Is It Safe to Put Hot Food in the Fridge? And More Food Safety Questions, Answered

Faced with a steamy pan of food that needs refrigerating — or six, on holidays and other feast days — we may find ourselves in an apparent predicament: Do we wait for the food to cool on the counter (and risk lingering too long at temperatures that let harmful bacteria proliferate)? Or do we rush it to the fridge, potentially warming everything inside?

Despite persistent lore, the United States Department of Agriculture and other agencies agree: Hot food can — and in many cases, even should — be placed in the refrigerator right away, as long as it’s portioned in small batches.

So where did this unexorcised fear of too-warm milk and eggs come from? It’s a relic of the refrigerator’s 19th-century predecessor: the icebox. Commonly made of wood and lined with metal, with a compartment at the bottom for a hefty block of ice, it was “basically an insulated box,” said Helen Peavitt, social historian and author of “Refrigerator: The Story of Cool in the Kitchen.”

If you put hot food in the icebox, she explained, “the ice, which often wasn’t cheap to buy unless you happened to live near a source or could get it delivered, would melt much faster and need replacing sooner to keep the cooling power of the icebox working properly.”

Modern appliances rebound more effortlessly, thanks to chemical refrigerants and evaporator fans that help cold air circulate. Still, there are ways we can be even smarter and more efficient. Read on for tips to make cooling food safer and easier on your appliances and your electrical bill.

How do you safely store hot food in the refrigerator?

Before being refrigerated, divide dishes like lasagnas into smaller portions.Linda Xiao for The New York Times. Food Stylist: Monica Pierini.

Experts agree that the safest way to refrigerate hot food is to divide it into smaller portions that will cool down fast. To do this, you might carve whole roasts like turkey or ham and divide soups and casseroles into shallow containers no more than two inches deep. If possible, cover them only loosely at first to let steam escape before sealing tight.

According to the Food and Drug Administration, it’s safe to move even piping-hot food directly to the fridge at that point (within two hours maximum, or one hour when the ambient temperature is above 90 degrees Fahrenheit), as long as there’s room for cold air to circulate around the food. However, the main downside, Ms. Peavitt said, “is that you’ll spend more on the electricity needed to keep the temperature down — basically transferring the extra heat from inside to outside the fridge.”

To avoid making your fridge do all the work, speed up the process by stirring the pan here and there, and nestling it into an ice water bath first (either a sink or a bigger pan or bowl will do).

Though refrigerators have come a long way from the icebox days, brands and models vary in efficiency and can harbor secret warm spots. A couple of inexpensive appliance thermometers will bring peace of mind. The fridge should be at 40 degrees Fahrenheit or below; the freezer should be at zero.

Should you put hot food directly in the freezer?

When freezing liquids, be sure to leave space at the top so they can expand.Christopher Testani for The New York Times. Food Stylist: Simon Andrews.

Ideally, no. The faster food freezes, the smaller and less disruptive its ice crystals will be, helping it keep more of its structure as it thaws, according to the U.S.D.A.: Meat and seafood will stay juicier, fruits and vegetables more intact, creamy, cheesy emulsions less prone to splitting.

So quickly ice down any food heading to the freezer or give it a stint in the fridge first. And when freezing liquids, be sure to leave space at the top so they can expand — not explode — as they freeze (an inch for pint-size containers, an inch and a half for quart-size and bigger), said Kantha Shelke, a senior lecturer of food safety regulations at Johns Hopkins University. Solids should get at least half an inch, too, so there’s clearance to make a tight seal and expand a bit.

What are the best containers for storing food in the fridge and freezer?

You have options. Dr. Shelke recommends glass containers — especially durable tempered glass — as they won’t absorb odors or stains and are safe for reheating in the oven and microwave, though they’re also relatively heavy and breakable. Silicone bags are lighter weight and not fragile, but they’re trickier to clean and need some pampering to do away with stubborn smells. And aluminum foil and freezer paper are handy for oddly shaped hunks of casseroles and meats.

But Dr. Shelke cautions against putting hot food directly into plastic containers, which can leach harmful chemicals, such as BPA, phthalates and potentially PFAS, especially as the plastic degrades with time and repeated contact with acidic and oily foods. And don’t store hot foods in single-use plastics like takeout containers and yogurt tubs, which aren’t designed for repeated use or heat exposure, Dr. Shelke said. Whatever you choose to use, it should be labeled freezer-safe.

Can I cool hot food outside if it’s 40 degrees Fahrenheit or below?

Yes, with some caveats. “Outdoor cooling can be helpful, but because temperatures can be unpredictable, it’s safest to use this as a temporary measure rather than a substitute for fridge or freezer storage,” said Betty Yaohua Feng, an associate professor in the Department of Food Science at Purdue University. A cooler with ice packs is a better option, especially for drinks and less perishable foods.

If you need to spill over into the outdoors, Dr. Feng recommends tightly sealing containers to keep out dust and wildlife that could carry pathogens, avoiding direct sunlight and making sure the temperature never rises above 40 degrees Fahrenheit.

Is there anything to keep in mind for the holidays, when there’s lots of warm leftovers to go into a crowded fridge?

Ms. Peavitt suggests clearing out your fridge before larger events and feasts, adding, “Not all foods that we keep in the refrigerator actually need to be there.” She listed unopened pickle jars, ketchup, lots of fruit and berries and peanut butter as prime examples that are often kept in the fridge and don’t need to be.

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