Nitrates and nitrites in vegetables and vegetable-based products and their intakes by the Estonian population

The content of nitrates were determined in 1349 samples of vegetables and ready-made food in 2003-2004 as a part of the Estonian food safety monitoring programme and the Estonian Science Foundation grant research activities. The results of manufacturers' analyses carried out for internal monitoring were included in the study. The highest mean values of nitrates were detected in dill, spinach, lettuce and beetroot. The mean concentrations were 2936, 2508, 2167 and 1446 mg kg^-1, respectively. The content of nitrites in samples was lower than 5 mg kg^-1. In total, the mean intake of nitrates by the Estonian population was 58 mg day^-1. The mean content of nitrates in vegetable-based infant foods of Estonian origin was 88 mg kg^-1. The average daily intake of nitrates by children in the age group of 4-6 years was 30 mg. The infants' average daily intake of nitrates from consumption of vegetable-based foods was 7.8 mg.     

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).     

冷藏对蔬菜中亚硝酸盐及硝酸盐含量的影响

目的 探索冰箱冷藏(4℃)条件下蔬菜中硝酸盐和亚硝酸盐含量随时间的变化,对冷藏食品的安全性进行评价.方法 分别采用重氮偶合分光光度法和麝香草酚分光光度法对生菜、菠菜、油麦菜及苦苣4种常用蔬菜在冷藏条件下其亚硝酸盐及硝酸盐的含量变化进行测定.结果 1～4d内,生菜、苦苣中的亚硝酸盐含量随着时间的延长逐渐增加;菠菜、油麦菜中亚硝酸盐含量分别在第2天和第3天达到最大,之后逐渐降低,而菠菜中亚硝酸盐含量在第4天又出现上升趋势.4种蔬菜中亚硝酸盐含量4d中最大值仅为0.419 4 mg/kg(生菜),均＜4 mg/kg的限量值.苦苣和油麦菜中硝酸盐含量在1～4d内逐渐上升.菠菜中硝酸盐含量第2天达到418.48 mg/kg,之后又降低至20.83 mg/kg.生菜中硝酸盐含量在第3天达到最大值317.26 mg/kg,之后逐渐下降,但均在安全范围内(432 mg/kg).结论 在4℃下冷藏4d后,4种常见蔬菜均可安全食用.可见,冷藏能有效减缓亚硝酸盐和硝酸盐含量的升高.     

Nitrate in vegetables: toxicity,content, intake and EC regulation

Nitrate content is an important quality characteristic of vegetables. Vegetable nitrate content is of interest to governments and regulators owing to the possible implications for health and to check that controls on the content are effective. Nitrate itself is relatively non‐toxic but its metabolites may produce a number of health effects. Until recently nitrate was perceived as a purely harmful dietary component which causes infantile methaemoglobinaemia, carcinogenesis and possibly even teratogenesis. Recent research studies suggest that nitrate is actually a key part of our bodies' defences against gastroenteritis. In this review are reported: (1) vegetable classification as a function of nitrate accumulation; (2) vegetable contribution to the total dietary exposure of nitrate; (3) European Commission Regulation No. 563/2002 which sets limits for nitrate in lettuce and spinach; (4) the maximum levels set in some countries for beetroot, cabbage, carrot, celery, endive, Lamb's lettuce, potato, radish and rocket; (5) the results of surveys on the nitrate content of vegetables in Italy and other European countries. Copyright © 2005 Society of Chemical Industry     

Survey of nitrate and nitrite contents of vegetables grown in Korea.

