蔬菜中硝酸盐和亚硝酸盐的污染

综述了硝酸盐和亚硝酸盐的危害、污染来源、蔬菜中的污染现状、蔬菜中硝酸盐积累机理及控制措施。     

蔬菜中硝酸盐和亚硝酸盐的污染

综述了硝酸盐和亚硝酸盐的危害、污染来源、蔬菜中的污染现状、蔬菜中硝酸盐积累机理及控制措施。     

定性风险-受益评估方法在蔬菜及蔬菜中硝酸盐摄入评估中的应用性研究

目的通过评估蔬菜及蔬菜中硝酸盐摄入的风险与受益,为我国食物或食物成分的风险-受益评估研究提供参考依据。方法以欧盟构建的BRAFO(benefit risk analysis for food)模型为基础,对蔬菜及蔬菜中硝酸盐摄入的风险与受益开展一级和二级分级评估,同时与摄入量评估相结合,定性比较蔬菜及蔬菜中硝酸盐摄入的风险与受益。结果蔬菜作为食物提供人类多种营养素,摄入蔬菜能够降低结肠癌、超重和肥胖、心血管疾病、Ⅱ型糖尿病等疾病的发生风险,蔬菜中硝酸盐可引起高铁血红蛋白血症的发生。由参考情景转为假设情景时消费者获得的受益大于风险,假设情景要优于参考情景(300 g/d),即推荐居民消费蔬菜300~500 g/d。结论分级评估的方式对食物开展风险-受益研究具有科学性和合理性,需要进一步加强人群流行病学、毒理学等方面的研究,优化模型参数,将概率评估与风险-受益评估研究相结合以减少风险-受益评估研究中的不确定性。     

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.     

蔬菜中硝酸盐与亚硝酸盐检测方法的研究进展

综述了亚硝酸盐和硝酸盐的检测方法,指出了各检测方法的优劣及其应用前景,对于监控蔬菜生产加工中硝酸盐和亚硝酸盐的含量,检测蔬菜产品的品质等具有参考意义。     

北京市蔬菜硝酸盐和亚硝酸盐污染状况评价

为了解北京市蔬菜中硝酸盐和亚硝酸盐的污染情况 ,于 2 0 0 3年 4月～ 8月从北京 15个菜市场采集应季蔬菜样品 ,共 4 0个品种 4 44份样品 ,用国标法 (GB T 5 0 0 9 33— 2 0 0 3)分析蔬菜中的硝酸盐和亚硝酸盐的含量。结果显示 :检测样品中 ,污染程度严重的占 33 1% ;中、重度污染的占2 3 6 % ;轻度的占 4 3 2 % ;硝酸盐的含量依次为绿叶菜类 >白菜类 >根茎类 >瓜茄类 >葱蒜类 >豆类 >果类 >水生植物类 ,但同一类蔬菜不同品种的硝酸盐的含量差别较大 ,从几倍到几十倍 ;同一品种的蔬菜中硝酸盐含量差别也很大 ,可能与产地、生长条件不同有关。蔬菜中亚硝酸盐含量相对较低 ,其含量与蔬菜的新鲜程度有关。研究结果提示需要制定限量标准 ,加强监督管理     

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.     

Dietary exposures to nitrate in the UK

Dietary exposures to nitrate have been estimated for two different groups of UK consumers. The daily dietary exposure of the general population was estimated from the UK 1997 Total Diet study to be 52mg/ day. Vegetables contributed approximately 70% to this total dietary exposure. Dietary exposure estimates for adult consumers of vegetables commonly eaten in the UK were 93mg/day and 140mg/day for mean and 97.5th percentile consumers, respectively. Dietary exposures to nitrate of UK consumers are similar to those in other European countries and are less than the Acceptable Daily Intake (ADI) for nitrate set by the European Commission's Scientific Committee for Food.     

A flow-injection spectrophotometric method for nitrate and nitrite determination through nitric oxide generation

A flow injection method with novel spectrophotometric detection for the determination of nitrite and nitrate in foodstuffs is presented. The method is based on the reduction of nitrite and nitrate to nitric oxide, with subsequent reaction with iron (II) and thiocyanate in an acid medium, forming FeSCNNO⁺. The absorbance of the complex, with a maximum at 460 nm, is proportional to the nitrite and nitrate concentrations. The NO is generated in two stages: (1) reduction of nitrate to nitrite in a cadmium copper reductor column and (2) reduction of the nitrite to NO in a sulfuric acid medium. The influence of reagent concentrations and manifold parameters were evaluated. Nitrite and nitrate can be determined in the range of 0.30–3.00 and 1.00–10.00 mg l⁻¹, respectively. The sampling rate of analyses was 30–40 h⁻¹ and, considering a sample of 5.0 g, the determination limit of the method was 20 and 13 mg kg⁻¹ of nitrate and nitrite, respectively. Nitrite and nitrate were determined in vegetables and meat products by the proposed method. The precision and accuracy of the proposed method were comparable to those of the reference spectrophotometric method (official AOAC reference method for the determination of nitrate in foodstuffs).     

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.     

