Encapsulation of omega-3 fatty acids in nanoemulsions and microgels: Impact of delivery system type and protein addition on gastrointestinal fate

Carefully designed delivery systems are required to encapsulate and protect omega-3 fatty acids in commercial food and beverage products, but then release them at the required site-of-action within the human gastrointestinal tract (GIT). Previously, we showed that the oxidative stability of flaxseed oil (a plant-based source of omega-3 fatty acids) encapsulated in nanoemulsion droplets or calcium alginate microgels (hydrogel beads) was improved using caseinate as a natural antioxidant. In this study, the impact of caseinate on the digestion of flaxseed oil encapsulated in these delivery systems was investigated using a simulated GIT. The flaxseed oil was incorporated into four delivery systems: nanoemulsions (NE); nanoemulsions mixed with caseinate (NE + C); hydrogel beads (HB); and, hydrogel beads containing caseinate (HB + C). The gastrointestinal fate of the flaxseed oil droplets depended on delivery system type and the presence of protein. The flaxseed oil in the nanoemulsions (NE and NE + C) was rapidly hydrolyzed within the simulated small intestine, with over 76% and 65% of free fatty acids (FFAs) being released in the first 5 minutes, respectively. Conversely, the flaxseed oil in the hydrogel beads (HB and HB + C) was digested much more slowly, with only around 37% and 22% being released in the same period. This knowledge may be useful for designing delivery systems to protect omega-3 fatty acids from oxidation in functional foods, while still allowing them to be released in the GIT.