But here's the problem: There isn't a universal “safe number” of uses. Oil degradation depends on the temperature, type of food, heating time, and oil type. Research shows that repeated frying increases chemical and physical degradation.
When cooking oil is heated, especially at high temperatures, it creates harmful chemical reactions like aldehydes, free radicals, and trans fats. Repeated heating can also cause the oil to break down and become less stable.
Every time oil is heated, its quality decreases. High temperatures and repeated frying can cause the oil to darken in color, develop an unpleasant smell, become thicker or stickier, and produce more degradation compounds.
There isn’t one exact number that applies to every type of cooking oil. How quickly oil degrades depends on factors like cooking temperature, type of food being fried, the time the oil has been heated, whether food particles are left in the oil, and how many times it has already been heated. So instead of counting only the number of uses, pay attention to the oil’s condition.
Signs that tell you to stop using the oil include:
- Strange or unpleasant smell
- The color changes to very dark
- Starts producing smoke quickly
- Excessive foaming
- The taste and smell of food become different
One sign alone doesn’t always mean that the oil is automatically unsafe. These are practical signs that the oil’s quality has deteriorated and it is time to stop using it.
What to do after you're done with the oil?
Once you're done with it, do not pour the oil down the sink because it can cause clogged pipes and problems in the wastewater systems. Instead, you have to let it cool, then store it in a suitable, sealed container, and bring it to the used-oil collection or recycle it.