Avoiding Chilling Damage in 'Hass' Avocado Fruit by Controlled Atmosphere Storage at Higher Temperature

Sea-freight distribution of `Hass' avocado (Persea americana) is by refrigerated containers, sometimes supplemented by controlled atmosphere (CA). With both refrigeration and CA prolonging the storage life of the fruit, there is a question as to whether the technologies can be traded. That is, by using CA at warmer temperatures to extend storage without the risk of chilling damage. In this project, the potential to avoid chilling damage by storing fruit at 7 degrees C in 2% O-2/2% CO2 CA instead of 5 degrees C in 2% O-2/2% CO2 CA or air has been investigated for fruit stored for 4 or 6 weeks. Increasing the storage temperature from 5 degrees C to 7 degrees C did not affect the quality of fruit immediately out of CA storage, with no significant difference in skin color, firmness, or skin disorders. Both CA storage regimes, at 5 degrees C or 7 degrees C, resulted in better fruit quality than for fruit that had been stored in air at 5 degrees C. Overall, CA at 7 degrees C was less effective at retarding the progression of ripening in storage than CA at 5 degrees C, although after 4 weeks of storage, fruit from both CA regimes took longer to ripen than the air-stored fruit. After 6 weeks of storage, there was no difference in ripening time between fruit that had been stored in CA at 7 degrees C or in air at 5 degrees C, with fruit that had been in CA at 5 degrees C still taking longest to ripen. However, the incidence of diffuse flesh discoloration ( DFD) in the air-stored fruit was high compared with that in fruit from CA at 7 degrees C or 5 degrees C. The main negative aspect to storing fruit in CA at 7 degrees C rather than at 5 degrees C was the higher incidence of rots in ripe fruit. While it was lower in the air-stored fruit, the incidence in fruit that had been stored in CA at 7 degrees C tended to be higher than that of the fruit stored in CA at 5 degrees C. It therefore appears that the potential for using CA at slightly higher temperatures to avoid chilling damage rests on the storage duration required and the risk of rots in the fruit.