The Studies On Extraction And Properties Of Hulless Barley Protein

As the first grain crops of the Tibetan area of China, the hulless barley not only has a high yield, but also nutritious. The protein was extracted from hulless barley which can broaden sources of protein and solve the problem of local barley surplus, turn the resource into economic advantages. In this paper, the protein of hulless barley was extracted and purified by cellulase andα-amylase from hulless barley rice, and then the functional and structural properties of the protein were studied.Based on the single-factor and orthogonal experiments, the optimal extraction conditions of hulless barley protein were as follows: sample/water ratio of 1:5, 15EGU/g of cellulase (enzyme/sample, E/S), hydrolyzing for 4.0h at 45°C and pH 6.5. The extraction rate of hulless barley protein could amount to 69.4% under optimal conditions. And the optimal purification conditions of hulless barley protein were as follows: sample/water ratio of 1:9, 50U/g ofα-amylase (E/S), hydrolyzing for 2.0h at 60°C and pH 6.5. The purity of protein could amount to 89.5%.The results of functional properties research showed that: the solubility of the hulless barley protein was the same as wheat gluten protein, it was decrease first but then increase with the increase of pH. These two proteins had different solubility with different temperature, the hulless barley protein had the best solubility at 50°C, but the best solubility of wheat gluten was at 45°C. With the protein concentration increased, the foaming capacity and foaming stability of these two proteins were increased gradually. When the pH was around the isoelectric point, the foaming capacity of these two proteins reached the bottom, but the foaming stability was the best. With the increase of concentration of sucrose, the foaming capacity of two proteins showed a downward trend, but the foaming stability was increased significantly. The emulsifying capacity and emulsifying stability of these two proteins were enhanced with increased of the protein concentration. Around the isoelectric point, the two proteins, emulsifying capacity and emulsifying stability reached the minimum value. In the given concentration of NaCl range, the emulsifying capacity and emulsifying stability of the two proteins were decreased with increased of the NaCl concentration. The gel could be formed when the protein concentration reached or exceeded of 10%, and with the increase of the protein concentration, the gel strength was also enhanced. The result of SEM showed that: most of the hulless barley proteins were complete for irregular spherical. The intermolecular arrangement was not close, and the particle size had big difference. The experiment obtained: content of the free–SH was only 10.12μmol/g and the amount of S-S was 19.15μmol/g. The results of IR showed that: there were clearly bands of characteristic absorption of amideⅠ, amideⅡandⅢin the hulless barley protein. The analysis of fitting the amideⅠdisplayed: theα-helix,β-sheet andβ-turn of the hulless barley protein was 19.73%, 44.60%, 35.67%. There were the typical features of absorption peaks of theα-helix,β-sheet andβ-turn of the hulless barley protein in the CD spectrum. The result what evaluated the CD spectrum's data indicated: theα-helix,β-sheet andβ-turn of the hulless barley protein was 18.15%, 48.27%, 36.47%.