It's been confirmed a number of places (see http://dinersjournal.blogs.nytimes.com/2008/08/11/harold-mcgee-on-eggs-trans-fats-and-sous-vide/ http://dinersjourna

It's been confirmed a number of places (see http://dinersjournal.blogs.nytimes.com/2008/08/11/harold-mcgee-on-eggs-trans-fats-and-sous-vide/ http://dinersjournal.blogs.nytimes.com/2008/08/11/harold-mcg... for another). 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.