How natural dietary antioxidants in fruits, vegetables and legumes promote vascular health

Oxidative stress disturbs the normal redox state within the human body, and thus may trigger many human chronic diseases including cardiovascular disease. Antioxidant properties of some bioactive components in plant-based foods have been proposed to be capable of controlling such disturbances. This hypothesis has initiated a great number of laboratory studies devoted to the understanding of the role of natural antioxidants in cardio-health promotion. This review summarizes these studies with an emphasis on major natural antioxidants found in three categories of plant-based foods (fruits, vegetables and legume) and mechanisms that these antioxidants may use in promoting cardio-health. Since different food categories possess different bioactive compounds with various antioxidant capacities, specific foods, when consumed together, may produce synergistic antioxidant interactions and in turn have more positive physiological effects on cardio-health than when consumed alone. This review also highlights research on antioxidant synergisms. We recommended strategically selecting foods that provide multiple levels of protection against the development of cardiovascular diseases.     

蔬菜中草酸检测技术的研究进展

草酸是植物体内普遍存在的一种简单二元有机酸,大量存在于蔬菜中。草酸可以参与细胞体内pH和渗透压等的调节,以及植物病原菌防御反应与铝毒害解除,具有重要的生理功能。同时,过量的草酸对人体具有许多不利影响。作为一种抗营养物质,大量食用含草酸的蔬菜会显著影响人体矿物元素的吸收和增加患肾结石的风险,因此研究草酸的测定方法具有非常重要的现实意义。蔬菜中草酸含量的检测技术主要有滴定法、光谱法、色谱法以及电化学方法。每种检测技术各有优点,也都存在一定的局限性。本文主要对蔬菜中草酸的检测技术进展进行了概述,以期为蔬菜中草酸的检测及快速检测技术提供基础参考。     

Application of a UV–vis detection-HPLC method for a rapid determination of lycopene and β-carotene in vegetables

The purpose of this paper is to optimize an HPLC method for the determination of lycopene and β-carotene in vegetables and compare it with a spectrophotometric standard method. Among the different conditions studied the most suitable ones for our samples were: extraction with hexane/acetone/ethanol (50:25:25 v/v/v), evaporation of the hexane layer, dissolution of the dry extract in THF/ACN/methanol (15:30:55 v/v/v) and injection on a C18 column with methanol/ACN (90:10 v/v) + TEA 9 μM as mobile phase (Φ = 0.9 ml/min) and λ_detection = 475 nm. Samples considered for analysis were: tomato, carrot, pepper, watermelon, persimmon and medlar. The HPLC method proposed showed adequate reproducibility (RSD < 10.5%), accuracy (100–109% recovery) and sensitive detection limits (0.6 μM for lycopene; 0.3 μM for β-carotene), with a simple preparation of the samples (one step direct extraction) and short run times (10 min) for the quantification of lycopene and β-carotene.     

蔬菜中硝酸盐检测方法对比研究

通过平行实验和加标回收实验,对常用于蔬菜中硝酸盐含量检测方法进行对比研究。结果:镉柱还原法标准偏差7.7,相对标准偏差0.22%;双波长法标准偏差18.65,相对标准偏差0.54%;苯酚法标准偏差23,相对标准偏差.0.7%。利用F-检验,对数据的精密度是否存在显著差异,进行评价;再进行t-检验,对测定结果的准确度做出评价。结论:镉柱还原法精密度准确度最高,双波长法次之,苯酚法是3种方法中最低的。     

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.     

Chlorophyll changes in some green leafy vegetables during cooking

Five green leafy vegetables commonly consumed in Nigeria (Talinum triangulare, Corchorus olitorius, Celosia argentea, Amaranthus hybridus and Vernonia amygdalina) were examined for their chlorophyll contents. These varied between 0.038% for Talinum triangulare and 0.137% for Vernonia amygdalina, with chlorophyll-a constituting between 68 and 75% of the total chlorophyll. By bringing the temperature of the leaves to 100°C, at least 56% of the total chlorophyll was lost, the rate of loss decreasing with the initial total chlorophyll content. When the leaves were blanched by immersion in boiling water, they showed a greater rate of chlorophyll loss. This was reduced when the pH was adjusted to 6.     

The contribution of fruits and vegetables to dietary intake of polyphenols and antioxidant capacity in a Mexican rural diet: Importance of fruit and vegetable variety

There is mounting evidence of the health-protective role of the consumption of fruits and vegetables, which are the major contributors to dietary polyphenol intake. Lack of knowledge about the consumption of phytochemicals in the Mexican diet makes it difficult to evaluate their health significance. The aim of this study was therefore to estimate the contribution of fruit and vegetable consumption to dietary polyphenol intake and dietary antioxidant capacity in a rural population in Mexico. Despite a low intake of fruits and vegetables (< 400 g/day) in the Mexican rural diet, the mean daily intake of dietary polyphenols (> 800 mg/day) and dietary antioxidant capacity (1000-2000 ??mol trolox equivalents/day) from fruits and vegetables was similar to those determined in the Spanish Mediterranean diet. Local fruits and vegetables consumed in the Mexican rural diet are rich in polyphenols with antioxidant properties and are important source of bioactive compounds and dietary fibers. Fruit and vegetable intake needs to be promoted and lifestyle and environmental factors enhanced to improve the health status of obese Mexican rural populations.     

臭氧在果蔬保鲜和农残降解上的应用

臭氧是一种强氧化剂，它可以杀灭果蔬上的微生物，去除果蔬释放的乙烯，抑制果蔬的呼吸作用，延长果蔬的保鲜期。臭氧还可以降解果蔬上的农药残留。尽管可能会对某些果蔬的品质造成损伤，但具有高活性、高渗透性和无毒降解产物的特点的臭氧在果蔬采后处理上有着巨大的应用潜力。