In daily life, many people wait until the oil in the pan is smoking before adding ingredients, but this practice poses health risks.Professor Wang Yishan from the Health Management Center of PLA No. 107 Hospital explains that when oil begins to smoke, its temperature often exceeds 200°C. At this point, many nutrients in the vegetables are destroyed, and carcinogens can easily form. Furthermore, at high temperatures, the fat-soluble vitamins and essential fatty acids in the oil are also damaged, reducing its nutritional value.
How can one enjoy delicious food while ensuring nutrients remain intact? Fan Zhihong, Associate Professor in the Department of Nutrition and Food Safety at China Agricultural University's College of Food Science, introduced the "onion skin test": toss onion skin into the oil. When it contacts the hot oil, it will form bubbles. These bubbles indicate the oil temperature.If few bubbles form around the peel, the oil is too cool; if the peel quickly turns yellow, the oil may be too hot. The ideal temperature is when the peel remains uncolored while small bubbles continuously form around it.For stir-frying or stewing, use soybean oil, sunflower oil, or peanut oil. For cold dishes, opt for sesame oil, olive oil, or flaxseed oil. Reserve coconut oil and palm oil for deep-frying. This blended approach leverages each oil's strengths, promotes nutritional balance, and enhances health benefits.