In Vitro Gastrointestinal Digestibility of Crystalline Oil-in-Water Emulsions: Influence of Fat Crystal Structure.

To investigate how the fat crystal structure affects lipid in vitro digestibility, 30% palm stearin-in-water emulsions were prepared after storage at different temperatures (4, 25, and 37 °C) for 1 h, which consisted of different polymorphic forms, sizes, and quantities of fat crystals. The variation of particle size ( d4,3), zeta potential, and microstructure during the gastrointestinal digestion and the free fatty acid (FFA) released in small intestine phase were investigated. After oral and gastric digestion, all of the emulsions underwent partial or complete coalescence and flocculation. During intestinal digestion, the d4,3 and zeta potentials did not notably affect lipid digestion. The FFA-released assay results indicated that the lipid digestion extent decreased as the fat crystal size and content of the β polymorph increased, and there was no obvious relationship between FFA release and fat crystal quantity or solid fat content (SFC). This study highlighted the crucial roles of fat crystal size and polymorphic form in regulating the digestion behavior of lipid-based O/W emulsions.