Interfacial rheological and wetting properties of deamidated barley proteins

The goal of the present study is to provide a detailed description of rheological and wetting properties of barley protein and establish a linkage between these properties and the protein structure. In order to achieve this goal, we first measure the interfacial properties, including interfacial tension and interfacial rheology (viscous modulus and elastic modulus). Secondly, we investigate the secondary structural changes of the deamidated barley protein and hydrolysates through FTIR. Thirdly, we measure molecular weight by using HPLC. Finally, we determine the wetting properties with dynamic contact angle measurements. The solubility of barley protein can be greatly enhanced by applying deamidation process. After deamidation, more flexible secondary structures are detected through FTIR analysis. These changes in secondary structure are reflected in interfacial properties. The interfacial protein concentration and rheological properties of protein samples are determined by interfacial tension measurement. The equilibrium interfacial tension and contact angle for protein solution decrease as the concentration of protein increases. The deamidated protein with large molecular weight parts shows the highest elastic modulus, while hydrolysates with low molecular weight shows the highest viscous modulus. The results also indicate that deamidated protein forms more stable film at interface compared to the low molecular hydrolysates.