Immunoreactivity and digestibility of high-pressure-treated whey proteins

The effect of high-pressure (HP) treatments on the IgG- and immunoglobulin E (IgE)-binding properties and digestibility of whey proteins was investigated. The formation of protein aggregates was important in whey protein isolate (WPI) and β-lactoglobulin (β-Lg) treated at 200 and 400 MPa at pH 6.8, but was not detected at pH 2.5. Treatment of β-Lg and WPI at 200 and 400 MPa increased binding to β-Lg-specific rabbit IgG and did not affect binding to IgE from allergic patients, but there was no apparent relationship between these responses and the degree of protein aggregation. HP treatment at 400 MPa promoted the hydrolysis of β-Lg by pepsin, but this increased susceptibility of β-Lg to proteolysis was progressively lost during the refrigerated storage of the HP-treated WPI. The higher digestibility of the HP-treated WPI with pepsin did not have an impact on the IgE-binding of the proteolysis products, as compared to non-HP-treated WPI, probably because of the release, in both cases, of specific IgE-binding peptides. Some of these immunoreactive fragments remained after hydrolysis with Corolase PP and probably accounted for a low, but detectable, IgE-binding response.