A scientific basis for the evaluation of the risk to public health arising from excessive dietary intake of nitrate in Korea is provided. The nitrate () and nitrite () contents of various vegetables (Chinese cabbage, radish, lettuce, spinach, soybean sprouts, onion, pumpkin, green onion, cucumber, potato, carrot, garlic, green pepper, cabbage and Allium tuberosum Roth known as Crown daisy) are reported. Six hundred samples of 15 vegetables cultivated during different seasons were analysed for nitrate and nitrite by ion chromatography and ultraviolet spectrophotometry, respectively. No significant variance in nitrate levels was found for most vegetables cultivated during the summer and winter harvests. The mean nitrates level was higher in A. tuberosum Roth (5150 mg kg(-1)) and spinach (4259 mg kg(-1)), intermediate in radish (1878 mg kg(-1)) and Chinese cabbage (1740 mg kg(-1)), and lower in onion (23 mg kg(-1)), soybean sprouts (56 mg kg(-1)) and green pepper (76 mg kg(-1)) compared with those in other vegetables. The average nitrite contents in various vegetables were about 0.6 mg kg(-1), and the values were not significantly different among most vegetables. It was observed that nitrate contents in vegetables varied depending on the type of vegetables and were similar to those in vegetables grown in other countries. From the results of our studies and other information from foreign sources, it can be concluded that it is not necessary to establish limits of nitrates contents of vegetables cultivated in Korea due to the co-presence of beneficial elements such as ascorbic acid and alpha-tocopherol which are known to inhibit the formation of nitrosamine.     

Nitrate and nitrite in vegetables from north China: content and intake

The contents of nitrate and nitrite in potato, cabbage, Chinese cabbage, scallion (shallot), celery, cucumber, tomato, eggplant and wax gourd taken from the north China market from 1998 to 1999 were determined. These vegetables provide the major contribution to the nitrate intake from the diet. The highest content of nitrate was found in celery followed by Chinese cabbage, cabbage, scallion, wax gourd and eggplant. For all the products, a great variation in the content of nitrate was found. Generally, the nitrite content was low. The average intake of nitrate and nitrite from these vegetables was estimated as approximately 422.8 and 0.68 mg day -1 , respectively.     

Vegetables antioxidant losses during industrial processing and refrigerated storage

Twenty-five vegetables (artichoke, asparagus, beetroot, broad bean, broccoli, Brussels sprout, carrot, cauliflower, celery, chicory, cucumber, eggplant, endive, garlic, green bean, leek, lettuce, maize, onion, pea, pepper, radish, spinach, Swiss chard and zucchini) were used to evaluate their antioxidant activity. All fresh vegetables studied were able to scavenge lipoperoxyl and hydroxyl radicals. All the vegetables also presented good total capacity antioxidant by TEAC assay except cucumber, endive, carrot and zucchini.Vegetables stored (7 days) in a home refrigerator recorded the same antioxidant activity as fresh samples, except cucumber and zucchini (lipid peroxidation) and broccoli, Brussels sprout and leek (TEAC).Canned vegetables showed a more pronounced loss of antioxidant activity than frozen vegetables compared with fresh vegetables.During the shelf life of the processed vegetables (8 months for frozen and 18 months for canned vegetables), some products showed losses (19–48%) of their lipoperoxyl radical scavenging capacity and total antioxidant activity.     

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.     

Average daily nitrate and nitrite intake in the Belgian population older than 15 years

The aim of this study was to assess the dietary intake of nitrate and nitrite in Belgium. The nitrate content of processed vegetables, cheeses and meat products was analysed. These data were completed by data from non-targeted official control and from the literature. In addition, the nitrite content of meat products was measured. Concentration data for nitrate and nitrite were linked to food consumption data of the Belgian Food Consumption Survey. This study included 3245 respondents, aged 15 years and older. Food intakes were estimated by a repeated 24-h recall using EPIC-SOFT. Only respondents with two completed 24-h recalls (n=3083) were included in the analysis. For the intake assessment, average concentration data and individual consumption data were combined. Usual intake of nitrate/nitrite was calculated using the Nusser method. The mean usual daily intake of nitrate was 1.38 mg kg(-1) bodyweight (bw) day(-1) and the usual daily intake at the 97.5 percentile was 2.76 mg kg(-1) bw day(-1). Exposure of the Belgian population to nitrate at a mean intake corresponded to 38% of the ADI (while 76% at the 97.5 percentile). For the average consumer, half of the intake was derived from vegetables (especially lettuce) and 20% from water and water-based drinks. The average daily intake of nitrate and nitrite from cheese and meat products was low (0.2% and 6% of the ADI at average intake, respectively). Scenario analyses with a higher consumption of vegetables or a higher nitrate concentration in tap water showed a significant higher intake of nitrate. Whether this is beneficial or harmful must be further assessed.     

