Textural changes during nectarine (Prunus persica) development, and ripening

Changes in nectarine (Prunus persica (L.) Batsch var nectarina (Ait.) Maxim. cv. 'Fantasia') texture were measured during the last 10 weeks of fruit development before commercial maturity, and during ripening. Both tensile and compressive textural characteristics of mesocarp tissue were measured using an Instron Universal Testing Machine. Developmental fruit softening was primarily a consequence of cell expansion. On three occasions during the developmental series we compared changes in texture during 3-5 days of postharvest storage at 20 degrees C with textural change dyer the same period on the tree, In the first-two periods the fruit were not physiologically mature and harvested fruit did not undergo normal ripening. The distinctive patterns of change in tensile and compressive properties-at these times were consistent with changes due to low turgor, as predicted by cellular theories, Harvested fruit from the third period (physiologically mature fruit producing ethylene at around 13 nmol kg(-1) h(-1)) showed an accelerated rate of ripening and softening compared with fruit left on the tree, Reductions in cell wall strength and cell-to-cell adhesion would explain the observed patterns of change in tensile and compressive properties of mature fruit, Scanning electron microscopy confirmed there was a change in the predominant cause of tensile failure from cell rupture in immature fruit to cell separation in mature fruit. A tensile parameter which correlated with this change is described.