So, you’ve bought a sous vide circulator. You’ve come home from the grocery store with two nice steaks and some high-quality plastic zipper-lock bags. You heat up the water bath to 130°F/54°C. You’re ready to put the steaks in the bags and then into the water bath and walk away for a couple of hours. But then you stop and you think, “Is this really safe?”
Vacuum Seal vs Zipper-lock Bags
- You don’t need to vacuum seal in order to sous vide
- We believe it is safe to cook via sous vide in plastic bags
- Use high-quality bags, like Ziploc or Glad
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The original concept of sous vide cooking entailed sealing cold food in thick plastic sheaths from which every bit of air was then electrically pumped, so the thin plastic clung to the contours of the food like a second skin. This approach of vacuum-sealing is still common, especially in restaurants. (Read our review on home vacuum sealers.) And being able to completely remove the air has advantages, but the home sous-vider can be perfectly content with our no-machine-needed method using zipper-lock bags.
When we started working with sous vide in the test kitchen, we had the same concern that those starting out at home sometimes do: We’ve heard about chemicals leaching from plastics. Isn’t it potentially dangerous to seal food in a plastic bag and then heat it up?
Cooking in Plastic is Safe
After reviewing the considerable amount of research that’s been done, we believe the answer is: It’s safe. Although some types of plastic have been found to release undesirable chemicals into food, especially under high heat or acidic conditions, the bags that we use for sous vide cooking are not among those plastics.
High-density polyethylene, low-density polyethylene, and polypropylene are considered the safest plastics. Many name-brand plastic bags are made with polyethylene and polypropylene. These types of plastic are resistant to the sub-boiling temperatures involved in sous vide cooking, and they are also considered safe in and of themselves: Even if you cut up and ate a polyethylene bag, there’s no toxicity risk.
Even nontoxic plastics, though, are sometimes manufactured with additives to give them extra strength, flexibility, slipperiness, or other characteristics. There are legitimate concerns about health effects from overexposure to some of those plasticizing additives, of which phthalates and BPA are the most famous.
Best Plastic Bags for Sous Vide
So how do you choose? We always use name-brand bags from brands that have well-documented manufacturing details. The zipper-lock bags we use are made from polyethylene or polypropylene. Our top pick is Ziploc Brand Freezer Bag with Easy Open Tabs.
SC Johnson, the manufacturer of Ziploc bags, publishes the ingredients it uses in all of its products, and Ziploc bags are made using polyethylene without additives. Glad also publicizes the fact that there are no plasticizers in its bags.
The bags made by the manufacturer FoodSaver for use with its vacuum sealers use plasticizer-free polyethylene with a layer of nylon on the outside. (The plastic wraps sold in supermarkets, such as Saran, are also made of safe polyethylene—commercial plastic wraps used in restaurants, however, can use PVC, which is not recommended for heating.)
For sous vide cooks who are still hesitant, there are reusable bags made of food-safe silicone that are marketed specifically for sous vide cooking. Some foods can be cooked in glass Mason jars instead of bags, although the rigid jar means heat can’t travel as well from the bath to the food (we account for this in our recipes that use Mason jars). These latter two options do have the added advantage of creating less waste.
Food Safety and Sous Vide
- Sous vide cooking is very safe thanks to its precision and control
- We cook most food at or above 130°F/54.5°C to reduce risk of harmful bacterial growth
- If cooking below 130°F/54.5°C, we sear meat before putting it in the water bath to kill surface bacteria
- It’s important to rapidly chill foods if you’re planning to keep them in the refrigerator
- Don’t sous vide raw garlic
Sous vide relies on cooking at low temperatures, often for long periods of time. But when it comes to temperature and time, what is safe?
Food safety is top of our minds, too.
“I believe sous vide is significantly safer than most cooking methods,” says Douglas Baldwin, a mathematician at ChefSteps, a Seattle-based food and technology company. He spent months creating pasteurization charts for his own book, Sous Vide for the Home Cook. “It’s so much more predictable.” But there are a few things you need to pay attention to as you cook.
What is Actually Dangerous When It Comes to Foodborne Illness?
