STUDIES ON APPLE PROTOPECTIN .1. EXTRACTION OF INSOLUBLE PECTIN BY CHEMICAL MEANS

The pectic material from Golden Delicious apples, strongly bound in the cell walls of parenchymatous tissues (not extractible with Cyclohexane-Diamino-Tetracetic Acid (CyDTA)) was extracted by: (i) successively, hot buffer, hot acid and cold sodium hydroxide, (ii) sodium carbonate (4°C then 20°C) and (iii) chlorite. The pectin extracts were analysed for uronide, neutral sugars and protein contents, and degrees of methylation and acetylation. They were also subjected to gel-filtration and ion-exchange chromatography. Subfractions obtained by ion-exchange were also analysed. Approximately 55% of the pectic material was not extracted by the CyDTA. Hot buffer, hot acid and chlorite extracted small amounts of relatively highly methoxylated and acetylated pectins. The most efficient extractants were the cold carbonate and the cold sodium hydroxide. They extracted saponified pectins that exhibited similar behaviour on gel-filtration and ion-exchange chromatography, showing two subfractions, of which one was rich in neutral sugars and had a high molecular weight. There was no evidence of phenolic interlinkages. © 1989.