Role of gel structure in controlling in vitro intestinal lipid digestion in whey protein emulsion gels

The impact of gel structure and rheology on the intestinal digestion of canola oil dispersed within oil-in-water emulsions gelled with whey protein isolate (WPI) was investigated. Four heat-set WPI-stabilized emulsion gels were formed using NaCl and CaCl2. The gels were characterized by microscopy, rheology, fluorescence cross-correlation, diffusion measurements and swelling tests. Free fatty acid release during in vitro intestinal digestion was monitored using a pH-stat titrator and modelled using the Weibull function. Generally, gel strength as well as the proportion of embedded oil droplets increased at higher salt concentrations. Gels made with lower salt concentrations were softer and microstructurally homogeneous, and broke down more rapidly leading to a higher rate of lipid digestion. With the firmer gels, digestion was delayed by the denser, more spatially heterogeneous protein matrix. Overall, the manipulation of gel strength and microstructure modified the extent and rate of lipid digestion in WPI-stabilized oil-in-water emulsion gels, which may serve as the basis for the development of emulsion-based processed foods for applications related to controlled release of nutrients or bioactive compounds.