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 on the Danish market: content and intake

The contents of nitrate and nitrite in lettuce, leek, potato, beetroot, Chinese cabbage and white cabbage on the Danish market were determined for 3 years in the period 1993-1997 as part of the Danish food monitoring programme. These vegetables are supposed to provide the major contribution to the intake of nitrate from the diet. Results for nitrate and nitrite in fresh and frozen spinach are also shown. The highest content of nitrate was found in lettuce followed by beetroot, Chinese cabbage, fresh spinach, leek, frozen spinach, white cabbage and potatoes. For all the products a great variation in the content of nitrate was found. For lettuce a characteristic variation throughout the year is clearly seen with the highest content in the winter period the lowest content in the summer period. Generally, the content of nitrite was low but in spinach high contents were found, probably due to improper storage conditions during transportation. The intake of nitrate and nitrite from these vegetables is calculated on the basis of two different consumption surveys. For both surveys the average intake of nitrate from the vegetables included in the monitoring programme is estimated to be approximately 40mg day^-1, whereas for nitrite the average intake is approximately 0.09mg day^-1. The total intake of nitrate and nitrite is estimated to be respectively 61mg day^-1 and 0.5mg day^-1.     

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.     

Nitrate and nitrite quantification from cured meat and vegetables and their estimated dietary intake in Australians

High dietary nitrate and nitrite intake may increase the risk of gastro-intestinal cancers due to the in vivo formation of carcinogenic chemicals known as N-nitroso compounds. Water and leafy vegetables are natural sources of dietary nitrate, whereas cured meats are the major sources of dietary nitrite. This paper describes a simple and fast analytical method for determining nitrate and nitrite contents in vegetables and meat, using reversed-phase HPLC-UV. The linearity R² value was >0.998 for the anions. The limits of quantification for nitrite and nitrate were 5.0 and 2.5 mg/kg, respectively. This method is applicable for both leafy vegetable and meat samples. A range of vegetables was tested, which contained <23 mg/kg nitrite, but as much as 5000 mg/kg of nitrate. In cured and fresh meat samples, nitrate content ranged from 3.7 to 139.5 mg/kg, and nitrite content ranged from 3.7 to 86.7 mg/kg. These were below the regulatory limits set by food standards Australia and New Zealand (FSANZ). Based on the average consumption of these vegetables and cured meat in Australia, the estimated dietary intake for nitrate and nitrite for Australians were 267 and 5.3 mg/adult/day, respectively.     

Prevalence of Nitrite and Nitrate Contents and Its Effect on Edible Bird Nest's Color

Edible bird nests (EBNs) are important ethnomedicinal commodity in the Chinese community. Recently, But and others showed that the white EBNs could turn red by vapors from sodium nitrite (NaNO₂) in acidic condition or from bird soil, but this color‐changing agent remained elusive. The aim of this study was to determine the prevalence of nitrite and nitrate contents and its affects on EBN's color. EBNs were collected from swiftlet houses or caves in Southeast Asia. White EBNs were exposed to vapor from NaNO₂ in 2% HCl, or bird soil. The levels of nitrite (NO₂^?) and nitrate (NO₃^?) in EBNs were determined through ion chromatography analysis. Vapors from NaNO₂ in 2% HCl or bird soil stained white bird nests to brown/red colors, which correlated with increase nitrite and nitrate levels. Moreover, naturally formed cave‐EBNs (darker in color) also contained higher nitrite and nitrate levels compared to white house‐EBNs, suggesting a relationship between nitrite and nitrate with EBN's color. Of note, we detected no presence of hemoglobin in red “blood” nest. Using infrared spectra analysis, we demonstrated that red/brown cave‐EBNs contained higher intensities of C‐N and N‐O bonds compared to white house‐EBNs. Together, our study suggested that the color of EBNs was associated with the prevalence of the nitrite and nitrate contents.     

