In recent years, the issue of pesticide residue on fruits and vegetables has gradually become a major concern for the public. To wash produce "cleaner," people have tried many methods, such as soaking in salt water or using vegetable and fruit detergents. Are these methods really effective?
Why do vegetables need to be washed before consumption?
Because vegetables often have significant pesticide residue. Several common methods of pesticide application include: applying it to the soil, spraying it directly onto the vegetables, and using a fumigation method (filling the entire greenhouse with smoke from burning pesticides). When pesticides are applied to the soil, they are absorbed by the entire plant.
Some people believe that washing the outside is sufficient, and at most, peeling the skin is enough. The truth is, however, that pesticides have often seeped into the vegetables. For example, with mushrooms, bell peppers, and cowpeas, how can we peel them?
As ordinary consumers, it is difficult to judge the level of contamination from the appearance of food. Therefore, residual pesticides are often absorbed into our bodies without our knowledge.
These parts of vegetables have the most pesticides
The vegetable stalks and stems are the parts with the most pesticide residue. For instance, the stalks near the root of Chinese cabbage and the indented part connected to the stem of bell peppers have more pesticides than other parts. It's best to discard these when eating.
Why do pesticides always accumulate in these parts of vegetables? Researchers from the National Engineering Research Center for Vegetables point out that this is related to the way vegetables grow and how pesticides are sprayed.
Take Chinese cabbage as an example. First, due to gravity, pesticides sprayed on the plant will flow down the leaves and stalks, collecting under the stalks. Therefore, the stalks will have a higher concentration of pesticides.
Second, because the stalks are close to the ground, the wind and sun exposure day and night reduce the chance of pesticides breaking down or degrading. Thus, pesticide residues on the stalks are more persistent. However, for vegetables like chrysanthemum stalks or flowering Chinese cabbage that do not have distinct stalks, this is not an issue.
As for bell peppers, even though they hang from the plant, they still follow this rule. Experts explain that because bell pepper plants are relatively short, pesticides are often sprayed from top to bottom, causing many pesticides to accumulate at the stem. Therefore, vegetables with uneven stems, like bell peppers, have this problem, while others like cowpeas and cucumbers do not.
Therefore, when we eat vegetables, it's best to cut off the stalks that are close to the ground. For vegetables like bell peppers, the stem should be removed before eating.
5 incorrect methods for washing vegetables
Using rice washing water: Rice itself can have pesticide and insect egg residue. Besides the problem of using dirty water to wash vegetables, there is usually only one basin of rice washing water, which is not enough volume to wash away pesticides. Vegetables soaked in it turn the basin into a pesticide pool, and that water would be dirtier than the unwashed vegetables. How could you use it to continue washing vegetables?
Using salt water: Salt water can make it easier for insect eggs and borers to fall off, but salt reduces the cleaning power of the water. Moreover, if the salt concentration is too high, it creates osmotic pressure, causing pesticides in the water to be absorbed into the fruits and vegetables, which is counterproductive.
Fruit and vegetable detergents: Many contain surfactants and complex ingredients. They should be rinsed off with plenty of water after use to avoid secondary residue issues.
Extending soaking time: Soaking for more than 30 minutes is not recommended, as it can lead to the loss of nutrients. Furthermore, the amount of pesticide that can be dissolved in water is limited, meaning the vegetables become clean and then re-contaminated, leaving the pesticide level in the water as high as on the vegetables.
Using an ozone machine to wash fruits and vegetables: This can only remove surface pesticides, and its cleaning power is about the same as water. Many pesticides cannot be broken down by ozone, and some fruits and vegetables contain nitrogen, which can react with ozone to form nitrates or nitrites. Additionally, there may be health risks if ozone leaks.
How to correctly wash vegetables?
For stem and gourd vegetables like cucumbers, bell peppers, carrots, and bitter melon, you can add a drop of dishwashing detergent to warm water and soak for 1-2 minutes. Then, scrub with a soft brush, paying extra attention to凹陷处, and rinse with clean water. If necessary, you can also peel them.
For leafy vegetables like Chinese cabbage and cabbage, you can remove the outer leaves, soak the inner leaves in warm water, and then rinse them one by one under running water.
For small-leafed greens like spinach, crown daisy, bok choy, and small cabbage, you can cut off the roots, shake them in water to clean, and then rinse with the roots pointing up under a faucet. The force of the water and the vibration will help remove residual pesticides.
In addition to washing, there are other methods that can help remove residual pesticides from vegetables.
Allowing freshly picked vegetables to sit in the air for 24 hours can allow some residual pesticides to break down into harmless substances. Therefore, vegetables that are not easily perishable, like winter melon, can be left to sit for a while.
Additionally, exposure to ultraviolet light can also break down and inactivate some residual pesticides in vegetables.
For vegetables like beans and cauliflower, you can blanch them in boiling water after washing, which can also eliminate residual bacterial pesticides.
Precautions for washing vegetables
When washing fruits and vegetables, be sure to choose a professional, all-natural produce detergent. If you don't have one, it's better not to use any detergent at all, because petroleum-based detergents do not have the function of removing residual pesticides and can leave their own residue. This not only fails to clean properly but also introduces secondary contamination. This is especially true for the dishwashing soap commonly found on the market. Think about it: even after rinsing dishes washed with dish soap multiple times with tap water, a residue remains, let alone when used to wash fruits and vegetables.
Many people make the mistake of adding detergent to the water first and then putting in the fruits and vegetables to wash. This washing method is incorrect. Because water has a diluting effect, the detergent is completely diluted by a large basin of water, which reduces its cleaning efficacy. It also prevents the detergent from fully contacting the surface of the produce, making it truly ineffective at removing residual pesticides.
Therefore, the correct way to wash is to first spray the produce detergent directly onto the surface of the fruits and vegetables, allow it to break down on its own, and then rinse with clean water.