Exploring the prebiotic potential of unpurified apple dietary fibre concentrate

Apple processing generates significant quantities of residues, harming the environment and leading to wasted functional ingredients, mostly Dietary Fibre (DF) and bioactive compounds. However, apple by-products could be introduced into the food chain as Unpurified Apple Dietary Fibre Concentrate (UADFC), which could serve as a health-promoting food ingredient. Hence, this study aims to characterise the nutritional and techno-functional properties of the UADFC and to evaluate its potential as a prebiotic. The results revealed that UADFC contained nearly 20% DF and a concentration of 4963 mg/kg of free phenolic compounds measured by HPLC. After in vitro gastrointestinal digestion, 5981 mg/kg of free phenolic compounds were found. The decrease in total phenolic compounds after in vitro colonic digestion (to 112 mg/kg) could be attributed to chemical transformations by the gut microbiota. Additionally, the digestion of UADFC increased the relative abundance of probiotic microorganisms such as Bifidobacterium and Lactobacillus spp., as analysed by qPCR. Furthermore, the digestion of UADFC released a significant amount of Short Chain Fatty Acids (SCFAs), particularly butyric acid (10.01 mM), as quantified using gas chromatography. This is likely related to the observed increase in Bifidobacterium and Lactobacillus spp. Based on these results, UADFC could be classified as a prebiotic.