Source: China's micro platform for science popularization
Expert in this paper: Liu Shaowei, Deputy Director and Professor of the Food and Drug Administration Research Center of East China University of Science and Technology, Doctor of Food Science of Pennsylvania State University, USA, and Postdoctoral candidate of Kansas State University, USA
Pesticide residue is a major problem in fruits and vegetables. In China, about 200000 people are poisoned due to food contaminated by pesticides every year, accounting for food poisoning One third of the population, and long-term intake of excessive pesticides will cause harm to multiple systems of the human body.
Many people are used to soaking vegetables for a period of time after washing to remove residual pesticides. In order to achieve better results, some people will extend the soaking time to 3-4 hours or even one night. But do you know that this seemingly healthy behavior will not only reduce the nutrient content of vegetables, but may even make them more "dirty".
The longer the soaking time, the better?
According to the solubility, pesticides can be divided into water soluble and fat soluble. Water soluble pesticides mainly include trichlorfon, ethephon, dimehypo, etc; Fat soluble pesticides are mostly organophosphorus pesticides, such as dimethoate and omethoate.
At present, most of the pesticides used for fruits and vegetables are fat soluble pesticides, because the permeability of fat soluble pesticides is far greater than that of water-soluble pesticides, and their control effect will be much better than that of water-soluble pesticides. But at the same time, this phenomenon also causes that the residue of fat soluble pesticides on the surface of fruits and vegetables is much higher than that of water-soluble pesticides.
The traditional method of soaking in water can only remove the water-soluble pesticides on the surface of fruits and vegetables, but can not remove the fat soluble pesticides, which are the main residues. In the process of soaking, water-soluble pesticides will dissolve in water and form an aqueous solution with a certain concentration. If the soaking time is too long, it is likely to cause pesticides in water to be re adsorbed by fruits and vegetables.
In addition, if the soaking time is too long, many water-soluble nutrients in vegetables such as vitamin C, vitamin B, calcium, magnesium, iron, zinc, etc. will dissolve in water, causing the loss of their nutrients. It has been found that when vegetables are soaked for more than 15 minutes, the loss rate of vitamin C content is more than 90%.
Therefore, the method of soaking fruits and vegetables with clean water for a long time is not scientific. It can not improve the removal rate of pesticide residues, and may even cause fruits and vegetables to re absorb pesticide residues and lose nutrients.
How to remove pesticide residues correctly?
So, the traditional soaking method is not feasible, how can we correctly remove pesticide residues?
1。 Blanching water: After washing vegetables, blanching water for 1-1.5 minutes can remove most of their fruit and vegetable residues without causing too much loss of vegetable nutrients. Taking cabbage as an example, rinsing with clean water can only remove 30% of its residual methamidophos content, while blanching for one minute can remove more than 90%.
2。 Peeling: For some fruits that cannot be blanched and vegetables with thick skin (such as cucumber, radish, etc.), agricultural residues can be removed by peeling. Common pesticides are only left on the surface of fruits, and the pesticide removal rate of peeling method can reach more than 90%.
3。 Weak alkaline water rinsing: The common weak alkaline water in the kitchen mainly includes rice washing water, flour water and baking soda water. The vast majority of pesticides are easy to decompose under alkaline conditions, so the removal rate of pesticide residues in fruits and vegetables washed with this kind of weak alkaline water is slightly higher than that of ordinary clean water.
4。 Rinsing with running water: Rinsing fruits and vegetables with running water instead of soaking them for a long time can not only improve the removal rate of pesticide residues, but also will not cause a large loss of nutrients. At the same time, we also remind everyone to wash vegetables before cutting to ensure the integrity of vegetables. This can not only prevent pesticides dissolved in water from penetrating into vegetables through the cut surface of vegetables, but also effectively prevent the dissolution or oxidation loss of water-soluble nutrients.
5。 Skillful cleaning with detergent: washing with clean water can remove most water-soluble pesticide residues, but for fat soluble pesticide residues, we need to use detergent. When cleaning fruits and vegetables, add 1-2 drops of edible detergent in the soaked water, soak for 3-5 minutes, and then rinse with water for 1-2 times to remove most of the fat soluble pesticide residues.
How to select low residue vegetables?
Besides learning how to clean fruits and vegetables, we should also learn how to select low residue fruits and vegetables to reduce pesticide intake from the source.
1。 Choose fruits and vegetables from regular sources
Most of us will choose meat products from formal sources, but we often do not have this concept when buying fruits and vegetables. In fact, fruits and vegetables in large supermarkets/farmers' markets/fruit supermarkets will undergo more stringent pesticide residue testing, and there will also be irregular market sampling during the sales process. Generally speaking, its pesticide residues will be lower and more stable than those sold by ordinary traders.
2。 Look at the appearance
We do not recommend consumers to buy fruits and vegetables with too bright appearance. Such fruits and vegetables may be more attractive due to excessive pesticide spraying; But at the same time, we also do not recommend consumers to buy "pesticide free" vegetables with insect eyes. This kind of vegetables may not be treated without pesticide, but only after the occurrence of diseases and pests. This kind of vegetables not only have pesticide residues, but also are likely to penetrate into the interior of vegetables through insect eyes, causing the pesticide residues to seriously exceed the standard. To sum up, consumers can choose fruits and vegetables with moderate maturity and normal color and appearance when purchasing fruits and vegetables.
3。 Smell
Before purchasing, you can smell the smell of vegetables. If the smell of vegetables is abnormal and slightly pungent, you should not buy them. This may be caused by a large number of pesticide residues with irritating taste. For bean sprouts, mushrooms and other foods, if they are white in color and have a pungent smell, they are likely to have been bleached through sulfur dioxide fumigation. Long term consumption of such bleached foods is harmful to human health, and consumers are advised not to buy them.
