Effect of Tea Polyphenols on Soy Protein-Stabilized O/W Emulsions in a Simulated Upper Gastrointestinal Model: An Interfacial Behavior Perspective

This study investigated the impact of tea polyphenol extract (TPE) on soy protein isolate-stabilized emulsions in a simulated gastrointestinal model. Drop shape analysis was utilized to assess the interfacial behavior of the soy protein isolate (SPI) with added TPE in situ during the bile salts displacement and the upper gastrointestinal digestion. The interaction between SPI and TPE led to significantly low surface hydrophobicity (H0) of 781.6 ( p < 0.05), a large particle size of 156.42 nm ( p < 0.05), and a more negative charge of -18.7 mV ( p < 0.05) with the 0.04% TPE addition. A thick interfacial layer of 2.33 mg/m 2 ( p < 0.05) was shown in the SPI-stabilized emulsion with TPE addition. The SPI-TPE layer exhibited enhanced resistance to bile salt displacement only in the simulated intestinal model. Additionally, TPE addition decreased the release rate of free fatty acid (FFA) to 26.8% during simulated gastrointestinal digestion without bile salts. However, bile salts were able to counteract the inhibitory effect of TPE on lipid digestion. A better understanding of the upper gastrointestinal digestion of protein-stabilized emulsion is valuable for food innovation purposes.