The FoodPrint Guide to Freezing

What Even Is Freezing?

Freezing (when matter in a liquid state transitions into a solid state) happens at different temperatures (or “freezing points”) for different substances. For water, that point is 32 F (or 0 C). Water freezes through a process of crystallization: Molecules slow down as they get colder, eventually falling into a crystal “lattice” that keeps them fixed in place.

In the context of food, we use freezing to prevent the growth of bacteria, mold, yeast, pathogens or other microorganisms, which keeps things from decaying or becoming dangerous to eat. Most microorganisms will become dormant at temperatures of 0 F (-18 C) or lower, though freezing does not necessarily kill them.

Freezing in snow, frost or ice was practiced long before the introduction of mechanical freezers. These days, there are a few methods you’ll see with more frequency. In an industrial setting, cryogenic freezing (or “flash freezing”) is most common and works much faster than most people can achieve at home. Clarence Birdseye, often acknowledged as the father of modern frozen food, invented a method that involved holding already-packaged food under pressure between chemically cooled metal plates; other techniques include blasting food with very cold air or immersing it in liquid nitrogen (which you may have also seen on “The Bear”).

The freezer compartments we see today in at-home refrigerators, which became standard around the 1950s, work by using vapor-compression with a refrigerant to remove heat and release it into your kitchen. It’s complicated, but here’s a simple-ish explanation.

What Can I Freeze?

Short answer: anything! Longer answer: anything, but some foods react better than others (and certain things aren’t really worth it). “What can’t I freeze?” is perhaps a more helpful question.

There’s a reason some foods seem different after defrosting. “Freezing can influence the texture of foods once thawed,” says Julia Skinner, founder of Root and author of 2022’s “Our Fermented Lives.” When larger ice crystals form, they can rupture the cell walls within a fruit, vegetable or cut of meat — not only compromising its structure but also causing it to lose more of its moisture while thawing, and sometimes even changing the flavor. For this reason, produce with very high moisture content (citrus, cucumbers, lettuce and other things mostly eaten raw) will probably not be quite the same.

If texture is not that important to the end product, it’s a different story. “Berries, for example, get soft if frozen then thawed,” Skinner says, but will work just fine in a pie, jam or smoothie.

Sometimes, the moisture loss can be a good thing, especially if you want access to those liquids: “We have found that vegetable and fruit-based purees tend to ice up more and separate when thawing,” says Evan Hennessey, chef at Stages at One Washington in Dover, New Hampshire. “We actually use [that] to our advantage when clarifying those juices.”

The impact of crystallization also explains why raw meat will usually hold up better in the freezer than meat that’s already been cooked. Cooking already reduces the moisture content, and after cooked meat loses even more liquid while defrosting, the final texture may not be ideal.

“Many foods do freeze well,” Skinner notes, but there are certain foods for which it might be worth lowering your freezing expectations:

• Skinner says she’s never had luck with avocados, though “If you use them frozen in smoothies they seem to work well.”
• Fried or otherwise crispy foods will likely go soggy.
• Freezing eggs will change their texture, especially for the yolk (which goes a bit gummy).
• Potatoes change texture and may become mealy if frozen after cooking.
• Emulsions like mayonnaise and creamy sauces will also be compromised by large ice crystals, and separate when thawed…
• …meaning tuna salad, macaroni salad and their peers probably won’t do well in the freezer, either.
• Many say it’s fine to freeze milk, yogurt and sour cream, though The Washington Post food section recommends against it. Butter, which generally freezes well, is an exception, as is ice cream — more on that later.

On the other hand, WaPo reported that some ingredients are actually best stored in the freezer, including yeast, flour and tomato paste. It’s also a great place to store nuts, especially oilier ones that easily spoil or start to taste stale, like pine nuts.

How Long Will Things Last?

According to the USDA, because 0 F temperatures will keep foods safe almost indefinitely, any guidance about how long something will last in the freezer is a matter of quality — basically, at what point is it not worth eating?

