China's catering is very distinctive, with complete cooking techniques. However, there is a bad habit in China catering, that is, everything has to be cooked, especially after the food is fried, its color, fragrance and taste are improved, which greatly increases the appetite. Fried food is a regular dish in restaurants, canteens and even family tables. There is no shortage of oil pans in food stalls and night markets. Fish, meat, tofu, potatoes, apples, bananas, vegetables and so on can all be fried in the pan. However, from the nutritional point of view, it is not appropriate to eat fried foods too much for a long time. Fried foods not only reduce their nutritional value, but also contain toxic and harmful substances that can cause cancer and bring great harm to human health.

frying means that food is cooked by high heat in boiling oil, and the oil temperature used is usually between 151℃ and 311℃. Under such high temperature, nutrients are quickly destroyed, vitamin C almost disappears, vitamin B2 and niacin are mostly lost, essential fatty acids in oil are greatly lost, and the digestion and absorption rate of protein is greatly reduced. Compared with the original food, the nutritional value of fried food is less than 1/3. However, the loss of nutritional value is only a small part of the harm of fried food, and another important factor is the toxic and harmful substances that pose a great threat to human health.

Acrylamide: Studies show that foods with high starch content, such as potatoes, biscuits, bread and cereal, are easy to produce another carcinogen-acrylamide after being fried, fried and baked at high temperature (1.21℃), and its content will increase with the increase of temperature. Acrylamide is a possible carcinogen in human body. Epidemiological observation shows that long-term low-dose exposure to acrylamide can cause drowsiness, mood and memory changes, hallucinations and tremors. Many kinds of fried starch foods, including French fries, contain a lot of acrylamide. For example, the acrylamide content of 1,111 grams of French fries is about 411 micrograms, and the World Health Organization (WHO) suggests that the acrylamide intake of each adult should not exceed 1 micrograms per day.

In addition, after frying the oil at high temperature for 11 minutes, the oil will change obviously, the color will become darker, the viscosity will increase, and smoke and bubbles will be generated. This shows that the oil has deteriorated and should not be used any more. Repeated use of oil, its nutrients are completely destroyed, and fatty acids undergo thermal cracking, thermal oxidation and thermal polymerization, which will produce n-alkanes, monoolefins, phenols, ketones and other harmful organic compounds. Animal experiments show that repeated use of edible oil will shorten the life span of Drosophila melanogaster by more than 31%, and increase the infertility rate of Drosophila melanogaster, and it has obvious carcinogenicity. To avoid toxic and harmful substances contained in fried foods, the most important thing is to improve food cooking methods and eating habits. Change the eating habits of fried and high-fat foods. Deep-fried food is high in calories, high in oil and oxidants, and frequent eating can easily lead to obesity, hyperlipidemia, coronary heart disease and cancer. The oil temperature of fried food should be strictly controlled, preferably at about 151℃, and the fire should not be too strong. If the oil temperature exceeds 211℃, the frying time should not exceed 2 minutes; Fried food should not be eaten more at a time, nor should it be eaten often;