In the program, the reporter bought two boiled peanuts from the market. The seller said that they were all boiled with water and refined salt, and nothing else was put. From the appearance and taste, these two boiled peanuts are no different from those cooked by themselves. Then the reporter cooked a peanut with water and refined salt according to the merchant's suggestion, and put it in a cool and ventilated place with the bought peanuts. After half a day, the peanuts cooked by myself began to feel sour and sticky, but from the market point of view, by the next day, the peanuts cooked by themselves were long and smelly; Although the bought peanuts have some sour taste, they look far less changed in appearance than the peanuts cooked by themselves. For the same boiled peanuts, the fresh-keeping time bought from the market is one day longer than that cooked by yourself. Why?

The reporter used a formaldehyde self-test tube to test the peanut juice bought in the market. The end result is that both kinds of peanuts contain formaldehyde.

As we all know, the harm of formaldehyde to human body is serious, and peanuts themselves do not contain formaldehyde, so where does the formaldehyde in boiled peanuts come from?

Ma, a senior experimenter in the Chemistry Laboratory of Qingdao University, said that some preservatives, such as sodium benzoate and sulfur dioxide, will be added to some foods, but some unscrupulous vendors will also add some non-food preservatives, such as sodium benzoate and formaldehyde, which are quite toxic, so the state explicitly prohibits their use in food.

The staff in the laboratory of Shandong Entry-Exit Inspection and Quarantine Bureau's Technical Center tested the formaldehyde of two kinds of peanuts purchased from the market. The results showed that the sodium benzoate in the two kinds of peanuts did not exceed the standard, but the formaldehyde content in them reached 22mg/kg and 30mg/kg respectively, which seriously exceeded the standard. Therefore, these boiled peanuts bought in the market are all added with non-food preservatives: formaldehyde, sodium bisulfate or formaldehyde.