Reducing Susceptibility of Grapefruit to Chilling Injury during Cold Treatment

Abstract

With the expected ban on ethylene dibromide fumigation, cold exposure remains the only quarantine treatment for citrus fruit against the Mediterranean fruit fly. Following a cold treatment, ‘Marsh’ grapefruit (Citrus paradisi Macf.) developed chilling injury (Cl), mostly in the form of slight peel pitting on 3% to 10% of the fruit depending on the season and on other factors. There was no difference in the incidence of Cl between fruit treated at 0°C for 10 days or at 2.2° for 16 days as regulations require. The cold treatment also enhanced decay development during long-term storage of the fruit at 11°. Mold rots developed on Cl peel pitting, and their incidence increased from 1.7% to 3.5% during a storage period of 12 weeks. The presence of the fungicide Thiabendazole (TBZ) in the wax coating of the fruit reduced the incidence of Cl by more than 50%. Delayed cooling, i.e., keeping the freshly harvested packed fruit for 6 days at 17°C prior to initiation of cold treatment, reduced the incidence of Cl by the same extent. By combining a TBZ treatment with delayed cooling, the susceptibility of grapefruit to Cl can be reduced, and cold treatment can be practiced with a low risk of Cl and subsequent decay development.

Tomato Fruit Temperature Before Chilling Influences Ripening After Chilling

“…Treatments that reduce symptoms of chill ing injury include conditioning near the chilling temperature, intermittent warming during chilling, low-pressure storage, in creased atmospheric C 0 2 levels, and pre treatm ents w ith Ca or eth ylen e (1 3 ). C h illing injury was reduced in fruit of bell pepper (12) and grapefruit (3,6), and seedlings of tomato (8,19) and ornamentals (15) by con ditioning at a cool, but nonchilling temper ature. Intermittent warming also can reduce chilling injury in citrus (4), cucumbers and sweet peppers (18), peaches and nectarines (2,17), and potatoes (7).…”