Once you bake with flour that was wheat three days ago, the bag on the supermarket shelf tastes like dust. Here's the science of why.

The germ is the flavor

Wheat has three parts — bran, endosperm, and germ. The germ holds the oils, the vitamins, and most of the flavor. Whole-grain flour keeps the germ, and the germ starts to oxidize the moment it's milled.

Stale is slow

It doesn't go bad overnight. It just goes flat — the oils turn, the aroma fades, and by the time it's been sitting for a year, you're baking with what's left of the flavor, not the flavor itself.

The fix

Buy flour that's milled to order, and bake it within a few months. It's the single biggest upgrade you can make, and it costs almost nothing extra.