How food protein structure can modulate the protein digestion behaviour: Evaluation by nutritional peptidomics

This study aimed to investigate the impact of protein aggregate structure on the nutritional valueof proteins, and especially on the extent of digestion, the nature and amount of peptides released.Ovalbumin was chosen as a model protein source. A range of four typical aggregate structures,from linear to spherical-agglomerated, were obtained after heating under different combinationsof pH and ionic strength. The non-aggregated and aggregated ovalbumins were digested usingan in vitro digestion model that simulated gastrointestinal digestion. The extent of digestion wasdetermined based on the disappearance of intact ovalbumin and the appearance of solublepeptides. The peptide profile of the digests was analyzed using LC-MS/MS.The extent of hydrolysis differed according to the aggregate structure with linear aggregatesbeing more extensively hydrolyzed than the spherical aggregates. The results suggest that thesurface area to volume ratio, and probably the degree of unfolding of its constituent proteinbefore ingestion are the major influencing criteria. Ovalbumin aggregation appeared to render anumber of peptide bonds accessible to digestive proteases, whereas these bonds were notaccessible in the native ovalbumin; moreover, cleavage sites appeared to be specific dependingon the structure of aggregates (fig.1). Nutritional peptidomics analysis by multivariate statisticalapproaches made it possible to connect the aggregate structure and the profile of generatedpeptides. For instance, it was possible to demonstrate that bioactive peptides were significantlypromoted after digestion of spherical and spherical-agglomerated aggregates.This work highlights the existing links between food structures resulting from technologicalprocesses and their breakdown during the digestive process. Such results imply that a fine tuningof unfolding and aggregation conditions can be used for targeted structuring that can lead to animprovement of the nutritional quality of food proteins