Abstract:Sports nutrition emphasizes not only the diversity of nutrients, but also their timing intake. Protein supplements are important sources for the requirements of sports nutrition. Currently, the leading products on the market are mainly protein powders, although some liquid beverages are available. However, no previous studies have reported their gastrointestinal digestive behavior and protein hydrolysis profiles. In this paper, five commercially available high-protein sport supplements and three high-protein foods were selected based on protein type and formulations. Their gastrointestinal digestive behavior and protein hydrolysis were evaluated using an in vitro digestion model. The results showed that the water dispersion of powder products had large particle size and were apt to form sediments. All products were sensitive to pH, but they showed different buffering capacity against pH reduction during the in vitro gastric digestion. Products with higher casein content showed a slower pH reduction. All samples tended to form aggregates in the simulating stomach environment. During gastric digestion, the viscoelasticity of the liquid products increased rapidly and decreased or reached a plateau, while the rheological properties of powder products remained constant. One of the liquid products had the highest protein hydrolysis degree (approximately 29%) after 30 min of mimicked gastric digestion, which was 1.5, 1.4, and 1.4 times higher than that of the selected powder products. At the end of gastrointestinal digestion, the protein hydrolysis of each product was in the range of 60%~80%. The hydrolysis degree of proteins in these sports supplements was higher than that in chicken and beef. In conclusion, protein types and product formulations affect the hydrolysis of high-protein sport supplements. The application of liquid formulation and concentrated milk protein might be more favorable for protein absorption than powders. The results in this study may provide data support for the precise design and development of high-protein sport supplements.
