Question
We are struggling with eggplant damage in transport and handling. We have problems with two things: ethylene damage (we think the calyxes are falling and flesh is browning; the produce is on mixed loads with apples, etc. on trucks) and chilling injury. We advise 14-16°C for fruit quality but I have read recommendations for quick cooling to 10°C after harvest with forced air cooling. What air temperature is best for cooling? How are the eggplants packed? Don’t you have chilling injury with this quick cooling after harvest?
Answer
A good reading of our Eggplant Produce Fact Sheet should be helpful to you. At a temperature of 14-16°C, dehydration will likely lead to browning of the calyxes and the impact of ethylene will be higher at the warmer temperatures. Ethylene, dehydration and chilling injury will all cause discoloration of the calyx; see examples in the photo album with the Eggplant Produce Facts. In a study on 3 types of eggplant grown in California we did not find chilling damage at 10°C. The days required to achieve visible symptoms of chilling injury at different temperatures below 10°C are summarized in the Eggplant Produce Facts. Eggplants are often wrapped in tissue paper to minimize scuffing and then packed in a carton box for forced air cooling; alternatively they are hydrocooled and packed in waxed cartons or containers with plastic liners. There is no evidence that I am aware for chill damage when eggplants (or any product for that matter) are forced air cooled (air temperatures are typically 7-10°C). It takes a long time to achieve chilling symptoms, much longer than the few hours needed to cool the eggplants. It is important, however, that the product not be left on the forced air cooler too long or excessive dehydration will occur (calyx drying and loss of gloss). For more information about forced-air cooling of fresh produce, consult the Cooling Manual by Jim Thompson and colleagues.
-Marita Cantwell