Co-products of black-currant and apple juice production: Hydration properties and polysaccharide composition

The sugar composition in cell walls of apple and black currant pomaces was investigated with or without solvent extraction. Extraction of polyphenols by solvents changed the sugar composition of cell walls by increasing the alcohol insoluble solids (AIS) contents and increasing glucose content. Water binding capacity was increased by the ethanol extractions, but decreased again after acetone treatments. The enzyme treatments used for juice extraction increased the swelling capacity but decreased the water binding capacity, probably by loosening the cell wall structure. They resulted in decreased degrees of methylation. Pectin extractability of black currant pomaces differed between the commercial pomace (higher Water Soluble Pectins fraction and Chelator Soluble Pectins fraction), and the experimental pomaces (higher Diluted Alkali Soluble Pectins fraction).