Sous vide--sealing food in plastic bags and cooking it in a constant-temperature water bath--is becoming a more and more popular cooking method. Its reputation for making perfect steaks, meltingly tender pork butt, and juicy chicken breast has made millions of people eager to try it. They haven't been disappointed.
Yet some people have misgivings about cooking sous vide. They’re concerned that cooking sous vide isn't safe. Using low temperatures to cook food seems like you're just asking for food-borne illnesses.
And what about all that plastic?
In fact, these are the three primary safety concerns with sous vide cooking that seem to get brought up on food forums and modernist cooking blogs over and over again:
1. Low temperatures
2. Vacuum sealing, and
3. Using plastic bags for cooking.
How justified are these concerns? Let's look at each one and see what we come up with.
Concerns about cooking food at low temperatures can be justified, and it has to be done properly. If food is left for more than a few hours at danger zone temperatures, bacteria can grow and result in food-borne illness.
For this reason, it's important that home chefs understand what the danger zone is and how to avoid it when cooking with sous vide.
The Danger Zone is the temperature range at which bacteria grow most rapidly on food and cause it to spoil. This temperature range is 39F-130F (4C-54C).
Foods most susceptible to bacterial growth at danger zone temps include meat, seafood, eggs, sauces, raw sprouts, and cooked vegetables, beans, and pasta.
Food should not be left at danger zone temperatures for more than 2 hours. (And yes, this includes thawing frozen meat, which is safest to do in a refrigerator.)
In summary: food should be stored at temperatures below 39F, cooked at temperatures of 130F and above, and not left at anything in between for more than 2 hours.
Food doesn't need to be fully pasteurized in order to be considered safe for most people (pregnant women and those with immune issues being two major exceptions). If it did, we could never enjoy a medium-rare steak or an over-easy fried egg. So while sous-vide cooked food isn’t always fully pasteurized, neither are many foods cooked in more traditional ways.
You want to be sure that your food is safe to eat, regardless of how you cook it. This is no more difficult with sous vide cooking than with any other method. You just have to keep your food out of the Danger Zone. If you do that, it will be safe to eat.
That's simple. Just follow these rules:
1. Cook food at 131F and above, giving it enough time for the internal temp to reach this point and stay there for at least 30 minutes. Use a probe thermometer to be sure the internal temp has been reached.
2. Or, if you cook food below 131F (such as salmon, which is going to be dry and overcooked at 131F), be sure to not leave it in more than 2 hours.
3. If you cook at 140F or above--such as for chicken, pork, and tough cuts of meat--you pretty much don't have anything to worry about as long as the entire piece of food reaches temps of 140F or above.
That's it; that's all you really need to do to avoid food-borne illness from sous vide cooking.
In reality, the chances of contracting a food-borne illness from sous vide cooked food is about the same as from any other cooking method, as long as you follow danger zone precautions. And as with all cooking, safe handling is important: wash your hands before handling food, avoid cross-contamination, wash food before using, and keep your work area clean.
Vacuum sealing creates an anaerobic environment, which is the environment preferred by one of the most toxic and dangerous food-borne pathogens known to man: botulism.
If you combine food sealed in an oxygen-free environment with cooking at warm-but-not-hot temperatures, aren't you just asking for botulism?
Once again, that depends mostly on how careful you are about danger zone issues. If you’re careful about food handling, have a clean working environment, and make sure the food’s core temperature reaches 131F or above, your risk of getting botulism from vacuum-sealed food is almost zero.
In fact, there are no known cases of botulism from sous vide cooking.
Botulism is certainly possible under anaerobic, low-temperature conditions. However, if you follow the precautions for avoiding danger zone issues, then you are most likely safe from botulism, as well.
Here's an excerpt from a cooking forum discussion about it botulism as it relates to sous vide cooking:
“There is absolutely real truth to improper sous vide cooking and botulism. Clostridium botulinum is an anaerobic organism - it grows when there isn't oxygen - like in sous vide vacuums and canned goods.The risk is that sous vide cooks both without oxygen and at temperatures so close to the perfect reproduction rate for the organism. If you cook it a little lower than recommended, you could be creating a perfect place to reproduce. Clostridium botulinum dies around 126 F - so most sous vide won't go lower than 130 F. The opponents state that the temperatures in general are far too low and if we were cooking for a few seconds, it would be. Luckily, pasteurization is a function of temperature and time. This is part of the sous vide magic. Bacterial death is a result of heat and time - if you have a high heat you may only need it for seconds. If you have lower, but sufficient heat, then as long as you cook it long enough (see recommended reading below) - then you can still pasteurize the food. Sous vide often cooks foods for hours and hours - either for taste and/or pasteurization sake.” (excerpted from: https://cooking.stackexchange.com/questions/18632/are-the-claims-legitim...)
This explains the situation very clearly. So if you follow the rules for the danger zone, botulism is extremely unlikely to be an issue with sous vide cooking.
