Antioxidant activity during in vitro gastrointestinal digestion and the mode of action with tannins of cowhide-derived collagen hydrolysates: The effects of molecular weight

In this study, collagen hydrolysates were prepared by autoclaving or its combination with enzymolysis. After it, the digestion pattern and antioxidant activity were estimated in vitro gastrointestinal digestion. Three MW (HMW-CH, 10-100 kDa; MMW-CH, 1-10 kDa; LMW-CH, <1 kDa) of collagen hydrolysates were obtained. After digestion, MW of these samples decreased to some extent, while their total MW composition still show a similar tendency to the undigested samples, i. e. HMW-CH > MMW-CH > LMW-CH. From gastric to intestinal phase, DPPH radical scavenging of HMW-CH increased from 5.45% to 35.19%. However, MMW-CH and LMW-CH increased from 47.35% to 52.90% and 49.84%-64.40% in the gastric phase, and then decreased to 27.94% and 21.69% in the intestinal phase, respectively. Meantime, the reducing power of these samples was lower in the gastric phase, but increased within 15 min of intestinal phase. After, the differences decreased and the final was LMW-CH (1.030) > MMW-CH (0.914) > HMW-CH (0.872). These results indicate that the lower the MW, the higher the antioxidant activity. In addition, the binding mode of them to tannins was analyzed by thermodynamic parameters. The results suggest that the main mode of interaction between HMW-CH and MMW-CH and tannins was hydrogen bonding, whereas LMW-CH and tannin was hydrophobic. Overall, these results are helpful for us to better understand absorption process of collagen hydrolysates and provide some theoretical and technological support for collagen consumed in food and medicine.