I don't know about parchement paper. Brown paper bags, as with most paper products, are treated with sulfur. I'm unsure if brown paper bags are a suitable substitute for parchement paper, however.
If brown paper bags outgassed sulfur, you'd probably smell it and your food would suffer.
BTW sulfur accounts partly for garlic's delicate perfume! <(;-)
[ June 01, 2001: Message edited by: kokopuffs ]