Blanching Isn't Just Par-Cooking

Photo by ilovebutter, CC BY 2.0, via Wikimedia Commons

Vegetables carry enzymes that keep breaking down color, flavor, and nutrients even after they're picked, which is why frozen vegetables go mushy and dull if they weren't blanched first. A brief plunge into boiling water, followed immediately by an ice bath, heats the vegetable just enough to permanently deactivate those enzymes, while also driving trapped air out of the plant tissue — which is what makes blanched green vegetables look more vividly colored, not less. Skip the blanch before freezing and the vegetables will still be technically edible months later, just faded, soft, and flatter-tasting than they should be.