Age-dependent plant protein digestibility and implications for epitope generation and hormonal secretion

Age-related changes in gastrointestinal function can impair protein digestion in later life, with consequences in nutrition, metabolic and immune responsiveness. In this work, the underutilised rapeseed and corn proteins, were compared with a pea protein isolate (PPI) under simulated adult and elderly conditions using tailored INFOGEST protocols. Rapeseed protein isolate (RPI) exhibited efficient protein hydrolysis under both adult and elderly gastrointestinal conditions, but the gastric digestibility of PPI was markedly reduced in the elderly condition. Corn protein meal (CPM) showed the greatest amount of insoluble material after gastrointestinal digestion, reflecting its limited susceptibility to enzymatic breakdown. Across all substrates, digests under elderly conditions were characterized by the appearance and persistence of longer digestion-resistant fragments. A clear increase in number and diversity of peptides homologous to known plant epitopes were found under elderly gastrointestinal conditions compared with adults. Soy, hazel nut, and lentil epitopes were identified RPI and PPI digests, wheat epitopes occurred for CPM, and peanut-reactive sequences were found in all substrates. The reduced digestive capacity under elderly conditions also affected enteroendocrine signalling, with substrate-specific effects. The most pronounced age effect was observed for CPM gastrointestinal digests, where CCK secretion was reduced under elderly gastrointestinal conditions. In addition, CCK and GLP-1 secretion were also diminished in elderly gastric digests relative to adult ones. These findings highlight the influence of plant protein source on digestibility, epitope release, and hormonal responses under age-relevant gastrointestinal conditions, offering valuable guidance for ingredient selection in food design and for developing nutritional strategies for aging populations.