FIA evaluation of nitrite and nitrate contents of liver pâtés

A comparative study on the nitrite and nitrate contents of 15 liver pâté brands, in a total of 45 samples (three batches per brand) is presented. The study was conducted on two different kind of pâtés: pork liver pâtés and fowl liver pâtés. For the simultaneous determination of nitrite and nitrate, an automated flow injection system with spectrophotometric detection was used. The manifold was based on the splitting of the flow after injection and subsequent confluence of the flow before reaching the detector, allowing the reduction of nitrate to nitrite in part of the sample plug on an on-line copper cadmium reductor column. Spectrophotometric determination was made after a diazotization coupling reaction. The levels of nitrites and nitrates ranged from 1.07 mg NaNO₂ kg⁻¹ ± 0.43 to 15.9 mg NaNO₂ kg⁻¹ ± 5.2 and from 24.5 mg NaNO₃ kg⁻¹ ± 2.7 to 207 mg NaNO₃ kg⁻¹ ± 14, respectively. The levels of concentration of these constituents were below the allowable limits. A significant dispersion in the results was observed between different brands and within some of the brands.     

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%.     

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.     

大白菜贮藏过程中硝酸盐和亚硝酸盐含量变化分析

在不同贮藏温度（0、10、20 ℃）、贮藏方式（未包装、0.04 mm PE保鲜袋包装）条件下贮藏大白菜（Brassica rapa pekinensis）16 d后,采用高效液相色谱法测定大白菜中硝酸盐和亚硝酸盐含量的变化。结果表明,在不同贮藏温度和贮藏方式条件下,硝酸盐和亚硝酸盐的含量随着贮藏时间的延长均呈现先增加、后降
低、再上升的趋势,其中硝酸盐的含量在整个贮藏期间,均在低于432 mg/kg的安全食用范围内;亚硝酸盐含量在20 ℃贮藏条件下贮藏7 d即超过了4 mg/kg的安全摄入量,而其他贮藏条件均在安全食用范围内。大白菜中硝酸盐与亚硝酸盐的含量在贮藏过程中随贮藏温度的降低而显著减少,到贮藏末期（16 d时）20 ℃和10 ℃贮藏大白菜中硝酸盐含量分别是0 ℃贮藏的1.2 倍和1.1 倍,亚硝酸盐含量分别是0 ℃贮藏的1.4 倍和1.2 倍。PE保鲜袋包装有助于减少大白菜在中、低温（10、0 ℃）贮藏中硝酸盐与亚硝酸盐的含量,但在高温（20 ℃）贮藏中其含量增加。因此,建议贮藏大白菜时最好采用PE保鲜袋包装和0～10 ℃的贮藏温度,以保证其硝酸盐和亚硝酸盐含量不超标。     

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.     

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。     

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.     

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 and nitrite contents in Cuban cheese of the Gouda type

The nitrate and nitrite contents in cheese of the Gouda type, produced by the Milk Complex of Havanna, were investigated and compared with those found in 5 types of imported cheese consumed in Cuba. No significant differences were found in the mean value (x) of NaNO₃, whereas in the mean value (x) of NaNO₂ differences were found when comparing all cheeses against each other. From these results it is inferred that the consumption of Gouda type cheese does not represent an important contribution to the daily intake of nitrates and nitrites, precursors in the synthesis of cancerogenic N-nitroso compounds.     

蔬菜硝酸盐污染现状及其食用安全性评价

通过分析测定9种主要蔬菜70个样品的硝酸盐含量,发现镇江地区根、茎、叶类蔬菜硝酸盐含量严重超标,其中尤以小青菜、茼蒿、芹菜、萝卜、蕹菜和苋菜最为突出,莴苣其次,生菜和土豆则较轻。同时评价了蔬菜的食用安全性,并提出了蔬菜硝酸盐污染的防治对策。     

甘肃省市售浆水中亚硝酸盐含量测定

了解甘肃省市售浆水中亚硝酸盐的含量。方法 对GB 5009.33—2010《食品中亚硝酸盐与硝酸盐的测定》方法做了改进,省略了沉淀蛋白质的步骤；并按照改进的方法测定了采集于2013年4月至8月的62份浆水样品中亚硝酸盐的含量。结果 62份样品中亚硝酸盐含量均低于2 mg/kg,平均亚硝酸盐含量为0.64 mg/kg；含菜浆水亚硝酸盐含量高于不含菜浆水。结论 依据GB 2762—2012《食品中污染物限量》中规定的蔬菜及其制品、腌渍发酵蔬菜中亚硝酸盐最大量为20 mg/kg,62份样品中亚硝酸盐含量均未超标。     