Nitrate and nitrite content in organically cultivated vegetables

The nitrate and nitrite content of leaf vegetables (Swiss chard, sea beet, spinach and cabbage), “inflorescence” vegetables (cauliflower) and fruit vegetables (eggplant and vegetable marrow) grown with organic fertilizers have been determined by a modified cadmium–Griess method. Samples were purchased from organic food stores as well as collected directly from an organic farm in Madrid (Spain). Nitrate levels were much higher in the leaf vegetables (especially Swiss chard species; average over the different samples and species of 2778.6 ± 1474.7 mg kg^{? 1}) than in inflorescence or fruit products (mean values between 50.2 ± 52.6 and 183.9 ± 233.6 mg kg^{? 1}). Following Swiss chard species, spinach (1349.8 ± 1045.5 mg kg^{? 1}) showed the highest nitrate content, and nitrite was found above the limit of detection in some samples only (spinach, 4.6 ± 1.0 mg kg^{? 1}; sea beet, 4.2 ± 0.7 mg kg^{? 1} and Swiss chard, 1.2 ± 0.4 mg kg^{? 1}). Some vegetables (spinach, cabbage and eggplant) had lower nitrate content in the samples harvested in summer, showing the influence of climatic conditions on the nitrate levels in a plant. The samples taken directly from the organic farm, with the exception of eggplant, had higher or slightly higher average nitrate values than samples purchased in the organic food stores, ranging from 117 to 1077%.     

Nitrate and nitrite levels in commonly consumed vegetables in Hong Kong

Levels of nitrate and nitrite in 73 different vegetables, a total of 708 individual samples grouped into leafy, legumes, root and tuber, and fruiting vegetables, which are traded mainly in Hong Kong, were measured. Where available, five samples of each vegetable type were purchased from different commercial outlets during the winter of 2008 and summer of 2009. Levels of nitrate and nitrite were determined by ion chromatography and flow injection analysis, respectively. Nitrate and nitrite levels of all samples ranged <4–6300 and <0.8–9.0 mg?kg^?1, respectively. Nitrate concentrations for the different groups, in descending order, were leafy?>?root and tuber?>?fruiting and legume vegetables. More than 80% of vegetables had mean nitrate concentrations less than 2000?mg?kg^?1, but mean nitrate concentrations of three types of leafy vegetables, namely Chinese spinach, Shanghai cabbage and Chinese white cabbage, were >3500?mg?kg^?1. On the other hand, nitrite concentrations were generally low –?<1?mg?kg^?1 on average. Nitrate in vegetables (i.e. Chinese flowering cabbage, Chinese spinach and celery) can be reduced significantly (12–31%) after blanching for 1–3?min, but not after soaking.     

重庆市菜园土壤与蔬菜硝酸盐和亚硝酸盐含量及相关性研究

研究重庆4 个农贸市场市售3大类19 种蔬菜73 个样品中硝酸盐含量及重庆市13 个主要蔬菜基地土壤和蔬菜的硝酸盐、亚硝酸盐含量及相关性。结果表明,重庆市售蔬菜不同种类及同种蔬菜不同部位的硝酸盐含量差异显著。大小顺序为叶菜类（X =1 619.73 mg/kg）＞茄果类（X =1 327.67 mg/kg）＞葱蒜类（X =
1 078.39 mg/kg）;莴苣叶（X=1 567.91 mg/kg）＞莴苣茎（X=1 871.62 mg/kg）。叶菜类全部超过了一级标准,污染指数高达9.09,污染程度最为严重;茄果类和葱蒜类超过一级标准的样本占81.3%和87.5%,污染指数分别高达8.85和6.56。重庆市13 个主要蔬菜基地不同蔬菜以及同种蔬菜不同部位的硝酸盐含量差异也显著,大小顺序为萝卜叶（X=745.97 mg/kg）＞莴苣茎（X=730.88 mg/kg）＞莴苣叶（X=693.32 mg/kg）＞白菜（X=617.63 mg/kg）＞萝卜根（X=575.74 mg/kg）。土壤中NO3－-N含量差异也显著,大小顺序为种植莴苣的土壤（X=75.24 mg/kg）＞种植白菜的土壤（X=47.05 mg/kg）＞种植萝卜的土壤（X=33.42 mg/kg）。蔬菜可食部分的硝酸盐与土壤中的NO3－-N含量呈极显著正相关关系,线性方程y=407.872＋4.796x。供试重庆市13 个主要蔬菜基地土壤及蔬菜可食部分的NO2－-N含量均较低且差异不显著,蔬菜中的亚硝酸盐含量和土壤中的NO2－-N含量也无显著相关性。     

