A new strategy for steady-state butyric acid encapsulation: Mechanism of starch-lauric acid-protein-butyric acid complex formation, release characteristics and prebiotic properties.

To address the low endogenous production and short half-life of butyric acid (BA), this study successfully constructed an AM-LA-WP-BA quaternary complex for the targeted delivery of butyric acid to the colon through hydrogen bonding and hydrophobic interactions, utilizing amylose (AM), lauric acid (LA), and whey protein (WP). Debranching pretreatment of the starch improved the stability of the starch-lauric acid-protein-butyric acid (SLPB) quaternary complex and its butyric acid encapsulation capacity. Analysis indicated that a 12 h debranching treatment resulted in the highest relative crystallinity of 75.6% for the complex, with the proportion of VII-type crystallites reaching 56.88% and the resistant starch content increasing from 36.51% to 58.41%. This endowed the complex with strong resistance to digestion, thereby enabling colon-specific release. Furthermore, in vitro fermentation studies revealed that SLPB not only directly released butyric acid but also served as a fermentation substrate to promote the proliferation of butyrate-producing bacteria (e.g., Ruminococcus, Eubacterium, and Blautia), thereby synergistically increasing colonic butyric acid levels. Therefore, compared with binary and ternary complex, SLPB quaternary complex exhibits superior structural order, stability, and digestion resistance. Through a dual mechanism, it effectively address colonic butyric acid deficiency, providing a novel design strategy for functional carriers in precision nutritional interventions.