Effect of combined application of heat treatments and plastic packaging onkeeping quality of 'Oroblanco' fruit (Citrus grandis L. x C-paradisi Macf.)

Combinations of various heat treatments with individual fruit sealing, pack aging in polyethylene liners or waxing were tested as means to control path ological and physiological spoilage of 'Oroblanco' fruit (Citrus grandis L, x C. paradisi Macf.). The following heat treatments were used: curing at 3 6 degreesC for 72 h, hot water dip at 52 degreesC for 2 min or 'hot drench brushing' at 52, 56 or 60 degreesC for 10 s, The standard packinghouse trea tment included waxing with addition of thiabendazole (TBZ) and 2,4-D isopro pyl ester. The fruit was stored for 2 weeks at 1 degreesC (simulated low-te mperature quarantine treatment), followed by 12-13 weeks at 11 degreesC (si mulated sea transportation to Japan) and 1 additional week at 20 degreesC ( simulated retail shelf-life period). The lowest weight loss and the highest firmness were observed with individually sealed fruit. Polyethylene liners were usually more efficient for weight loss control than waxing. However, the liner packaging enhanced the risk of postharvest disease development, i f not accompanied by appropriate decay-controlling measures. Applying TBZ, hot water dip or curing controlled the development of postharvest pathogens , especially that of Penicillium molds. In another trial, both hot drench b rushing at 56 or 60 degreesC and hot water dip reduced decay incidence. Hot drench brushing at 60 degreesC and hot water dip slowed fruit softening an d reduced buttons abscission. In addition, the hot drench brushing at 60 de greesC significantly delayed the loss of 'Oroblanco' green rind color, espe cially at the stylar and stem ends of the fruit. The hot dip at 52 degreesC inhibited yellowing only when combined with individual seal-packaging. (C) 2000 Elsevier Science B.V. All rights reserved.