STUDIES ON APPLE PROTOPECTIN .4. APPLE XYLOGLUCANS AND INFLUENCE OF PECTIN EXTRACTION TREATMENTS ON THEIR SOLUBILITY

Hemicelluloses were extracted from apple cell walls with 1 M and 4 M sodium hydroxide and 8 M urea after depectinisation by a chelating agent, by a chelating agent and dilute sodium hydroxide or by a chelating agent and a pectin-lyase. The extracts were fractionated on Sephacryl S 500 and DEAE Sepharose CL-6B. The bulk of the hemicelluloses were solubilised by 4 M sodium hydroxide. The main hemicellulose was a fucogalactoxyloglucan. Some low-molecular-weight mannans were also present. Part of the xyloglucans could be extracted by urea after pectin extraction by a chelating agent or by pectin-lyase but not after pectin extraction by dilute sodium hydroxide. Dilute sodium hydroxide probably insolubilised some of the pectins and hemicelluloses.