Any food cooked in hot fat is fried. The method of heat transference is the same whether there’s just a little fat in the pan (sautéing), the fat comes partway up the sides of the food (shallow-frying), or the fat completely envelops the food (deep-frying). When food is added to hot oil, its surface dehydrates and the water droplets are evaporating. Meanwhile, through a series of Maillard reactions, its sugars and proteins break down to create complex flavor and golden-brown color.
I have been warned about using virgin oils for frying. I was contacted by a close friend after I posted information on the use of frying with virgin oils. The fact is, frying is Extra virgin is not a problem at all, as long as you respect the frying temperatures. More importantly understanding the theory of frying is as important as the oil you use.
In frying there are three stages; settling period, constant rate and the falling period. Paying careful attention to the bubbles will give you a good sense as to whether or not you are over frying. The bubbles swirl and heat the surface very quickly to the wet bulb temperature 100ºC. When bubbles stop the water droplets disappear, and you are crusting the food and the constant rate period is coming to an end. Now be careful not to burn the food. When the crust is done the temperature moves quickly into the center of the food. This is what takes practice and timing based on the thickness and moisture contents of the foods.
Just so you know, frying foods spend less than 1/10 of their time in contact with the hot oil. But if the oil isn’t hot enough to cook the food quickly, the food absorbs excess oil and fat. If the oil is too hot, components in the oil begin to break down. Heating the oil to the right temperature, means the food will absorb little excess oil.
One last point, between the batter and the food’s crust is the build up of condensation and at the time you remove the food from the frying oil, the water droplets condense and pull the oil into the food by creating a vacuum. So the key is to not overload the fryer, and immediately after frying blot.