Abstract: Lentinus edodes β-glucan (LEBG) was extracted from the fruiting bodies of Lentinus edodes. The average molecular weight of LEBG was measured to be 1.868 × 106 Da. Monosaccharide composition analysis showed that LEBG was composed of arabinose, xylose, mannose, glucose and galactose with a molar ratio of 0.72:1.61:2.61:92.75:2.34. Infrared (IR) spectroscopy showed that LEBG was a polysaccharide containing pyranose ring. Addition of LEBG to wheat starch and corn starch increased both their loss modulus and storage modulus. Dynamic rheological measurements revealed the interaction between LEBG and starch. During in vitro digestion, the rates of enzymatic hydrolysis of wheat starch and corn starch supplemented with LEBG were significantly lower than those without LEBG. This difference may be due to the fact that LEBG and starch are intertwined, enhancing the structure of the gel network. At the same time, both starches with LEBG showed lower levels of rapidly digestible starch and predicted glycemic index and higher levels of slowly digestible starch and resistant starch, indicating that LEBG has an inhibitory effect on the in vitro digestion of starch. In the visualization experiment, we further confirmed that starch was wrapped by LEBG. Ultrafine Lentinus edodes powder could also inhibit in vitro starch digestion due to its β-glucan. This study has indicated that LEBG shows promise for developing low-glycemic-index starchy foods.

Key words: Lentinus edodes β-glucan, rheological properties, starch, in vitro digestibility, predicted glycemic index