The effect of transglutaminase-induced polymerization in the presence of cysteine on β-lactoglobulin antigenicity

The effect of polymerization by the enzyme transglutaminase (TG) on the antigenicity of β-lactoglobulin (β-Lg) was investigated. Polymerization was carried out using 7% heat treated β-Lg and 5–50 U TG g−1 substrate or 7% untreated β-Lg in the presence of 0.05–0.4 mol L−1 cysteine (Cys) and 25 U TG g−1 substrate. The electrophoretic profile of polymerized samples showed bands corresponding to high molecular mass. For antigenicity evaluation, sera from BALB/c mice sensitized with native β-Lg, β-Lg polymerized by 25 U TG g−1 (β-Lg HT TG) or polymerized in 0.25 mol L−1 Cys (β-Lg Cys TG) were used. Animals sensitized with β-Lg Cys TG showed lower levels of IgG1 and IgE than those immunized with native β-Lg or β-Lg HT TG. These results suggested that polymerization in the presence of Cys modified or hid epitopes, reducing the potential antigenicity of β-Lg, whereas heat treatment followed by polymerization did not lead to a reduction in antigenicity.