General Question

Jeruba's avatar

Cover a dish with oiled aluminum foil?

Asked by Jeruba (48931points) March 13th, 2009

Here’s a good-looking recipe for vegetable lasagne.

The recipe is designed to be baked ahead and frozen. The instructions for heating begin: “To Bake From Frozen: Remove plastic wrap; cover baking dish with lightly oiled aluminum foil, and place on a large rimmed baking sheet.”

Oiled aluminum foil? What’s that about? And which side is supposed to be oiled? I never heard of this before.

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18 Answers

augustlan's avatar

I’ve never heard of it either, but it makes sense. Oil the underside, and the cheese won’t peel off when you remove the foil. Kind of brilliant, actually!

steve6's avatar

It will help caramelize (brown) the top layer of the dish.

Jeruba's avatar

Browning = caramelizing? Always? I would have thought it would brown best uncovered.

So—is Aug right, then?—inside?

How do you oil aluminum foil?

steve6's avatar

It does brown better uncovered. The problem is it also dries out easier. I would guess the oil is also to keep it from sticking on the underside.

steve6's avatar

@Jeruba add an f and you’ve got foil!

augustlan's avatar

I’m guessing you could spray it with non-stick spray, or brush a little oil on the foil. When I cook lasagna, I take the foil off for the last 15 (I think) minutes to brown the top. I always do lose a little cheese to the foil though. I think I’ll try this next time.

Lightlyseared's avatar

It’s foil that you’ve covered in oil. Just like when they say lightly butter a baking tray.

bythebay's avatar

Whenever I cook lasagna, or anything that will actually be in close proximity to the aluminum foil, I always spray the foil with non-stick spray before actually covering the dish. As @augustlan mentioned; you won’t lose any cheese or other good stuff.

Also, the difference in the two sides of the foil is only there as a byproduct of the manufacturing process. There is negligible difference in reflectivity and therefore, no meaningful top or bottom.

AlfredaPrufrock's avatar

That does look like a good recipe!

I would spray it with non-stick spray, bake it covered for the majority of the time so the foil steams the cooking of the lasagna, then take the foil off for the last 10 minutes or so.

I make crepes and use them instead of lasagna noodles. Yummy. Makes a lighter tasting lasagna.

marinelife's avatar

Because lasagna is so thick, you need the foil so the dish won’t dry out before it is heated through.

The oiling (I would also go with non-stick spray) is to prevent the cheese sticking as Augustlan said.

AlfredaPrufrock's avatar

You need the steam to cook the dish, Especially if you’re putting a frozen casserole in the oven.

I’m glad you posted this; I’ve signed up to take dinner to a neighbor where the mom was in a terrible freak accident (she’s okay, but it’s a long mend) and the family prefers not to eat meat.

laureth's avatar

Acid is the enemy of aluminum. Tomatoes are full of acid. I imagine the oil would be a sort of barrier between the tomato acid and the aluminum.

When I’ve kept non-oiled foil over something tomatoey in the ‘fridge for a while, I’ve seen the acid actually eat through bits of the foil and leave holes. The aluminum then gets into the food, and it’s not very healthy to eat. (Among other things, an excess of aluminum in the diet is implicated in Alzheimer’s disease later.)

This is the same reason that you shouldn’t cook tomato sauces in aluminum pots.

Actually, I never thought to oil the foil, I just avoided using it – so thanks for the tip! :)

Lightlyseared's avatar


The people who suggested that screwed up their research because they had no grasp of statistics.

laureth's avatar

@Lightlyseared – Huh. It was what I’d always heard, but after you said that I went and looked. It appears that the Alzheimer’s Society says there’s circumstantial evidence linking the two, but that it’s unlikely. Also, Canada seems to think the jury’s still out.

Looks like I learned something new today. :) Thanks for pointing that out.

steve6's avatar

We had the Al discussion a few weeks ago (in detail).

Jeruba's avatar

Thanks for great answers, folks. I will try this too when covering lasagne. And I think I will also try that yummy-sounding recipe.

When I said “which side?” I just meant “side facing lasagne or side not facing lasagne.” When you have no idea of the purpose, the answer isn’t obvious.

evelyns_pet_zebra's avatar

I read somewhere that the shiny side of aluminum foil gets that way from having oil on it during the manufacturing process. Not sure where I read that, maybe it was on Fluther. I spend an awful lot of time on Fluther anymore. Of course, it oculd have been on snopes or maybe one of my favorite skeptic sites.

sorry if that is off topic.

laureth's avatar

@steve6 – Sorry, I must have missed it. (I miss a lot of discussion here when I’m doing things like work, school, reading books, and cuddling with my spouse.)

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