Freezing and Food Safety
Check your freezer to ensure that it is at 0 degrees F or colder. A dedicated refrigerator-freezer thermometer is a must. You can usually get a set of two, one for the fridge and one for the freezer, for less than 10 bucks.
Freezing doesn't kill foodborne bacteria, but it massively slows down their ability to reproduce, which is why freezing prevents food spoilage. Once thawed, those bacteria wake back up and go about their business, which means it's time to either eat or cook that food.
Most foods don't fare well in a home freezer beyond two to three months, although guidelines for specific foods vary and this is generally a matter of quality rather than food safety.
Tips for Freezing Foods
Use resealable plastic containers or freezer bags, not glass, which can crack when subjected to rapid changes in temperature. And remember that freezer bags and sandwich bags are not the same thing. Freezer bags are made of thicker plastic, and the plastic itself contains an additive that prevents it from becoming brittle in the freezer, which ordinary sandwich or storage bags do not.
Freeze in individual portions where possible. Speeds defrosting and avoids waste. For example, divide soups and stews into smaller bags, like one or two portions apiece, rather than freezing an entire batch in a single container.
Smaller sheet pans are handy for freezing berries, banana slices, green beans and other small items so they don't stick together. Spread them on the sheet pan, freeze, then transfer to freezer bags.
Think of freezing as a way to preserve freshness rather than merely avoiding spoilage. In other words, freezing food when it's at its peak of freshness will give you a better result after you thaw it. Freezing blueberries once they start to go mushy will only give you mushy thawed blueberries.
Removing every last bit of air from resealable containers or zip-top freezer bags is nearly impossible, which means that some amount of freezer burn is inevitable after awhile. But if you plan to do a lot of freezing, a vacuum sealer, which does remove all the air, might be a good investment.
Cool cooked foods thoroughly before freezing. Not only does adding hot foods to the freezer cause a food safety hazard (because of the extra time the cooling food will spend in the so-called food temperature danger zone), but putting something hot into the freezer warms up the other foods that are in there, which can cause them to become unsafe.
Thawing Frozen Foods
In some cases, your frozen items can be used straight from the freezer. Examples are frozen berries that are going straight into a smoothie, or frozen dollops of tomato paste that are going straight into a soup, sauce or chili. Indeed, it's possible to cook frozen chicken breasts, or even a whole turkey straight from the freezer (although this last is definitely not the preferred technique).
In other cases, though, you'll need to thaw the food before working with it, and the safest way to do that, especially for high protein foods like meat, poultry and fish, is to move it to the refrigerator overnight. Trying to defrost frozen meats, fish or poultry at room temperature, or using warm or hot water, can lead to a case of food poisoning.
Here are some specific tips and guidelines for freezing various foods.
Freezing Fresh Meat and Seafood
With these foods it is especially important to freeze them right away, as soon as you get it home, if you know you are planning to freeze them. In other words, don't hold raw meat in the fridge for three days and then freeze it.
Remove from styrofoam or plastic supermarket trays. Divide ground meats into portions or patties before freezing. Double-wrapping (either two layers of plastic wrap or a layer of wrap and then zip-top freezer bag) will extend shelf-life and prevent freezer burn.
Store up to 2 to 3 months in the coldest part of the freezer, i.e. the back, away from the door. Thaw in the refrigerator overnight before cooking.
Freezing Fresh Produce
The best way to freeze fresh vegetables is to blanch them first. Veggies need to be prepped for blanching in different ways (e.g. cutting broccoli into florets, peeling carrots and then slicing, seeding and slicing peppers, trimming stems from green beans and so on), but the general idea is to get the food into whatever form it will be eaten in.
Next, boil for a minute or two, then immediately transfer to an ice-water bath to halt the cooking. Then after draining and drying thoroughly (wet veggies will develop frost), spread on a sheet pan, freeze and then transfer to zip-top freezer bags.
Freezing fruits is similar, but you can skip the blanching. Note that you can freeze whole bananas in their peels. The peels will turn brown, but the fruit inside will stay bright and fresh. Store for 2 to 3 months.
Leafy vegetables like lettuce and kale as well as tomatoes and other produce with high water content don't freeze well.
You can freeze fresh herbs by chopping them, mixing them with a small amount of water or olive oil and then freezing this mixture in ice cube trays. Once frozen, transfer the cubes to zip-top freezer bags.
Freezing Dairy and Eggs
With whole eggs, the problem is that the expansion caused by freezing can cause the egg to burst its shell. Additionally, hard-cooked eggs can turn rubbery when frozen.
The best way to freeze whole eggs is to crack them into a bowl, lightly beat with a pinch of salt or sugar (depending on whether you're using for a sweet or savory dish) and freezing in a resealable container. Think about how many eggs you'll need and freeze them in that amount. You can also freeze the yolks and the whites separately.
Whole milk can be frozen, although it will separate, which will affect its quality when thawed, but you can still cook and bake with it. It's only when drinking it that you'd notice the difference.
Heavy cream freezes well but half and half doesn't. Dollops of whipped cream freeze nicely on a parchment-lined sheet pan (transfer to freezer bags).
Cheese can be frozen, cut into pieces and double wrapped. Cottage cheese and sour cream will turn grainy. Sticks of butter freeze extremely well but whipped butter doesn't.
Freezing Soups and Stews
When freezing soups and stews (which includes things like chili), take care to chill them completely in the refrigerator, at least until the fat rises to the top and hardens (which usually means overnight). Scrape off that fat and discard it, then transfer the soup to resealable containers or freezer bags.
You can almost always freeze a whole unbaked casserole (which includes lasagna) in its baking dish by wrapping it tightly with foil. Then thaw overnight before baking or transfer directly to a cold oven, heat the oven and bake. Allow extra time to ensure it's cooked through, and remove the foil during the last 20 minutes or so to crisp the top.
You can also parbake a casserole or lasagna and then freeze, thaw and reheat. But remember to bake it slightly less than all the way the first time as it will cook further during reheating. You should see bubbling sauce, and an instant read thermometer in the center should read at least 160 F.
Freezing Baked Goods
Baked breads, cakes and brownies can be fully cooled, then double-wrapped and frozen for 2 to 3 months. Unlike highly perishable foods, these items can be thawed, still wrapped, at room temperature. This includes cupcakes, muffins and quickbreads.
Cookies can be frozen in a resealable container or bag, but you can also freeze the dough, either in rolls (slice then bake) or in individual balls which you can bake directly from the freezer.