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.