Pre-grated, bagged cheese can be kind of depressing. For one thing, it's coated with a dusting of cornstarch to prevent the shreds from sticking to each other, which subtly changes the experience, says beachmouse. For another, it's usually poor-quality cheese. "All you'll find pre-grated are the lowest quality, most boring cheeses out there—an exception being the quality in-store-grated Parmigiano and such that you can find at places like Whole Foods, but even then that's only a good thing if you're going to use it all right away," says BobB. "Which brings up the freshness factor—all that extra surface area allows the cheese to dry out and lose flavor quickly. Grate your own as you need it, and you control the quality AND the freshness."
But is there ever a time for pre-grated cheese? "I wouldn't use it in a cheese sauce," says onceadaylily, "but I have noticed that the pre-shred melts and browns more quickly in an oven dish. I suppose that is because it is drier (that is the downside of the surface area exposed), which doesn't make it taste better, to me, but can give a nice ... chewiness. If you're in the mood for that. I've had such occasions." Just check the stuff carefully for mold, says chef chicklet, as "sometimes you'll find small little green flecks in the pre-shredded stuff and it ain't parsley."
Discuss: Grated cheese