Pesticide residues in leafy vegetables,stalk and stem vegetables from South Korea: a long-term study on safety and health risk assessment

South Korea has a unique food culture. South Koreans enjoy wrapping meat and eating or making kimchi (traditionally fermented Korean food) and eating using raw leafy vegetables, stalk and stem vegetables. Therefore, there is a high chance of being exposed to pesticide residues of vegetables. The objective of this study was to investigate pesticide residues in leafy vegetables, stalk and stem vegetables from South Korea. A total of 8496 samples were mainly collected from Gwangju and Jeonnam area (the largest production region of leafy vegetables, stalk and stem vegetables) in South Korea from 2010 to 2014. A total of 230 pesticides were used for multi-residue analysis of pesticides. Among 8496 samples, 61 different pesticides (1029 times) were detected in 890 samples, of which 118 samples (1.4%) exceeded the Korea maximum residue limits (MRLs). Samples exceeding the MRLs were mostly found in leafy vegetables (brassica lee ssp. namai, leafy lettuce, spinach, perilla leaves, crown daisy, marsh mallow, aster scaber, pimpinella brachycarpa) and Chinese chive. Procymidone, dimethomorph and azoxystrobin were the most frequently found pesticides. A risk assessment of pesticides exceeding the MRLs was evaluated by calculating the estimated daily intake (EDI) and the acceptable daily intake (ADI). The ratio of EDI to ADI was 0.003–30.4%.     

Occurrence of fungicide and insecticide residues in trade samples of leafy vegetables

The aim of this work was to report on a total of 23 fungicides and insecticides residues in 75 green and leafy vegetables (Swiss chards, Spinaches and Lettuces) collected from Ourense (NW Spain) by Spring 2007. The pesticides in the study samples were extracted with acetonitrile; the extracts were then cleaned-up by solid-phase extraction and concentrated before determination by PTV (Programmable Temperature Vaporization Injector) – GC-ITMS. Use of analyte protectants mixtures provided the best results in terms of effective compensation for matrix-induced enhancement effect. Pesticide residues were determined above the maxima residue limits (MRL) in 15 of the 75 analyzed samples, with a total of 18 violations of the MRL (three of the samples did not fulfil with two different pesticide MRL). The highest concentrations of fungicides were found in lettuce (procymidone, 12 mg/kg) and the highest concentrations of insecticides were found in Swiss chard (cypermethrin, 6 mg/kg). More positives for fungicides were detected and at larger concentrations than insecticides, especially for lettuces. Accumulation of pesticides in lettuces is higher than for the other leafy vegetables. The findings of this study pointed to the following recommendation: the need for a monitoring program for residues of iprodione and procymidone, together with cypermethrin, in food crops at the national level.     

Nitrate-N determination in leafy vegetables: Study of the effects of cooking and freezing

Nitrate upon reduction to nitrite can cause methaemoglobinaemia or act as precursor in the endogenous formation of carcinogenic nitrosamines. The leafy vegetables are the major vehicle for the entry of nitrate into the human system. The present study was conducted to establish a flow injection analysis (FIA) technique to investigate the nitrate-N contents of four commonly consumed fresh leafy vegetables (Chinese cabbage, celery, lettuce and English cabbage) from market in Fiji. Two extraction techniques (activated carbon and alkaline extraction) were assessed to extract nitrate-N and the activated carbon extraction was preferred over alkaline extraction and applied. The recoveries of spiked nitrate-N in vegetable matrices ranged from 90.40% to 112.80% in activated carbon extraction with an average of 100.62%. The effects of cooking (boiling, baking and frying) and deep-freezing on the nitrate-N contents were also studied. Nitrate contents in selected leafy vegetables were determined by FIA coupled with Greiss protocol involving sulfanilamide and N-(1-naphthyl)ethylenediamine dihydrochloride as color reagents. Nitrate was determined in the linear range from 1.0 to 20.0 mg L⁻¹ with the method detection limit of 0.042 mg L⁻¹ (0.34 mg kg⁻¹). The results of the study show that nitrate contents in fresh leafy vegetables ranged from 1297 to 5658 mg kg⁻¹. Boiling reduces nitrate content by 47–56% whereas frying in Soya bean oil elevates nitrate content by as much as 159–307%. No significant change was observed in nitrate content after baking. The deep-freezing of the selected leafy vegetables shows that nitrate-N content fluctuates slightly from the original nitrate-N values over the seven day period. The FIA throughput was 38 samples h⁻¹.     

