Cell-wall polysaccharides in the fruits of Japanese quince (Chaenomeles japonica): extraction and preliminary characterisation

The study of the cell-wall polysaccharides of the fruits of Japanese quince (Chaenomeles japonica) was achieved in two stages: (i) preparation of alcohol insoluble solids (AIS) from the different tissue zones and entire fruits of two genotypes and (ii) treatment of the AIS with extractants. The AIS represented an average of 32 g/100 g entire dry fruit and 4 g/100 g entire fresh fruit. A sequential extraction scheme allowed the separation of the cell-wall material into its major components (cellulose, pectins and hemicelluloses). The AIS was composed of 30 g pectins/100 g AIS, 8 g hemicelluloses/100 g AIS and 60 g cellulosic residue/100 g AIS. 100 g entire dry fruit (800 g entire fresh fruit) contained 11 g pectins, 3 g hemicelluloses and 18 g cellulosic residue. Pectins were mostly located in the flesh of the fruit, they were more efficiently extracted with hot dilute acid than with other extraction media and they had a high degree of methylation (DM) and a low degree of acetylation (DAc). Sequential extraction allows a first fractionation of the pectins. Hot dilute acid extracted pectins substituted with long Ara side-chains, whereas cold dilute alkali extracted pectins with more numerous but shorter side-chains. No difference was pointed out neither in the quantity of polysaccharides extracted from the two genotypes studied nor in the composition of these constitutive polysaccharides.