One of the great things about casseroles is that they're one of the easiest foods to freeze. With just a few simple tricks, you'll have a freezer stocked with delicious meals for future dinners.
To Pre-Bake or Not
In most cases, the best course is to not bake your casserole before freezing it. The reason is that the processes of baking and then freezing, only to re-bake again from the freezer when it's time to eat, cause all kinds of changes in the various ingredients of your casserole.
Pasta expands and absorbs water when baked, and when that water freezes, it crystallizes, altering the pasta's texture. Baking it a second time (when you pull it from the freezer) causes those crystals to evaporate as steam, leaving the pasta mushy. Similar changes occur when freezing dairy products, which can separate. Fats, proteins and starches likewise undergo various changes when subjected to baking, freezing and then re-baking.
And while casseroles are largely quite forgiving of all this, the fact is that overall, the quality of your casserole will suffer less if you only bake it once.
Your best bet is to prepare the casserole recipe as usual up until the point of putting the assembled casserole in the oven. At that point, pack your assembled ingredients into a container and pop it in the freezer.
The Best Containers For Freezing
Knowing in advance that you're going to be freezing your casserole before baking helps you decide what sort of container to use for storage.
You can certainly freeze it in whatever glass or ceramic casserole dish or metal pan you plan to bake it in, provided it is safe for both the freezer and the oven, or to be more specific, freezer-to-oven, which is the case for borosilicate glass such as Pyrex. The only downside is that this ties up that particular dish in your freezer.
If you know you'll be freezing your casserole, you can also build it, freeze it and bake it in a disposable foil pan. In either case, make sure the casserole dish is tightly covered with foil before freezing.
But, perhaps the best trick to line your baking dish with heavy duty foil, then build the casserole in the foil-lined dish, fold the foil over the top, then freeze. Once the casserole is frozen solid, simply remove the foil packet full of casserole from the dish—leaving the foil wrapped casserole in the freezer and liberating your baking dish. When it's time to bake, simply replace the casserole in the dish, and bake as usual. This method also prevents the risk of the glass baking dish from cracking, if it is placed directly from freezer into a hot oven.
How to Avoid Freezer Burn
What is freezer burn? It is the dry patches underneath the ice crystals that form on frozen food. The ice crystals themselves are simply moisture that's been pulled out of the food by the freezing process. In the freezer, moisture seeks the coldest spot, the exact location of which differs from freezer to freezer, but is not in the food itself. Therefore, the moisture is pulled to the surface, where it becomes trapped by the wrapper or container and forms ice crystals.
In most cases, you can just brush off the frost and be fine. Sometimes, there may be a dry discolored patch, which will, if eaten, have a different texture than the surrounding areas. However, it is still completely safe to eat.
The other good news is that while freezer burn can definitely affect large pieces of meat, for instance, that are frozen for a long time, it's not so much a problem with casseroles. Frost, yes, but not freezer burn. That's because freezer burn only happens at the surface, and casseroles usually have some sort of sauce on the surface, and sauce can't really dry out like the surface of a piece of meat can.
Frozen Casserole Shelf Life
Assuming your freezer is set to 0 F, or colder, your casserole will keep in the freezer for three to six months. You can freeze most casseroles for up to 3 months with little to no loss in quality. After three months, you may start to see some frost on the surface, although it's still safe to eat up for up to six months.
How to Reheat Frozen Casseroles
There is no reason to thaw your casserole before baking it. In fact, if you do defrost the casserole, you risk a soggy final product as liquid from any sauce may pool at the bottom of the casserole during defrost.
However, remember to modify the cooking time. A frozen casserole will take twice as long to cook as the original recipe calls for. So 45 minutes becomes 90. But do bake it at the same temperature as the original recipe calls for, and peel off the foil covering during the last 15 minutes of baking so that the top has a chance to brown.
Finally, if you are baking a casserole in a glass baking dish that has also been in the freezer, place the casserole in a cold oven and pre-heat with the dish inside. Placing a frozen glass baking dish into a hot oven runs the risk of the glass breaking with the dramatic change in temperature. Avoid this step by using a metal or foil pan to freeze in, or by using the foil packet method and a from-the-cabinet baking dish as described above.