Pectin-based emulsion gels prepared by acidic and ionotropic methods for intestinal targeted delivery in vitro

Considering the different potential roles of the small intestine and colon in the functions of bioactive components, this study was performed to design a pectin-based controlled delivery system targeting different intestinal sections according to emulsification gelation methods (i.e., pectin gelated with acidified ethanol, iron, and calcium: PE-H, PE-Fe, and PE-Ca, respectively). The properties and targeted delivery of pectin-based emulsion gels were compared. All emulsion gels exhibited similar diameter and acceptable roundness with naringin encapsulation efficiency of approximately 90%. Cross-sections of PE-H, PE-Fe, and PE-Ca exhibited loose networks, large voids, and dense structures, resulting in diverse time dependence during digestion. Furthermore, PE-Ca showed the fastest completion of gelation and exhibited excellent hardness properties, suggesting that it would have the strongest anti-digestive effect. PE-Fe showed time- and pH-dependent swelling behavior in simulated intestinal fluid. Simulated digestion experiments indicated burst release and slow release of naringin from PE-H and PE-Fe, respectively, due to their differences in pH responsiveness and time dependence; a similar amount of naringin was released from PE-Ca after enzyme-triggered digestion in simulated colon fluid. Overall, distinct emulsion gels achieved targeted disintegration in intestinal sites. PE-H and PE-Fe would contribute to the rapid and sustained release of naringin in the small intestine, respectively, whereas PE-Ca would contribute to naringin release in the colon. These findings provide new insights for the future design of specific delivery systems that can be used in the functional food industry; they indicate the robust potential for including pectin in emulsion-based foods with targeted functions.