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One of the frustrating issues people can run into is floating sous vide bags. There are several things that can cause this floating, with the most common being an excess of air in the bag. Another cause is by buoyant food such as several types of vegetables or frozen chicken.
In addition to being a hassle, floating bags can also be dangerous since any of the food that is out of the water will not be held at the proper temperature. This can potentially result in unsafe conditions and bacterial growth.
The amount of floating can range greatly. Some bags might barely raise to the top of the water bath while some may fill completely with air and be so buoyant they push the top of your container off.
There are several ways you can combat the floating and some are more effective than others depending on what is causing it.
If your sous vide bags are floating due to air in them, the easiest way to fix it is simply to remove all the air. This can entail mastering the water displacement method for Ziploc bags, getting a FoodSaver-type sealer or even a chambered vacuum sealer.
While removing the air upfront is the easiest solution, not everyone can afford a great vacuum sealer. Also, some meat and vegetables are really hard to work with, even with the higher-end sealers. In addition, many fruits and vegetables put out gasses as they are cooking, regardless of how well the air was removed initially.
So here are a few more tricks and tips you can use to prevent your bags from floating.
One option is to periodically open your sous vide bag, let the air out, and then reseal the bag. This trick works great when gas is being released during the cook, such as with certain vegetables or frozen foods. It is also much easier if you are using Ziploc bags since they are designed to be opened and closed.
If you are using vacuum sealed bags, you can often make them longer than normal, giving you more room to work with when resealing. However, you want to be very careful not to suck up any juices that might have been released in the bag.
If you are dealing with a bag that is just floating a little bit, you can often secure the top in place using a clip, such as these alligator clips I use. This will prevent it from moving around too much and floating to the top.
This is especially effective if you make your sous vide pouch large enough that the food can be at the bottom of the container while the bag stretches from the top to the bottom. This will give it a little more stability and help prevent floating. It will also give you a little more room at the top of the bag for the air to accumulate without affecting the food below it.
These clips also work well in conjunction with some of the other techniques I'll mention below, since they are easy to use to attach the sous vide bags to the side of the container or other items.
Another solution for sous vide bags that are trying to float is to weight them down. The extra weight will counteract the bouyancy of the air or food and help hold the bag in place.
There are many options for weighting down a bag, including:
When using the weights, many people suggest just placing them in the bag with the food. However, I and many other people feel it's best to separately seal the weights, then place the sealed bag in with the food or simply attach it to the outside of the sous vide food bag with a clip or cling wrap.
Sealing the weights separately will ensure that no flavor is transferred between the items. It also means you are 100% certain no harmful chemicals leach out of the weights. Not to mention that cleanup is a lot easier if your weights haven't been simmering in meat juice for hours!
Many people have sous vide racks or use covers on the water bath to help hold down floating bags. When the bags are just lightly floating, often times the added friction and placement of racks can help hold them down.
When it comes to racks, there are many options including:
Racks are also great when you have multiple bags in the water bath and you want them to stay in place and not bunch up. This aids in circulation and even heating of the items, which is very important with multiple bags. The racks can also be used with the other options discussed including weighting down the bags and leaving the tops open.
If you just can't get the food to stay in the rack, you can always tie it on with butchers string or silicon ties. Make sure you only tie a sous vide bag to something like a rack that the water can easily circulate through.
Other people who have not purchased racks yet also have some inventive solutions to holding the bags in place.
To simulate a rack, some food people will use stainless steel strainers or flexible stainless steamer baskets. It's also often possible to wedge a large metal serving spoon above the bag.
Some people force the bag into place using a variety of items. Many use a heavy ceramic plate or bowl to hold the bag in place. Others use their metal pot lids. Glasses and mugs are also sunk next to the bags to prevent them from moving.
A few people even just stick a brick into the water, though I'm not sure how well it would hold up over time!
A favorite method I had read about and have been experimenting with is to hold the bags in place with magnets.
You can place one magnet on the outside of the water bath and either a magnet or piece of metal on the inside of the water bath that is attached to the sous vide bag. It's usually best to have the item on the inside not be in the pouch with the food, as some metals can transmit flavors and might not be food safe.
If you are using a metal pot, you can use just 1 magnet on the inside of the water bath and it should work just fine.
Some magnets can't be heated though, so make sure the one you get can withstand the temperatures used in cooking.
I also highly recommend sealing the magnets separately from your food as they are often not food safe.
If your bag is filled with air and clipping or weighting it down doesn't work, you often need to take more drastic measures.
The physics behind the water displacement method ensure that all the air is pushed to the top of the bag but it will then often cause the bags to float once too much of it accumulates. This happens both with Ziploc bags and vacuum sealed ones.
If this regularly becomes an issue for you with certain types of food you can simply leave the bag unsealed. Make sure that the sous vide bag is long enough to reach above the water line where you can clip it in place. The pressure of the water will prevent air from entering the bag while the pressure of escaping air can force its way out.
You can still seal most of the bag if you want, leaving just a corner open, or using a knife to cut a small hole in an already sealed bag. Just make sure the opening is out of the water.
Make sure that if you do this, that the food itself stays below the water line at all times.
In this lesson we discussed several ways that you can prevent sous vide bags from floating.
Do you know anyone that is struggling with sous vide and would find this information helpful? Why not do them a favor and send them a link to this Exploring Sous Vide email course or get them a printed version of this course!
Thanks again and happy cooking!
Jason Logsdon, Amazing Food Made Easy