Because it is coated with silicone polymer, kitchen parchment is grease- and moisture-proof, as well as nonstick. So we use it often in baking, where it ensures delicate cakes and cookies slide free with ease.
Those same properties had Jennifer Trone of New York City, a caller on Milk Street Radio, wondering whether parchment might be a better choice than foil when roasting vegetables.
To determine whether foil or parchment was best for roasting vegetables, we prepared lightly oiled carrots, potatoes, cauliflower, green beans and eggplant three ways: on an unlined sheet pan coated with cooking spray, on a parchment-lined pan (no cooking spray) and on a foil-lined pan (no cooking spray).
The parchment-lined pan performed slightly better than the foil-lined pan at preventing the vegetables from sticking, though not dramatically so, and both performed better than the unlined tray.
But neither browned the vegetables as well as the unlined pan. That’s because the foil and parchment act as a slight barrier to heat transfer. So while lining the pan offers a bit less sticking and easier cleanup, you do sacrifice some of the flavorful high-heat charring of an unlined pan.
Another consideration: Parchment doesn’t tolerate high heat. The recommended maximum temperature for kitchen parchment is 425 to 450°F. Though parchment’s silicone coating is heat-safe to temperatures up to 500°F, the paper itself is not. Like all paper, parchment burns at any temperature over 450°F. Even in a 500°F oven, parchment is unlikely to ignite, but it will scorch and become extremely brittle. Bleached kitchen parchment, however, has been treated with chlorine and can emit toxic substances called dioxins when heated above 450°F.
For all these reasons, we prefer roasting on unlined baking sheets.