Physicochemical Properties and Bioaccessibility of Phenolic Compounds of Dietary Fibre Concentrates from Vegetable By-Products

The agro-food industry generates a large volume of by-products, whose revaluation is essential for the circular economy. From these by-products, dietary fibre concentrates (DFCs) can be obtained. Therefore, the objective of this study was to characterise (a) the proximal composition by analysing soluble, insoluble and total Dietary Fibre (DF), (b) the physicochemical properties, and (c) the phenolic profile of artichoke, red pepper, carrot, and cucumber DFCs. In addition, the bioaccessibility of phenolic compounds was also evaluated after in vitro gastrointestinal and colonic digestions. The results showed that the DFCs had more than 30 g/100 g dw. The water holding and retention capacity of the DFCs ranges from 9.4 to 18.7 g of water/g. Artichoke DFC presented high concentration of phenolic compounds (8340.7 mg/kg) compared to the red pepper (304.4 mg/kg), carrot (217.4 mg/kg) and cucumber DFCs (195.7 mg/kg). During in vitro gastrointestinal digestion, soluble phenolic compounds were released from the food matrix, chlorogenic acid, the principal compound in artichoke and carrot DFCs, and hesperetin-7-rutinoside in red pepper cucumber DFCs. Total phenolic content decreased after in vitro colonic digestion hence the chemical transformation of the phenolic compounds by gut microbiota. Based on the results, DFCs could be good functional ingredients to develop DF-enriched food, reducing food waste.