CTAB污染对蔬菜中硝酸盐含量的影响

通过盆栽的方法,用阴离子表面活性剂十六烷基三甲基溴化铵(CTAB)对小白菜、空心菜、胡萝卜三种常见蔬菜进行处理,采用比色法测定不同浓度梯度处理后其茎叶部分的硝酸还原酶和硝酸盐含量变化。研究表明:CTAB对蔬菜的品质产生了不良影响。中低浓度的CTAB处理使小白菜、胡萝卜、空心菜的硝酸盐含量都有所上升,但并没有改变硝酸盐在蔬菜体内的分布。CTAB处理对蔬菜中叶绿素含量及硝酸还原酶的活性也有显著影响,其变化规律因蔬菜种类的不同而不同。      

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。     

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.     

蔬菜中硝酸盐的含量

<正>用大量氮肥栽培的蔬菜虽获得很高的产量,但积聚了大量的硝酸盐。硝酸盐在蔬菜里的最大允许量,卫生学家们还没提出统一规定。萨克西提出在每1公斤生蔬菜里硝酸盐的最大允许含量为500毫克。按此含量,限定成人每夭食用蔬菜400克,儿童50克。劳伦兹提出在每一公斤生蔬菜里硝酸     

贮存条件对蔬菜及其食品中硝酸盐、亚硝酸盐含量的影响

对不同温度、容器等贮存条件下蔬菜及菜汤中NO3-和NO2-含量状况的研究。结果表明:不论是在新鲜蔬菜还是菜汤中,这两种有害物质的含量均随贮存温度的升高而相应增加,且含盐菜汤中的含量高于无盐菜汤;在同种温度条件下,3种不同质地容器贮存的菜汤中NO3-特别是NO2-的含量差异较大,均为铝容器>不锈钢容器>铁容器。     

卷烟中硝酸盐含量对烟气成分的影响

对卷烟中硝酸盐的热解反应、产物、产物转化及其对烟气成分的影响，做了较深入的分析，对卷烟配方设计、添加剂的使用、烟气分析等有一定参考价值。     

蔬菜中硝酸盐和亚硝酸盐含量分析与评价

通过对7种蔬菜不同处理的硝酸盐及亚硝酸盐含量进行分析,探讨其在蔬菜中的变化情况,为人们合理食用蔬菜提供科学依据。     

太原市蔬菜硝酸盐污染状况与防治对策

分析了太原蔬菜主产区6大类14种蔬菜中硝酸盐和亚硝酸盐含量,并对蔬菜硝酸盐污染现状进行了评价,提出防治蔬菜硝酸盐、亚硝酸盐污染危害的对策。     

蔬菜中硝酸盐和亚硝酸盐的测定及含量分析

采用超声提取、活性炭柱脱色和微孔膜过滤等步骤对蔬菜进行预处理,离子色谱法测定蔬菜中硝酸盐和亚硝酸盐含量。探讨不同贮藏条件下4种蔬菜中硝酸盐和亚硝酸盐含量的变化情况。结果表明:无论常温贮藏还是低温贮藏,贮藏7d内,4种蔬菜中硝酸盐含量变化基本上是呈下降趋势,亚硝酸盐含量均呈现先急剧上升后近于平稳的趋势,但常温贮藏的亚硝酸盐含量高于低温贮藏,除韭菜外,其它蔬菜中亚硝酸盐含量均低于限量标准4mg/kg。     

蔬菜硝酸盐含量检测方法的比较

通过测定变异系数和加标回收率对常用于蔬菜中硝酸盐含量检测的盐酸萘乙二胺法、苯酚法和双波长法进行了精密度和准确度的比较。结果显示,盐酸萘乙二胺法的精密度和准确度最高,变异系数为0.16%,加标回收率在106%～109%之间;双波长法稍差于盐酸萘乙二胺法,其变异系数为0.26%,加标回收率在95%～100%之间;苯酚法最差,其变异系数为2.98%,加标回收率在90%～95%之间。考虑到操作步骤和所用试剂的安全性,认为双波长法是最适于安全、快速、大批量地检测蔬菜中硝酸盐含量的方法。     

