When do you decide it's time to change your frying oil?
– Bob del Grosso, Chef-Charcutiere, Hendricks Farms & Dairy, President, Tarocorp, Telford, PA
The longevity of your frying oil depends on a number of factors: what kind of oil, what are you frying, how much of it are you frying, how often and how well are you filtering, for how many hours is the oil in use and at what temperature, and how clean is the equipment?
As oil is used, food particles, high temperatures and repeated use lower the smoking point and eventually result in rancidity that gives your food off-flavors. The trick, of course, is to maximize the number of baskets of food the oil can cook before it breaks down.
Keeping the fryer clean, filtering the oil daily (or after each meal service), keeping the oil cool and covered when not in use, keeping the temperature at 375 F or lower, replacing all the oil at once rather than periodically topping off, salting food only after frying, and using oils designed for deep frying are all helpful in extending the oil’s life.
To determine if the oil needs to be changed, commercial test kits are available. These kits are particularly useful in operations where fried items are a major part of the menu mix or where fluctuations in volume mean that fryer use is inconsistent. If you want to go the low-tech route, your senses can do a pretty good job as well. Look for a darkening color or a change in viscosity, smoking or frothing, and any sort of off-odor. At the first sign of any of these factors (hopefully not in the middle of a busy service), it is time to change the oil.