Reusing cooking oil may seem like a cost-effective and environmentally friendly solution, but is it a good idea?

Cooking oil works wonders in the kitchen: it perfectly browns fried chicken, adds flavour to garlic and onions, let's you make homemade doughnuts. But once you're done with cooking, you're left with a a big pot of oil you may not know what to do with.

Is it safe to reuse cooking oil?

Yes, cooking oil can be reused but with caution. With each cooking cycle, oil degrades, especially if it's improperly stored or overheated. Under repeated heat, oil undergoes chemical transformations: it can produce toxic and carcinogenic compounds, promote inflammation, hypertension, and even increase the risk of certain cancers. It also loses its nutritional qualities—good fats like omega-3s decrease, while unhealthy trans fats increase.

How to properly reuse cooking oil

Some good practices can help limit risks:

• Control the temperature: Stay between 175°C and 190°C for optimal frying. Beyond this threshold, the oil reaches its smoking point and deteriorates more quickly.
• Use a thermometer: This affordable tool helps maintain a stable temperature, preventing overheating that accelerates the formation of unwanted compounds.
• Choose the right oils: Some oils tolerate heat better than others. Avoid oils high in polyunsaturated fats (like soybean or sunflower), which break down quickly. Instead, choose oils that are stable when cooked, such as peanut oil, avocado oil, rice bran oil, canola oil, or neutral vegetable oil.
• Even the best oils don't last forever: limit their reuse to 2 or 3 times, depending on the type of cooking and the care you take with them.

Tips to extend the lifespan of your cooking oil

• Adding a little fresh oil each time you cook helps dilute the degraded compounds and stabilize the temperature.
• Strain the oil after each use using a fine filter, cheesecloth or paper towels to remove food residue that can accelerate its deterioration.
• Store the oil properly: Once it has cooled (lukewarm, to avoid burns), pour it into an airtight container, opaque if possible, to protect it from light. Keep it away from heat, in a cupboard or in the refrigerator depending on the type of oil used.

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