[Kitchen Witch]

Seasoned or flavored oils (walnut, olive oil, lard, drippings) should not be used because they have a low smoke point. Blended vegetable oils, pure corn oil, sunflower oil, soybean oil, rape seed oil (canola oil) have a high smoke point. Peanut oil will greatly impact flavor. Never mix oils.

Everyone knows that high heat, water and burnt food particles break down the oil's smoke point. Oil should be replaced immediately if you notice excessive smoking at normal temperatures, strong oil discoloration, a rancid smell, excessive foaming around the food.

Many foods are battered with bread crumbs, flour, spices, salt, egg and the like. Many frozen foods have ice crystals on their surface which adds water and volatility to the deep frying. All of these are extraneous to the food and to the oil, creating an oxidation environment that can be detrimental to food and oil quality. These extraneous materials can be considered "pro-oxidants" which catalyze, in the high temperature agitating environment of deep frying, undesirable break down of components in the oil.

Oil darkens with use because the oil and food molecules burn when subjected to high/prolonged heat. The more you use the oil, the more slowly it will pour. Its viscosity changes because of changes to the oils molecular structure. When smoke appears on the oil's surface before the temperature reaches 375* F, the oil will no longer deep fry properly.

Filtering helps to keep the oil fresher. The cones are nice - not all households have the use for a cone. The large filtering machines in the restaurant are nice too - just not for the average kitchen.

For home use, some will refrigerate the oil to be used again. It is not recommended because bringing chilled oil to room temp causes excessive splattering during the heat up process.

Some recommend just cooling, covering and storing in a cool dark place for up to 3 months. To me (and this is my opinion) that is much too long.

Always check the oil before using it - check for color, smell, or excessive foaming. If you see any of this - discard.

And there are those that say only use the oil once if frying fish or chicken.

Once I use oil for fish - I don't use it for anything else except fish. It's not "flavor" to me to fry a batch or two of fries (or anything else) in that oil.