Release of Free Fatty Acids (FFA) during In VitroDigestion
The release of Free Fatty Acids (FFA) from both emulsions was closely
monitored at various time points during intestinal digestion, and the
results are depicted in Figure 7. The lipid digestion profiles of the
emulsions produced by HPH and MF displayed similar patterns,
characterized by an initial rapid increase in FFA levels followed by a
more gradual rise over time until reaching a relatively stable final
value.
Although there were no significant differences observed between the KO
emulsions prepared by HPH and MF during the initial stages of digestion,
some distinctions became apparent in the profiles of fatty acid release
and the initial rates of lipid digestion. Notably, the MF-prepared
emulsions exhibited a lower initial rate of lipid digestion. This
difference can be attributed to alterations in the surface area of
lipids exposed to digestive enzymes, a factor that is inversely
proportional to the mean droplet diameter. As the digestion process
advanced, the oil droplets within the homogenized emulsion tended to
aggregate. This aggregation resulted in a reduction in the surface area
of the oil droplets, limiting lipase’s access to the droplet surfaces.
This phenomenon aligns with findings from another study (Qin et al.,
2016), which reported that the rate and extent of lipid digestion in aβ -carotene emulsion increased with decreasing mean droplet
diameter (small ≈ medium >> large). Moreover,
it’s worth noting that the MF-prepared emulsion exhibited a higher final
extent of FFA release compared to the HPH-prepared emulsion. The final
release of FFA from the MF-prepared emulsion reached approximately
80.72±1.05%, whereas the HPH-prepared emulsion released only
67.41±1.6% of FFAs. Several factors may contribute to this difference,
including the resistance of colloidal particles to digestion and the
potential hydrolysis of lipids before analysis due to emulsion
instability. It is noteworthy that the HPH-prepared emulsion exhibited
numerous non-digested lipid droplets, as observed through confocal
microscopy (Figure 5A). This observation aligns with the relatively low
extent of lipid digestion by the end of the small intestine phase. These
findings emphasize the role of smaller particle size in nanoemulsions in
enhancing the bioavailability of encapsulated hydrophobic nutraceuticals
by facilitating more rapid and complete digestion of the lipid phase.