Abstract:To investigate the in vitro digestive properties of fish oil with different proportions of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), based on an in vitro gastrointestinal digestion model (GIT), O/W fish oil emulsions with different ratios of EPA/DHA (5.13, 2.45, and 1.34) were prepared. The changes in the particle size, ζ-potential, and microstructure during digestion, as well as the release behavior of fatty acids during digestion in the small intestinal, were investigated. The results showed similar variation trends for fish oil emulsions with different EPA/DHA ratios. Despite this, each emulsion exhibited unique digestive characteristics. Specifically, all three initial emulsions showed higher stability, with strong negative charges, ranging from -40.02 to -43.77 mV, as well as relatively uniform particle size distributions (0.1-1.0 μm). After oral and gastric digestion, the absolute value of charge of each system decreased significantly (P<0.05), exposing the inner lipid phase. In addition, particle size was found to follow a multi-peak distribution and was mainly concentrated in the range of 10~100 μm. During small intestine digestion, the particle size of each system decreased significantly to 8-13 μm (P<0.05). The release of the free fatty acids (FFA) was 103.21% (EPA/DHA ratio of 5.13), 73.54% (EPA/DHA ratio of 2.45), and 62.51% ((EPA/DHA ratio of 1.34). These results suggest that the relative proportion of EPA and DHA is an important factor influencing fish oil emulsion digestion. This study provides a basis for the determination of the recommended daily EPA and DHA-rich marine lipid intake and the design of fish oil delivery systems.
