**1. Introduction**

Despite their toxicity, pesticides are widely used to protect crops against insects, weeds, fungi, and other pests. Accordingly, pesticides are indispensable for food productivity and quality [1]. The application of pesticides may result in residues on vegetables, and these specified derivatives can induce adverse health effects (acute and chronic effects, such as reproductive harm, carcinogenicity, neurological toxicity, and cell dysplasia) [2,3]. Therefore, excessive consumption of residual pesticides via raw or processed vegetables is dangerous for consumers and thus warrants an effective removal strategy.

Globally, studies have been conducted to derive methods that can be utilized for pesticide residue removal from various types of vegetables. Many studies have used methods, such as peeling/trimming, washing/rinsing, soaking, and blanching/boiling, mainly for fruits and fruiting vegetables [4–12]. Tomatoes, oranges, cucumbers, and strawberries have been mainly employed in these studies. However, as these fruits can be peeled and washed relatively easily, it is comparatively simple to remove pesticide residues on these fruits compared to those on vegetables, especially leafy vegetables. Notably, the pesticides analyzed in these studies were limited to those used in fruits and fruiting vegetables. The removal of pesticide residues from the outer skin of certain fruits and fruiting vegetables by peeling or trimming is reported to be the most efficient approach to reduce pesticide residues [13]. However, it is difficult to apply these methods to leafy vegetables, as they cannot be peeled or trimmed. Therefore, the removal method of various

**Citation:** Yang, S.-J.; Mun, S.; Kim, H.J.; Han, S.J.; Kim, D.W.; Cho, B.-S.; Kim, A.G.; Park, D.W. Effectiveness of Different Washing Strategies on Pesticide Residue Removal: The First Comparative Study on Leafy Vegetables. *Foods* **2022**, *11*, 2916. https://doi.org/10.3390/ foods11182916

Academic Editors: Dapeng Peng and Yongzhong Qian

Received: 6 September 2022 Accepted: 14 September 2022 Published: 19 September 2022

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pesticides from vegetables must be investigated. As leafy vegetables cannot be peeled, they are relatively difficult to clean; only attached dust, insects, and foreign substances can be removed. In addition, owing to the large surface area of these vegetables, pesticide residues are likely to remain on their surfaces [14].

Leafy vegetables are used in various cuisines worldwide. Hence, an efficient method is required to remove pesticide residues from leafy vegetables in households. Among all methods, washing (tap water) is known as the most common and efficient method of pesticide residue removal in general households [15]. However, as many pesticides are hydrophobic, washing with tap water is inefficient for pesticide residue removal [16]. Cooking is known to be effective at removing some volatile pesticides but is ineffective at removing less volatile pesticides [11]. Therefore, depending on the characteristics of pesticides, various removal methods should be used. In particular, a removal method suitable for the characteristics of pesticides with a high frequency of use and high detection rate is necessary [13].

Several studies investigated the removal of pesticide residues from leafy vegetables. For example, washing spinach with tap water removed 0–48% of boscalid, deltamethrin, iprodione, mancozeb, and propamocarb [17]; washing Chinese cabbage with electrolyzed water removed 32–38% of chlorpyrifos, prothiofos, and deltamethrin; and blanching (5 min at 88 ◦C) spinach removed 0–72% of boscalid, deltamethrin, iprodione, mancozeb, and propamocarb [17,18]. However, studies using these methods, particularly washing with water, are scarce and are limited to only a few leafy vegetables.

In general, different methods are used to remove pesticide residues, including washing or blanching, in South Korea and other countries. Accordingly, studies comparing the effectiveness of removing various pesticide residues from various leafy vegetables are warranted. The objective of this study was to evaluate the effectiveness of various methods used in households to remove pesticide residues from agricultural products. Agricultural products, particularly leafy vegetables, were selected based on long-term research results obtained in the largest production area of leafy vegetables in South Korea and Food Safety Management Guidelines for 2021: lettuce, perilla leaves, spinach, crown daisy, and ssamchoo (*Brassica lee* ssp. *namai*) (Figure 1). The pesticides used were azoxystrobin, chlorantraniliprole, chlorfenapyr, diniconazole, fludioxonil, imidacloprid, indoxacarb, lufenuron, pyraclostrobin, and thiamethoxam [19,20].

**Figure 1.** Sampling and processing scheme.

Leafy vegetables are widely consumed in Asia in (1) salad, (2) kimchi, (3) seasoned vegetables, (4) meat wrapping, and (5) vegetable soup. Herein, nine pesticide residue removal methods were selected (alkaline electrolyzed water washing, blanching, boiling, sodium bicarbonate solution washing, washing with detergent, tap water washing-running water, tap water washing-stagnant water, ultrasonic cleaning, and vinegar water washing) for comparison (Figure 1).

To the best of our knowledge, the removal efficiency of the selected pesticides in vegetables, especially leafy vegetables, remains largely unknown. The aim of this study was to determine the effectiveness of nine pesticide residue removal methods on the removal of pesticide residues from leafy vegetables.

### **2. Materials and Methods**
