milk chocolate

There is milk in milk chocolate. So why doesn’t milk chocolate need to be refrigerated? I know that baked things containing milk, such as scones or cornbread won’t spoil as quickly as raw milk, but they will spoil eventually. But a chocolate bar will last sort of indefinitely.

Two things are important here:

firstly, unless you’re talking about UHT milk, normal pasteurised milk contains microorganisms which cause it to go off. Refrigeration slows, but doesn’t stop, their growth.
When you bake something, the heat of cooking sterilises it. In order to spoil, it needs to be reinfected by microorgnisms or mould spores, so it should last longer.

Secondly, the amount of water and sugar in a food can affect whether anything can live on it. If the sugar concentration is high enough, microorganisms cannot live on it. A good example is honey, which I believe was found still edible in the Great Pyramid (no cite I’m afraid!) I think this is caused by the different solution concentrations inside and outside the cells of a microorganism which destroys them by osmosis.

I guess milk chocolate lasts practically forever for the second reason - its sugar concentration is high.

wait a minute… for something to go bad it also needs water. if it is dry the organisms that make it go bad cannot live. yes?

Sailor–yes, more or less. However, just because something is dry doesn’t mean that there’s no water in it. There’s bound to be a bit of residual fluid. Also, there is water in the atmosphere, so micro-organisms can draw on that.

It’s my duty; my duty as a complete and utter bastard.–Arnold J. Rimmer.

Lytic cell destruction, as matt mentioned, is a big part of keeping sugary foods from rotting. Keeping the fatty component from going rancid, though, is more difficult. There was a news article just a couple of months ago about something (bioflavonoids, I think) in chocolate keeping the various fats (from milk and the cocoa itself) from turning.

Sure, I’m all for moderation – as long as it’s not excessive.

Well I very much thank you! As a chef I wonder about these things. I remember wondering why does bread usually spoil faster than pastries? Obviously, sugar is probably the reason. Chocolate coated pastries last even longer! I knew that cooking sterilizes food, but I’m also aware that some foods, after cooking, will spoil in only a few hours unless kept above a certain temperature. Whereas other foods, like cookies, or smoked meats etc, will last longer or even relatively indefinitely. I’ve long known the ability of salt to preserve food, but it never occured to me that sugar is also a preservative. Sure makes sense though, as candied fruit is basically fruit that is cured with sugar. And I can see how the amount of moisture has an effect; fruit juice or jelly left out will spoil quickly, but a bowl of sugar or hard candy will last an eternity.
Anyway, thanks for the info, very helpful. About the fat going rancid, cocoa butter is definitely very stable in pure form; it is even sold as a hand lotion. And like most vegetable fats, like canola or olive oil, it will not spoil quickly. I believe butter or even margarine spoils more quickly because, besides fat, they also contain a large amount of water.
Here is another question: why will ants swarm over honey but not sugar?