Why is cider brown when apple juice is yellow?

…asks reader Gordon. Nice one. Squeeze a load of apple pulp and what comes out is fairly clear, fairly golden. Give it a few minutes and suddenly it looks like the cider we all know: cloudy and brown with a noticeably duller (though still fabulous) flavor. What happened?

In a word: enzymes. Even though it looks like there’s only juice running out of a cider press, there’s quite a bit of apple flesh in there too, albeit in very small pieces. That flesh contains enzymes — non-living protein molecules that perform specific chemical tasks — which are specifically designed to spring into action as soon as they’re exposed to oxygen. Some of them begin disassembling molecules called phenols, transforming them into pigments which turn the bits of apple flesh brown (for more on why they do this, see this post right here). Thus the more bits of apple flesh that get left in the cider, the browner it becomes, which is why commercial juice makers go to great lengths to filter their squeezings as soon as they’re, um…squeezed.

But there are other ways of combating enzymes. Being proteins they’re senstive to temperature and so can be “denatured” (i.e. “wrecked”) with heat. This is a big part of the reason why larger cider and apple juice makers almost always pasteurize their product. The other reason is to kill off any dangerous microbes, but more on that later. The down side of heating apple cider is that it gives you a “cooked” apple flavor, but the compromise is generally worth the peace of mind, especially if you have small children. But I digress…