What FSSAI guidelines say about reusing cooking oil that has been fried repeatedly

In many homes, oil left over after frying is strained, stored in a container and used again for the next round of frying, so that none of it goes to waste. But oil that has been heated repeatedly, whether called reused cooking oil, repeatedly heated oil or oxidised cooking oil, can affect health.

Heating oil again and again causes oxidation and chemical changes in it. The colour, smell and quality of the oil can change. Heating oil at a high temperature or for too long raises the chance of harmful compounds forming.

When oil is used repeatedly for frying, Total Polar Compounds (TPC) form in it. If their level rises, the oil may no longer be fit for human consumption. The Food Safety and Standards Authority of India (FSSAI) has said oil should not be used once its TPC content goes above 25%. The authority's guidelines state that repeatedly fried oil has been linked to high blood pressure, diseases of the blood vessels and liver problems.

Oxidation in repeatedly heated oil can produce some harmful substances. If such oil is consumed over a long period, concerns about heart health can grow. A drop in the oil's quality also changes the taste and smell of food. Even so, it would not be right to assume that eating food cooked in oil used once will cause illness every time. The quality of the oil depends on how long it was heated, at what temperature and how many times it was used.

The signs of spoiled oil are listed as follows: the oil turns dark, becomes thick, starts to froth, gives off smoke or smells odd. If this happens, the oil should be thrown away.

According to the FSSAI guidelines, reheating oil should be avoided, and if necessary its use should be kept limited. Where possible, it is better to use fresh oil for frying. If used oil has to be kept, it should be strained and stored in an airtight container away from light. Oil should not be poured down the sink, as it can block the tap and the drainage. Using less oil at home, limiting fried foods and checking the quality of oil before use are habits that can help health.