Structural and digestive characterization of peanut skin procyanidins encapsulated with different proportions of inulin and whey protein

Despite of health promoting effects, the application of peanut skin procyanidins (PSP) has been restricted by their poor stability and limited bioavailability. This study aimed to enhance its stability and bioavailability through encapsulation. The effects of varying inulin-to-whey protein ratios on the encapsulation, release, gut microbiota modulation effects and metabolism of PSP during in vitro gastrointestinal digestion and colonic fermentation were investigated. Overall, higher whey protein/inulin ratio exhibited better encapsulating effects. Increasing the whey protein ratio in wall materials increased PSP encapsulation efficiency (exceeding 98 % after optimization), enhanced thermal stability and decreased the mean particle size and zeta potential of microparticles. Scanning electron microscopy analysis indicated reduced structural porosity with higher whey protein proportions, which likely contributed to the reduced release ratio of PSP during simulated gastrointestinal digestion. In vitro fermentation was performed using microparticles encapsulated with 75 g/L whey protein and 125 g/L inulin. Encapsulated PSP significantly enriched short-chain fatty acid-producing bacteria and reduced pathogenic bacteria. Furthermore, encapsulation increased levels of bioactive degradation products and promoted microbial biotransformation of flavan-3-ols. This optimized encapsulation system provides a novel nutritional delivery platform for enhancing the bioavailability and health-promoting functions of polyphenol-rich ingredients in functional foods and nutraceuticals.