Differential contribution of grape peel, pulp, and seed to bioaccessibility of micronutrients and major polyphenolic compounds of red and white grapes through simulated human digestion

Abstract The composition and bioaccessibility of grape polyphenols and minerals is influenced by grape variety and matrix. Grape constituents may be determinant for the absorption of bioactives and are crucial for exploring grape by-products as functional food ingredients. In this study, the peel, pulp, and seeds of Vitis labrusca L. grapes were characterized by LC-DAD and ICP OES and changes in polyphenols, macro- and microelements were monitored using simulated human digestion. The pulp and seeds were characterized by flavanols, and the peels were high in phenolic acids. After the digestion, the highest bioaccessibility was found for quercetin (85%), while anthocyanins diglucosides were more bioaccessible in the gastric phase (153% and 113% for malvidin and cyanidin, respectively). The digestion of grape peels resulted in higher bioaccessibility of most minerals, suggesting the nutritional value of this constituent. These changes provide a step further towards applications and bioactive relevance of the grape parts.