Storing your fruits:? Be aware of ethylene gas generating fruits!

(Written by Dr. CHOW YN at 2010-10-28 21:01:45; revised at 2011-12-24)

Try answering this simple senior high secondary school Biology question: What effects does ethylene(C2H4) have on plants?

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The most common answer  should be: it cause the senenscence and ripening of plants, especially fruits.

In fact ethylene is generated and given off by many ripening fruits and plant materials that have been damaged. This article looks at the implication of this phenomenon on the way you should store your fruits. The detailed chemical, physical and biological properties of ethylene is found here.         Ethylene is an odourless and colourless gas that is made up of two carbon and four hydrogen atoms. Because different types of plants and different parts of a plant (such as whole plants, flowers or fruits) have different sensitivities to the ethylene thus exposure to the same quantity of ethylene by different types of plant and plant parts will have different effects. For those who are very interested in the effects of ethylene on greenhouse crops, Cornell University’s Department of Horticulture provides a very comprehensive details of this phenomenon. In this site, a series of photographs on experiements with different plants (on the effects of ethylene exposure) are shown. North Carolina State University’s Deparment of Horticultural Science have published a great leaftlet on the effects of ethylene on a large number of plants, listing among others, the sensitivey range, concentration & exposure duration and visible symptoms on ethlyene effects on these plants. Apples as good generators of ethyleneThere are other factors which speed up the ripening process, by putting fruits in a warmer environment (like room temperature in Malaysia) will speed up ripening, conversely, putting fruits and vegetables in the refrigerator will generally slow down the ripening process and allow these to be kept for a longer period. But the spoiler of this axiom here is not other than ethylene. Remember, to all intend and purposes, the refrigerator is an enclosed space and the ethylene produced by the plant materials can only escape when you open the door! An article that have been published by Lifehacker recently spoke on the need to store apples separately from other fruits toavoid causing over-ripening of more sensitive fruits and vegetables. Produce Picker Blogcast provide a good account on why and how this can happen. However, these articles seemed to give the impression that among all the fruits and vegetables that we usually have in the house only apples can do these. In fact this is further than the truth! The humble banana is also a prolific producer of ethylene while ripening and putting banana next to other fruits has been shown to supercharge the ripening process of other more “susteptible” fruits. For the same reason, one will never store banana inside a refrigerator. One physcial property of ethylene that we need to know is that, ethylene with a molecular mass of 28 is lighter than air which has an average molecular mass of 28.97. So any ethylene produced by fruits and vegetables is going to rise up. Banana in fruit stallNow it does not require a genius to tell us that at the local fruits shop we see banana being hung on lines/wires from the beams of the ceiling, well above other fruits. This is so that any ethylene produced by the banana can escape easily (since ethylene is lighter than air)! If one pays enough attention, one will find out that a good ventilation system is a must for all fruit shops….otherwise they will have a big problem on hand if most of the fruits ripe pre-maturely and shortern their shelf-lives! So after knowing all these facts, you should know that after buying a bunch of banana, the best way to store it is to hang it as high as possible, unless of course you want to use the ethylene generated by the banana to ripen other fruits!

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