It's About Twine
Hardware store string, unwaxed dental floss, cotton twine, linen twine—just which should you use to tie that roast?
A recipe calls for kitchen twine, but the only twine you have is a skein from the hardware store. Should you use it? Probably not. Because it's not intended for use with food, it's probably not foodsafe. Still, we thought we'd give it a try, pressing into service some nylon twine from the hardware store. Although it didn't melt or burn, the Day-Glo yellow colorant leached onto the pork roast we had tied with it.
A common recommended alternative to kitchen twine is unwaxed dental floss, but it is so thin that while being tied on to a piece of meat it often cuts through it. After cooking, this whitish, almost translucent filament is all but invisible and so can be difficult to remove. We also found that dental floss is particularly ill suited to grilling because it easily singes and then breaks.
As for bona fide kitchen twine, you can buy cotton or linen. We found linen twine easier to tie, as it holds a nice tight overhand knot on its own. In addition, it pulls away from the cooked meat easily, taking a minimum amount of seared crust with it. That said, cotton twine worked nearly as well as linen and is a more economical choice.