Polysaccharides reduce in vitro IgG/IgE-binding of β-lactoglobulin after hydrolysis

We investigate the influence of charged polysaccharides such as gum arabic and low methylated pectin (LMP), and of un-charged polysaccharides such as xylan, on the in vitro digestibility of β-lactoglobulin (β-lg) and on the in vitro IgG- and IgE-binding of its digestion products. β-Ig was hydrolyzed by pepsin, and then by a trypsin/chymotrypsin mixture, in dialysis bags. SDS–PAGE electrophoresis was used to determine protein hydrolysis and immunoblotting in the presence of cow’s milk, and rabbit or human antibodies were used to assess the in vitro IgG- and IgE-binding of the digestion products. The results showed that polysaccharides influenced protein digestibility. The IgG- and IgE-bound hydrolysis products were dependent on the enzymatic hydrolysis and on the presence of polysaccharides. In all cases, IgG-binding was lower in the presence of any of the polysaccharides, and IgE-binding was non-existent or considerably reduced with LMP and xylan. In this study, LMP and xylan were the polysaccharides that most effectively reduced the immuno-reactivity of the hydrolysis products. The eventual reduction of in vivo allergenicity of milk-based food products has to be confirmed.