Firmness and activities of polygalacturonase, pectinesterase, β-galactosidase and cellulase in ripening durian harvested at different stages of maturity

The changes in ripening durian aril firmness, water-soluble pectin and polygalacturonase, pectinesterase, beta-galactosidase and cellulase activities were determined in fruit harvested at two stages of maturity. Polygalacturonase activity was low in unripe durian aril and increased markedly during ripening. The development of polygalacturonase activity paralleled the formation of water-soluble pectin and decline in firmness. Pectinesterase, beta-galactosidase and cellulase activities were high in unripe durian aril and only pectinesterase and beta-galactosidase activities increased slightly while cellulase activity was present throughout during ripening. Water-soluble pectin and polygalacturonase and pectinesterase activities were greater in more mature durian aril than in less mature durian aril, whereas firmness and the activities of beta-galactosidase and cellulase were less in the more mature durian aril. The roles of polygalacturonase and pectinesterase in softening of ripening durian aril are discussed. (C) 1999 Elsevier Science B.V. All rights reserved.