新鲜蔬菜的添加对发酵香肠成熟过程中理化指标变化的影响

将新鲜蔬菜（芹菜、洋白菜、菠菜）添加到发酵香肠的加工中,以期替代化学合成硝酸盐的作用,生产出更加安全的肉制品。本实验以冷却猪通脊肉和背膘肉（8∶2）为原料,添加萨科WBL-45复合菌株和各种辅料制作发酵香肠,分为5组:阴性对照CK组,不添加硝酸盐;阳性对照SN组,添加0.3 g/kg的硝酸盐;芹菜QC组,添加6.3%芹菜浆;菠菜BC组,添加8.1%菠菜浆;洋白菜YBC组,添加9.0%洋白菜（使得硝酸盐含量均为0.3 g/kg）。研究3种新鲜蔬菜替代化学合成硝酸盐对发酵香肠理化性质的影响。实验结果表明:3组蔬菜发酵香肠（QC、BC和YBC组）在干燥成熟期间,色泽（菠菜发酵香肠呈现鲜亮绿色除外）、TBARS值、TVB-N值和亚硝酸盐残留量变化表明蔬菜发酵香肠的品质显著优于CK组（p<0.05）,亚硝酸盐残留量仅在3.63⁵.46 mg/kg范围,远远低于国家限量标准（30 mg/kg）,产品安全性高。添加蔬菜后的发酵香肠在成熟期间,产品的p H、水分含量和Aw的变化与对照组（CK和SN组）相比差异不显著（p>0.05）,表现为p H先升后降的变化趋势,水分降低至21.07%²6.84%,Aw值降低至0.849⁰.881,表明蔬菜的添加不会影响到产品的成熟过程。      

A survey of nitrate and oxalate content in fresh vegetables

A survey of nitrate and oxalate ((COO⁻)₂) content in fresh vegetables was conducted in Bari (Italy) over 15 months (from March 1994 to May 1995). A total of 327 samples (edible portions and related sub-samples) were taken from 26 different vegetable types on the wholesale fruit and vegetable market. The data revealed that leaf vegetables (namely rocket, celery, parsley and spinach) contained higher levels of nitrate than bulb, root, shoot, inflorescence and tuber vegetables. Higher oxalate levels were found in spinach and Swiss chard. Based on consumption data for the whole population provided by the National Institute of Nutrition, daily nitrate intake from vegetables was calculated to be 71 mg. Over 30% of nitrate intake was derived from the consumption of lettuce and Swiss chard. © 1999 Society of Chemical Industry     

Changes in nitrate and nitrite content of four vegetables during storage at refrigerated and ambient temperatures

The nitrate and nitrite contents of four kinds of vegetables (spinach, crown daisy, organic Chinese spinach and organic non-heading Chinese cabbage) in Taiwan were determined during storage at both refrigerated (5 ± 1°C) and ambient temperatures (22 ± 1°C) for 7 days. During storage at ambient temperature, nitrate levels in the vegetables dropped significantly from the third day while nitrite levels increased dramatically from the fourth day of storage. However, refrigerated storage did not lead to changes in nitrate and nitrite levels in the vegetables over 7 days.     

