Curing to prevent chilling injury during cold disinfestation and to improve the external and internal quality of lemons

Abstract

In 1988, 2 experiments were undertaken to test the effect of curing on the external and internal quality of lemons. The experiments were designed to determine the optimum postharvest handling regime for protecting lemons from chilling injury during the cold disinfestation process that is necessary for entry into markets such as Japan. In experiment 1, a mixture of Eureka and Lisbon lemons was cured for 0, 2,4, 8, 16, or 32 days at ambient temperature, then cold disinfested at 1¦C for 16 days and stored for 4, 8, or 16 weeks at 10¦C. In experiment 2, a mixture of Eureka and Lisbon lemons was treated with either thiabendazole (TBZ) (500 mg a.i./L) or sodium ortho-phenyl phenate (SOPP) (200 mg a.i./L) by bulk dipping before processing, or by an in-line spray during processing. The fruit was then cured for 0, 2, 4, 8, 16, or 32 days, cold disinfested as above, and stored at 10¦C for 28 days. Curing for 16 days reduced chilling injury symptoms in experiment 1 but increased oleocellosis in experiment 2. Curing for 16 days also reduced the incidence of fungal breakdown caused by Penicillium spp. and Geotrichum candidum Lk. ex. Pers. When used as a bulk dip for pretreating lemons prior to curing, TBZ was more effective at controlling fungal breakdown than when used as an in-line spray, and more effective than SOPP used as a bulk dip or in-line spray. Red spotting of the rind was also reduced by bulk dipping in TBZ. Curing for 4 or more days produced increases in extractable juice. Development of yellow colour occurred during curing for 16-32 days and was enhanced by storage at 10¦C. Curing for at least 4 days, when used in conjunction with a bulk dip of TBZ (500 mg a.i./L), can be used to protect lemons against fungal breakdown and to increase juice. Curing for 16-32 days can be used to develop even yellow coloration of the fruit and to decrease chilling injury.