Never heat Oil

Of course. This is an excellent and important question, as the stability of cooking oils is crucial for both health and culinary results.

Here’s a detailed breakdown of the risks associated with heating olive oil and rapeseed oil (often known by its branded name, Canola oil in some countries).

The Core Concept: Smoke Point vs. Oxidative Stability

Most people focus solely on smoke point (the temperature at which an oil starts to smoke and break down visibly). However, a more important health metric is oxidative stability—how resistant an oil’s fats are to reacting with oxygen and breaking down into harmful compounds when heated.

When oils break down, they form:

• Harmful compounds: Free radicals, aldehydes, and polar compounds which are linked to inflammation and chronic diseases when consumed regularly.
• Negative culinary effects: Loss of nutritional value, degradation of flavor, and unpleasant odors.

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1. Heating Olive Oil

The Myth:

“For years, a common myth stated that extra virgin olive oil (EVOO) has a low smoke point and should only be used for cold dishes. This is largely incorrect and has been debunked by modern research.”

The Reality:

• Smoke Point: High-quality EVOO actually has a moderately high smoke point, typically between 190°C – 215°C (375°F – 420°F). This is perfectly suitable for most forms of cooking, including sautéing, pan-frying, and oven roasting.
• Oxidative Stability: This is where EVOO truly shines. It is remarkably resistant to breaking down due to two factors:
  1. High Monounsaturated Fat Content: Its primary fat is oleic acid, which is very stable under heat.
  2. Antioxidants: It is rich in natural antioxidants (like Vitamin E and polyphenols) that protect the oil from oxidizing. These compounds essentially “take the hit” from heat and oxygen, preventing the harmful breakdown of the fats.

Risks and Recommendations:

• Risk Level: Low to Moderate, depending on the grade and temperature.
• Best For: Sautéing, light pan-frying, roasting, and baking. It is not ideal for deep-frying or very high-heat searing for extended periods, as this will eventually degrade its delicate flavors and antioxidants.
• Which Olive Oil to Use?
  • Extra Virgin Olive Oil: Perfect for most cooking. Its stability and flavor make it a great choice.
  • Refined Olive Oil (or “Light” Olive Oil): Has a slightly higher smoke point (closer to 240°C / 465°F) and a more neutral flavor, making it excellent for higher-heat cooking where you don’t want an olive oil taste.
• Key Takeaway: It is not only safe but beneficial to cook with olive oil. The fear of heating it is outdated.

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2. Heating Rapeseed Oil (Canola Oil)

The Profile:

• Smoke Point: Refined rapeseed oil has a high smoke point, around 200°C – 230°C (400°F – 450°F), making it suitable for high-heat cooking like frying.
• Oxidative Stability: This is its main point of concern.
  • High Polyunsaturated Fat (PUFA) Content: Rapeseed oil contains a significant amount of omega-6 polyunsaturated fats (linoleic acid). PUFAs are the most vulnerable to oxidative damage when heated. They have multiple double bonds in their chemical structure that break easily under stress.
  • Processing: Most conventional rapeseed oil is highly refined using high heat, chemicals, and deodorization. This process removes natural antioxidants (like Vitamin E) that would otherwise protect it, making it less stable. Furthermore, this industrial processing can create small amounts of trans fats.

Risks and Recommendations:

• Risk Level: Moderate to High, especially when reused (e.g., in deep fryers) or heated to very high temperatures repeatedly.
• Best For: It is widely used for deep-frying in restaurants due to its low cost and high smoke point. For home use, it’s acceptable for occasional pan-frying or baking.
• The Big Concern: Repeated heating or overheating leads to significant formation of harmful oxidative products. Using rancid or repeatedly heated oil is detrimental to health.
• Key Takeaway: While it has a high smoke point, its low oxidative stability makes it a poorer choice for high-heat cooking compared to more stable oils. If you use it, avoid reusing it and do not let it smoke.

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Comparative Summary Table

Feature Extra Virgin Olive Oil Refined Rapeseed/Canola Oil Primary FatMonounsaturated (stable) Polyunsaturated (unstable) + Monounsaturated AntioxidantsVery High (protects from oxidation) Very Low (removed during refining) Smoke Point Moderate-High (190-215°C / 375-420°F) High (200-230°C / 400-450°F) Oxidative StabilityExcellent (Very resistant to breakdown) Poor (Prone to oxidation and forming harmful compounds) Best Use Sautéing, roasting, pan-frying, dressings Not recommended for high-heat. Acceptable for occasional medium-heat cooking. Main Risk Degradation of flavor and antioxidants if overheated. Formation of harmful oxidative products when heated.

General Best Practices for Heating Any Oil

1. Don’t Let It Smoke: If your oil starts to smoke, it’s a clear sign it’s breaking down. Turn off the heat, carefully discard the oil, let the pan cool, and start again.
2. Choose the Right Oil for the Job: Use oils with high oxidative stability (like olive, avocado, or coconut oil) for cooking.
3. Avoid Reusing Oil: Especially with oils high in PUFAs like rapeseed, corn, or sunflower oil. Each heating cycle creates more harmful compounds.
4. Store Oils Properly: Keep them in a cool, dark place to prevent them from going rancid before you even use them.

Final Verdict: Based on oxidative stability, extra virgin olive oil is a safer and better choice for heating than refined rapeseed (canola) oil for most everyday cooking tasks. The high antioxidant content and stable fat profile of olive oil make it far more resistant to creating harmful compounds.