There's a silicone bag available:

http://www.amazon.com/Lekue-1-Liter-Fresh-Bag-Clear/dp/B0049...

I fully expect plastics labelled with e.g "up to 90 degrees C" to not release anything unwanted into my food if I stay well below that temp. I'd also expect the label to have a wide margin to dangerous temperatures.

In theory you can use anything that handles the temperature, such as silicone. You could in theory force your food into a jar with a bit of oil.

You might be making matters worse with a jar: those with screw-on lids have a plastic lining in the lid that's traditionally PVC with plasticizers which are considered to be bad for health. To make matters worse, oil will support the migration of the plasticizers out of the plastic.

food in jar with oil = confit, a fairly popular, and very long lasting, preparation in the sous-vide at home world.

Yes: you can use glass jars with liquid (oil, marinade, etc.) inside them. Make sure the jar isn't too large; there's potential safety issues with ramp-up temperature of the center of the jar vs the outside.

You can use mason jars if you are worried about plastic.

That works for things that perfectly fill a mason jar, but not well otherwise; the giant air pockets are an issue.

I find it generally easier to cut items into portion sizes before cooking them sous vide.

- It makes the size more manageable in your water bath. - You don't have to worry as much about temperature ramp-up time between outer surface and core of food item. - For delicate proteins, means there's less handling of the item post-cooking.

-Jeff

I completely agree, I'm just stating the alternative. Sometimes standard freezer ziploc bags aren't even big enough. I was doing a large prime rib a while ago and has to use the larger size freezer bags that aren't normally available at my grocery store. If you used something else you would need a large amount of butter/liquid to get rid of the air.

You can get differently-sized jars, though. I've got a pretty wide variety of sizes for different stuff.

I still use bags most of the time, because I don't think running a cooker at 55 deg C with bags rated for 90 deg C is going to be an issue.

Are plastics known for breaking down at 134 degrees f?

Additives to plastics break down at lower temperatures. EVA breaks down at around 149f (you meant f, right, because nothing is cooked sous vide over boiling temperature).