Effect of High-Pressure Processed Apples on Phenolic Metabolites, Short-Chain Fatty Acids, and Human Gut Microbiota Using a Dynamic In Vitro Colonic Fermentation System

<b>Background/Objectives</b>: Consuming apples regularly has positive effects on human health due to their anti-inflammatory and antioxidant properties, which have been associated with their phenolic composition. To enhance the bioactive properties of apple phenolic compounds, high-pressure processing (HPP) has been studied as a tool to improve their extraction during gastrointestinal digestion with the aim of increasing their bioaccessibility and the amount that reaches the colon unchanged, which can serve as substrates for bacterial fermentation. This study aimed to analyze the impact of an HPP-apple ingredient on the metabolism of human gut microbiota using an <i>in vitro</i> dynamic simulator of gastrointestinal digestion and colonic fermentation (GID-CF) that allowed us to study the three colon regions separately (ascending-AC; transverse-TC; and descending-DC). <b>Methods</b>: Apples were HPP-treated (400 MPa/5 min) and lyophilized to obtain an HPP-apple ingredient in powder form. A GID-CF was employed to study the continuous intake of the HPP-apple ingredient for 14 days at 37.5 g/day. <b>Results</b>: The HPP-apple ingredient produced a significant accumulation of phenolic metabolites mainly in the DC, with benefits on human health. The main phenolic metabolites formed were phloroglucinol, 4-hydroxyphenylacetic acid, 4-hydroxy-3-methoxyphenylacetic acid, 3-(3-hydroxyphenyl)-propionic acid, and 3-(4-hydroxyphenyl)-propionic acid. A PCA revealed a perfect separation of the three colon regions based on the phenolic precursors and metabolites. The microbiota-modulatory effects were attributed to the increase in <i>Bifidobacterium</i> spp. and <i>Lactobacillus</i> spp. populations and the butyric acid (SCFA) concentration. <b>Conclusions</b>: The results obtained highlight the health benefits and potential prebiotic-like effect of the HPP-apple ingredient on the gut microbiota.