Protein breakdown and release of antioxidant peptides during simulated gastrointestinal digestion and the absorption by everted intestinal sac of rapeseed proteins

- Simulated digestion was employed to research rapeseed soluble proteins (RSPs).
- Protein breakdown and peptides release occured during simulated digestion.
- Hydrolysis degree and antioxidant activities of RSPs increased with digestion time.
- Fraction with MW below 307 Da in RSPs was easily absorbed by isolated everted sac.

The main objective of the study was to evaluate the bioaccessibility of rapeseed soluble proteins (RSPs) by simulated gastrointestinal digestion and isolated intestine methods. In the gastric phase, the degree of hydrolysis (DH) of RSPs increased from 2.6% to 8.2%, while the surface hydrophobicity (H0) decreased from 62.8% to 59.1%. Further digestion in the intestinal phase brought DH and H0 to 18.2% and 50.5%, respectively. Scavenging DPPH and hydroxyl radical abilities and reducing power of RSPs increased slightly after digestion by pepsin, however, a distinct increment was achieved after subsequent digestion by trypsin. Molecular weight distributions indicated that RSPs above 3000 Da decreased significantly from 87.0% to 24.1% after digestion, revealing these fractions were more easily digested by gastrointestinal proteases than those below 3000 Da. The absorption of RSPs by intestine reached the maximum (28.6%) at the concentration of 5 mg/mL after incubation for 60 min. For the fraction below 307 Da, the absorption efficiency increased with incubation from 20 to 60 min.