I receive the Postharvest newsletter, and find it very interesting! I would like to know if any research has been done on the use of ethylene absorbers for apples, and the efficacy thereof or not.
If so, would this differ for certain varieties, e.g. Royal Gala, Golden Delicious, Granny Smith or Red Delicious? (C.F.)
Research has been done on ethylene absorbers for apples, and a number of strategies have been tested, with some success. I'm familiar with the use of potassium permanganate absorbers and catalytic oxidizers (Swingtherm). Ozone lamps (which absorb ethylene by oxidation by singlet oxygen at the lamp surface, sometimes mediated by a titanium glass catalyst) might also be effective. As you probably know, apples produce a lot of ethylene in storage if they are harvested close to the ideal maturity. CA storage greatly reduces production and response to ethylene and this is probably one of the reasons that it is so effective. The spectacular effects of 1-MCP on quality of stored apples is another demonstration of the importance of reducing the effects of ethylene in apples. I'm copying Beth Mitcham on this reply - she is closer to the current state of play than I.
I agree with Michael's comments. The trick with ethylene scrubbing is to get the ethylene concentration low enough. Usually it must be below 1ppm for benefit. This can be challenging for varieties that produce more ethylene, such as Royal Gala, and easier for those that produce less ethylene, such as Granny Smith. The temperature of the fruit will also influence ethylene production. You will want to have the fruit temperature at 0 degrees Celsius or very close to that temperature.