Raspberry dietary fibre: Chemical properties, functional evaluation and prebiotic in vitro effect

Raspberries have high content of antioxidants; however, there is a lack of information about the functional composition of their dietary fibre. In this work, the total dietary fibre and its soluble and insoluble fractions were analysed for extractable and hydrolysable (poly)phenols, non-starch polysaccharides and functional properties with physiological effects and health implications (fat and water retention and swelling capacity, glucose diffusion retardation index, osmotic pressure and antioxidant capacity). Additionally, their prebiotic effect was assessed by an in vitro fermentation model by the analysis of short chain fatty acids. Results show that raspberry fibre contained mainly hydrolysable (poly)phenols; insoluble dietary fibre was the fraction richest in these compounds and also had the highest antioxidant and fat retention capacity, whereas soluble dietary fibre underwent greater hydration. The in vitro fermentations showed that (poly)phenols were responsible to a great extent for the raspberry prebiotic-like effect, in comparison with the fibre fractions. The results confirm that raspberry dietary fibre fractions could be used as functional and prebiotic ingredients for the development of food products with enhanced physical and nutritional properties.