Influence of dietary lipid physical properties and supramolecular structure on digestibility and nutritional functionality

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Food properties are important determinants of their biological fate, including their ability to be digested in the gastrointestinal (GI) tract. For lipids to be absorbed, they must first be solubilized (i.e. made bioaccessible) through complex emulsifying, hydrolyzing and solubilizing processes. There is extensive knowledge about how lipid structure and physical properties (e.g. melting temperature, solid fat content, crystal morphology, distribution within droplets) influence functionality in foods. However, our understanding of how to optimize these parameters to tailor bioavailability and metabolic response is in its relative infancy. For example, what role does triacylglycerol (TAG) polymorphism play in digestive lipolysis? Does the amount and arrangement of crystallinity in an emulsion droplet alter the release of encapsulated lipids or constituent fatty acids? Can TAG crystallinity be engineered to alter colloidal behaviour, and hence gastric emptying, lipemic response and satiety? This proposal aims to address these questions through the application of basic physicochemical analyses, in vitro digestion methods and human research tools. It supports the long-term goal of understanding the relationships between food physicochemical properties and metabolic response. This research targets a better understanding of the physical basis of lipid digestion. It specifically aims to determine the role of TAG supramolecular (vs. molecular) structure and physical properties in GI processes. Emulsions will be produced containing different solid fat contents and crystalline properties (e.g. size, shape, polymorph, location in droplets), using tempering, shear, and emulsifier-lipid combinations. They will be exposed to conditions representative of the upper GI tract using static or dynamic digestion models, with sampling to study lipolysis, bioaccessibility and changes in colloidal and physical state. Experiments with tempered trimyristin droplets will address the hypothesis that interfacial lipolysis is faster for lipids in relatively less dense polymorphic forms. In vitro digestion methods and biochemical and biophysical techniques will also be coupled to investigate the processes of encapsulated lipid and fatty acid solubilization, in relation to TAG melting temperature and crystallinity. Lastly, because digesta microstructure can be influenced by lipid crystallinity and physical properties, and in turn impact gastric processing, human studies of gastric emptying by ultrasound, lipemia, and satiety ratings will be incorporated to examine emulsions structured with crystalline TAG. In summary, there are significant knowledge gaps about the physical basis of digestion that preclude a sufficient understanding of how lipids contribute to metabolic function. By focusing on the role of TAG physical properties, this work will generate novel insights to support the development of evidence-based food products and dietary recommendations for lipids.