Pesticides and heavy metals levels in Egyptian leafy vegetables and some aromatic medicinal plants

A total of 835 samples of leafy vegetables and some aromatic medicinal plants were collected from five different areas of Egypt during 1999. Ninety-seven per cent of the leafy vegetables were contaminated with heavy metals with 39% exceeding the maximum limits for each element. Cadmium was detected in 78 of 116 samples of leafy vegetable, although without any exceeding the maximum limits. However, lead was detected in 99 samples, of which 39 exceeded the maximum limits (0.3 mg kg^-1) and 56 medicinal plant samples of 70 had lead levels above 0.5 mg kg^-1. Copper was detected in 69 medicinal plant samples, of which 58 samples contained levels higher than 10 mg kg^-1. However, cadmium was only found in 43% of samples with only two of 70 samples above the maximum limit. Seventy-three per cent of the samples of medicinal plants were contaminated with pesticide residues, of which 44% contained amounts that exceeded maximum residue limits. Malathion was the most frequently found pesticide residue, being detected in 203 of 391 (52%.) samples, followed by profenofos, which was detected in 131 of 391 (33%) samples.     

苏南某市叶类蔬菜含氯有机农药残留状况分析及风险评估

目的了解苏南某市叶类蔬菜中含氯有机农药的残留状况及其质量安全现状。方法利用气相色谱法对采集自该市农贸市场、大型超市、种植基地及散户的6种主要叶类蔬菜中5种代表性的含氯有机农药(百菌清、三唑酮、氟氯氰菊酯、氯氰菊酯和氰戊菊酯)进行定量检测分析,采用食品安全指数开展暴露风险评估。结果 5种含氯有机农药在蔬菜样本中均有不同程度的检出,平均检出率为13.8%,百菌清、氯氰菊酯2种农药在部分蔬菜样本中的残留超标,超标率分别为0.4%和0.9%。6种叶类蔬菜的农药安全指数平均值均小于1,说明被检蔬菜的安全状态可为消费者所接受。但百菌清在菠菜和生菜中的安全指数均大于1,表明百菌清对菠菜和生菜质量安全的影响风险超过了可接受的限度。结论该地区主要叶类蔬菜的整体质量较安全,被检农药的残留状况总体良好,但对菠菜和生菜生产中百菌清的使用需加大监督管理力度,确保消费者食用蔬菜的安全性。     

Effects of storage condition and domestic cooking on the quality and nutrient content of African leafy vegetables (Cassia tora and Corchorus tridens)

BACKGROUND: The main objective of this research was to determine changes in nutrient content of two African leafy vegetables, Cassia tora and Corchorus tridens, on cooking and storage under different temperature conditions, i.e. room storage (20 °C), refrigerated storage (4 °C) and frozen storage (?18 °C). RESULTS: The leafy vegetables were analysed for moisture, colour (Hunter L, a, b), texture, total chlorophyll, ascorbic acid, dehydroascorbic acid and total phenolics. Results indicated that the degradation of ascorbic acid was highest as a result of frozen storage, followed by room temperature storage. The dehydroascorbic acid content was correspondingly high in frozen stored leafy vegetables, whereas it was undetectable in the room temperature and refrigerated stored materials. The total phenolic content of the leaves increased with storage time while the total chlorophyll content decreased under all storage conditions. Domestic cooking resulted in significant additional losses of ascorbic acid following storage under all temperature conditions, with only 1–10% retention in the leaves and 50–60% retention in the cooking water. The green colour of the leafy vegetables was retained best under refrigerated and frozen storage, while the peak force and toughness of the leaves increased upon storage under all conditions. The moisture content of the leafy vegetables did not show any significant difference on storage. CONCLUSION: This study is one of few to report nutrient content changes on the same raw material stored under various temperature conditions and cooked domestically. Refrigerated storage resulted in the highest retention of ascorbic acid and green colour in the leafy vegetables. Copyright © 2009 Society of Chemical Industry     

