Allergenicity of peanut protein isolate after in vitro gastric and pancreatic hydrolysis assessed in the presence of plant polysaccharides

Abstract

Rationale This study presents the influence of gum arabic, low methylated pectin (LMP) and xylan on the in vitro hydrolysis of peanut protein isolate (PPI) and on the allergenicity of the digestion products. Methods PPI was hydrolyzed during a two-step in vitro hydrolysis by pepsin, trypsin and chymotrypsin (T/C) mixture. Hydrolysis by T/C mixture was done in dialysis bags with MW cut-offs (MWCO) 1,000 or 8,000 Da. Evaluation of PPI digestibility was performed by SDS-PAGE electrophoresis and immunoblotting was assessed on the peptic and T/C digestion products in and out of the dialysis bags. Results PPI was not digested by pepsin. Hydrolysis by all digestive enzymes showed retention of some proteins in dialysis bags in presence of gum arabic and xylan, while LMP increased PPI digestion. The immunoblots revealed a difference on the IgE/IgG binding of undigested PPI. After peptic digestion, the IgE did not recognize proteins with MW 17 and 15 kDa, contrary to the IgG. The by-products released through the dialysis bags during T/C hydrolysis were not immuno-reactive, while the retentates were recognized by IgG and IgE, particularly peptides with MW <20 kDa. The IgE-binding with peptides of retentate containing xylan from the dialysis bag with a MWCO 1,000 Da was not as great. Conclusions Reduction of PPI hydrolysis was probably due to non-specific interactions between polysaccharides and proteins. According to these results, it seems that linkages between polysaccharides and proteins or peptides did not mask IgG epitopes. Inversely, IgE-binding epitopes were reduced by digestion and by the presence of xylan.