Combination of whey protein isolate and Sargassum sp. extract on microstructure, tribological properties, and in vitro protein digestibility of reconstituted high-protein beverage models

Food component interactions are important as they affect the properties of food and its digestibility. Combinations were investigated of different protein concentrations and Sargassum sp . extract on the viscosity, lubrication properties, and in vitro protein digestibility after reconstitution using water to obtain 10 % or 15 % protein content as high-protein beverage models. A low (5 % w/v, named 5W) or high (10 % w/v, named 10W) concentration of whey protein isolate was combined with the Sargassum sp. extract, using different hot-water extraction methods (at 50 ± 5°C, SE-LT or 70 ± 5°C, SE-HT), followed by heating at 75 ± 5°C for 3 min before lyophilization. After reconstitution using water, the 5W+SE-LT and 5W+SE-HT samples displayed Newtonian-like flow behavior with independent particle sizes, resulting in improved lubrication properties and promoting rapid protein digestibility. However, the 10W+SE-LT and 10W+SE-HT samples had the best lubrication properties and delayed protein digestibility, based on the shear-thinning behavior of their larger particle sizes and higher viscosity. The FTIR results revealed distinct conformational transitions within the Amide I region between the two concentrations. The 5W (+SE-LT/HT) samples were characterized predominantly by loosened beta-sheet aggregates, whereas the 10W (+SE-LT/HT) samples exhibited a prevalence of random coil structures. Therefore, the preparation using different protein concentrations and combinations of Sargassum sp . extract played a role in determining the resultant properties and nutrient digestibility of the food samples that could be further utilized for texture-modified foods.