Aiheeseen liittyen T-magissa Dr.Lonnie Loweryn pähkäilyä..:
(
http://www.t-nation.com/findArticle...3227C2B5D4B8D9B38F94.ba13?article=04-026-diet )
Is there some concern over how oils react to high heat? How long or hot can I fry oil before it becomes riddled with unhealthy trans fatty acids?
A: The short answer regarding trans fats is: don’t worry about it! The long answer is more interesting, though. First, aside from some extreme circumstances, the cooking of vegetable oils simply doesn’t create trans fatty acids because heat alone doesn’t do this. A catalyst of some kind is needed and that doesn’t happen in most home kitchens.(5, 17)
Even elaidic acid, which is the most-consumed trans fat in the American diet, isn’t formed from healthy, monounsaturated oleic acid (cis type) by heat alone. As practical proof, consider that elaidic acid is solid at room temperature; so no matter how long or hot you keep your olive oil (mostly oleic acid) during cooking, it doesn’t turn into a solid in the pan when the meal is done.
This is not to say that oils can be used and re-used indefinitely. Trans fat isomerization may not occur but several other aspects of quality do diminish. Smoke point and oil darkening are good practical indicators that the oil is losing quality such as antioxidant capacity, triglyceride breakdown, fatty acid oxidation (rancidity), etc.(1, 13, 16)
Again, long-chain highly unsaturated oils (fish, flax) are at greater risk. Perhaps oil re-use limits are more of a concern to restaurants with deep fryers, etc. I don’t really use enough oil in cooking to save the pour-off for future use. Besides, the oil picks up the flavors of the last meal; I don’t usually want that. If you do recycle oil at home, just recognize that there is some loss in quality each time and a limit perhaps of a half-dozen fryings is pushing it.(1, 16)
The mere existence of published limits constraining multiple fryings grosses me out a little. I mean, how many days or weeks would a cook re-use a batch of oil to save money? If you want to stay on your diet, think about this the next time you walk into a restaurant for a fried meal.
5. Enig, M. Trans fatty acids are not formed by heating vegetable oils. In: Wise Traditions in Food, Farming and the Healing Arts: winter 2003. Weston A. Price Foundation.
http://www.westonaprice.org; accessed June, 2004.
http://www.westonaprice.org/know_your_fats/howtransform.html
7. Gifford, K. Dietary fats, eating guides, and public policy: history, critique, and recommendations. Am J Med. 2002 Dec 30;113 Suppl 9B:89S-106S.
