Is Sous Vide Cooking Safe?

Sous vide cooking promises perfect results every time, but does this perfection come at a cost? This is a question on many minds since the practice uses plastic bags for cooking and involves low cooking temperatures (even though for prolonged periods).

The word “plastic” itself is foreboding enough and when used in the context of cooking becomes an outright abomination. The other issue is cooking on low temperatures which raises the concern for letting harmful bacteria thrive. And then there is the whole business about vacuum sealing the food before submerging it in a water bath.

So naturally skepticism isn’t far behind when it comes to the integrity of food prepared in (seemingly) less-than-optimal cooking conditions.

You may well wonder if you’re putting your health at stake just to enjoy a delicious steak.

The Science behind Sous Vide

Sous vide involves vacuum sealing raw or partially cooked foods in plastic bags. You submerge the bag in a hot water bath for anywhere between a few hours to a few days. The temperature settings are low and once cooked, your food comes out full of flavor and nutrition.

So to determine if this slow cooking technique is indeed safe or not, here’s addressing its main concerns:

Are plastic bags safe?

The simple answer for this will vary depending on the kind of plastic bag you use. If you are using food grade plastic or BPA-free versions, you are safe.

This plastic is inert which means that it doesn’t react with food or water. This also keeps the food free of any contamination. Polyethylene bags are the best in this regard because they are inert and they do not pose any harm to the human health. Inert plastic doesn’t contain additives which may otherwise leach into food and impact your health adversely.

This type of plastic is also resistant to the sub-boiling temperatures used in sous vide cooking. So as long as you are using food grade, BPA free plastic, you have nothing to worry about.

On the other hand, if the bags contain BPA, they can seriously threaten your health. BPA mimics hormones present in the human body and can disrupt normal body functions.

Some studies conducted in animals also show that excessive exposure to BPA may also cause cancer in later stages on life. The effects of this chemical are more pronounced in infants and young adults. So if you are using phthalate-free or BPA-free plastic bags, then you do not need to fear.

Is low-temp cooking safe?

The USDA has specified a ‘danger zone’ which is a temperature range, cooking in which can be harmful for health. The danger temperature zone is between 40 and 140oF. According to the USDA, any food held in this range for more than two hours can be harmful for the body as bacteria thrive in this temperature. This is the range in which pathogenic bacteria increase in number and cause food-borne diseases.

Now there is a buffer zone within this temperature range above which bacteria growth becomes retarded. So when food is cooked at the 130oF mark, bacterial growth stops. In fact, increasing the temperature up a notch to 135oF would actually kill any bacteria present in the food.

Since sous vide cooking is all about precise temperature, and most cooking is done around the 130-140oF mark, pasteurization becomes possible. This makes sous vide cooking a much safer cooking technique than conventional methods. Also, the latest models of sous vide cookers come with keep-safe technology so they will let you know if you are cooking in the danger temperature range.

In addition, some research states that cooking at low temperatures is actually beneficial because it helps retain the nutritional value of foods. Vitamins and minerals in food break down at high temperatures which is why conventional methods can strip the food of its nutritional value. In sous vide, nutrients are retained since they don’t get broken down. Also, there is no likelihood of burning since heat dissipates into the food, instead of just heating on the outside.

Is Cooking Under Vacuum Safe?

Vacuum sealing creates an anaerobic environment which is ideal for the growth of certain bacteria that grow in such conditions. This means that these bacteria grow in the absence of oxygen.

The most harmful bacterium in this regard is C.botulinum which produces toxins when it has the right temperature in the absence of oxygen. It causes a disease called botulism which is certainly possible under anaerobic, low temperature conditions. But if you follow given precautions for staying out of the danger zone area, then you should also be safe from botulism as well.

So if you cook at given sous vide temperatures and for the given times, you should be able to effectively kill off this bacteria. It is important to realize that working at the right temperatures is only half the equation. The other half is all about the timing. Killing harmful bacteria becomes possible because you cook at a certain temperature for a prolonged period of time. Together, the two pasteurize the food making it safe for consumption.

Also, make it a point to always refrigerate your food in case there are leftovers.

Some stipulations

Never attempt sous vide cooking without the proper equipment. For instance, regular cooking thermometers aren’t precise enough. Invest in a proper sus vide immersion circulator or cooker to get the time and temperature right.


Sous vide cooking can be done right if you invest in the right equipment. A quality immersion circulator with give you precision and control over your timing and temperature. Food grade plastic bags will remove the concern for leaching and storing the food correctly will keep it safe for future consumption.

So follow the safety rules and the instructions of your sous vide machine for safe cooking. Overall, sous vide is considered a very safe cooking technique. So much so that one of its earliest uses was to use sous vide for preparing hospital food.

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