What different methods of vacuum sealing exist?

External vacuum sealer

A vacuum pump device is clamped to the outside of a bag, pulls out as much air as possible and seals the plastic. While these machines are less costly, light and small, and often accomplish a basic result, the performance is not able to remove as much air as a chamber vacuum sealer. They also present a challenge when liquids are in the bag, since the pump will pull any content from the bag that isn’t heavier than the pump can pull.

Chamber vacuum sealer

A chamber vacuum sealer is a device that creates a low pressure within a chamber before sealing the bag. Equipped with a powerful pump, it can pull up to 99.9% of air from the bag.

It is important to understand two additional considerations when working with a vacuum sealer:

When using an external vacuum sealer, how can I vacuum seal bags that contain foods with larger amounts of liquid?

- Simply put all the ingredients into a large (1 gallon/3.8 liter) sized zip closure freezer bag, remove as much air as possible from the bag and either zip close or use vacuum sealer to seal only without removing air to guarantee a great seal.

- Elevate vacuum sealer to a level that makes it hard for the pump to pull up the liquid. This slows the process of rising liquid and allows you to press the seal button before it reaches the seal area.

What should you do if a pouch floats?

Ideally there is nothing but the thin plastic between the food and the water. That allows for efficient heat transfer and even cooking. Having little air in the bag can be solved by putting some weight on it, like a porcelain plate.

If the bag was properly vacuum sealed and did not float at the beginning of the cooking process and all the sudden developed air inside the bag, you should thoroughly check if that food was not contaminated with bacteria and thus has developed into a food safety risk. If the cooking water has taken on color or food aroma, it is an indicator that the bag is not properly sealed and you should discard it.

Compressions & Infusions

Depending on the vacuum level, the food may be compressed and change texture from the compact packaging. When adding liquids, the vacuum sealing process creates a rapid infusion—especially with more porous foods. This can add benefits to flavor and texture, but may not always be a desired result. For example, a delicate fish filet or chicken breast may become very dense in texture. Therefore, the PolyScience® Chamber Vacuum Sealer features customizable vacuum levels.