I’m sure all growers are aware of ethylene. It is produced by all fruits at different rates, and it is usually necessary to reduce it to low levels to control fruit maturity.
In some fruit (e.g. bananas) ethylene is actually used to ripen the product.
Measuring ethylene levels
Measuring ethylene levels has been difficult, especially at levels between 0.5 ppm and 1 ppm that are needed to control apple maturity.
However, recent developments from several suppliers has meant that ethylene can now be measured accurately down to less than 1 ppm.
These analysers can be either portable or incorporated into a centralised control system.
Since background levels in air (depending on location) can be up to 2 ppm, you can appreciate that it is important to use a correctly designed and proven analyser.
Methods to control ethylene
Smartfresh™: Use of Smartfresh has proven to be a very efficient treatment; and results speak for themselves.
Filter pads: Organic fruit growers can install specially impregnated filter pads in the CA room. However, care needs to be taken that there is sufficient capacity placed in the room to ensure effective control during the storage period.
Since organic fruit is generally picked more mature (to improve flavour), it would be important to measure ethylene levels regularly during CA storage. It is very important to ensure that over-mature fruit is not CA stored.
Scrubbers: Ethylene scrubbers utilising electrically heated catalysts have been available for some years. These units, if sized correctly, can control ethylene effectively below 0.5 ppm.
I have had some experience with measuring and controlling ethylene in kiwifruit CA storage in New Zealand. There was no difficulty in achieving the low levels required for longer term storage of this fruit using the heated catalyst machine that we supplied.
Effects of ethylene
There is some evidence of reduction in rots in trial work when ethylene levels are controlled below 1 ppm.
Research indicates that when ethylene levels start to rise in CA storage, fruit needs to be marketed as soon as practical.
Once ethylene levels take off—reaching levels above 2 ppm—it is not possible to get them back under control with equipment sized to control ethylene at normal levels.
Next step for quality fruit
Growers are constantly striving to produce the best quality fruit for the market. An investment in an accurate ethylene analyser seems a logical next step in determining ethylene levels in your stores.
For contact details and other great articles see the May-June 2012 issue of Tree Fruit
