チュウゴクナシ‘鴨梨’果実の軟化と細胞壁多糖類およびその分解酵素活性

The softening characteristics of Chinese pear 'Yali'fruit,based on changes in the rates of respiration and ethylene production,flesh hardness,the content of cell-wall polysacchairides and the activities of their degraging enzymes were determined,in comparison with Japanese pear 'Nijisseiki' and European pears 'la France' and 'Bartlett'.Rates of respiration and ethylene production in 'Yali','la France' and 'Bartlett' fruits increaced with the advance of ripening,showing the most significiant increase of ethylene production in 'Yali' fuit.Decrease of flesh hardness during ripening was rapid in 'la France' and 'Bartlett' fruits,but slow in 'Yali' and 'Nijisseiki' fruits.Though rapid increase of pectinmethylesterase activity in 'la France' and 'Bartlett' fruits was observed with concomitant decrease of hardness,the same activity was maintained at a lower level in 'Yali' and 'Nijissiki' fruits.Increase in polygalacturonase activity during ripening was rapid in 'la France' and 'Bartlett' fruits,Cellulase activity increased with the decrease in flesh hardness in 'la France' and 'Yali' fruits,whereas its increase was slight during ripenig in 'Nijisseiki' and 'Bartlett' fruits.Increase in the content of hydrochloride-soluble pectin during flesh softening were very slight in 'Yali' and 'Nijisseiki' fruits in contrast with their marked evidence in 'la France' and 'Bartlett' furits.From the results obtained above,its seemes that long-term hardness maintenance in Chinese pear 'Yali' fruit during ripenig was due to lower activity by degrading enzymes of cell-wall polysaccharides,compared with those in other pear fruits.