Sticky wickets
Sticky cooking oil is caused by the oil going rancid - either from improper storage or excessive aging, or from heating the oil too high in the presence of salts and acids. Corn oil is probably more likely to go rancid than coconut oil because it is much higher in polyunsaturated fats - which tend to go rancid quicker than monosaturated or fully saturated fats, such as in coconut oil.
Anyway, I just bought some fresh corn oil and popped up another batch in the Easy Pop. I liked the taste of the popped corn (used three tbs corn oil), and didn't notice it was sticky at all.
A rancid oil will also tend to get viscous. I noticed this happening with a small consumer size deep fryer. The peanut oil, after a while, would get thick, and that's when I would change it out. The resistance of saturated fats to rancidity probably accounts for the popularity of hydrogenated vegetable oils for deep fat fryers in many restaurants in the past. But now with the information getting out about the dangers of trans fats, I suppose places with deep fryers are turning to stuff like palm oil or coconut oil instead. Even lard would be more healthful than a hydrogenated shortening (and it's great in pie crusts!).
For those with a chemistry interest, the rancidity is basically oxidation, in which the double bonds of unsaturated fats are broken and attached to oxygen, and often cross-linked with other rancid fats. This thickens the solution, and is the process by which oil finishes are formed - as in linseed oil, oil paints, varnish, etc. Cross linked fats are useful because they form protective coatings on things, but they are not good to eat.
It's a bit of a two edge sword - doctors and nutritionists recommend unsaturated fats because they are better for the body, but if they are allowed to go rancid before consumption the benefit probably vanishes, and might even be replaced by some toxicity.
I am often reminded of a bit I saw Julia Child do. As she was adding gobs of butter to some recipe, she remarked that butter was far better for one than margarine or other "made up" shortenings. This was back in the 70's, long before the general alarm was raised about trans fats. That lady knew her stuff!
Sticky cooking oil is caused by the oil going rancid - either from improper storage or excessive aging, or from heating the oil too high in the presence of salts and acids. Corn oil is probably more likely to go rancid than coconut oil because it is much higher in polyunsaturated fats - which tend to go rancid quicker than monosaturated or fully saturated fats, such as in coconut oil.
Anyway, I just bought some fresh corn oil and popped up another batch in the Easy Pop. I liked the taste of the popped corn (used three tbs corn oil), and didn't notice it was sticky at all.
A rancid oil will also tend to get viscous. I noticed this happening with a small consumer size deep fryer. The peanut oil, after a while, would get thick, and that's when I would change it out. The resistance of saturated fats to rancidity probably accounts for the popularity of hydrogenated vegetable oils for deep fat fryers in many restaurants in the past. But now with the information getting out about the dangers of trans fats, I suppose places with deep fryers are turning to stuff like palm oil or coconut oil instead. Even lard would be more healthful than a hydrogenated shortening (and it's great in pie crusts!).
For those with a chemistry interest, the rancidity is basically oxidation, in which the double bonds of unsaturated fats are broken and attached to oxygen, and often cross-linked with other rancid fats. This thickens the solution, and is the process by which oil finishes are formed - as in linseed oil, oil paints, varnish, etc. Cross linked fats are useful because they form protective coatings on things, but they are not good to eat.
It's a bit of a two edge sword - doctors and nutritionists recommend unsaturated fats because they are better for the body, but if they are allowed to go rancid before consumption the benefit probably vanishes, and might even be replaced by some toxicity.
I am often reminded of a bit I saw Julia Child do. As she was adding gobs of butter to some recipe, she remarked that butter was far better for one than margarine or other "made up" shortenings. This was back in the 70's, long before the general alarm was raised about trans fats. That lady knew her stuff!
