Changes in Pectinmethylesterase, Polygalacturonase and Pectic Substances of Ethanol- and Ethylene-treated Bananas during Ripening

Abstract

Investigation was made on the effect of postharvest application of ethanol and ethylene on softening, respiration, activities of pectinmethylesterase and polygalacturonase, and changes in the total pectic substances and water-soluble pectin in banana during ripening. Peel color development, total soluble solids (as an estimate of total sugar) and acidity were also monitored.
Ethanol hastened ripening of bananas but was less effective than ethylene. The respiratory peak of ethylene-, ethanol-treated and control fruits was observed after 4, 8 and 11 days of storage. The fruits were edible ripe at or shortly after CO2 peak and the firmness at this time was comparable to the control. As the fruits softened, polygalacturonase activity increased, total pectic substances decreased and the water-soluble pectin increased. Polygalacturonase activity was low in the pre-climacteric stage, increased during the climacteric and reached a level of 17 to 18 times the initial in post-climacteric phase. The control was slow to ripen and its polygalacturonase activity was always lower than in treated fruits. The activity of pectinmethylesterase was not readily related to the decrease in firmness. The total soluble solids increased to 20-22% during ripening and the increase was most rapid in ethylene-treated fruits and slowest in the control. Acidity in all samples increased slightly during ripening.