Isolation and characterisation of cell wall material from olive fruit (Olea europaea cv koroneiki) at different ripening stages

Olive fruit (Olea europaea cv koroneiki) were picked at the immature green, green, turning and purple ripening stages and cell wall material was isolated. During ripening the sugar composition changed and the level of methyl esters and acetyl groups in the cell wall decreased. The cell wall material of green and purple olives was fractionated by successive extractions with 0.05 M NaOAc buffer, 0.05 M cyclohexane-trans-1,2-diaminetetra-aceta (CDTA) and 0.05 M NH4-oxalate in 0.05 M NaOAc buffer, 0.05 M NaOH, 1 M KOH, 4 M KOH and 6 M NaOH. The amount of pectic material extracted with NaOAc buffer increased considerably during ripening. The molecular weight distribution and the sugar composition of the pectic polymers hardly changed. The yields and the sugar composition of the hemicellulose-rich fractions showed little change throughout development. The molecular weight profiles of the hemicellulosic fractions were similar. For further study, the hemicellulose-rich fractions were fractionated by anion-exchange chromatography. The fractions had similar elution behaviours and all contained a xyloglucan-rich pool and four xylan-rich pools. The yields of the subpopulations differed for the 1 and 4 M KOH fractions. During ripening no detectable changes in the sugar composition and the molecular weight distribution of the xyloglucan-rich and xylan-rich fractions were found. (C) 2000 Elsevier Science Ltd. All rights reserved.