Repeated frying of soybean oil can not dissolve many impurities and cause astonishing carcinogens. 报错

Place of experiment: Food Analysis Laboratory of Food College of Heilongjiang Bayi Agricultural Reclamation University

Instructor: Zhang Aiwu Senior Laboratory Teacher

Experimenter: Xu Bingzheng, Yang Yijie, Shen Yan (all graduate students)

The results showed that insoluble impurities in soybean were higher than the national standard after frying once, and the carcinogens in soybean were doubled after frying.

Soybean fried food is very popular, but some citizens, especially young housewives, make it difficult to enjoy the delicious food.

Xiao Wang, who works in municipal organs, called and said, "Every time we fry something, the oil in our house is thrown away, but since my mother-in-law came to our house, the soybean oil has been reused several times and is reluctant to throw it away." I've heard that this oil is not good. I want to ask what's wrong with it.

This issue of "More Genuine Laboratory" will help you to solve this question.

Pre-test Popularization of Science

The main edible oil in the north is soybean oil, which we often call soybean oil. It contains rich linoleic acid, which can significantly reduce serum cholesterol content and prevent cardiovascular diseases. Soybean also contains a lot of vitamin E, vitamin D and lecithin, which are very beneficial to human health. In addition, the human digestibility and absorptivity of soybean oil is as high as 98%, so soybean oil is also an excellent edible oil with high nutritional value.

However, after repeated use of soybean oil fried food, cooking food, fried over-heated food, will produce benzopyrene.

Benzopyrene is a kind of organic compound with obvious carcinogenic effect, which can easily lead to lung cancer, gastric cancer and so on. For every 1% increase in benzopyrene content in human living environment, the mortality rate of lung cancer rises by 5%. Frequent consumption of fried and barbecued foods contaminated with benzopyrene can accumulate carcinogens and increase the risk of malignant tumors.

实验人员对炸过的豆油进行过滤处理。

Experimental process

According to the national standard of oil and fat, insoluble impurities in crushed soybean oil are less than 0.05%. The so-called insoluble impurities are substances outside oil. Insoluble impurities exceed the standard, indicating that the oil is not qualified. This experiment is to determine insoluble impurities in five samples.

Reporters purchased a bottle of soybean oil at random, and according to the daily family cooking and frying food habits, a total of four fried food. After each explosion, an experimental sample was extracted after cooling and precipitation, and a total of 5 samples were counted for the unfried crude oil.

Crude oil is numbered as Sample 1, fried once as Sample 2, and the other three samples are analogous in turn.

In order to detect insoluble impurities in grease, petroleum ether must be added to the grease to dissolve it, then the dissolved grease is filtered by filter paper, weighed after drying, and the weight changes before and after the filter paper are calculated, so as to calculate the percentage of insoluble impurities in different samples.

experimental result

After more than an hour of careful experiments, three experimenters calculated the percentage of insoluble impurities in five samples.

No. 1 crude oil: 0.03%; No. 2 primary frying oil: 0.72%; No. 3 secondary frying oil: 1.17%; No. 4 third frying oil: 1.24%; No. 5 fourth frying oil: 1.31%.

Expert Interpretation

From the above test, it can be seen that only crude oil No. 1 meets the requirements of the national standard.

The insoluble impurities of sample 2 were higher than those of national standard, and the insoluble impurities of sample 3 (twice fried oil) and sample 2 had a large span.

It can be concluded that soybean fried once, and continue to use it to fry food, long-term consumption of the human body is more harmful.

Several suggestions

Therefore, the family used frying oil once, it is best not to fry food again, the citizens can fry the upper layer of the more clear part of the scoop out, used to make cold dishes such as non-heating.

In addition, frying oil is more prone to rancidity than new oil. Contact with air and high temperature will accelerate the rancidity and decomposition of oil and fat, and produce substances affecting health. Citizens had better put a lid on the frying oil and use it as soon as possible.

Fried food is a kind of high-calorie food, which can easily lead to obesity, hyperlipidemia, coronary heart disease, and even cancer. Therefore, it is not necessary to eat more at one time, nor should it be eaten regularly.

When frying food, when the oil temperature exceeds 200 C, the best time is not more than 2 minutes.

In addition, after eating fried food, citizens should eat more vegetables and fruits, because vegetables and fruits contain more flavonoids, which can reduce the harm of the body after eating fried food.

Some people or restaurants who often fry food can choose special frying oil to reduce the harm of repeated frying. Fried oil is a blending oil with high smoke point, which is made up of various vegetable oils in a certain proportion.