Don't be superstitious about high-tech dishwashers

Wash pesticide residues? Don't be too superstitious about these so-called high-tech vegetable washers.

In recent years, when the pesticide residues in fruits and vegetables exceed the standard, newspapers often appear, which makes people worry about food safety, at the same time, it also promotes the demand of removing agricultural residues in fruits and vegetables. In this context, dishwashers with the banner of ozone, ultrasound, plasma and other high-tech came into being, and were popular with consumers.

However, while these high-tech products are selling well, some people have raised doubts. Are these washing machines really effective in removing pesticide residues? What are their principles for removing pesticide residues? Will the nutrients of fruits and vegetables be destroyed in the process of removing agricultural residues? To this end, the reporter interviewed experts in related fields.

Reporter inquiry found that the dishwasher on the market is mainly divided into three types: plasma sterilizer, ozone cleaner and ultrasonic cleaner. It is said that these washing machines, which cost nearly 1,000 yuan, can not only remove agricultural residues, fungicides, hormones and nutrients, but also remove growth hormones, lean meat concentrate, hookworm virus and antibiotic residues in seafood and aquatic products. However, for ordinary consumers, it is difficult to tell whether the dishwasher is really safe and effective.

"I doubt the function of this kind of equipment to remove agricultural residues. From the current scientific evidence, I do not think that fruit and vegetable cleaners and fruit and vegetable disinfectors are effective equipment. Although they may play a role in some specific circumstances, they are not of great value in general." Dr. Yun Wuxin, a member of the Scientific Squirrel Society, told Sci-tech Daily that neither the cleaning machine nor the disinfector had answered the key questions of removing and degrading agricultural residues in principle. Zhu Yi, an associate professor at the School of Food Science and Nutrition Engineering, China Agricultural University, holds similar views. She said that there are many kinds of pesticides used in reality, and different pesticides have different principles in the fight against pests and diseases. Therefore, it is impossible for a sterilizer with only one function to "shut down all the people without opening it", and it is impossible for all fruits and vegetables to have an efficient effect of removing agricultural residues.

In the advertisements of various dishwashers, manufacturers always produce a bunch of "authoritative test reports" and various dazzling experiments. However, this is all a trick to take advantage of the lack of expertise of consumers. For example, some manufacturers claim that the degradation rate of pesticides can reach a fairly high level. In fact, they add a specific pesticide to the water to determine the amount of the pesticide after treatment, thus obtaining a high "degradation rate". In fact, this pesticide does not represent the actual pesticide on fruits and vegetables, and the pesticide in water is completely different from that on fruits and vegetables. At the same time, the market of vegetable washing machine is also very chaotic, the scale of enterprises varies, the quality of products varies from good to bad, and the phenomenon that merchants arbitrarily exaggerate the function of products is everywhere. Some experts said that the diversity and non-standardization of technical schools are common problems in the dishwasher industry in China.

Ozone disinfection may be the most common type of dishwasher on the market at present. In fact, ozone is a strong oxidant, which can destroy the structure of some pesticides and degrade them. This kind of cleaner has a good effect in removing easily oxidized pesticide residues, but the experiment found that using ozone cleaner to remove pesticide residues not only takes a long time, but also requires a higher ozone concentration. Usually the ozone concentration and action time of household ozone cleaner are not up to the experimental standard. More importantly, the hazards of small molecular substances produced by pesticide residues after degradation have not been assessed, and the risk of these substances may be higher than that of pesticide residues. At the same time, owing to the wide variety of pesticides, ozone is not necessarily effective in eliminating all pesticide residues. Businessmen'propaganda is only aimed at certain specific situations. Wang Shiwen, Director of Ozone Committee of China Federation of Industrial Economics, also said that the principle of ozone cleaner is to use ozone to decompose pesticide components, and its effect is closely related to the concentration and quality of ozone. Experiments show that the removal rate of organophosphorus pesticides by 4 mg/l ozone in 30 minutes is 60%-70%, which requires large ozone instruments rather than household washing machines. From the current market situation, the ozone cleaner has limited gas production and low conversion rate of ozone dissolved in water. The general concentration of ozone is only 0.1 mg/l-0.2 mg/l, and its decomposition effect of pesticides can be imagined. Generally, it is good to remove 10-20% of the agricultural residues on the surface of fruits and vegetables. In addition, ozone treatment may affect the nutrient composition of some leafy vegetables. A study by Sun Yat-sen University showed that the total vitamin C loss of pakchoi was nearly 30% after ozone treatment.