Effect of heat treatment on lupin reactivity against rabbit polyclonal antibodies after in vitro gastrointestinal digestion

Abstract

Despite the growing interest in lupin as a source of protein, due to its potential to decrease the environmental footprint of food supply, its allergenic properties have not been fully explored. This study focused on lupin's potential to induce allergic reactions in food‐sensitized individuals. The antigenic properties of lupin proteins were investigated after exposing lupin protein isolate as well as lupin flours to an in vitro digestion. The effect of thermal treatment, on the digestibility and immunoreactivity of the proteins was also investigated. Protein breakdown was analyzed by SDS‐PAGE, but also by evaluating the distribution of peptide sizes and the extent of hydrolysis via quantifying the free N‐terminal amino acid content. Immunogenicity was assessed by Western blot analysis using a commercial antibody. The individual or combined effects of the food matrix and processing were noted after gastric digestion of the lupin flours, as some of the protein fractions showed resistance toward pepsin activity and caused responses to the commercial antibodies, particularly the fractions likely associated with α‐conglutin (20 kDa) and γ‐conglutin (17 kDa). Gastric digestion of lupin flours also revealed the possibility of formation of neo‐allergens, which warrants future identification. However, after the intestinal phase, lupin proteins underwent complete hydrolysis, with no observed responses toward the specific antibody used. Nevertheless, these findings underscore the need for further research employing sera from allergic patients to lupin in order to avoid potential false‐negative results.