From lesser‐known to super vegetables: the growing profile of African traditional leafy vegetables in promoting food security and wellness

There are hundreds of traditional leafy vegetables and wild food plants of horticultural and nutritional significance in Africa. These lesser‐known crops and wild food plants that are highly adapted to harsh growing conditions thrive with little care and are available when other sources of food fail or are out of season. They are rich in micronutrients and are often the cheapest sources of many essential vitamins and minerals in many localities. Many of them are very important functional foods in African traditional diets and are rich in nutraceuticals, including polyphenols, tannins, flavonoids and flavonols, that exert demonstrable antioxidant, free radical scavenging and enzyme inhibition activities and have antimicrobial properties that provide scientific justification and possible mechanisms for their use in the management of a wide range of ailments, including diet‐related, non‐communicable diseases such as diabetes, hypertension and cardiovascular diseases. African traditional leafy vegetables are invaluable in promoting food security and wellness in Africa on account of their availability and affordability, their great nutritional value, chemotherapeutic and health‐promoting properties and other unique qualities. Long recognised by the rural populace as quality food items, they are becoming more popular even with the more affluent urban elites. There is the need to develop improved management practices for these super vegetables to promote their cultivation and boost their exploitation for food security and wellness in Africa. © 2018 Society of Chemical Industry     

Endogenous levels of nitrites and nitrates in wide consumption foodstuffs: Results of five years of official controls and monitoring

The massive introduction of nitrogen fertilisers, necessary to maximise the global food production, has brought about an increase of the residual amounts of nitrites and nitrates in the products. Notoriously, these compounds may exercise toxic effects.     

Development and validation of an HPLC method for the determination of thiamine and riboflavin in green leafy vegetables using clara-diastase

There is no literature on the use of the currently available form of clara-diastase (≥ 35 U/mg; Fluka Product No. 86959) in the analysis of vitamins B(1) and B(2) . Consequently, a method for the determination of total riboflavin and total thiamine in green leafy vegetables by high-pressure liquid chromatography (HPLC) following sample preparation by sequential acid hydrolysis, enzymatic hydrolysis with clara-diastase ≥ 35 U/mg, and for B1, derivatization to thiochrome, was developed and validated. Prepared samples are run at 35 °C on a 250 × 4.6 mm column of 5 μm Kromasil 100 C(18) , using a 0.8 mL/min flow of a 72:28 mixture of 5 mmol/L ammonium acetate and methanol as mobile phase and fluorescence detection. The linear response ranges and limits of detection are, respectively, 3.0 to 60.0 and 0.15 ng/mL for B(1) , and 3.1 to 155.0 and 0.103 ng/mL for B(2) . Of the 4 green leafy vegetables examined, young turnip tops had the highest B(1) and B(2) levels (0.19 and 0.20 mg/100 g fresh weight), followed by spinach (0.12 and 0.09 mg/100 g), lettuce (0.11 and 0.05 mg/100 g), and chard (0.04 mg/100 g).     

Monitoring programme on nitrates in vegetables and vegetable-based baby foods marketed in the Region of Valencia,Spain: levels and estimated daily intake

This study was carried out to determine the current levels of nitrates in vegetables and vegetable-based baby foods (a total of 1150 samples) marketed in the Region of Valencia, Spain, over the period 2000–2008, and to estimate the toxicological risk associated with their intake. Average (median) levels of nitrate in lettuce, iceberg-type lettuce and spinach (1156, 798 and 1410 mg kg^?1 w/w, respectively) were lower than the maximum limits established by European Union legislation. Thirteen fresh spinach samples exceeded the regulatory limits. Median nitrate values in other vegetables for which a maximum limit has not been fixed by the European Commission were 196, 203, 1597, 96, 4474 and 2572 mg kg^?1 w/w (for potato, carrot, chard, artichoke, rucola and lamb's lettuce, respectively). The estimated nitrate daily intakes through vegetables consumption for adult, extreme consumers and children were found to be about 29%, 79.8% and 15.1%, respectively, of the acceptable daily intake (3.7 mg kg^?1). The levels (median = 60.4 mg kg^?1 w/w) found in vegetable-based baby foods were, in all cases, lower the maximum level proposed by European Union legislation. The estimated nitrate daily intake through baby foods for infants between 0–1 and 1–2 years of age were 13% and 18%, respectively, of the acceptable daily intake.     

