What Is Sous Vide? Meaning, Method and Equipment

Sous vide is a way of cooking food sealed in a bag or pouch in water that is held at one precise temperature. The water is set to the temperature you want the food to finish at, so the food heats to that temperature all the way through and cannot go past it.

The water is too cool to brown food, so meat gets a short sear in a hot pan after the bath if you want a crust.

What the term means and how to say it

Sous vide is French for "under vacuum". It is pronounced "soo-VEED", with the stress on the second word, following the pronunciation in Merriam-Webster.

The name describes the pouch, not the water. Douglas Baldwin's guide to sous vide cooking defines the method by two features: the raw food is vacuum sealed in heat-stable, food-grade plastic pouches, and it is cooked with precisely controlled heat.

Restaurant chefs have cooked this way since the 1970s, according to Baldwin's review of sous vide cooking in the International Journal of Gastronomy and Food Science.

A true vacuum is not required at home. America's Test Kitchen states that you do not need to vacuum seal in order to cook sous vide, and a zipper-lock bag with the air pushed out by the water displacement method also works.

How sous vide works

A pan, grill or oven is much hotter than the temperature you want inside the food. The outside overcooks while the center catches up, and the result depends on pulling the food off the heat at the right moment.

A sous vide bath removes that timing problem. The water sits at the final temperature, and Baldwin's guide states that food cannot overcook when the bath is just above its desired final core temperature. A steak comes out the same doneness at the edge as at the center.

Three facts explain why a water bath does this well:

• Water carries heat well. Baldwin's guide puts the thermal conductivity of water at 23 times that of air, so a bath heats food much faster than air at the same temperature.
• A circulating bath is steady. The same guide reports that circulating water baths typically have temperature swings of less than 0.1°F (0.05°C).
• The pouch keeps water out and juices in. Vacuum packaging prevents moisture and flavor compounds from evaporating during the cook, and it lets heat pass efficiently from the water to the food.

Temperature and time do separate jobs. The temperature sets the doneness. The time is set by how thick the food is, because heat has to travel to the center, and by how tough it is.

Tough cuts need extra time because collagen has to dissolve into gelatin. Baldwin's guide says collagen begins to dissolve above 122°F to 131°F (50°C to 55°C) and that prolonged cooking can more than double the tenderness of meat.

Sous vide baths run below boiling. Baldwin's guide says you usually cook at 130°F (54.4°C) or higher. The calculator's pasteurization floor is one degree above that, at 131°F (55°C). Vegetables sit at the top of the range, because the material that holds their cells together starts to dissolve around 180°F to 185°F (82°C to 85°C), according to Baldwin's review.

The basic steps

A sous vide cook has five steps. The how to sous vide guide explains each one in full.

1. Set the bath to the temperature for the doneness you want. The calculator gives the temperature and time for each food, doneness and thickness.
2. Season the food and seal it in a bag with the air removed.
3. When the water is at temperature, lower the bag in. Baldwin's guide warns that pouches must be completely submerged and not packed tightly or overlapping, or the food can undercook.
4. Leave the food in the bath for the time its thickness needs.
5. Take the food out of the bag, pat it dry and sear it. Baldwin's guide suggests a heavy skillet with oil that is just starting to smoke, or a blowtorch.

What equipment sous vide needs

You need something that holds water at a set temperature, a container, bags, and a hot pan for the finish.

Anova's overview of sous vide describes immersion circulators as devices that clamp to an existing pot, and notes that water ovens do not circulate the water, which can lead to uneven results.

Some electric pressure cookers have a sous vide program built in. The Instant Pot sous vide guide covers which models have it and how it compares with a circulator.

For bags, America's Test Kitchen reports that high-density polyethylene, low-density polyethylene and polypropylene are considered the safest plastics, and that many name-brand bags are made from them.

What sous vide is good at

• Even doneness. The whole piece reaches the bath temperature, so the edge is the same doneness as the center. The doneness guide shows what each temperature produces.
• Repeatable results. Baldwin's review describes the method as giving almost-perfect reproducibility, because the same temperature and time give the same result each time.
• Flexible timing. Food can stay in the bath past the minimum time without getting hotter. It does keep getting softer, so the calculator shows a best window and a maximum.
• Tender tough cuts. A long cook at a low temperature dissolves collagen without taking the meat to well done. That is the approach behind the chuck roast and short ribs guides.
• Cooking ahead. Baldwin's guide describes a cook-chill routine: seal the food, pasteurize it, chill it fast in ice water, then refrigerate or freeze it. The meal prep guide covers that routine.
• Cooking from frozen. Food sealed and frozen flat can go straight into the bath. It takes longer to heat through, and the frozen food guide explains how much longer.

What sous vide is bad at

• Browning. Baldwin's guide says the browning reaction becomes noticeable around 265°F (129°C). No water bath gets near that, so food comes out of the bag without a browned crust. Meat needs a sear after the bath.
• Speed. Thick food takes time to heat to the center, and collagen takes longer still to dissolve. A thick cut takes hours, and tough cuts can take a day or more. The cooking times chart lists the range by food.
• Mixed meals in one bath. One bath holds one temperature. Baldwin's guide notes that vegetables need much higher temperatures than meat, so they cannot share a bath with a steak.
• Last-minute meals. You need the equipment, the bags and the time. The cook is hands-off, but it has to start hours before the meal.

Sous vide and food safety

Sous vide is safe when temperature and time are chosen together. Heat kills bacteria over time, and America's Test Kitchen, citing the FDA and Baldwin, states that most food pathogens are killed at 130°F (54.4°C) given enough time.

The calculator draws its line one degree higher. 131°F (55°C) is the lowest temperature in the pasteurization tables it uses. At 131°F (55°C) and above, meat held long enough is pasteurized, and the lower the temperature, the longer the hold. Poultry settings start higher, at 135°F (57.2°C) for duck breast and 140°F (60°C) for chicken breast.

At 130°F (54.4°C) and below, the calculator prints this warning on meat, fish and shellfish:

On a recommended result the maximum at those temperatures is never more than 2 hr 30 min. A piece too thick to warm through in that time is marked not recommended. The explainer on whether sous vide is safe covers pasteurization and the limits below 131°F (55°C) in more detail.