The point of this mode of cooking is that it's low temp, below the temperatures at which plastics in high-quality freezer bags become an issue (Ziploc confirmed this to Dave Arnold earlier this year).
Make sure you're using Ziploc specifically -- as in that brand. Other manufacturers may have their own formulations for their plastics, including non-heat-stable plasticizers. I contacted Trader Joes, for example, when writing Cooking for Geeks, and they disclosed that their plastics are NOT heat safe.
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.
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.
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.
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.
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).