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Friday, October 19, 2012

Climacteric fruit

Among the many tales in Barry Estabrook's book, Tomatoland, an alleged expose of the industrial tomato farming practices in America, he describes this practice of tomatoes being picked hard and green, and then "artificially gassed until their skins acquire a marketable hue". Choosing words evocative of Nazi execution of prisoners, this is a carefully orchestrated illustration of the "appeal to nature" fallacy.

Truth is, tomatoes are just climacteric fruit; like bananas and persimmons.

Ripening hachiya persimmons
Climacteric fruit continue to ripen after they have been picked; the trigger for ripening is the gas ethylene. Ethylene is a small hydrocarbon, and can be the by product of oil processing; but plants also endogenously produce ethylene gas as a hormone. Make no mistake - regardless of source, the two are chemically identical. This is why adding a banana can speed up ripening in other fruit - bananas react to ripening by producing more ethylene (in biology, this is called a positive feedback loop).

So, at an industrial scale, climacteric fruit ripening can be sped up by increasing the ethylene concentration in the atmosphere. Nothing fancy, nothing nefarious. No comment, however, on the fact that cheap supermarket tomatoes taste ... well, bland. That's a genetic change linked with why the tomatoes are slow to ripen in the first place.

PS - A couple of non-climacteric fruit: strawberries and most grapes. These do not continue to ripen post picking.

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