In vitro accessibility of β‐carotene from cooked Sri Lankan green leafy vegetables and their estimated contribution to vitamin A requirement

Vitamin A deficiency is an important issue for public health in Sri Lanka, where pro‐vitamin A carotenoids from green leafy vegetables provide most of the dietary vitamin A. The objective of this study was to analyse the β‐carotene content of seven types of green leafy vegetables and calculate the contribution of one traditionally cooked portion to the recommended daily allowance (RDA) of retinol. The total amount and in vitro accessibility of β‐carotene were determined using HPLC. The in vitro method simulates the conditions in the human intestinal tract. The all‐trans‐β‐carotene content in the fresh blanched vegetables ranged from 149 µg g^?1 dry weight (DW) in leaves of Alternanthera sessilis (mukunuwanna) to 565 µg g^?1 DW in Amaranthus caudatus (thampala). One portion (100 g) of green leaves cooked without fat (coconut) only contributed from 140 to 180 µg mg^?1 of the recommended daily allowance. A. sessilis, Centella asiatica (gotukola), Spinacea oleracea (nivithi) and A. caudatus, cooked with coconut fat contributed 140–680 µg mg^?1. However, stir‐fried or ‘malluma’ preparations (with coconut products) of Sesbania grandiflora (kathurumurunga) and Manihot esculenta (manioc) may provide more than 1.59–4.37 times the RDA of retinol. These results show that not only the choice of green leaves used but also the addition of fat while cooking is of great importance. Copyright © 2005 Society of Chemical Industry     

Nitrate in leafy vegetables,culinary herbs,and cucumber grown under cover in Estonia: content and intake

The content of nitrate in leafy vegetables, culinary herbs, and cucumber was determined during the years 2006–2008. All samples of Estonian origin, except white cabbage, were grown under cover. Seasonal differences in nitrate concentrations were observed in lettuce and spinach. Nitrate concentrations in lettuce were 22% and those in spinach were 24% higher in winter crops compared with samples collected in summer. The mean nitrate level was 3023 mg kg^–1 for fresh lettuce and 2337 mg kg^–1 for spinach. On average, 11.6% of fresh lettuce and spinach samples nitrate concentration exceeded the maximum level specified in European Commission Regulation No. 1881/2006. The mean levels were 999 mg kg^–1 for imported iceberg lettuce and 1287 mg kg^–1 for frozen spinach, which are below the maximum European Commission limits. Parsley, dill, basil, thyme, and rucola contained high concentrations of nitrate from mean levels of 2134 mg kg^–1 for parsley up to 8150 mg kg^–1 for rucola. Mean nitrate concentrations ranged from 382 to 1115 mg kg^–1 for white cabbage and Chinese cabbage, respectively. The per capita mean daily intake of nitrates related to the consumption of leafy vegetables, culinary herbs, and cucumber for the whole Estonian population was 31.3 mg day^–1, which comprised 14.2% of the acceptable daily intake (ADI).     

Determination of nitrates by a novel ion chromatographic method: occurrence in leafy vegetables (organic and conventional) and exposure assessment for Italian consumers

A novel ion chromatographic method to detect nitrates in vegetables was developed, and the nitrate contents in green salad (a mixture of endive and prickly lettuce), lettuce, chicory, rocket and spinach were determined from Italian markets in 1996 -2002. These leaf vegetables were included because they are currently supposed to provide most of the nitrate intake in the typical Italian diet. The highest content of nitrate was detected in chicory (6250 mg kg -1 ) and rocket (6120 mg kg -1 ), which are consumed in large quantities in some regions of Italy. Green salad and lettuce contained less nitrate (highest values = 4200 and 3300 mg kg -1 , respectively), but because they are consumed more generally, they provided 60% of the total intake of nitrates. Only a few samples were above the legal limits, with seasonal variation. A significantly higher nitrate content was found in organically grown green salad and rocket than in those conventionally produced. These data indicate that the average intake of nitrates from leafy vegetables is below the acceptable daily intake, i.e. 3.7 mg nitrate ion kg -1 body weight day -1 , but the total intake should be monitored to protect groups at risk, such as children and vegetarians.     

