Triacylglycerol Crystallinity and Emulsion Colloidal Acid Stability Influence In Vitro Digestion Lipolysis and Bioaccessibility of Long-Chain Omega-3 Fatty Acid-Rich Nanoemulsions

This study investigated the relationships between emulsion droplet triacylglycerol (TAG) crystallinity and colloidal acid stability on in vitro digestion microstructure, lipolysis, and docosahexaenoic acid (DHA) bioaccessibility. Oil-in-water (o/w) nanoemulsions (20 wt%) composed of 50/50 DHA-rich algal oil with either palm stearin (PS) or olein (PO), and either acid-stable Tween 80 (2.0 wt%; AS) or acid-unstable soy lecithin (2.2 wt%; AU) were fast or slow cooled to 37 °C after microfluidization. Similar particle size distributions and D_3,2 (~131-142 nm) and D_4,3 (~208-239 nm) values were achieved. All emulsions were highly electronegative (~-45-70 mV) and differences (<i>p</i> < 0.05) were due to emulsifier type, as expected, and cooling rate. Next, emulsions were subjected to INFOGEST in vitro digestion for analysis of intestinal lipolysis by free fatty acid titration and DHA bioaccessibility. As expected, AU emulsions flocculated, forming larger aggregates during the gastric phase. Slower lipolysis was observed for the AU emulsions (<i>p</i> < 0.05), attributed to gastric phase aggregation, and lower 2 h lipolysis was observed for the PS emulsions (~74-77%) based on the presence of crystallinity. DHA bioaccessibility was high (~57-88%), especially for the AS emulsions (<i>p</i> < 0.05). Therefore, emulsion colloidal acid stability and TAG physical state significantly impacted emulsion gastric microstructure, digestion, and bioaccessibility.