Experts interviewed by

: Zhu Yi, associate professor of School of food science and nutrition engineering, China Agricultural University. In order to wash fruits and vegetables more “clean”, we think of many ways, soak them in salt water, add fruit and vegetable detergent Do these methods really work? This issue of “life times” reporter interviewed Zhu Yi, associate professor of School of food science and nutrition engineering, China Agricultural University, to summarize “common mistakes in washing fruits and vegetables”.

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were soaked without washing. If the fruits and vegetables are directly immersed in water without washing, the water-soluble pesticide residues will be dissolved in water, which is equivalent to soaking fruits and vegetables in diluted pesticide. Because the concentration of pesticide residues in water is higher than that in fruits and vegetables, these pesticides will permeate into the tissues of fruits and vegetables, which will increase the pesticide residues in fruits and vegetables tissues and aggravate the pollution of fruits and vegetables. Therefore, it is suggested that we should use running water to wash repeatedly before soaking. The soaking time of

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was too long. The main component of pesticide residues is organic phosphorus, which is not water-soluble, so long-term immersion can not work. Moreover, if the vegetables are soaked in water for a long time, the residual pesticides will decompose into the water, forming a certain concentration, leaving pesticide on the surface of vegetables. In particular, leafy vegetables such as spinach and cabbage, which are soaked in water for a long time, have little effect on the removal of pesticides. Therefore, it is recommended that the fruits and vegetables should not be soaked for more than 30 minutes, because in addition to causing nutrient diversion loss, the pesticide dissolved in the water is limited, which means that it is clean and polluted.

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were washed after removing the pedicel or cut first and then washed. Generally speaking, when cleaning strawberries and other fruits with fruit stalks, do not remove the fruit stalks first, because the pesticides will be brought into the fruits and cause pollution. At the same time, it is not recommended to clean vegetables after cutting, because a large amount of nutrients will be lost in the water when the vegetables are cut into small pieces. In addition, during the cleaning process, some pesticide residues may adhere to the section of vegetables. Therefore, the practice of first washing and then cutting is more scientific.

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use fruit and vegetable detergent. Many fruit and vegetable detergents contain interfacial active agents, and the ingredients are complex. After use, they should be washed with plenty of water. Studies have shown that there is no significant difference between washing with detergent and washing with water for removing pesticide residues. On the contrary, it may lead to secondary pollution, and detergent consumption may also be harmful to human body. Therefore, it is unnecessary to use detergent to clean fruits and vegetables. The concentration of

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was too high. The main function of light salt water is to dissolve protein. Therefore, salt water can make the eggs and moths fall off easily. However, it is difficult to effectively remove pesticide residues on the surface of fruits and vegetables. Some data show that salt can make pesticides more stable. It is not advisable to soak fruits and vegetables with salt water, especially for green leafed vegetables. Salt water will damage the cell membrane of vegetable leaves, which will not only lose nutrition, but also cause pesticide residues to enter the vegetables. Moreover, if the concentration of brine is too high, osmotic pressure will be formed, so that pesticides in water enter fruits and vegetables, which is counterproductive. ▲

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