Structural Characteristics, Rheological Properties, and Antioxidant Activity of Novel Polysaccharides from “Deer Tripe Mushroom”

Abstract

The polysaccharide was extracted by water extraction and alcohol precipitation method from “deer tripe mushroom,” which was domesticated and bred from wild Auricularia delicata in Zambia. The structure of the deer tripe mushroom polysaccharide (DTMP) was characterized by gas chromatography-mass spectrometry (GC-MS), Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR), scanning electron microscope (SEM), and other analytical techniques. And the rheological and gel properties and antioxidant capacities of the polysaccharide were studied. The results showed that DTMP was mainly composed of mannose, fructose, glucose, and galacturonic acid, of which the galacturonic acid was the main component. By calculation, the molar ratio of mannose : fructose : glucose : galactoacid in DTMP is 0.8 : 14.8 : 1.0 : 26.32. The polysaccharide was mainly composed by α-1,4-glycosidic bond. DTMP solution showed a shear-thinning (pseudoplastic) behaviour, and its pseudoplasticity was more obvious at a concentration of 2%. The power law model was used to evaluate the viscosity curves of DTMP, and its viscosity and consistency indices both increased as the concentration increased, whereas both indices decreased as the concentration decreased. The viscosity of the polysaccharide solution changed as the pH changed: the polysaccharide solutions had a higher viscosity at pH = 10. DTMP showed gel-like behaviour (G′ ＞ G″), and the gel strength enhanced with the increase of concentration (2%–10%). In addition, the antioxidant experiment of DTMP showed that it had good antioxidant activity, and there was a significant dose-effect relationship between its activity and concentration in the low concentration range.