In vitro protein digestibility of RuBisCO-enriched wheat dough: a comparative study with pea and gluten proteins

Growing demand for sustainable, plant-based protein sources has stimulated interest in new ingredients for food enrichment. This study investigates the nutritional and digestive implications of enriching wheat dough with RuBisCO, in comparison to pea protein-enriched and gluten-enriched doughs. The protein quality and digestibility of these enriched doughs were analysed through dough characterization, in vitro digestion experiments and biochemical analysis of digesta. Our findings indicate that an enrichment at 10% of RuBisCO or pea proteins improves the chemical score and the in vitro PDCAAS (IV-PDCAAS) score of wheat dough as compared to the control dough. Digestibility assays suggest that RuBisCO introduction modifies the protein hydrolysis kinetics: the nitrogen release is lower during gastric digestion but larger during intestinal digestion than other samples. The analysis of the protein composition of the soluble and insoluble parts of digesta, using size-exclusion chromatography, reveals that the protein network in RuBisCO-enriched dough is more resistant to gastric hydrolysis than the ones of other doughs. Indeed, non-covalently bound peptides and disulfide-bound protein aggregates partly composed of RuBisCO subunits remain insoluble at the end of the gastric phase. The digestion of these protein structures is then mostly performed during the intestinal phase. These results are also discussed in relation to the digestive enzymatic cleavage sites, the presence of potential enzyme inhibitors, the protein aggregation state and the secondary structures of the protein network in each dough type.