Olive fruit cell wall: Degradation of pectic polysaccharides during ripening

Olive fruits at three stages; of ripening (green, cherry, and black) have b een studied. After cell wall isolation, the compositions of the cell wall a nd that of the phosphate-soluble polysaccharides were determined. In cell w alls, decreases in arabinose, xylose, glucose, and uronic acid levels were observed, together with a slight increase in mannose on ripening. At the be ginning of ripening, fragments of pectic polymers were the major constituen ts of the phosphate-soluble fraction, with the hemicellulosic ones increasi ng toward the end of the process. The molecular weight of the fragments sol ubilized was similar to6 kDa. After cell wall fractionation, the pectic pol ysaccharides soluble in imidazole and sodium carbonate were also studied. I n both fractions, between the green and cherry stages of ripening, a signif icant loss of homogalacturonans took place. Between the cherry and black st ages of ripening, rhamnogalacturonan side chains were also released in addi tion to homogalacturonans. In any of the pectic fractions,changes in appare nt molecular weight were quantified.