Effect of polymerization with transglutaminase on in vitro digestion and antigenicity of β-lactoglobulin

The in vitro digestibility of β-Lactoglobulin (β-Lg) denatured by heat or chemical (0.1 or 0.25 mol L−1 Cys) treatments, polymerized or not by transglutaminase (10 or 25 U g−1 protein), and the antigenicity of the products before and after in vitro digestion, was investigated. The polymerization was more efficient in the presence of Cys than after heat treatment. The addition of Cys, associated or not with polymerization, increased digestibility by more than 20% as compared to untreated β-Lg. The pepsin digest of the polymerized β-Lg showed lower reactivity towards IgE than the untreated or denatured β-Lg. After digestion by pepsin and pancreatin, untreated and heat treated β-Lg still showed antigenic activity, whereas the products released from β-Lg denatured by Cys and from the polymerized samples showed no reactivity towards IgE. The polymerization of chemically denatured β-Lg facilitated the action of the gastrointestinal enzymes, and their digestion products presented low antigenic properties.