Seriously, Stop Reheating Leftovers in the Container They Came in. Here's Why

CNET

28-05-2025

When hunger and laziness coalesce, reheating last night's takeout or the leftover pasta you took home from a restaurant in the microwave seems like the best idea. But if you don't do it properly, you could be ingesting microplastics and harmful chemicals.
But is plastic contamination as dangerous as experts say? All signs point to yes. Study after study has shown that the resulting chemical exposure of microplastics could pose significant health risks, linking to increases in medical issues like infertility and even cancer.
Most takeout containers are not heat-safe
Most black plastic containers are not microwave-safe.
Image by Marie LaFauci / Getty
"If you're using takeout containers to reheat food, they need to be labeled as heat-safe," advises Ricardo Jarquin, executive chef of Loews Coral Gables in Miami. "Most restaurants do not use them because they're more expensive."
Aluminum, cardboard and paper-based containers are typically plastic-free and safe to store and reheat food. Cheap plastic takeout containers are mostly not safe and should never be used to reheat food. Styrofoam is even worse because it melts in the microwave, a clear indication that it is an unsafe vessel for reheating food.
Read more: These 7 Takeout Containers Don't Belong in the Recycling Bin
What to use instead of plastic
It might sound like more work but bringing your own food storage container for leftovers is the safest bet.
FreshSplash/Getty
So what's the best way to reheat that delicious meal? We chatted with Jarquin, who has overseen culinary operations and food safety protocol for major hotel chains including Four Seasons, Hilton, and Marriott, as well as Hope Montgomery, owner of Brick & Mortar in St. Petersburg, FL, to get the skinny on safe use of takeout containers.
Ideally, the restaurant is using compostable paper, aluminum or cardboard products, which can be found at Brick & Mortar and is Montgomery's material of choice. A surefire way to guarantee that food is stored and reheated in a heat-safe container (whether by initial temperature or via microwave) is to simply use your own.
"The safest containers are BPA-free, or even better, glass ones like Pyrex," recommends Jarquin. "Stainless steel and aluminum are great, too, just not for the microwave."
One of our favorite options is this colorful 10-piece set that offers the convenience of multiple sizes. This means you can limit the shape to accommodate the amount you plan to reheat or take home from the restaurant, from an entire entree to a few bites of dessert.
Beware of plastic containers marketed as microwave- and freezer-safe
Many plastic containers are marketed as "freezer- and microwave-safe," but that's not the case.
Rubbermaid
Many plastic containers are marketed as "freezer- and microwave-safe," but that's mostly marketing jargon. Plastic containers should really never be frozen or microwaved. Ziploc and Rubbermaid are facing a lawsuit for advertising its plastic-based containers as "microwave safe" and "freezer safe." When heated, plastic containers are found to leach chemicals into food. When frozen, the plastic often breaks off, which can contaminate food.
How to reheat food safely
Deli containers may be considered food-safe but glass and ceramic are safer options for reheating food in the microwave.
Julien McRoberts/Getty
Even more important than reheating your food so it tastes good is making sure it's safe to eat. Never reheat your leftovers in a non-heat-safe vessel. That includes most cheap plastic containers used by restaurants, such as plastic clamshells or black plastic containers. Deli containers like the ones you get your grocery store chicken salad in are considered "food safe" for storage but it's still not recommended to use them to reheat food at high temperatures.
When reheating food in the microwave, always use glass or ceramic. Keep any containers, lids or utensils that contain plastic or rubber out and use for serving only.
How to reheat food so it tastes good
An air fryer is one of our favorite ways to reheat leftovers.
ThaiAside from the risks of plastic exposure when hot food is stored in those containers, you'll want to ensure that reheating leftovers maintains the overall quality.
"Though microwaving is quick and easy, better results can often be achieved by reheating on the stovetop," says Montgomery. "A little extra fat like olive oil and butter, as well as seasoning, can also be helpful," she adds, noting that this doesn't pertain to some dishes like her restaurant's famed beef tenderloin carpaccio, which should be consumed within its entirety on location.
Jarquin echoes these sentiments. "You get a much better result when reheating leftovers in a frying pan or in the oven," he stresses, revealing that some dishes may even taste better when enjoyed the next day. "At Americana Kitchen, the rigatoni with vodka sauce keeps getting tastier the next day. Also, any of our pizzas or the mushroom pasta definitely gets better the next day. The flavors soak in even more and the texture stays great when reheated slowly," he says.
Other foods recommended by Jarquin for enjoying at home after dining include "stews, curries, chili, and lasagna," which are typically items where the flavors can keep developing overnight.
Concerns about bacteria growth
Food, including cooked rice, can develop bacteria quickly if not stored properly.
Chris Monroe/CNET
Another risk to consider with leftovers is the rapid formation of bacteria that can lead to often brief yet sometimes serious illnesses. In short, the longer food sits out, the quicker these spores grow.
"The general rule is that it takes about two hours at room temperature and one hour if it's really hot out" (usually above 90 degrees Fahrenheit), said Jarquin. "After that, bacteria can grow quickly and you don't always see or smell it. That's why it's important to either serve food hot, chill it fast or keep it properly stored."
Read more: I'm Not Messing Around With Leftover Rice - You Shouldn't Either
At the end of the day, if you're even the slightest bit fearful of microplastics and/or foodborne illnesses, no leftover is worth the temporary satisfaction. Accept your losses and task yourself with whipping up your own homemade delicacy to ensure safe, plastic-free bites within the comfort of your own kitchen.
For a comprehensive guide to food safety protocol, check out the CDC's Four Steps to Food Safety.