response to a column about tossing vegetables in olive oil and
roasting them in a 400 degree oven, a reader from Connecticut
writes: "My wife and I often roast vegetables as you
described. But we recently heard that olive oil, when used
with high heat, creates (compounds) that are definitely not
good for us. We are now concerned about using olive oil in
cooking and baking and are somewhat confused as to what we
should do. Do you have any knowledge or information about such
heat can definitely damage the integrity and nutritional value
of cooking oils, say food chemists. Especially when the oil is
heated beyond its "smoke point." How do you know
when it reaches this level? It emits a harsh odor and sets off
your smoke alarm. When oils begin to smoke, they release
volatile and sometimes dangerous compounds into your food.
vary in their smoke point. Extra virgin olive oil, for
example, disintegrates at a lower temperature than refined
olive oil. And the practice of reusing the same oil over and
over — such as in deep fat frying — causes it to become
rancid much more quickly.
conducted on "thermally stressed culinary oils" show
they can produce toxic substances known to harm health. And
valuable omega-3 fats are destroyed when vegetable oils are
heated above their smoke points. Exposure to light and oxygen
can accelerate the deterioration of cooking oils as well, so
where we store them becomes important. Here are some other
consuming fried foods as much as possible. Duh. When you do
cook in oil, use high monounsaturated fats such as olive and
canola oils. These may be better able to resist oxidative
damage when heated than oils that are high in polyunsaturated
fats such as corn or safflower oils.
extra virgin unrefined oils for salad dressings and lightly
sautéed dishes. Use more refined oils for cooking at higher
temperatures. Extra virgin olive oil, for example, has a smoke
point of about 320 degrees F. whereas refined olive oil begins
smoking at around 410 degrees.
oils like peanut, walnut, sesame and grapeseed for dishes that
require higher cooking temperatures. These oils generally have
smoke points of 400 degrees or higher.
your cherished flaxseed, hemp and poppyseed oils for recipes
that require little if any heat. These oils have a high
propensity to become rancid even at low cooking temperatures.
needs to char foods with ghastly high temperatures anyway?
According to a technical paper on this topic from Oklahoma
State University, most foods cook well at temperatures between
325 and 375 degrees F. Maybe we could even turn the heat down
a bit with our olive oil tossed roasted vegetables.