Question
We utilize your compatibility chart frequently as a guideline for produce storage, but due to limited storage rooms at each of our facilities sometimes we still have to mix high ethylene producers and ethylene sensitive produce and I would like to be as informed as possible when I make my mixing decisions. I note in many instances that ethylene levels should be below 1ppm, but looking at Zespri’s regulations, kiwifruit, for example, has to be stored at a maximum of 0.02ppm, therefore kiwifruit is far more sensitive than “below 1ppm.”
I am sure that produce such as Lettuce and Broccoli are far more sensitive than 1ppm and probably so are many more commodities. Are there any studies covering the actual sensitivity of each commodity? Fresh produce facts pages simply states these commodities are simply ‘’sensitive, or ‘’very sensitive’’ to ethylene, rather than ‘’x’’ level is safe.
I am also looking for information regarding how quickly ethylene has an effect. Eg. a lettuce placed in a 2ppm environment for 1/2 a day – what has this done to the shelf life and quality for the consumer? My guess is that the supermarket wouldn’t notice the damage, but the consumer has lost value.
Any feedback would be great, thanks. (B.R.)
Answer
We know that many products are sensitive to ethylene in the storage environment, and the negative effects of ethylene exposure include accelerated ripening, increased susceptibility to disease, accelerated yellowing, and increased bitterness (in carrots). However, this response is very much a time/temperature relationship. Thus, for lettuce, russet spotting is caused by ethylene at temperatures above 4°C, but storage at the proper temperature (0°C) eliminates the problem. Kiwifruit is a special case where even at 0°C ethylene at very low levels can result in accelerated softening. Our advice, where mixing ethylene producing and ethylene sensitive product is unavoidable, is to maintain the proper storage temperature (close to 0°C for temperate products, 10°C for chilling-sensitive products) and ventilate with at least one air exchange per hour of exterior air drawn from above the storage building. These two measures will reduce the sensitivity of the product to ethylene, and reduce the level of ethylene to which they are exposed.
-Michael Reid