Characterization and functional evaluation of oat protein isolate-Pleurotus ostreatus β-glucan conjugates formed via Maillard reaction

Oat protein isolate is nutritious but with poor processing functionality. Pleurotus ostreatus beta-glucan with good processing functionality can be conjugated with oat protein isolate via Maillard reaction, leading to an improved utilization of protein in food industry. Therefore, we produced conjugate with oat protein isolate and Pleurotus ostreatus beta-glucan via Maillard reaction under controlled dry-heating conditions. The formation of conjugates with high molecular weight was identified by a new band of sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The analysis of amino acid composition showed that cysteine and lysine were the dominant Maillard reaction sites of oat protein isolate and Pleurotus ostreatus beta-glucan. Changes in spatial configuration of conjugates caused reduction in their surface hydrophobicity of proteins and intrinsic fluorescence intensity. Fourier transform infrared spectroscopy analysis of conjugates suggested that Maillard reaction could cause the C=O stretching vibration, as well as the C-H and N-H deformation vibration. Circular dichroism analysis indicated that the secondary structure of conjugates was altered by decreasing the contents of a-helix and beta-sheet and increasing the contents of beta-turn and random coil. The surface structure of conjugates was loose and porous using scanning electron microscope. Furthermore, Maillard reaction could improve the solubility, emulsifying property and thermal stability of oat protein isolate. Our findings confirm the potential of protein-carbohydrate conjugate formed by Maillard reaction, to improve the application of instable but valuable proteins in food industry.