Oil-in-water emulsions are widely encountered in the food and health product industries. However, the unsaturated fatty acids in emulsions are easily affected by light, oxygen, and heat, which leads to oxidation, bringing forward difficulties in controlling emulsion quality during transportation, storage, and retail. Proteins are commonly used as emulsifiers that can enhance the shelf, thermal and oxidation stability of emulsions. Polyphenols are commonly found in plants and members of the family have been reported to possess antioxidant, anticancer, and antimicrobial activities. Numerous studies have shown that binding of polyphenols to proteins can change the structure and function of the latter. In this paper, the formation of protein–polyphenol complexes (PPCs) is reviewed in relation to the latters' use as emulsifiers, using the (covalent or non-covalent) interactions between the two as a starting point. In addition, the effects polyphenol binding on the structure and function of proteins are discussed. The effects of proteins from different sources interacting with polyphenols on the emulsification, antioxidation, nutrient delivery and digestibility of oil-in-water emulsion are also summarized. In conclusion, the interaction between proteins and polyphenols in emulsions is complicated and still understudied, thereby requiring further investigation. The present review results in a critical appraisal of the relevant state-of-the-art with a focus on complexes' application potential in the food industry, including digestion and bioavailability studies.

Gastric emptying refers to a process in which the stomach discharges its contents into the small intestine to further digest and absorb nutrients. Understanding the mechanisms of gastric emptying and relationships between food and individuals is of paramount importance for the design and manufacture of novel and healthy foods. For ethical and cost reasons, in vivo tests are not always possible. In vitro digestion models therefore play a key role in current exploration of gastric emptying. This review outlines the mechanisms and physiology of gastric emptying, including calories, viscosity, composition of the food, age and gender of the individual. In addition, recent progress on in vitro static and dynamic gastric digestion models and future research trends are included in this review.