Biopolymer interactions during gastric digestion: Implications for nutrient delivery

Foods are composed of a wide variety of biopolymers (e.g. proteins and polysaccharides) that interact during processing and formulation, resulting in the development of the different structures and physical characteristics of food products. Although a wealth of information on protein-polysaccharide interactions in model food systems is available, there is a considerable challenge in understanding the nature and implications of these interactions in the environment of the human digestive tract. Several liquid foods containing complex mixtures of biopolymers have been shown to undergo major re-structuring and phase changes during gastric digestion, and these re-structured entities may influence some of the physiological processes. This review brings together some of the current knowledge on biopolymer interactions and gastric digestive physiology, with emphasis on the intragastric structuring of liquid food systems. Major emphasis is placed on gastric processing, as critical interactions and structure formation and disintegration occur in the stomach region. The potential impact of the gastric re-structuring of liquid foods on the rate of delivery of nutrients is discussed, where appropriate. The gastric digestion behaviour of selected natural colloidal dispersions (plant-based and bovine milk), including the mechanisms of protein-protein interactions and gastric re-structuring, are discussed. Understanding the relationship between gastric re-structuring and the rates of nutrient digestion will be vital for developing future foods with specific health attributes.