烹饪过程对空心菜和卷心菜硝酸盐潜在安全风险的影响

研究4种烹饪（油炒、汽蒸、微波和水煮）过程对空心菜和卷心菜中硝酸盐、亚硝酸盐和抗氧化能力的影响,并通过抗氧化性/体内亚硝酸盐比（antioxidant/in vivo nitrite ratio,A/N）值评价其硝酸盐潜在安全风险。结果表明,油炒会同时提升叶类蔬菜的硝酸盐含量（28.03%～49.57%）和铁离子还原能力（108.88%～218.35%）,而水煮则相反。微波和汽蒸在降低蔬菜硝酸盐含量（31.25%～46.61%）的同时提升铁离子还原能力（76.35%～112.99%）。基于可食用性和A/N值评价结果,在烹饪2 min内空心菜和卷心菜分别选择水煮和油炒烹饪对硝酸盐潜在安全风险的控制效果更好。微波是两种叶类蔬菜相对安全的烹饪方式,但不宜超过4 min,而汽蒸更适宜长时间烹饪（>4 min）。     

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.     

Estimated intake of intense sweeteners from non-alcoholic beverages in Denmark

In 1999, 116 samples of non-alcoholic beverages were analysed for the intense sweeteners cyclamate, acesulfame-K, aspartame and saccharin. High contents of cyclamate close to the maximum permitted level in 1999 of 400 mg l^-1 were found in many soft drinks. The estimated intake of the sweeteners was calculated using the Danish Dietary Survey based on 3098 persons aged 1-80 years. The estimated intake with 90th percentiles of 0.7, 4.0 and 0.2 mg kg^-1 body weight (bw) day^-1 for acesulfame-K, aspartame and saccharin, respectively, was much lower than the acceptable daily intake (ADI) values of 15, 40 and 2.5 mg kg^-1 bw day^-1 for acesulfame-K, aspartame and saccharin, respectively. However, the 90th percentile of the estimated cyclamate intake in 1-3 year olds was close to the ADI value of 7 mg kg^-1 bw day^-1; and the 99th percentile in the 1-10 year olds far exceeded the ADI value. Boys aged 7-10 years had a significantly higher estimated intake of cyclamate than girls. The 90th percentile for the whole population was 1.8 mg kg^-1 bw day^-1. After the reduction in the maximum permitted level in the European Union in 2004 from 400 to 250 mg cyclamate l^-1, the exposure in Denmark can also be expected to be reduced. A new investigation in 2007 should demonstrate whether the problem with high cyclamate intake is now solved.     

Nitrate and nitrite contents of some fresh and processed Egyptian vegetables

The nitrate and nitrite contents of sixteen fresh vegetables, widely consumed in Egypt, were determined. The highest values of nitrate were observed in leafy vegetables, followed by root vegetables and then pulses. Of the leafy vegetables, spinach, roquette and chard contained the highest concentration of nitrate. Nitrite concentrations were detected at low levels in a few samples, while the others were free of nitrite.Cooking had the effect of lowering the levels of nitrate in all types of fresh vegetables studied; no nitrite was formed during cooking.Storage of frozen vegetables for six months decreased the levels of nitrate, while nitrite was formed at low levels after storage for three or four months.     

A survey of nitrate and nitrite content of fruit and vegetables grown in Slovenia during 1996-2002

Monitoring of nitrate (NO₃^-) and nitrite (NO₂^-) content in agricultural products in Slovenia has been carried out since 1996. The results of monitoring over the period 1996-2002 are presented. During this time 924 samples of 14 different agricultural products (potato, lettuce, apples, carrot, silage maize, cabbage, grapes, peaches, string beans, cereals, pears, cucumbers, strawberries and tomato) were analysed. The samples were taken at the time of maturity directly from growing sites and they were analysed using segmented flow analysis. The average nitrate contents were the highest in lettuce (1074 mg kg^-1), cabbage (881 mg kg^-1), string beans (298 mg kg^-1) and carrot (264 mg kg^-1), and they were moderately high in potato (158 mg kg^-1), silage maize (122 mg kg^-1), strawberries (94 mg kg^-1), cucumbers (93 mg kg^-1) and cereals (49 mg kg^-1). Low nitrate contents (below 6 mg kg^-1) were found in fruit (grapes, peaches, apples and pears) and tomato. With the exception of cereals (8.9 mg kg^-1), apples (1.5 mg kg^-1), potato (1.2 mg kg^-1) and pears (1.0 mg kg^-1) the content of nitrites did not exceed 0.5 mg kg^-1. It may be concluded that the results of the monitoring were in most cases similar to the results of investigations obtained in other countries.