Application of Cudrania tricuspidata leaf extract as a washing agent to inactivate Listeria monocytogenes on fresh-cut romaine lettuce and kale

The present study aimed to examine the antimicrobial activity of silkworm thorn (Cudrania tricuspidata) leaf extract (CTLE) and its application as a washing agent for fresh-cut romaine lettuce and kale. The antimicrobial activities of CTLE at various concentrations against Listeria monocytogenes were determined using disc diffusion and viable cell count assays, and CTLE exhibited strong inactivation of L. monocytogenes. In particular, after the treatment with 0.4% CTLE, the protein content of L. monocytogenes cells was significantly (P < 0.05) decreased from 507.21 to 254.58 μg mL⁻¹, and damaged cells were observed by scanning electron microscopy. CTLE washing resulted in approximately 2-log reduction of microbial growth, similar to that of 0.01% NaOCl. In addition, CTLE washing did not affect the quality of romaine lettuce and kale. Therefore, these results suggest that CTLE is applicable as a new washing agent for inactivating L. monocytogenes on fresh-cut romaine lettuce and kale.     

超声提取-离子色谱法检测市售常见15种蔬菜中 7种单糖和双糖

目的建立离子色谱-脉冲积分安培检测法(IC-PAD)测定蔬菜中的水溶性的半乳糖、葡萄糖、木糖、果糖、蔗糖、乳糖和麦芽糖方法。方法采用水浸提超声提取及膜过滤法处理蔬菜样品,以DIONEX Carbo Pac PA10阴离子交换柱为分析柱,以DIONEX Carbo Pac PA10为保护柱,以Na OH与CH3COONa的组合溶液作为流动相,采用梯度淋洗程序分离,脉冲积分安培检测。结果 7种糖的检出限分别为3、4、3、6、6、4和3μg/L,且均具有较宽的线性范围(0.05~20 mg/L)。15种蔬菜样品测定的相对标准偏差在1.48%~6.41%之间,7种糖的加标回收率在90%~97%之间。结论本方法检测糖简便快捷、分离效果好、无需衍生、灵敏度高,适用于蔬菜中的常见糖组分的分析。     

Determination of endogenous concentrations of nitrites and nitrates in different types of cheese in the United States: method development and validation using ion chromatography

Nitrites and nitrates can be present in dairy products from both endogenous and exogenous sources. In the European Union (EU), 150 mg kg^–1 of nitrates are allowed to be added to the cheese milk during the manufacturing process. The CODEX General Standard for Food Additives has a maximum permitted level of 50 mg kg^–1 residue in cheese, while in the United States (U.S.) nitrates are unapproved for use as food additives in cheese. In order to be able to investigate imported cheeses for nitrates intentionally added as preservatives and the endogenous concentrations of nitrates and nitrites present in cheeses in the U.S. marketplace, a method was developed and validated using ion chromatography with conductivity detection. A market sampling of cheese samples purchased in the Washington DC metro area was performed. In 64 samples of cheese, concentrations ranged from below the method detection limit (MDL) to 26 mg kg^–1 for nitrates and no concentrations of nitrites were found in any of the cheese samples above the MDL of 0.1 mg kg^–1. A majority of the samples (93%) had concentrations below 10 mg kg^–1, which indicate the presence of endogenous nitrates. The samples with concentrations above 10 mg kg^–1 were mainly processed cheese spread, which can contain additional ingredients often of plant-based origin. These ingredients are likely the cause of the elevated nitrate concentrations. The analysis of 12 additional cheese samples that are liable to the intentional addition of nitrates, 9 of which were imported, indicated that in this limited study, concentrations of nitrate in the U.S.-produced cheeses did not differ from those in imported samples.     

叶菜类蔬菜中农药残留及膳食暴露风险评估

目的 了解叶菜类蔬菜农药残留现状,并评估农药残留的膳食暴露风险.方法 随机采集主要叶菜类样品682批,采用NY/T761—2008《蔬菜和水果中有机磷、有机氯、拟除虫菊酯和氨甲基酸酯类农药多残留的测定》方法检测105项农药残留,分析叶菜类蔬菜农药残留现状,并结合我国居民蔬菜消费情况,用每日允许摄入量和急性参考剂量分别对...