China is a major user of pesticides, with over one-third of crops using organophosphate pesticides. Due to its excessive use and high residue, both humans and livestock are at risk through the food route. Research on the elimination of organophosphate pesticides has also been conducted both domestically and internationally, but most of the research focuses on the treatment of pesticides in soil and wastewater, using physical and biological degradation methods; In the application of organic phosphorus pesticide residue elimination in fruits and vegetables, the efficiency and cost of physical methods will become obstacles to industrial promotion. Biodegradable bacteria are too sensitive to the environment and have poor stability. Currently, most chemical methods used in industry introduce secondary pollution, which are not ideal methods for eliminating organic phosphorus pesticide residues in fruits and vegetables.

Micro acidic electrolyzed water (hypochlorous acid water) has mild physical and chemical properties, and the active ingredients will gradually decompose. Its oxidation-reduction potential will gradually decrease and return to normal, gradually reducing to ordinary water without residue or pollution to the environment. After the process is completed and discharged, it will not cause any pollution to the environment.

Soak the contaminated chives in 500 mL of tap water, NaClO solution, and slightly acidic electrolyzed water (hypochlorous acid water). The pH of both NaClO solution and slightly acidic electrolyzed water (hypochlorous acid water) is around 6.0, the effective chlorine concentration is 79.66 mg/L, the room temperature is around 25 ℃, the time is 15 minutes, and the chives are left to stand. Afterwards, take out the chives, dry them in the shade, process them separately, and test for pesticide residues.

The removal effect of pesticides in chives by different solutions was studied, and the results are shown in Figure 1. From the figure, it can be seen that chives contaminated with tap water, NaClO solution, and slightly acidic electrolyzed water (hypochlorous acid water) can all reduce the content of dimethoate and chlorpyrifos in chives to a certain extent. The contact between tap water and chives can cause a small amount of residual LeGuo and Chlorpyrifos to detach from the surface, reducing them by 35.14% and 21.63%, respectively. Effective chlorine in NaClO solution and slightly acidic electrolyzed water (hypochlorous acid water) has oxidizing properties, which can convert P=S into P=O and to some extent, destroy the cyclic structure and decompose pesticides. The content of LeGuo and Chlorpyrifos in chives soaked in NaClO solution decreased by 47.79% and 66.75%, respectively. The removal rates of slightly acidic electrolyzed water (hypochlorous acid water) reached 66.02% and 72.55%, respectively. From this, it can be seen that slightly acidic electrolyzed water (hypochlorous acid water) has a better washing effect on contaminated chives than NaClO solution.

① The effect of effective chlorine concentration in slightly acidic electrolyzed water (hypochlorous acid water) on the removal rate of pesticides

Research has shown that the effective chlorine concentration in electrolyzed water has a significant impact on the removal rate of organic phosphorus pesticides in chives. The removal rate of Leguo first increases and then decreases with the increase of effective chlorine concentration. When the effective chlorine concentration is around 10 mg/L, the removal rate reaches the maximum value of 78.59%, and then decreases to around 52% and tends to stabilize. The removal rate of chlorpyrifos remains at around 70% after the effective chlorine reaches around 10 mg/L. From the graph, it can be seen that when the effective chlorine concentration is higher than 30 mg/L, the removal rate of two organic phosphorus pesticides by acidic electrolyzed water tends to stabilize and remains at a relatively high level. The possible reason is that as the concentration of effective chlorine in acidic electrolyzed water increases, the form of effective chlorine changes, resulting in a decrease in HOCl content and a relatively saturated removal effect on organophosphorus pesticides. From this, it can be concluded that at room temperature of 25 ℃ and a treatment time of 15 minutes, when the effective chlorine concentration is around 30 mg/L, slightly acidic electrolyzed water (hypochlorous acid water) can effectively remove pesticide residues of dimethoate and chlorpyrifos from chives.

② The effect of different treatment times of slightly acidic electrolyzed water (hypochlorous acid water) on pesticide removal efficiency

According to Figure 3, it can be seen that after soaking in slightly acidic electrolyzed water (hypochlorous acid water) for different treatment times, the removal results of Leguo and Chlorpyrifos in chives were evaluated. Within 5-30 minutes, at the same level of effective chlorine concentration, there was no significant difference in the removal rate of pesticides in chives with the prolongation of the action time of slightly acidic electrolyzed water (hypochlorous acid water) (p>0.05). This proves that the process of removing dimethoate and chlorpyrifos from chives by slightly acidic electrolyzed water (hypochlorous acid water) is different from the general chemical reaction process, and is a short-term process, possibly due to certain active substances in the electrolyzed water.

③ The effect of different treatment temperatures on pesticide removal efficiency of slightly acidic electrolyzed water (hypochlorous acid water)

The removal efficiency of two organic phosphorus pesticides from chives was studied using slightly acidic electrolyzed water (hypochlorous acid water) with pH 6.0 and effective chlorine concentration of 79.66 mg/L at 20, 30, 40, and 50 ℃, respectively. The results are shown in Figure 4. It can be seen that the removal rate of organic phosphorus pesticides in chives does not show significant changes with increasing temperature (p<0.05). At temperatures of 20, 30, and 40 ℃, the removal rate of dimethoate by slightly acidic electrolyzed water (hypochlorous acid water) was higher than 50%, but decreased by 43.80% at 50 ℃. As the temperature increases, the removal rate of chlorpyrifos by slightly acidic electrolyzed water (hypochlorous acid water) increases, and at 50 ℃, the removal rate increases to 86.51%. During the gradual heating process of slightly acidic electrolyzed water (hypochlorous acid water), the active ingredients will also be affected by heat, either accelerating the effect or losing and evaporating.

In summary, temperature has little effect on the removal of organic phosphorus pesticides from chives by slightly acidic electrolyzed water (hypochlorous acid water), while temperature has a significant impact on the physicochemical properties of food. Continuing to increase temperature will damage the quality of food. From a comprehensive perspective, controlling the processing temperature at around 20 ℃ can achieve the ideal effect of removing organophosphorus pesticides.

Experimental results have shown that slightly acidic electrolyzed water (hypochlorous acid water) has better removal efficiency than NaClO solution with the same effective chlorine concentration; When the effective chlorine concentration is around 10 mg/L, the removal rates of dimethoate and chlorpyrifos reach 78.59% and 70%, respectively. As the effective chlorine concentration increases, the removal rates of organophosphorus pesticides tend to stabilize and remain at a relatively high level; At a certain effective chlorine concentration, with the extension of reaction time, the removal rate of organic phosphorus pesticides by electrolyzed water can reach a stable value in a short period of time and then remain stable; When the temperature of electrolyzed water is within the range of 20-50 ℃, it has no significant effect on the removal efficiency of two organic phosphorus pesticides, and 20 ℃ can be used as the optimal treatment temperature.  

This experiment confirmed the removal effect of slightly acidic electrolyzed water (hypochlorous acid water) on organic phosphorus pesticide residues, indicating that slightly acidic electrolyzed water (hypochlorous acid water) can be used as a new technology for removing organic phosphorus pesticides from fruits and vegetables, and has great application prospects.

Part of this article is excerpted from "Food Industry Technology"

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