Alice,
I am trying to convince my good friend not to save the grease she cooks with for re-use. Instead of draining grease out of a pan after frying it, she saves and stores it to use again. It seems to me that grease that is cooked once is bad enough, twice must be horrible. Am I unjustly picking on her, or am I right that there is an even greater health risk when you cook with pre-cooked oil/grease?
Dear Reader,
Reusing cooking oil has been done for ages. There really isn't a problem, if done properly. The greatest hazard is allowing the fat to become rancid (spoiled) and deteriorated to the point it produces undesirable flavors and odors. Besides ruining what would have been a perfectly good meal, rancid oils also contain free radicals that are potentially carcinogenic.
To understand how to best re-use oil, it is important to know about smoke points — the temperatures at which oil begins to decompose. If you heat oil to a temperature that is too high, it produces smoke fumes. Acreolin, a substance that makes your eyes burn, is given off as well.
The optimal temperature to fry foods at is 190°C (375°F). At higher temperatures, the food will burn on the outside, and at lower temperatures, the food absorbs too much oil and tastes greasy. Different oils have different smoke points. Oils with higher smoke points are better for frying. The following is a list of smoke points:
| Type of Oil |
Smoke Point Temperature |
| safflower oil |
265°C |
| sunflower oil |
246°C |
| soybean oil |
241°C |
| canola oil |
238°C |
| corn oil |
236°C |
| peanut oil |
231°C |
| sesame oil |
215°C |
| olive oil |
190°C |
| lard |
183 - 201°C* |
| (*varies depending on the diet fed to hogs and the part of animal fat that is derived) |
Each time the oil is re-used, the smoke point becomes lowered. This is due to:
- foreign matter in the oil (such as batter)
- salt
- the temperature to which the oil was heated
- exposure to oxygen and light
- length of time the oil remained heated
- the number of times the oil was reused
Combining different types of oils also lowers the smoke point.
When oil becomes deteriorated, it appears dark and thick (viscous). It may have an off odor, and smoke appears before it reaches 190°C. If the oil smells funky and old, better to toss it away and replace it with fresh oil.
To re-use oil safely, use these tips:
- Strain it through a few layers of cheesecloth to catch any food particles. Be careful with hot oil, though, because you can easily get burned.
- Shake off excess batter from food before frying it.
- Use a good thermometer to fry foods at 190°C.
- Turn off the heat after you are done cooking. Exposing oil to prolonged heat accelerates rancidity.
- Don't mix different types of oil.
- Store oil in a cool, dark place.
- Avoid iron or copper pots or pans for frying oil that is to be reused. These metals also accelerate rancidity.
- Alice
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Is reusing cooking oil safe?
