colostrum from being digested by the calf. The objectives of the study were to establish a test to determine anti-trypsin activity and test the hypothesis that freezing, acidification, and heat treatment alter anti-trypsin activity compared with untreated bovine colostrum. A photometric assay was established to determine anti-trypsin activity. The activity was expressed in milligrams of inhibited trypsin per milliliter of colostrum. Anti-trypsin activity was measured in untreated colostrum, frozen colostrum (-20°C for 24 h), colostrum acidified using 10% formic acid in a way that it was present as 1% in the sample, and colostrum heat treated according to 2 different protocols (60°C for 60 min and 63.5°C for 30 min). In our study, trypsin inhibition in 40 untreated colostrum samples (0.80 mg/mL, SEM 0.03) corresponded to that observed in frozen colostrum samples (0.79 mg/mL, SEM 0.03). In these first analyzed 40 and 59 extra samples (in total 99 samples), the anti-trypsin activity of frozen colostrum (0.85 mg/mL, SEM 0.01) was compared with colostrum subjected to acidification (0.84 mg/mL, SEM 0.01), heat treatment at 60°C for 60 min (0.65 mg/mL, SEM 0.02), and heat treatment at 63.5°C for 30 min (0.61 mg/mL, SEM 0.02). Acidification did not significantly affect trypsin inhibition. Both heat treatment protocols significantly reduced anti-trypsin activity. In the future, when investigating the effects of postharvest storage and processing on bovine colostrum, the influence on anti-trypsin activity should be evaluated in addition to the effects on immunoglobulins and other components.