Juices, Fibres and Skin Waste Extracts from White, Pink or Red-Fleshed Apple Genotypes as Potential Food Ingredients

Abstract

This study measures and compares the bioactive content and appearance attributes of juices, dietary fibres (DFs) and skin wastes of three apple genotypes (white fleshed (WF), pink fleshed (PF) and red fleshed (RF)). The juices of the PF and RF apples had more appealing and stable colours and much greater total extractable polyphenol content (TEPC) (RF had the highest, 3.40 mg catechin equivalent/mL juice) and vitamin C (PF had the highest, 14.2 mg/100 mL juice), compared with the WF apple. DFs isolated from the three apples using aqueous and ethanolic methods varied in bioactive profiles as a function of genotype. The TEPC and antioxidant activity (AA) of the fibres decreased in the order of PF > RF > WF. The total DF (TDF) in the fibre obtained using the aqueous method decreased in the order of RF > PF > WF. The ethanolic method yielded higher neutral monosaccharide (NM) and slightly greater TDF contents than the aqueous method. More polyphenol species were detected in the PF fibres, especially those obtained using the aqueous method. The polyphenol content in the apple skin decreased in the order of RF > WF > PF, with PF having slightly more pectic polysaccharides. As a whole, the RF apple appeared to be the best genotype as the potential source for juice, fibre and skin waste extract (SWE) ingredients. The PF apple would be the second best genotype for juice and fibre ingredients. The skin of the RF and WF genotypes would provide a good source of polyphenols. There is potential for promoting RF and PF apple genotypes because of their excellent nutritional values. The aqueous fibre preparation method used herein containing no solvent treatment and freezing steps represents an industrial-scale cost-effective alternative to the conventional ethanolic methods used for producing DFs whilst retaining polyphenols.