Microwaving steam-in-bag veggies, rice and other foods is a quick and convenient way to meal prep. You heat the bag for a few minutes, and the contents are ready to eat — no portioning, chopping or washing required. But how safe is it to use these? Could the plastic from the packaging seep into the foods and cause health concerns?
“There is ongoing scientific debate about the long-term effects of low-level exposure to … some plastics, especially under high heat,” said Bryan Quoc Le, food scientist and founder of Mendocino Food Consulting. “While most modern steam bags are … [free of BPA and other harmful chemicals, there are still concerns] about lesser-known additives and the cumulative impact of plastic use.”
We spoke with experts about the safety of using steam-in-bag food products — and whether there are alternative cooking methods they recommend instead.
So, how risky is it to consume steam-in-bag foods?
Steam-in-bag food products aren’t only popular because of their convenience, but they also offer a few safety benefits.
“[They] are designed for minimal handling from production to plate, reducing the risk of cross-contamination in home kitchens,” explained Darin Detwiler, a food safety expert and professor at Northeastern University. Plus, they are “typically frozen or vacuum-sealed, extending shelf life well beyond that of fresh produce,” Detwiler added.
However, concerns exist about the risks associated with using and heating plastic packaging, particularly when one is consistently exposed to microplastics (tiny pieces of plastic) over time.
“Microplastics can enter food through contaminated water, environmental exposure and plastic packaging,” Le said. While more research is needed, “early studies link … [them] to inflammation, hormone disruption and possible immune effects.”
That said, steam-in-bag foods are generally considered safe when you carefully follow the instructions on the packaging, he added.
“These products are made from food-grade, microwave-safe plastics that meet FDA standards and undergo … testing to ensure they don’t leach harmful chemicals, like BPA or phthalates,” he explained.
Still, there’s a chance you could be exposed to low levels of chemicals and microplastics by using them, said Jamie Alan, associate professor in the department of pharmacology and toxicology at Michigan State University.
“We come into contact with microplastics every day … [they’re] everywhere,” she said. “And we are still trying to understand their long-term health risks.”
Should we avoid using ‘steam-in-bag’ foods?
While “there’s not yet conclusive evidence” on how they affect our health, “minimizing avoidable plastic exposure where practical — especially at high heat — is a reasonable precaution,” Detwiler explained.
Alan recommends looking for ways that work for your individual life to limit exposure.
“For example, if you usually consume vegetables steamed in these bags, perhaps you can continue to do so while drinking water out of non-plastic containers,” she said. “It would take quite a bit of resources and effort to completely avoid exposure to microplastics.”
Is there a safer method?
“Plastics degrade with repeated or excessive heating, so alternative methods may offer added peace of mind — especially for frequent use,” Le explained.
Detwiler said transferring the food from the steam-in-bag to a glass or ceramic dish before microwaving can be a safer alternative. You can use the directions on the bag as general guidelines, but you shouldn’t solely rely on this, he added.
“Those instructions are calibrated specifically for cooking inside the bag, where steam builds up and circulates heat more effectively,” he said.
When heating in a dish, he recommends using a food thermometer to make sure the internal temperature of the food reaches at least 165°F (74°C). You can also cover the dish with a microwave-safe lid to help the heat distribute evenly. To avoid cold spots, pause the cooking midway so you can stir or rotate the food, he advised.
When you do microwave steam-in-bag foods, follow these important steps.
“Using [steam-in-bag products] exactly as directed is important, since overheating or improper use can compromise their safety,” Le said.
A few key safety tips from Detwiler:
- Pay attention to the heating time and power level of the microwave. Undercooking could allow bacteria to survive, such as Listeria, Salmonella, or E. coli, and overheating increases the risk of chemicals leaching into the food.
- Don’t reheat the bags. “They’re single-use only and not designed to withstand repeated heating.”
- Don’t store food in the bag after microwaving. “Transfer leftovers to food-safe containers to avoid prolonged exposure to heat-softened plastics.”
- Don’t use the bag if it’s “damaged, punctured or warped.” This could increase the risk of contamination and plastics leaking into the food. When cooking, the “bag may [also] leak steam prematurely” and cause “uneven heating or failure to reach safe temperatures.”
- Don’t microwave only some of the contents. “The remaining food may not receive adequate steam or time to cook safely.” If you want to only heat some of the food, transfer it to a microwave-safe dish instead.
“Occasional use of steam-in-bag products is unlikely to pose significant harm,” he said. “But like any tool in the kitchen, they work best when used correctly and with awareness.”