Changes in pectic substances and cell wall hydrolases during ripening and storage of apple fruits
Byun, J.K.; Her, J.S.; Chang, K.H.; Kang, I.K.
Journal of the Korean Society for Horticultural Science 34(1): 46-53
Changes in flesh firmness, alcohol-insoluble substances (AIS), total pectic substances (TPS), and cell wall hydrolases of 'Tsugaru', 'Jonagold' and 'Fuji' apple fruits during ripening and storage were investigated. Flesh firmness was rapidly declined in 'Tsugaru' and 'Jonagold', while slowly in 'Fuji' during ripening and storage. Among the cultivars the contents of AIS, TPS and insoluble pectic substances (IPS) were highest in 'Tsugaru' and lowest in 'Fuji' and they declined greatly until the harvesting time. However, contents of AIS, TPS, and IPS were not changed during storage of 'Jonagold' and 'Fuji' apples, while they declined continuously up to 40 days after initiation of storage in 'Tsugaru'. Water-soluble pectin (WSP) declined until the harvesting time, while increased during the storage. WSP contents of fruits before harvest were highest in 'Tsugaru' and lowest in 'Jonagold' among the cultivars. No differences were observed in WSP between 'Tsugaru' and 'Fuji' during storage, whereas WSP contents were significantly lower in 'Jonagold'. Versene-soluble pectin (VSP) declined through the maturation, but slowly increased during the storage. In general, VSP in 'Fuji' was higher than in 'Tsugaru' and 'Jonagold' during the storage. Activity of beta-galactosidase increased continuously during the maturation and storage, and the rate of increase was highest in 'Tsugaru'. Activities of polygalacturonase (PG) in all cultivars were very low through 20 days before harvest, while they were highest at harvesting time in 'Tsugaru' and 'Jonagold' and at 20 days after initiation of storage in 'Fuji', and then declined in all cultivars. Pectinmethylesterase (PME) activity was declined with fruit maturation in all cultivars, and 'Tsugaru' and 'Jonagold' showed higher activities of that than 'Fuji'. However PME activity of 'Fuji' compared to 'Tsugaru' and 'Jonagold' increased significantly during storage.