Stir-frying with smoking oil might seem like a culinary flourish, but don’t underestimate the hazards of kitchen fumes! Recently, there’s been a trending topic about “an inconspicuous cooking habit leading to cancer.” It discusses the practice of heating oil until it smokes while stir-frying.
However, while the topic is partly correct in advising against heating oil to the point of smoking, the claim that “high temperatures cause unsaturated fatty acids in vegetables to oxidize and form trans fatty acids with a trans configuration” is illogical and lacks evidence.
Trans fatty acids generated from smoking oil during stir-frying are negligible.
Firstly, for unsaturated fatty acids to transform into trans fats, they require both high temperatures and catalysts. Without catalysts, merely high temperatures do not readily produce trans fats.
During the refining process of vegetable oils, temperatures are much higher and duration longer than stir-frying, yet the formation of trans fats typically remains around 2% or less. Even when oil is heated to the point of smoking during stir-frying, the trans fats formed are negligible and can be disregarded.
Kitchen fumes from smoking oil are a significant source of indoor PM2.5 particles.
However, the act of heating oil until it smokes indeed poses significant harm, though unrelated to trans fats.
Oil contains impurities like free fatty acids and phospholipids. When the oil temperature reaches a certain level, these impurities vaporize into various volatile compounds, creating “smoke.” These smoke particles are tiny and constitute a significant source of indoor PM2.5 particles. If you were to place an air purifier or PM2.5 monitor in the kitchen, you would observe that smoking oil while cooking a dish can increase PM2.5 levels from tens to hundreds. Cooking with smoking oil essentially creates haze indoors that you inhale.
Kitchen fumes contain various harmful components with different adverse effects on health.
- Acrolein in kitchen fumes has strong irritant effects on the eyes and respiratory tract, and it was even used as a chemical weapon during World War I.
- Kitchen fumes also contain polycyclic aromatic hydrocarbons, which, when inhaled, increase the risk of lung cancer similar to smoking.
Surveys have shown that chefs and middle-aged to elderly women who are frequently exposed to kitchen fumes have significantly higher levels of carcinogens in their blood. Even if they don’t smoke, their incidence of lung cancer is noticeably higher than those not exposed to fumes.
- Kitchen fumes contain various free radicals.
Exposure to high levels of free radicals in kitchen fumes accelerates skin aging over time.
- The harmful effects of kitchen fumes on pregnant women are particularly evident and can affect fetal development.
Therefore, pregnant and breastfeeding women need to avoid kitchen fumes.
“Unrefined oils” or “crude oils” have low smoke points and readily produce kitchen fumes.
The temperature at which oil begins to smoke is called the “smoke point,” which is closely related to the impurities in the oil. Unrefined oils such as “cold-pressed oils” or “crude oils,” often termed “crude oil” in the food industry, contain numerous impurities, resulting in a lower smoke point. For example, the smoke point of cold-pressed sunflower oil is less than 110°C, while that of cold-pressed soybean oil and peanut oil is approximately 160°C. In contrast, a relatively good quality cold-pressed sesame oil can have a smoke point close to 180°C.
Through refining, various impurities in vegetable oils, such as free fatty acids and phospholipids, are almost entirely removed, significantly raising the smoke point. Generally, the smoke point of refined vegetable oils is above 230°C.
During stir-frying, the oil is typically heated to “70-80% hot,” corresponding to temperatures roughly between 210°C and 240°C. This means that unrefined oils are unlikely to reach the temperatures required for stir-frying without smoking, while refined oils are unlikely to smoke.
To mitigate the hazards of kitchen fumes, consider the following three measures:
- Reduce frying and stir-frying and opt for cooking methods such as stewing, boiling, and steaming that do not produce kitchen fumes.
- If frying or stir-frying is necessary, choose highly refined vegetable oils with high smoke points instead of low smoke point “unrefined oils” or “crude oils.”
- Install a powerful range hood, turn it on before heating the oil, and continue running it for some time after cooking to effectively remove kitchen fumes.
Thank you for reading! ” Sitestorys “
