The Sous Vide Vacuum Conundrum
|SVS Zip Pouch
|FoodSaver Clamp Vacuum 2240
That being said, using a vacuum sealer is considerably more convenient. Especially if you are cooking products that tend to float or you are going to be using like 50 bags. Most consumers are familiar with the food saver style vacuum sealer. The foodsaver is an example of an external clamp vacuum sealer. These sealers suction the air out of a bag and then heat-seal. If your bag contains liquids, then you are likely to remove some liquid as well, which can affect the quality of the seal and also make a huge mess. There are ways to mitigate this, including freezing the liquids and double bagging, but they have their own challenges.
|VacMaster VP210C Chamber Vac
Chamber vacuums operate by placing your bag into the vacuum and putting the open end under a sealing bar. The vacuum sealer then removes all of the air from the entire chamber, including the bag. Since the air pressure stays equal both inside of the bag and outside (in the chamber), the liquid doesn't get sucked out of the bag.
At this point, you are probably wondering why someone would spend 700$ on a chamber vacuum when 130$ buys you an external clamp vacuum sealer. The truth is, there aren't that many cases where a chamber vacuum is essential for low temperature cooking techniques. Apart from the ability to vacuum liquids you can also control the strength of the vacuum. The vacuum strength can be used to influence the texture of the product. The chamber vacuum is not just useful for sous vide, as it is also handy for other techniques, including: compression, rapid marination and infusion of liquids. While clamp vacuum sealers can sorta do some of those techniques, there are limitations, including lack of control and degrees of effectiveness.
|Handy vacuum charts