CELL-WALL CHANGES IN PEAR FRUIT SOFTENING ON AND OFF THE TREE

Changes in ethylene production and polyuronides in pear fruit on and o ff the tree were investigated. In 'Marguerite Marillat' fruit, flesh f irmness changed little after the optimum time for harvesting (OTH). By contrast, firmness of 'La France' fruit decreased gradually after OTH , reaching an average of 30 N for fruit left on the tree for 28 days a fter OTH. The amount of water-soluble polyuronides increased slightly during ripening on the tree. In both cultivars, the amount 28 days aft er OTH was less than one-third of that in fruit harvested at OTH and r ipened off the tree. Ethylene production did not increase substantiall y until 28 and 14 days after OTH in 'Marguerite Marillat' and 'La Fran ce' fruit, respectively. Pears off the tree softened to less than 10 N independently of harvest date and cultivar. The amount of water-solub le polyuronides in fruit softened after harvest increased significantl y from that at harvest. In both cultivars, the texture of fruit harves ted at 14 days and 28 days after OTH and ripened did not become butter y and juicy. Those fruit had less water-soluble polyuronides than frui t which developed a buttery and juicy texture. (C) 1998 Elsevier Scien ce B.V. All rights reserved.