Caffeic Acid Release from Inulin Caffeate: A Comparative Study with Spray-Dried Inulin Microparticles Under Gastrointestinal Digestion

This study compared the physicochemical properties of inulin caffeate, where caffeic acid (CA) was covalently bound to inulin (CA-Inu, degree of substitution: 0.07), with CA spray-dried inulin microparticles (Mp(CA/Inu)), as well as release profiles of CA from CA-Inu and Mp(CA/Inu) under in vitro simulated gastrointestinal digestion. Encapsulation by spray drying was optimized using a Central Composite Design, achieving an encapsulation efficiency of 98%. CA was rapidly released from Mp(CA/Inu) during the oral and gastric phases, followed by a slight decrease in the intestinal phase due to interaction with digestive enzymes. In contrast, no release of CA was detected from CA-Inu during the oral and gastric phases. Approximately 30% was released in the intestinal phase, with a further increase in the colonic phase, especially in the presence of inulinase. This strategy, based on the covalent binding of phenolic compounds to biopolymers, can promote targeted delivery in the later stages of gastrointestinal digestion.