Flavonoid content of several vegetables and their antioxidant activity

Several vegetables were selected to study their flavonoid contents and antioxidant activities. The results showed that both green and purple leaves of sweet potatoes (185.01 and 426.82 mg kg⁻¹ respectively) and the outer leaves of onion (264.03 mg kg⁻¹) possessed higher amounts of flavonoids, and more than 85% of free radical scavenging activities were evaluated by using 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH), superoxide and hydroxyl radicals. In addition, green leaves of sweet potatoes and the outer leaves of onion showed higher reducing power and higher antioxidant activity in a linoleic acid system as compared to cabbage, spinach, potato and crown daisy. Blanching of green leaves of sweet potatoes for 30–60 s retained more flavonoids and higher free radical scavenging activities as compared to more than 1 min of blanching. The storage test showed that green leaves of sweet potatoes stored at 4–10 °C maintained better quality than those stored at room temperature. © 2000 Society of Chemical Industry     

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     

几种叶菜储藏中硝酸盐、亚硝酸盐含量及硝酸盐还原酶活性研究

对小白菜,大白菜、包菜、菠菜等4种蔬菜在室温储藏过程中硝酸盐、亚硝酸盐含量及硝酸盐还原酶活力进行分析。结果表明,储藏前后小白菜NO-3含量均超出国家标准;储藏3d后小白菜和菠菜中NO-2含量超标,该2种菜不适宜储存后食用。对4种叶菜储藏中NRA进行检测,其变化无一定规律。对4种蔬菜储藏3d内的NO-3含量的降解速率及其相应的NRA进行分析,4种蔬菜NO-含量的变化与NRA变化未呈现一定相关性。     

Evaluation of the nitrate content in leaf vegetables produced through different agricultural systems.

The nitrate content of leafy vegetables (watercress, lettuce and arugula) produced by different agricultural systems (conventional, organic and hydroponic) was determined. The daily nitrate intake from the consumption of these crop species by the average Brazilian consumer was also estimated. Sampling was carried out between June 2001 to February 2003 in Campinas, S?o Paulo State, Brazil. Nitrate was extracted from the samples using the procedure recommended by the AOAC. Flow injection analysis with spectrophotometric detection at 460 nm was used for nitrate determination through the ternary complex FeSCNNO+. For lettuce and arugula, the average nitrate content varied (p < 0.05) between the three agricultural systems with the nitrate level in the crops produced by the organic system being lower than in the conventional system that, in turn, was lower than in the hydroponic system. For watercress, no difference (p < 0.05) was found between the organic and hydroponic samples, both having higher nitrate contents (p < 0.05) than conventionally cultivated samples. The nitrate content for each crop species varied among producers, between different parts of the plant and in relation to the season. The estimated daily nitrate intake, calculated from the consumption of the crops produced by the hydroponic system, represented 29% of the acceptable daily intake established for this ion.     

Effect of nitrogen fertiliser on the nitrate contents of field vegetables grown in Britain

The nitrate and percentage organic nitrogen contents of 14 vegetable and two arable crops were measured after they had been grown with different levels of N-fertiliser. Foliage crops always contained substantial quantities of nitrate which increased with increase in the rate of N-fertiliser application. Grain of legumes and cereals, storage roots of carrots, parsnips and sugar beet, and onion bulbs and leeks contained no detectable amounts of nitrate even when N-fertiliser application rates were very high. Storage roots of red beet, swede and white turnip contained more than 3 mg NON g^?1 dry weight when grown with exceptionally high levels of fertiliser-N but contained very little when grown with the optimum amount of fertiliser-N or less. An equation was developed that linked NON to percentage organic-N for those parts of plants that could accumulate nitrate. It gave good fits to the data from seven crop species grown at a range of different levels of N-nutrition. It is estimated from the foregoing data and a survey of household food consumption that the average British person consumes about 60 mg NON week^?1 in field vegetables. If N-fertilisers were withheld consumption would be about 30 mg and if excess were applied it would be about 120 mg NON week^?1.     

Organic and conventional fertilisation procedures on the nitrate,antioxidants and pesticide content in parts of vegetables

Different parts of plant foods are generally discarded by consumers such as peel, stalk and leaves, which could however possess a nutritional value. However, few studies have analysed the composition of these marginal foods. The phenolic compound, flavonoid, polyamine, nitrate and pesticide contents of parts of vegetables that are usually discarded – but which were cultivated according to conventional and non-conventional procedures – were analysed to provide suggestions on how to improve the consumption of these parts and to reduce the production of urban solid waste. Few, but significant, differences between the two manuring procedures were observed. Higher nitrate content and the presence of organochlorine pesticides were found in conventional cultivated papaya peel, lemon balm leaves, jack fruit pulp, and beet stalk and peel. Discarded parts of plant foods such as stalk, leaves and peels can be used as a source of antioxidant compounds, such as phenolic compounds.     

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.     

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。