Effects of highland barley protein and β-glucan addition on the flour structure, bread quality and starch digestibility of whole wheat bread

Whole wheat bread is rich in nutrition, but its starch digestibility is unsatisfactory. Thus, how to reduce its digestibility has attracted much attention. This study investigated the effects of highland barley protein and beta-glucan on the pasting properties, and thermal properties of whole wheat flour to reveal the mechanism of highland barley protein and beta-glucan regulating the in vitro digestibility. The digestibility results showed that beta-glucan and protein could slow down starch digestion to some degree. The cross-section structure determination results indicated that beta-glucan and protein decreased the porosity. The differential scanning calorimetry and thermogravimetric analysis results showed that beta-glucan and protein increased the onset of pasting, decreased the peak temperature and enthalpy of pasting and decreased the thermal stability. The Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy results revealed a blue-shift in the -OH position of the bread added with protein and beta-glucan (from 995.59 to 996.07 cm(-1)), indicating that the hydrogen bonding might form intramolecularly. In this study, the addition of highland barley protein and beta-glucan was proved to be helpful in decreasing the in vitro digestibility and showed modification in the texture quality of bread, which might be suitable for diabetic patients.