First, let’s talk about what’s dangerous. A few types of bacteria in particular are responsible for most foodborne illness: Salmonella, Escherichia coli, and Campylobacter jejuni. Salmonella, a resilient group of bacteria that is most commonly found in poultry and eggs, is ingested by chickens, and then contaminates their muscle tissue, intestines, and ovaries. Salmonella can migrate into the muscle of chickens, meaning that they are contaminated not just on the surface but also inside the meat. Escherichia coli is a general group of bacteria that reside in the intestines of many animals, including humans. But if ingested, some strains of E. coli can wreak havoc. Campylobacter jejuni is a spiral-shaped bacteria that causes one of the most common diarrheal illnesses in humans in America.
Food pathogens won’t let you know that they are there. Unlike the microorganisms that let you know when the food in your fridge has spoiled, these pathogens can’t be seen, smelled, or tasted. But they can be controlled—with acid, with salt, and even with some spices. But, most important, they can be controlled with temperature.
What is Pasteurization?
To “pasteurize” is to heat food to a temperature for a certain amount of time in order to reduce enough of the pathogens to deem it safe. We often pasteurize in sous vide cooking.
In the fridge, bacterial action and reproduction slow way down; we can keep food in there for days or weeks without worrying about pathogens growing. And at the temperatures reached when we boil or bake food, the bacteria are killed. It’s between those low and high temperatures that bacteria are happiest, so that’s where extra care is called for.
When food sits between 40°F/4°C and 140°F/60°C, it is often said to be in the “danger zone” for bacterial growth. It’s between these temperatures that potentially harmful bacteria can thrive. But what is not often referenced is that danger—and, thus, safety—isn’t just about temperature. It’s also about time. “Most people, when they talk about food safety, they oversimplify,” explains Baldwin.
For example, the FDA recommends cooking chicken breast meat (which is comprised of 5 percent fat) to 165°F/74°C in order to pasteurize it. When the center of the meat reaches that temperature, virtually 100 percent of Salmonella is killed immediately. When brought to 160°F/71°C, it takes 14 seconds to kill the Salmonella. At 155°F/68°C, it takes 50 seconds. At 150°F/65.5°C, our favorite temperature for chicken, it takes 3 minutes. We don’t recommend cooking chicken at 136°F/58°C—it’s a little more like chicken sashimi, really—but you can. It will just take 69 minutes at that temperature to be safe.
With enough time, most food pathogens are killed at 130°F/54.5°C, according to the FDA and Baldwin. For our sous vide recipes, this is our magic number. We cook almost everything either at or above that temperature. (When cooking in a water bath set to 130°F/54.5°C, the food will eventually become that temperature as well.) As an extra precaution, if we plan to cook meat below our magic temperature, the first thing we do is sear it in a hot pan in order to kill off any bacteria on the surface before we circulate (for example, see Butter-Basted Rib-Eye Steak).
Recipe Sous Vide Butter-Basted Thick-Cut Rib-Eye Steaks
A nicely cooked rib-eye steak is a culinary showstopper but is also a challenge to pull off. But with the help of sous vide, preparing steak at home is suddenly a sure bet.
Of course, nothing is perfect, so if you are immunocompromised or prefer to exercise greater caution for other reasons, please proceed with care. It’s important to note that the risk of eating steak prepared to medium-rare in our sous vide recipes is not any different from the risk of eating steak that is grilled to medium-rare. “For the most part, if your steak is seared, then the bacterial load is safe,” says Baldwin. “That’s why the food code allows you to have seared medium-rare steak.”
Safety for ground meat is different than for whole cuts of meat. While the inside of whole cuts of beef are sterile, harmful bacteria can be present throughout ground meat. (Of course Salmonella in poultry can be present throughout, whether the meat is ground or whole.)
Also important: Even when food is pasteurized, it isn’t safe indefinitely. The food either needs to be eaten immediately, or rapidly chilled and then refrigerated. What does “rapidly chilled” mean? It involves plunging still-sealed bags into a large ice bath to stop the cooking, let sit until chilled, and then refrigerate it for later. And once the food is in the refrigerator? Don’t leave it there too long. As Dave Arnold, author of Liquid Intelligence and an early sous vide adopter, warns, “If you store it improperly, you can get some microaerobic situations, like listeria can grow on cheese and meat slowly at refrigeration.”
And one final note: We’ve chosen not to circulate any raw garlic in our sous vide recipes. This is because garlic is particularly susceptible to Clostridium botulinum (or botulism), especially in a warm, anaerobic environment (like sous vide). If we don’t cook raw garlic before circulating it, we use granulated garlic powder, or we leave garlic out entirely.