Eliminating Ethylene Sensitivity | LifeSpan
Ethylene is the most important of the volatile organic compounds produced in trace quantities from the respiratory reactions. Ethylene is a ripening hormone that can initiate the climacteric surge in fruit. It may achieve this result with as little as 0.1 ppm of ethylene present in the produce tissue. As well as ethylene being produced by fruit and vegetables, ethylene may be introduced into the storage environment. The burning of fossil fuels will always produce trace quantities of ethylene.
Thus the exhaust fumes from trucks entering a refrigerated van will contain small amounts of
ethylene, as will the exhaust fumes from petrol or gas fork trucks used inside coolstores.
Different produce has different sensitivity to ethylene. Whilst some fruit are sensitive to less than1 ppm, other fruits and vegetables require levels well above 100 ppm to initiate ripening or other metabolic responses. Also produce has different rates of ethylene production. Generally produce that is sensitive to ethylene only produces very low levels of ethylene. Hence mixed loads of produce may contain some produce that generates large quantities of ethylene, and other produce that is sensitive to these levels of ethylene.
Given the range of options that can lead to ethylene initiated metabolic response in fresh produce, there are only two alternatives to prevent such responses in sensitive produce. Either ethylene needs to be scrubbed from the atmosphere surrounding the produce to levels below 0.1 ppm, or alternately the produce must be desensitised to the presence of ethylene. In commercial practice, ethylene cannot be scrubbed to below 0.1 ppm inside an MAP package unless there is substantial gas circulation in the headspace. Hence LifeSpan deals with ethylene by desensitising the produce.
We have determined that if an MA contains more than approximately 5% carbon dioxide, then it is
possible to block the molecular sites in the produce where ethylene normally attaches to allow
enzymic reactions to proceed. If ethylene is blocked from attaching to the produce, then the
ethylene cannot initiate metabolic responses. This result has occurred because the relatively high levels of carbon dioxide in the atmosphere (5% CO2 vs. 1 ppm of ethylene) attach to every
molecular site in the produce even though carbon dioxide is not strongly attracted to these sites.
The LifeSpan approach means that ethylene levels can become quite high inside the MA package
without any negative consequences. We do not have to be concerned with the source of the
ethylene, and mixed loads may be quite acceptable.
