First, select the right pot. Opt for a stainless steel rather than an iron pot because the latter will hasten rancidity. For the same reason, choose a tall and narrow, rather than a squat and wide, pot to minimize surface area. Oxygen is an enemy of oil.
The longer an oil is heated, the more quickly it will decompose. Therefore, do not preheat the oil any longer than is necessary. If you are cooking more than one batch of food, add each new batch without delay (unless time is needed to adjust the cooking temperature). Turn off the heat immediately after removing the last batch from the oil.
Some cookbooks recommend heating the oil until a slight haze appears on the surface. This is poor advice because smoke indicates that your oil is decomposing - and it does not reveal the exact temperature, which is the information you want. The best way to ascertain temperature is with a quality deep-fat frying thermometer. Its use is recommended even if you have a rheostat on an electric deep-fat fryer, because such thermostatic controls are seldom sufficiently accurate.
Your oil can be tainted by the bread crumbs and other particles that are scorched within a minute after they detach themselves from the frying food. Shake off loosely attached crumbs before adding the food to the oil. When crumbs do fall off the food into the oil, remove as many as possible with a small strainer or slotted spoon before they have a chance to burn.
As soon as the oil cools to a safe temperature for handling, funnel it through several layers of cheesecloth into its original bottle or, preferably, into a clean glass jar. Choose a storage container whose volume approximates the volume of the oil, because the more ullage (the air space between the lid and the liquid), the quicker the oil will oxidize, and therefore the quicker it will become rancid.
Light also damages oil, so keep your supply tightly covered in a dark, cool cupboard. Better yet, refrigerate the oil once it has been opened.
** Asian Recipes **