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I was just wondering if there was a specific term to refer to fruits when they have undergone oxidation. That is, their flesh turns a yellowish-brown. This usually happens when the fruit has been left in the open air. I seem to remember that a few years ago, someone told me it was called "rust". However, I think "rust" usually refers to a plant disease that is fungal, isn't it? Or does rust refer to both? I've searched up the dictionaries, but it doesn't seem to be so.

Is there a single term for this?

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1  
I'm really tempted to say Fruit(2)O. :) –  gmcgath Dec 24 '12 at 17:55

5 Answers 5

Normally, this is just referred to as browning, or that the fruit (or vegetable) has turned brown. Per the recipes area at How Stuff Works:

the browning reaction results from the oxidation of phenolic compounds in the fruit under the action of an enzyme called polyphenol oxidase (PPO), which is common in plant tissues.

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An oxidized fruit is more likely to be called

ripe

or

overripe

than anything else. 'Rust' is a fungal organism like smut, blight, mold, mildew, or scum that actually grows on the fruit, and none of these are connected with ripeness or oxidation. They may of course occur at the same time (as well as bruising, when the fruit naturally falls off the branch).

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6  
I don't think this is what the O.P. is talking about. If you cut an apple open (whether or not it's overripe) and leave it in the air for several hours, it turns brown. This is a natural oxidation process, and can be delayed by putting lemon juice on it. This has nothing to do with the color change due to ripening. –  Peter Shor Sep 19 '11 at 18:14
    
@Peter: Oh. That makes sense. But the rest is still appropriate, confirming the OPs idea that 'rust' is a separate thing altogether. –  Mitch Sep 19 '11 at 18:18

I think you are right - the oxidation of fruit is called rust according to WiseGeek.

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P.S. Other sources like Your Mother was a Chemist call it browning of fruit. –  Bill Sep 19 '11 at 9:19
    
P.P.S. According to an explanation provided by David A. Katz in a science experiment, the oxidation process is known as enzymatic browning and occurs at warm temperatures when the pH of the plant material is between 5.0 and 7.0. Also, the brown pigments are known as melanins. –  Bill Sep 19 '11 at 10:11
    
WiseGeek says it's "a form of rust". It's not clear to me whether he's actually saying it's called rust, or whether he's just saying the chemical process is the same in the browning of fruit and the rusting of iron. –  Peter Shor Sep 19 '11 at 18:10
    
@PeterShor - Fair point, which is why I did further research, and discovered that it's commonly referred to as browning of fruit, even in the scientific community. Maybe I should add my P.S. and P.P.S. notes to the answer? I think whoever is reading this, though, will get the general idea. –  Bill Sep 19 '11 at 23:10

I've just heard the word "brown'.

The apples get brown after cutting, unless they are dipped in a water and lemon juice mixture to keep them from going brown.

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I understand "go brown", but "get brown"? –  Billy Sep 20 '11 at 4:46
    
"Become brown"? It may not be proper grammar, but that is what is said in at least parts of the US: "go brown", "get brown", "going brown", "getting brown", and "went brown" are all used. –  thursdaysgeek Sep 20 '11 at 17:40
    
I was just checking you hadn't made a typo. I've never heard "get brown". It sounds odd to my ears. –  Billy Sep 20 '11 at 21:34
    
@Billy: Now don't get angry. Or should it be become angry, be being angry ...? –  Kris Dec 29 '11 at 4:49

Because this process also often happens when the fruit undergoes some trauma (hail, landing on a hard surface), I would also call it bruising of the fruit.

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I think that "bruise" implies that the discolouration is due to trauma, and that using it to describe fruit that's turned brown simply through ageing would be misleading. –  Rupe Aug 5 at 9:50

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