Effect of temperature on softening and the activities of polygalacturonase and pectinesterase in durian fruit

Durian fruit (Durio zibethinus Murr. cv Chanee) were ripened at 12, 27 and 34 degreesC (85 +/- 5% RH). When held at 27 degreesC, the aril of durians softened rapidly, concomitant with a decrease in alkali-soluble pectin, a marked increase in water-soluble pectin and a large increase in polygalacturonase (EC 3.2.1.15) activity. Pectinesterase (EC 3.1.2.11) activity was high at harvest and changed little. Fruit stored at 34 degreesC showed the same rate of softening as fruit held at 27 degreesC, whereas polygalacturonase activity (and the amount of water-soluble pectin) was considerably lower. Durians stored at 12 degreesC showed virtually no softening and had low polygalacturonase and pectinesterase activities and small changes in water-soluble pectin. It is concluded that there is a positive correlation between. softening and pectin degradation. No correlation was found between softening and pectinesterase activity, while the softening is correlated with polygalacturonase activity. (C) 2002 Elsevier Science B.V. All rights reserved.