Response of Tarocco Oranges to Picking Date, Postharvest Hot Water Dips, and Chilling Storage Temperature

Tarocco blood oranges (Citrus sinensis Linn. Obsek) were harvested monthly from November to April and dipped in water at 53 °C for 3 min before storage at 3 °C for 10 weeks and 1 additional week at 20 °C, which simulated a marketing period (SMP). Untreated fruit were used as control. No treatment damage was observed in fruit harvested in March. In contrast, hot water dipping caused severe damage to the peel in fruit picked earlier and later in the season. Susceptibility to chilling injury (CI) was greatest in fruit harvested between November and January, less in February, and negligible in March and April. Prestorage hot water dipping effectively alleviated CI in all samples, especially those which showed greater susceptibility. There was little rotting in fruit harvested between November and Januay, while fruit harvested between February and April exhibited a greater susceptibility, which varied with picking date. Hot water dipping gave beneficial effects on decay control of fruit harvested in February and March but was detrimental for fruit harvested in April. Fruit mass loss gradually increased with maturity stage and was seen to be promoted by hot water dips during both cold storage and SMP. The influence of hot water dipping on respiration rate, endogenous ethylene, maturity index (evaluated by °Brix/juice titratable acidity ratio), ethanol concentration in the juice, and electrolyte leakage from the flavedo tissue was nonsignificant. It was concluded that prestorage hot water dipping at 53 °C may be viable in limiting CI and decay control of Tarocco oranges during 10 weeks of cold storage and subsequent SMP when they are harvested at mid-season, January−February, but may be harmful to fruit harvested early or late in the season. Keywords: Citrus; chilling injury; harvest date; heat treatments; storage; rots; fruit quality