How food protein structure can modulate the protein digestion behaviour: Evaluation by nutritional peptidomics
Résumé
This study aimed to investigate the impact of protein aggregate structure on the nutritional value
of 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 combinations
of pH and ionic strength. The non-aggregated and aggregated ovalbumins were digested using
an in vitro digestion model that simulated gastrointestinal digestion. The extent of digestion was
determined based on the disappearance of intact ovalbumin and the appearance of soluble
peptides. The peptide profile of the digests was analyzed using LC-MS/MS.
The extent of hydrolysis differed according to the aggregate structure with linear aggregates
being more extensively hydrolyzed than the spherical aggregates. The results suggest that the
surface area to volume ratio, and probably the degree of unfolding of its constituent protein
before ingestion are the major influencing criteria. Ovalbumin aggregation appeared to render a
number of peptide bonds accessible to digestive proteases, whereas these bonds were not
accessible in the native ovalbumin; moreover, cleavage sites appeared to be specific depending
on the structure of aggregates (fig.1). Nutritional peptidomics analysis by multivariate statistical
approaches made it possible to connect the aggregate structure and the profile of generated
peptides. For instance, it was possible to demonstrate that bioactive peptides were significantly
promoted after digestion of spherical and spherical-agglomerated aggregates.
This work highlights the existing links between food structures resulting from technological
processes and their breakdown during the digestive process. Such results imply that a fine tuning
of unfolding and aggregation conditions can be used for targeted structuring that can lead to an
improvement of the nutritional quality of food proteins.
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