How hot does oil have to get for it to start to change, does anyone know? Particularly for olive oil / peanut oil. Also, if heating fats causes the change, and so everyone says ‘No Frying!’, why is roasting or something any better - fats are getting heated to high temperatures as well aren’t they?
I could be being really stupid about this but can someone enlighten me?
DC
You ain’t being stupid on this.
Don’t worry about creating trans-fats on the stove at home. It typically takes super high heat (you might get hot enough in the oven), a metallic catalyst (typically a “rare” metal is used), the presence of hydrogen, and a rather long time. I wouldn’t keep reusing previously cooked oil as it still degrades and other things can form as well as depleting the oil of anything really usefull.
The main reason that “everyone” says no frying is that it adds fat to the foods cooked in it. Roasting is thought to be better because the fat is allowed to drain off, at least if it’s on a rotisserie (sp?). Don’t worry about eating fat, as long as you’re within you calorie limits. There is some speculation as to the balance of saturated, poly-, and mono- unsaturated fats though.
As to the trans-fats, stay away from the bags, boxes, and wrappers (with certain exceptions like salad green mixes and fresh/frozen/canned with no sugar/salt added fruits and vegetables) and you’ll eliminate 99% of your concern.
If you decide to still use them though, look for partially hydrogenated oil or just hydrognated oil and avoid them.
Based on the research I’ve done, I agree that it takes a metal catylyst and super high temperatures that cannot be produced in a home kitchen to hydrogenate fat. But I have heard that heating oil past its smoke point does make it less healthy. I’m not exactly sure why or what properties change.
[quote]jsbrook wrote:
… But I have heard that heating oil past its smoke point does make it less healthy. I’m not exactly sure why or what properties change.[/quote]
As I understand it has something to do with increased oxidation of the fatty acids.
From what I’ve heard from Berardi, I think he said it’s not the fact that the oil changes to trans fat, which I don’t think happens. It’s more of a concern that it destroys the parts of the fats that we want to eat.
Thats why we are suppose to use saturated fats to cook at high heats, because the part of the fat that we want doesn’t get destroyed. Then with mono and polyunsaturated we should eat at a low temp so we can get the most benefits from the fat.
so what I am trying to say is, we eat mono and poly at low heats, saturated can be used to cook, and all this is to get the most benefits from the fats.
I hope that’s somewhat understandable.
http://health.msn.com/centers/cholesterol/articlepage.aspx?cp-documentid=100171340
Though somewhat elementary, the Harvard Medical Journal actually published a decent article about fats and how we should be consuming upwards of 40% of the calories in our diet from it.
Interesting points oil, however 1) what sat fats should be used - butter smokes pretty quickly at least for me and burned butter isnt awesome on my steak.
2) agree regarding not heating polys, especially flax oil - i thought peanut oil / olive oil was a bit diff, apart from say EVOO where it could kill all the phytonutrients etc etc. As such i never cook with EVOO - been using peanut oil lately.
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Don’t heat your butter that hot. It should sizzle, not smoke and go brown. What I typically do is to put the butter in the pan before it gets to hot and let it melt. Then swirl it around to coat the bottom. When it “clears” slightly is when I add the food to cook in it.
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You shouldn’t have problems with the peanut oil. If you want that olive oil taste just get a virgin olive oil instead of EVOO to cook with (grilling, light sautee).