EFFECTS OF LOW PREHARVEST TEMPERATURE ON SCALD SUSCEPTIBILITY AND BIOCHEMICAL-CHANGES IN GRANNY-SMITH APPLE PEEL

An over-tree mist system provided evaporative cooling of the 'Granny S mith' apple fruit. The temperatures of fruit under mist, control (with out mist) and air were recorded from 1 September until harvest. Fruit were harvested when 30, 60, 80, 100, 120 and 160 h at less than 10 deg rees C had been recorded. Fruit maturity indices (flesh firmness, solu ble solids, titratable acidity, starch index, internal ethylene concen tration and color), lipid composition, membrane permeability, antioxid ant concentration and activity were evaluated at harvest and after 60, 120 and 180 days of storage at 0 degrees C plus 7 days at 20 degrees C. Superficial scald was evaluated after storage and a shelf life peri od. Maturity indices significantly changed during the harvest period. However, there was no significant difference between maturity indices of fruit under mist and control at the same harvest date. Fruit at the first harvest date without mist had accumulated 30 h at less than 10 degrees C and 100% of them developed storage scald, while fruit of the same harvest date under mist had accumulated 60 h at less than 10 deg rees C and developed 82% scald. Superficial scald decreased to 16% on fruit exposed to T<10 degrees C for 100 h and was negligible on fruit exposed to T<10 degrees C for 120-160 h. Total lipids, waxes and fatty acids of apple peel increased with duration of temperature less than 10 degrees C. Unsaturated fatty acids significantly increased on fruit with 100-160 h exposure to less than 10 degrees C. Fruit exposed to l ess than 100 h at less than 10 degrees C had higher electrolyte leakag e of peel tissue discs than fruit with more than 100 h at less than 10 degrees C. The concentration and activity of peel antioxidants signif icantly increased with the low temperature duration before harvest. (C ) 1998 Elsevier Science B.V. All rights reserved.