Abstract: In this paper we compared the digestibility in vitro of highland barley and wheat flour and investigated the effects of β-glucan concentration and molecular mass from highland barley on its starch digestibility in vitro. Furthermore, a possible mechanism for the low glycemic index of highland barley β-glucan was proposed based on its rheological properties and interaction with α-amylase. The results showed that the in vitro starch digestibility of highland barley was significantly lower than that of wheat flour. The viscoelasticity of β-glucan solution increased with the increase in its concentration and molecular mass, its inhibitory effect on α-amylase activity became stronger, and it became more effective in delaying starch digestion. These results indicated that the high viscosity of highland barley β-glucan solution could be regarded as a potential mechanism for the low starch digestibility of highland barley.

Key words: highland barley, β-glucan, starch, digestibility