In French, sous vide means “under vacuum.” In practice, however, sous vide cooking does not require a vacuum.
Typically, sous vide-prepared food is cooked in a plastic bag immersed in a temperature-controlled water bath. Air is evacuated from the bag. Eliminating air brings food and flavorings into intimate contact and provides other obvious benefits:
- Without air pockets, the surface of the food is in close contact with the water outside the bag — only a thin film of plastic separates food from water. This proximity allows the water bath to quickly and thoroughly heat the food since water conducts heat 23 times more efficiently than air.
- Without air in the bag, it’s easy to keep the food underwater.
Many high-end restaurants use vacuum chambers to evacuate air from sous vide food bags. Though they sometimes use vacuum chambers to alter food texture or infuse food with flavoring liquids, for most sous vide dishes the vacuum chamber simply removes air from cooking bags. The food in the bag is, in fact, not in a vacuum: it’s at atmospheric pressure.
The home cook does not need a vacuum chamber to remove air from sous vide bags. Indeed, you don’t need a vacuum bagging system at all, though appliances such as the FoodSaver and Seal-a-Meal, or even the Ziploc Vacuum and Reynolds Handi-Vac, work well.
Instead, you can use any sealable bag for sous vide, as long as you previously check that it won’t melt or deform in very hot water. (Actually, you should do a bit more research: make sure that it’s food-grade plastic and that it’s designed for high-temperature cooking.) Here’s how to eliminate air from a bag without the assistance of a vacuum:
- Gather a piece of low-tech equipment — a small bucket, almost filled with water.
- Put the food you want to cook in your sous vide bag. Partially zip the sous vide bag closed.
- Put the sous vide bag inside the bucket and slowly push the bag into the water.
- You’ll see water pressure force the sides of the sous vide bag tightly around the food. Gradually submerge the sous vide bag on a diagonal, keeping the open corner just above water, then zip the bag closed.
It’s now ready for the water bath.
Click on the video tile in the sidebar to see Pam McKinstry demonstrate the technique.
Aside from its simplicity, a bucket of water has a significant advantage over home vacuum sealers: the process won’t extract liquid from a food bag, so you can use it with marinades and sauces.
By the way, you can also use the filled basin of your sous vide machine in lieu of the bucket and save an extra step.