Cooking in plastic bags is probably the least attractive thing about the sous vide method. After all, aren't we all trying to cut down on our plastic use in an effort to reduce waste and decrease our carbon footprint? Of course we are!
And isn’t heated plastic supposed to be bad? Can’t it leach nasty chemicals into our food?
Again, there can be cause for concern. If you’re going to use plastic bags for cooking food, you have to know what you’re doing. But once you educate yourself, you’ll find that using plastic for sous vide is actually quite safe--as long as you use the right plastics. And you can even do it in such a way that you reduce your plastic use rather than increase it.
There's no getting around it: if you're gonna sous vide, you're gonna use plastic. But using good practices CAN minimize your plastic use.
I love cooking sous vide for so many reasons. But using plastic bags is not one of them. When I first started cooking with sous vide, I hated all the plastic I was going through. However, sous vide is so convenient and the results are so great that I wasn't willing to stop using it.
The truth is, whether you use sous vide or not, you're going to go through a lot of plastic in the kitchen. Almost all the food we buy comes in some form of plastic wrap or container. We freeze food in plastic, we store food in plastic bags and containers. Plastic wrap, plastic bags, Tupperware, and Rubbermaid are all parts of pretty much everyone's kitchen landscape.
So in reality, using sous vide bags doesn't really add that much to our overall carbon footprint. But if you're concerned about it, as I was, there are some things you can do.
Here's what I've done to reduce my plastic use in sous vide cooking:
I use the same bag for freezing as I do for cooking. When I freeze meat, I pre-season so it's ready to just pop into the sous vide for a couple of hours. (Bonus: This also hugely simplifies meal prep!) Now, some people say it can toughen meat to freeze it in a bag with salt, but I haven't noticed any issues with it. If you do, just salt it after the sous vide cook and before finishing.
I use the bags for storage after cooking if there are leftovers. I always try to seal as close to the top of the bag as possible so I can re-seal it for this purpose. You must be sure to chill quickly and make sure the food stays below 40F until ready to eat again--otherwise the anaerobic environment could be a problem.
I re-use bags when possible. Sometimes bags don’t get terribly dirty, so they’re easy to wash, dry, and re-use. I do this with vacuum bags and food storage bags. If a bag had raw meat in it, or something sticky that doesn’t wash out easily, I throw it. But I re-use bags that are easy to wash out.
When possible, I use mason jars for sous vide. This doesn’t work for many foods because the water has to reach as much surface area as possible. However, it is possible for making foods like yogurt and creme brulee, which both cook really well sous vide. Eggs are also great for sous vide: they come in their own hermetically sealed package, so they don't require any container at all.
Reusable bags are new on the scene, but they offer a fantastic solution to the plastic problem. These bags can be used thousands of times and are dishwasher safe. Expect to see more and more of these as sous vide cooking gains popularity. (Some are already for sale on Amazon for a very reasonable price.)
Also of concern is the safety of cooking in plastic bags. The biggest concern with using plastic bags is that when they're heated to certain temps, they can leach harmful chemicals like Bisphenol-A (BPA).
People have gotten very savvy about this in recent years. They’ve stopped using plastic containers in the microwave or re-using plastic containers for food storage. Many have even stopped using plastic water bottles because they can degrade over time, especially if left too long in the sun.
Having said that, nearly all food-grade plastic is now BPA-free, particularly plastics designed for food storage and microwave heating purposes. This includes vacuum sealer bags and zip-type food storage bags: both are BPA-free and both are considered safe for sous vide use.
But plastic is a complex substance, and it may still have potentially harmful chemicals in it that can break down under high heat conditions.
If that's a concern for me, then why am I not worried about using plastic bags in a sous vide cooker?
Here's why: all sous vide is done at temperatures below boiling, and boiling temp (212F) is the temp at which plastics begin to break down.
Also, all sous vide bags--at least from reputable manufacturers--are BPA-free, so even if they did break down, they wouldn’t leach harmful chemicals into your food. (But they won’t break down, so no worries there.)
Here's a great web site with a short video about sous vide and plastics. This is a medical site, and it also goes into some detail about different types of plastics and what to know about them. This is from 2012, so it's a few years old, but still good information.
Also, here's a short article from Modernist Cuisine about plastics and sous vide. This article is from 2013, so it also may not contain the latest information. But in all the research I've done, I have not found any indisputable concerns with cooking food in BPA-free plastic at sous vide temperatures. And I believe that the folks behind Modernist Cuisine, who are scientists first and food lovers second, would be up-to-date on the concerns surrounding sous vide cooking.
For more information on vacuum sealing, check out my article Why Every Kitchen Needs a Food Vacuum Sealer.
I have been a fan of sous vide for several years now. Along with some of the world's greatest chefs and scientists, and based on the most compelling research, I believe that sous vide cooking is safe. I encourage you to do your own research and draw your own conclusions. I hope this article will help with that.
Melanie Johnson is a freelance writer with a background in engineering and technical communications. She is also a longtime home chef who loves kitchen technology and wants to inspire others to love their time in the kitchen. You can read more of her articles at The Rational Kitchen.