Implementation of enzymatic hydrolysis to improve the digestibility of rapeseed albumins

Rapeseed proteins are known to be a promising source of plant proteins. Recent works allowed to produce a high-quality isolate of the rapeseed albumin (RA) fraction, with low antinutritional level. The study of the in vitro digestibility of this isolate was carried out. A static digestion model was implemented, adapted from the international consensus of the COST Infogest network. Digestibility was then assessed using Size-Exclusion Chromatography analyzes, based on an original published methodology and evaluated via the protein conversion rates into targeted peptide fractions. A poor in vitro digestibility of this RA isolate was nonetheless highlighted (15%), due to a gastrointestinal proteolysis resistance and particularly to acidic digestion by pepsin during gastric phase.

In this research, we were interested in improving the digestibility of RA by enzymatic hydrolysis while preserving its attractive techno-functional properties. Indeed, the implementation of this process can lead to the formation of small peptides, less effective in reducing interfacial tensions and stabilizing the emulsions and foams formed. Alcalase, Flavourzyme and Prolyve were used to obtain 12 hydrolysates with various degrees of hydrolysis (DH) and compositions.

Hydrolysis with Alcalase and Prolyve produced hydrolysates consisting of small peptides with improved digestibility. Flavourzyme was an adequate protease to produce partial hydrolysates which, interestingly, consisted of >50% intact proteins and small peptides. The best digestible and functional RA hydrolysate was ultimately selected to allow the best compromise between enzymatic cost and production time. The optimal industrial implementation conditions have been identified to produce this hydrolysate from RA isolate, which has great potential as a foaming or emulsifying ingredient in food formulations and/or to enrich a food or drink with lysine and sulfur. Thus, the enzymatic proteolysis of RA implemented rationally could be a good way to valorize rapeseed proteins from rapeseed meal in food industry.