EFFECTS OF DIPHENYLAMINE, GIBBERELLIC ACID, DAMINOZIDE, CALCIUM, HIGH CO2 AND ELEVATED TEMPERATURES ON QUALITY OF STORED BARTLETT PEARS

Abstract

Bartlett pears (Pyrus communis L.) were subjected to preharvest sprays of butanedioic acid mono(2, 2-dimethyl hydrazide (daminozide) and gibberellic acid (GA3) and to prestorage treatments with CaCl2, diphenylamine (DPA), high CO2 and elevated temperatures. Treated and control fruit were evaluated for skin color, firmness, soluble solids and titratable acidity at harvest and after a storage period of 60 d at 0 °C. Incidence of core breakdown was assessed on fruit ripened for 7 d at 20 °C immediately after cold storage. Pears dipped in CaCl2, CaCl2 + guar gum and calcium chelate (THIS®) + guar gum solutions had less breakdown than untreated fruit. Appreciable skin injury in the form of small black lesions was evident in the pears dipped in calcium solutions. Washing the fruit 7 d after treatment reduced but did not eliminate the incidence of injury. Prestorage treatments with CO2 (10 d at 15% CO2), heat (two or more days at 30–40 °C) and DPA (2000 mg L−1) also reduced the incidence of core breakdown. Preharvest sprays of daminozide resulted in a higher incidence of core breakdown in 2 of the 6 yr, while GA3 foliar sprays caused a higher incidence of breakdown in one year only. Fruit firmness, soluble solids and titratable acidity levels were not affected by treatments in a consistent manner.Key words: Core breakdown, skin color, firmness, soluble solids, titratable acidity, skin injury, Pyrus communis