厦门市售蔬菜重金属、硝酸盐和亚硝酸盐污染研究及评价

为了解厦门市蔬菜中有害重金属、硝酸盐和亚硝酸盐的污染情况,于2004年8月至2005年12月从厦门市各超市、农贸市场、蔬菜批发市场和蔬菜产地上采集46个品种532份蔬菜样品,用国标法(GB/T5009.11-17-1996、GB/T5009.33-2003)分别分析蔬菜中的重金属、硝酸盐和亚硝酸盐的含量。结果表明,检测样品中Pb、Cd、As、Hg、硝酸盐和亚硝酸盐的平均值分别为0.0099、0.083、0.056、0.003、1090.3、0.59mg/kg;根据国家标准1-2,仅部分品种如菠菜、甘蓝、花菜、萝卜的铅超标,有潜在污染风险;大部分蔬菜中砷、汞、镉三种重金属的含量都较低,潜在的污染风险不大。硝酸盐污染程度严重的占36.5%;中、重度污染的占20.2%;轻度的占43.3%,硝酸盐含量依次为嫩茎叶菜类>根茎类>花菜类>瓜菜类>鲜豆菜>茄果类>水生蔬菜类,各样品间含量差别较大;而蔬菜中亚硝酸盐含量相对较低。     

Nitrate and Nitrite levels in carrot roots

The nitrate and nitrite levels were determined in two carrot varieties, cultivated in three Experimental Stations of Varieties Assessment in different regions of Poland in 1987–1989. The results obtained were analysed against soil conditions (kind and composition, richness), agrotechnical background (length of vegetation period, harvest time) and climatic conditions (air temperature and precipitation). The nitrate level in carrot was estimated at av. 349 mg KNO₃/kg. Significant differences were found in nitrate levels depending on place and year of cultivation. The most significant effects of the studied factors on the nitrate level had soil richness in potassium and magnesium as well as length of vegetation period. The studied carrot displayed a high level of nitrites (av. 3.1 mg NaNO₂/kg), which might have resulted from a microbiological reduction of nitrates occurring between harvest and the time of performing analyses.     

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）。     

京郊主要蔬菜产品器官硝酸盐与亚硝酸盐含量分析与评价

对京郊52种蔬菜产品,以及同一种类不同品种、同一品种产品的不同部位的硝酸盐、亚硝酸盐和VC含量等进行测定。结果表明：供试蔬菜产品器官的硝酸盐含量在不同种类、品种及其不同部位间存在明显差异。以蔬菜鲜质量器官中硝酸盐含量均值计算,根菜类(420.66mg/kg)＞叶菜类(281.24mg/kg)＞茎菜类(279.54mg/kg)＞果菜类(176.54mg/kg)＞花菜类(157.93mg/kg);同种蔬菜品种间的硝酸盐含量相差1.13～5.48倍;产品器官不同部位的硝酸盐含量也有较大差异,如结球叶菜硝酸盐含量外叶＞中叶＞内叶,叶柄＞叶片,黄瓜果实顶部、基部＞中部,果肉＞果心,萝卜根皮＞根肉。各供试蔬菜产品器官的亚硝酸盐含量多在1mg/kg以下,个别蔬菜种类如茼蒿可达6.74mg/kg,不同蔬菜种类、品种和部位间亚硝酸盐含量差异不如硝酸盐含量差异明显。果菜类、叶菜类和花菜类蔬菜产品器官的VC含量普遍较高,如辣椒可达146.56mg/100g,但品种间VC含量差异不显著。由此可见,目前京郊蔬菜产品器官中的硝酸盐和亚硝酸盐含量多在安全范围内,但仍建议消费者科学合理进行蔬菜种类搭配以保障人体健康。