Electrostatic interactions with anionic polysaccharides reduced the degradation of pepsin soluble undenatured type II collagen during gastric digestion under pH 2.0

Abstract

According to our previous research, the structure of pepsin-soluble undenatured type II collagen (SC II) was severely damaged after gastric digestion under pH 2.0, which might make it lose its biological activity. In the present study, the protective effects of guar gum (GG), xanthan gum (XG) and carrageenan (CG) on the gastric digestion of SC II under pH 2.0 were explored by in vitro simulated gastric digestion. Based on the results of sodium dodecyl sulfonate polyacrylamide gel electrophoresis (SDS-PAGE) and circular dichroism spectroscopy (CD), anionic polysaccharides including XG and CG improved the gastric digestive stability of SC II. After digestion, the content of SC II with intact structure in XG-SC II and CG-SC II group was 1.52–3.10 and 1.99–2.73 times of that in control group, while the protective effect of GG was limited (only 1.03–1.42 times). The results of rheology, ζ-potential, confocal laser scanning microscopy (CLSM) and CD showed that, at the ratio of 0.1:1–0.2:1, CG could improve the thermal stability of SC II to protect it from degradation, while XG could form insoluble complexes with SC II and slightly prevent the binding of pepsin; at the ratio of 0.4:1–1.5:1, both CG and XG could form extensive insoluble complexes with SC II, which might hinder the binding of pepsin, and thus inhibited the gastric digestion of SC II. Therefore, through electrostatic interaction, a small amount of CG could have a great protective effect on the gastric digestion of SC II under pH 2.0, while XG required a higher dosage.