Air in Bags After Immersion?

You don't mention what temperature you're cooking at, but it's quite common to get some gas in the bag, particularly with higher temperature cooks - rather than air, it's likely water vapour. Never having had the luck to use anything but a clamp style sealer, I don't know if this can occur even with chamber type sealers or whether the pressure they create inside the bag is sufficient to stop it. It shouldn't occur on every cook though, particularly low temperature, short cooks.

It can be frustrating as it can sometimes cause the bag to float, which can impair the cooking, however it's usually correctable by either weighing the bag down or using a bag with sufficient 'extra' that, when placed vertically, the gas just rises to the top of the bag, with the food remaining completely immersed below.

As Lee says, the slight expansion of the vacuum pouch is water vapour not air and is a function of the cooking temperature. Adding something to the bag, eg stainless steel rod or glass beads will help to keep the bag under water. If you do this you might prefer to double bag the food.

I have had a long 100hr cook of ox tail where the bag somehow floated to the surface and really ballooned up which is a good indication that there's some unhealthy bacteria at work, in which case its bin time.

For long cooking times you need to consider sterilising the surface of the meat as well as making sure the bag is fully immersed.

The cook times and temps varied. The gassing(?) comes early in the cooking cycle and hasn't been extreme. I did 137*F - 48 hour ribs that had just enough air to make them float, so I used plates to hold them under.

It's just driving me nuts because the bags are tight before they go in and then a bit later the bag is loose with air. If it had a leak I would imagine water would be sucked into the bag.

Has anyone tried deeply chilling the meat before bagging?

To TonyB
"For long cooking times you need to consider sterilizing the surface of the meat as well as making sure the bag is fully immersed."

When you say "...sterilizing the surface of the meat...", do you searing it in a skillet or some other method (I'm new to Sous Vide).

Ed, for solid muscles, you can quickly run a blowtorch over the surface of the meat or my preference would be to immerse the vacuum packed meat in 80C+ water for 30-60 secs. You could use boiling water if your bags are recommended for 100C temps.

Thanks Tony, I normally use a torch to give meats that "normal" look :)but I too would prefer setting the bag in 176C+ water-bath prior to cooking for long periods.

At the present time, I'm using a Vollrath induction counter top unit and a non-electronic probe thermometer for sous-vide cooking. I'll be upgrading to Fresh Meals Solutions system in January.