Hyperimmunised bovine milk and whey: influence of pH and enzymatic treatments on the antigen-binding capacity of immunoglobulin G.

Background: Hyperimmunised bovine milk and whey (whole and defatted) were submitted at 37°C to different pH values (between 1 and 10) and enzymes (pepsin, trypsin and chymotrypsin) at their optimum pH and the IgG immunoactivity against Campylobacter jejuni was measured by means of ELISA assays.

Results: The kinetic antigen-binding capacity (ABC) losses follow a hyperbolic-type equation. The ABC of IgG is strongly reduced at low pH (1 and 2) and the effect is lower at alkaline pH (8 and 10). The presence of pepsin (at their optimum pH of 2) almost completely reduced the IgG ABC after 2 h of treatment. The ABCs are higher in whole products (milk and whey). The influence of trypsin and quimotrypsin on the ABCs is moderate (ABC losses lower that 25%).

Conclusions: The ABC of IgG obtained from hyperimmunised bovine defatted milk and whey is largely reduced in conditions similar to those found in the human digestive tract. Only whole milk can maintain around 40% of their initial ABC. IgG encapsulation or other methods to protect the immunoglobulin activities could be an alternative to use these type of products in final foods formulae.