Impact of different biopolymer networks on the digestion of gastric structured emulsions

Abstract

The deliberate design of food structures that impact on lipid digestion has received increasing attention because of the need for solutions to combat nutrition related concerns such as obesity and metabolic syndrome. In this study we examined how the hierarchical structure of foods can impact lipid digestion by incorporating gastric structuring emulsions in different biopolymer networks, namely i) a thermally reversible gelatine network, ii) a colloidal casein network, and iii) a concentrated starch particulate dispersion. The digestive breakdown of these emulsion filled biopolymer gels was followed by fat digestion kinetics in vitro and human clinical study (in vivo), rheological measurements and confocal laser scanning microscopy. The parent caseinate/monoglyceride (CasMag) stabilised emulsion underwent extensive partial coalescence upon exposure to gastric juice and as a result had very slow lipolysis (in vitro and in vivo). When the emulsion was incorporated within the biopolymer networks the rates of lipolysis were strongly correlated with the extent of partial coalescence of the CasMag emulsion, which was directly influenced by the structure and breakdown properties of each different biopolymer network. The way that biopolymer networks alter the digestion of the parent CasMag emulsion is likely affected by; i) how well the digestive juices mixed with the network/emulsion and, ii) the frequency and speed of droplet encounters, both of which have a direct impact on the ability of emulsions to undergo flocculation and (partial) coalescence. This knowledge may have important implications for the design and testing of real foods to understand and control the digestive behaviour of food nutrients.