Intestinal digestion of fish oils and ω-3 concentrates under in vitro conditions

A comparative study of the in vitro bioaccesibility of omega-3-oils (salmon oil, SO; tuna oil, TO; enriched-omega-3 oil as triacylglycerols (TAGs), omega-3-TAG; and enriched-omega-3 oil as ethyl esters (EEs), omega-3-EE) was performed after treatment with pancreatin (pancreatic lipase as major lipolytic enzyme) at pH 7.5. Aliquots were taken at different times of digestion for analyzing the evolution of lipid products. The micellar phase (MP) formed at 120 min of digestion was isolated, its total lipid content was extracted and its composition in lipid products was analyzed. The rate of hydrolysis of omega-3-TAG concentrates was continuous throughout the time of reaction (51% hydrolysis of TAGs at 120 min), whereas the digestion of SO and TO was initially faster but stopped after 10 min of reaction (35 and 38% hydrolysis of TAGs at 120 min of SO and TO, respectively). A poor hydrolysis of EEs took place for the omega-3-EE oil (around 7% hydrolysis of EEs at 120 min). The MP of omega-3-TAG oil, SO, and TO mainly consisted of free fatty acids (FFAs) and MAGs. The MP from digested omega-3-EE oil consisted of FFAs and undigested EEs. Therefore, the highest degree of hydrolysis and inclusion of lipid products in the micellar structure was found for the omega-3-TAG oil, but compared to fish oils long times of digestion were required. This experience also shows for the first time the MP composition from omega-3-concentrates in the form of EEs.