Microstructural Changes During In Vitro Digestion
Figure 5 provides visual insights into the microstructural
transformations occurring in KO emulsions produced by HPH and MF at
different stages of digestion. These observations were made using
confocal fluorescent microscopy, where the oil phase was stained red and
the protein phase was stained green. The aim was to visually assess how
emulsions formed by different homogenization methods offer protective
effects during digestion. In the initial test group, fine and uniform
droplet distributions were evident, with no signs of aggregation or
coalescence, aligning with the findings presented in Figure 1 A and B.
During the oral phase, minimal changes in droplet structure were
observed. However, a slight degree of aggregation was noted in the
stomach phase, likely due to the decrease in pH and protease-induced
hydrolysis.
During the small intestine phase in the MF-prepared emulsion, at 0
minutes, there was a gradual release of lipids in response to bile
extract and pancreatin digestion. Over time, an increasing number of
lipids were observed, and by the small intestine phase at 120 minutes,
complete lipid release had occurred. These findings align with prior
research by Zhao et al. (2021), which demonstrated that high oleic palm
oil encapsulated in nanoliposomes via MF exhibited smaller
particle sizes and polydispersity indices. This encapsulation
effectively shielded the oil from the harsh acidic conditions of gastric
digestion and allowed for the controlled release of core materials
during in vitro digestion. In contrast, the control group
exhibited extensive droplet aggregation or coalescence throughout the
digestion stages, likely due to the inferior protective capabilities of
the wall formed by HPH. This indicated that HPH-prepared emulsions were
less stable compared to KO-in-water emulsions produced via MF.
These findings underscore the superiority of MF as a method for
generating uniform and stable emulsions that effectively protect KO from
oxidation and hydrolysis, ensuring efficient absorption in the small
intestine.