Foaming peanut oil?
Making enchiladas last night, I decided to fry the tortillas in peanut oil. (No particular reason, it's just what was at the front of the cabinet.) This is a new bottle of oil (Companion brand from the Chinese market) and I immediately noticed that it had a much more intense peanut smell than others I've used.
But the real surprise came after I'd fried a few tortillas. The oil began to foam. A lot. It wasn't overheated (375F), but it formed bunches of bubbles that clung to the tortillas like crazy. It was like dipping them in sudsy water.
Is this a normal thing with peanut oil? Is a less-refined oil going to smell "peanuttier" and foam more than something that's more refined? Or there something wrong with the oil or my technique?
Thanks in advance...
Okay, more info...
The oil is brand-new, it's preservative-free, it's never been heated before, and it didn't give off any smoke or have the funky smell and taste that oils get when they have been overheated and start to deteriorate. In fact, it had a very pleasant, intensely peanutty aroma.
And it didn't foam on its own. The tortillas definitely had a little moisture on them, and I have no doubt that the bubbles formed around water vapor from the food.
What was weird was the surface tension of those bubbles. Normally you can drop moist food into oil and bubbles form, rise, and dissipate. Here they formed and stuck around on the surface. For a minute or so, the pan looked like it had been filled with sudsy water.
Eventually, the bubbles subsided. But they were a lot more persistent than I'm used to seeing. Weird.
I'm with Uncle Bob on this one; sounds like unrefined oil. Refined peanut oil does not have a peanutty aroma, has a much higher smoke point and is what you need for deep fat frying. Unrefined oil, when used as you did, acts exactly as you described, foam- and bubble-wise, as the glycol and fatty acids in the oil start to break down after a short period of over-heating. I'm assuming your frying temp was in the 350-375* range.
Refined fats that have been used numerous times for frying will also eventually break down, and foaming will develop on the surface; at that point, the fat needs to be discarded.
I suggest you save your peanut oil for dressing salads, etc.
I just made some ghee or clarified butter today. I was careful to simmer it a long time to evaporate out as much water as I could. I thought it would be better for deep frying than refined oils, with all the solvents and chemicals they add in processing it. When I heated the oil there was hardly any spitting showing that there was very little water in it. However, when I lowered the potato into it, it foamed up just like the peanut oil described above, very sudsy and I had to hold the basket half in/half out of the fat. Yet ghee is recommended for deep frying and is supposed to have a high smoke point. I guess homemade versions are not nearly as refined as shop bought ones which have the various interfering organic compounds removed etc. Maybe I should try a lower temperature, but my deep fat fryer has only one default thermostat setting.
two totally different reasons oil will foam:
1) high concentration of MCTs (medium-chain triglycerides); this doesn't apply to peanut oil, so unless the pan or fryer was contaminated with coconut or palm oil from a previous use, that's not the problem in your case.
2) the oil has begun to deteriorate.
get a new bottle.