Effect of ultrasound and high-pressure homogenization on functional properties of date seed protein

Date kernel is a plant-derived byproduct that has the potential to be converted into a high-value-added food ingredient, such as protein concentrate, in the food industry. High-intensity ultrasound and high-pressure homogenization, which are alternative methods for improving the functional properties of food protein, are effective physical treatments for modifying protein functionality. Solubility is the main criterion that primarily influences other functional properties of protein concentrates such as emulsification, foaming, water, and oil binding. The aim of this study is to improve the techno-functional performance of date seed protein concentrate (DSPC) by maximizing solubility by high-intensity sonication (HIUS) and high-pressure homogenization (HPH). In the first stage of the study, the effect of ultrasonic homogenization at different amplitudes (40, 60, and 80%) and times (5, 10, and 15 min) on the functional properties of the DSPC was investigated using the response surface methodology (RSM). The face centered-central composite design (FC-CCD) showed that the optimal process conditions of HIUS were at 80% amplitude for 15 minutes. In the second stage of the study, the influence of HPH at different pressures (50, 100, and 150 MPa) and protein concentrations (1, 2, and 3%) on the functional properties of the DSPC was analyzed using the Response Surface Methodology (RSM). A pressure of 150 MPa and a protein concentration of 1% were the optimum HPH conditions for maximizing the solubility. The optimum HIUS and HPH treatment conditions for physicochemical and functional properties of the ultrasonically treated date seed protein concentrate (DSPC-US) and the high pressure treated date seed protein concentrates (DSPC-HPH) were determined. The properties of DSPC-US and DSPC-HPH were compared to the native date seed protein concentrate (DSPC-N). The results revealed that the solubility of all DSPC samples treated by both HIUS and HPH was significantly (p<0.05) higher than native DSPC. In addition, emulsion activity/stability, foaming, activity/stability, antioxidant activity, and oil-binding capacity increased after HIUS and HPH homogenization treatments, while water-binding capacity decreased. These changes in the techno-functional properties of the DSPC-US and DSPC-HPH were explained by the modification of the physicochemical structure of the DSPC (particle size, zeta potential, SDS-PAGE, SEM, FTIR, DSC, free SH content, surface hydrophobicity, and intrinsic emission). This work demonstrated that HIUS and HPH could be effective treatments for enhancing the functional properties of date seed protein concentrate.