Effects of Processing on the Compositions and Physicochemical Properties of Fibre Concentrate from Cooked Fruit Pomaces

Abstract

This study examined the influence of applied technologies namely desugaring, grinding, and bleaching on the compositions (cellulose, hemicelluloses, lignins, and pectins), physicochemical properties (water-holding capacity (WHC), swelling capacity (SWC), oil-holding capacity (OHC)) and the colour of dietary fibre (DF) during the production of fibre concentrates from unusual cooked apple and pear pomaces. Thermogravimetric analysis (TGA) and optical microscopy were also performed to monitor process-induced modification. All the processing conditions affected the compositions and physicochemical properties of DF. The bleaching treatment induced the greatest changes on DF producing yellow cellulose-rich fibre concentrates with improved WHC from 3.2 to 10.0 g/g and improved SWC from 4.0 to 8.8 ml/g. Otherwise, reduction of the particle size influenced hydration properties and colours of DF. WHC and SWC tended to increase with the particle size whereas smaller granulometric size increased the lightness of fibres. Desugaring increased the DF content in both pomaces by 1.2-fold with slight modification of apple insoluble dietary fibre ratio. Fibre concentrates had improved WHC and SWC up to 1.4-fold. All processes had no significant effect (p < 0.05) on OHC of DF except with ultrafine apple fibre concentrates. Results showed that processing had overall positive effects on DF contents and hydration properties of pomaces from cooked fruits. Bleached fibre concentrates from apple pomace had the highest WHC (10.0 g/g) whereas that of pear had the highest fibre content (89.9 %). Fibres from cooked fruit pomaces may therefore be used as textural ingredients or functional foods.