Foodsafety.gov has a handy chart for estimating the lifespan of many foods, and the National Center for Home Food Preservation also offers some guidance. Some basics:

• Fruits and vegetables can last eight to 12 months.
• Processed meats like cold cuts and hot dogs are best within one to two months, and ground meat will last closer to three or four…
• …while other meats can last up to a year when frozen raw. The larger the cut (or animal, like a whole turkey), the longer it will stay good.
• Fish is best when used within three to six months of freezing.
• Casseroles, soups, stews and frozen entrees are generally best within the three-month mark.
• For one of the most common freezer items, we asked Alec Jaffe, founder and CEO of Alec’s Ice Cream: “A sealed container can last up to two years,” he said; “the colder the better, and try to avoid temperature fluctuations…ice cream does not like big changes in temperature.”

One big thing you can do to prolong the life of your frozen foods is to limit their exposure to air. The phenomenon known as “freezer burn” is often caused by exposure to the cold, dry air inside the freezer, leading parts of food to become overly desiccated. “Some foods are more liable to freezer burn,” says Skinner, including “foods with a high moisture content.” Airtight containers, and wrapping materials like foil and freezer paper, are your friend.

How Do I Defrost?

First of all, don’t do it on the counter (or outside). Tempting as it is, this puts food into what the USDA calls the “danger zone” — the range between 40 F and 140 F where dangerous bacteria can grow rapidly. (Remember, freezing won’t kill any microorganisms.) The agency’s Food Safety and Inspection Service has a helpful guide to defrosting safely. Best case scenario, you’ll have enough lead time to defrost in the most reliable way: by taking your food out of the freezer and moving it next door to the fridge.

A somewhat faster method is to package your frozen food in a leakproof wrap or bag and submerge it in cold water, never warm, changing the water frequently and using the ingredient immediately once it’s thawed. Faster yet, use the microwave. It might be a little uneven — maybe some parts will start to cook, or some will remain on the icy side — but it works in a pinch.

Hennessy shared a defrosting technique to help clarify frozen liquids like broths or juices: After freezing the liquid into a flat slab, he places it in a perforated, cheesecloth-lined pan (with a catch pan underneath) and lets it thaw slowly in the fridge. “The impurities and fats are caught in the cheesecloth and we are left with a much cleaner, more pure tasting stock.”

Some foods can be reheated or cooked without defrosting first, though it will, of course, take longer.

• Prepared foods and dishes, such as casserole, can generally go straight into the oven.
• Frozen slices of bread do fine in the toaster.
• Frozen fruit can be cooked directly into syrups or desserts like pies, or blended into a smoothie.
• Vegetables and meat can also be cooked from frozen, but meat can be easier to work with and create a better end product when defrosted first.
• Frozen meat should not be used in a slow cooker, since it may lead to the growth of bacteria.
• Eggs and dairy products are best thawed in the fridge before using.

If a frozen ingredient seems like it won’t provide the most pleasant eating experience on its own, throw it into a stew, risotto or casserole or mix into a cake batter or other baked good. If it smells off, don’t eat it.

What Else Can Freezing Do?

Sometimes, you’ll be using freezing not to preserve something but to make something new. Ice cream is a classic example. “It’s a great thing to make at home,” says Jaffe, who says “you can get really wild with the flavors.” (Try incorporating squishy fruits, citrus rinds and other food that might go to waste.) Again, the size of the ice crystals matters. “The magic behind making creamy ice cream from a molecular standpoint is in adding the perfect amount of fat and sugar molecules to keep the ice crystals super tiny,” Jaffe explains. Though it’s possible to make ice cream directly in a home freezer, you’ll also have to incorporate air — usually done via churning in an automatic or hand-crank ice cream maker — to nail the texture. 

If you don’t own an ice cream maker, try Skinner’s simple vegan version. “I make a ton of frozen treats,” she says, “but when I was testing recipes for [my online course] ‘Preserving Abundance’ I fell in love with making vegan banana ice cream.” The recipe is almost too good to be true, and works great even with bruised or browning fruit: “Basically just mash up a banana, freeze it (stirring a couple times, maybe once every hour or two), then enjoy.”

As a fine dining chef, Hennessey regularly plays around with freezing in his restaurant kitchen. A recent favorite trick? “Similar to the viral frozen [shaved] fruit dessert trend that’s going around, I enjoy doing a similar technique with vegetables,” he says. “We intentionally freeze whole onions without the peels, then microplane them in their frozen state to purposely obtain a soft onion puree that we can sweat in butter for things like risotto or slow-cooked beans.”