白肋烟达白杂交种亲本烟碱转化率分析及改良效果

采用烟碱转化株早期诱导鉴别方法,对白肋烟达白系列杂交种及亲本材料不同烟株的烟碱转化率进行了分析测定,并配置了改良杂交种.结果表明,不同杂交种生物碱组成和含量存在显著差异,其中达白1号和达白2号烟碱转化问题相对较小,但群体中仍然不同程度存在转化株,总转化株比例分别为10.9%和23.7%,其中多为低转化株.达白3号问题比较突出,所测烟株全部为转化株,且转化程度较高,多为高转化株,平均烟碱转化率达到38.3%.达白1号的2个亲本MSKYl4和达所26均存在一定比例的转化株.对达白1号群体中转化株的产生均有贡献.达白2号的母本MSVA509多为非转化株,父本达所26对烟碱转化的贡献较大.达白3号父本达所27总转化株比例和高转化株比例都接近100%,是造成达白3号杂交种高烟碱转化株比例的主导因素.严格选择非转化株配置改良杂交种,群体中烟碱转化率显著降低.     

2-氯乙基磷酸诱导白肋烟烟碱提前转化的有效性

为评价2-氯乙基磷酸诱导烟碱提前向降烟碱转化的有效性,对湖北和海南两个白肋烟产地的3个白肋烟品种(系)和1个改良品种,进行了2-氯乙基磷酸早期诱导烟碱转化效果研究,并与正常调制的烟叶进行对比分析。结果表明,经过2-氯乙基磷酸处理后,除湖北恩施种植的鄂烟1号外,其余试验品种(系)群体平均烟碱转化率均高于正常调制后的烟叶,其中B21群体平均转化率和高转化株比例高于其它品种;湖北恩施种植的3个品种(系)早期诱导和正常调制在转化株鉴定结果的一致性上比海南高,其中湖北恩施种植的TN90和海南种植的改良鄂烟1号的转化株数超过正常调制出现的转化株数;利用2-氯乙基磷酸早期诱导鉴定筛选留种非转化株,使鄂烟1号后代转化率分别由改良前的22.10%和16.93%降为3.98%,转化株比例尤其是高转化株的比例分别由改良前的48%和27%降为2%。     

基于不同烟碱转化株鉴别标准的白肋烟品种改良效果

在采用不同烟碱转化株鉴别标准对TN86进行改良的基础上,对不同改良种的烟叶经济性状、烟碱转化率和TSNAs含量进行比较分析,以探讨采用不同转化株鉴别标准进行白肋烟品种改良的效果。结果表明,以烟碱转化率低于2.5%作为选择标准得到的改良种1（PNC<2.5）烟碱转化率稳定,上部叶比常规种低37.7%,中部叶低38.3%;总TSNAs含量低,比常规种低17.9%;产量、产值及上中等烟比例也明显优于其他改良种,且后代变异系数最小。改良种2（PNC<3）和改良种3（PNC<5）的烟碱转化性状分离明显,TSNAs含量较高。综合来说,烟株烟碱转化率2.5%作为区别转化株和非转化株的标准较为可靠,选择PNC<2.5的烟株进行留种或制种可以保证后代群体中出现转化株的频率最低,能够更有效地降低降烟碱含量和烟草特有亚硝胺的形成和积累,提高烟叶的香味品质。      

白肋烟不同类型转化株烟碱转化率的叶位间和叶点间变异

采用气相色谱法对具有不同烟碱转化能力白肋烟烟株不同叶位和叶点的烟碱转化率进行测定。结果表明,非转化株和高转化株不同叶位以及同一叶片不同叶点的烟碱转化率分布比较一致,变异性较小,非转化株各样品烟碱转化率均在2%以下,高转化株烟碱转化率均在85%以上,不表现烟碱转化的嵌合特征,取样部位对转化株鉴别效果无显著影响。低转化和中转化烟株,不同叶位烟叶和不同叶点间烟碱转化率存在较大的变异性,表现明显的嵌合特征,低转化株不同叶位烟叶烟碱转化率的变异范围为2.5%～4.8%,不同叶点的变异范围为2.6%～7.0%;中转化株不同叶位烟碱转化率的变异范围为2.51%～90.6%,不同叶点的变异范围为2.7%～66.9%。由于一部分叶片和叶点的烟碱转化率低于3%的现行转化株鉴别标准,取样部位会对转化株的鉴别效果产生影响,降低转化株鉴别标准十分必要。     

打顶及仿生型信号分子对白肋烟不同烟碱转化率株系的影响

为降低白肋烟烟碱转化率、提高烟叶品质,对白肋烟B37不同转化率株系采用打顶和打顶后涂抹仿生型信号分子(BSM)两种方式处理,分别测定了不同处理烟株烟叶的超氧化物歧化酶(SOD)活性、丙二醛(MDA)含量、生物碱含量,并分析了生物碱比例和烟碱转化率的变化.结果表明:打顶使不同转化率株系的烟叶SOD活性增加且高转化率株系增加幅度大,BSM处理也增加了SOD活性,但高转化率株系增加幅度较小.打顶使烟株的MDA含量增加,但高转化率株系增加幅度较小;BSM处理后烟叶MDA含量下降,高转化率株系烟叶MDA含量下降幅度较大.BSM处理后烟叶4种生物碱含量及总生物碱含量总体上有所降低,其中降烟碱的降低幅度最大.BSM对非转化株上部叶和中部叶烟碱比例影响较小,而对高转化株系B37-38的作用最大,其上部叶和中部叶烟碱比例分别提高了15.52和10.40百分点;B37-38上部叶和中部叶降烟碱比例分别降低了15.16和10.03百分点.从非转化株系至高转化株系随着烟碱转化率的提高,BSM处理其降烟碱的比例降低幅度增加,BSM对高转化率株系的影响较大.     

节杆菌对烟叶的降烟碱作用

应用节杆菌(Arthrobacter spp.)K7和K3菌株菌悬液处理K326的采收后烟叶,并测定烘烤后烟叶烟碱含量.结果表明,烟叶经节杆菌茵悬液处理后,烟碱含量均有不同程度的降低,在田烟上使用效果略好于地烟,K7菌株对田烟的降烟碱效果好于K3茵株.K7和K3茵株茵悬液处理分别使田烟下部叶烟碱含量降低39.7%和34.9%,上部叶烟碱含量降低29.5%和29.2%,中部叶烟碱含量降低28.4%和26.1%.对各处理单料烟的评吸结果表明:节杆菌处理后,烟叶的香气质、香气量增加,烟气细腻,刺激性减轻,劲头有所下降且余味改善.两菌株对中部叶香气质的影响最大.     

晾制湿度对白肋烟烟碱向降烟碱转化的影响

通过控制烟叶在变黄-褐变期的晾制湿度,研究了晾制过程中湿度对白肋烟中烟碱向降烟碱转化的影响.结果表明,不同晾制湿度下高转化株主脉的烟碱转化率均高于叶片,非转化株除低湿处理B21的第15叶位外,其余处理烟碱转化率表现出与高转化株相同的趋势.高转化株叶片烟碱含量在低湿处理时最高,非转化株叶片烟碱与降烟碱含量皆因品种与叶位的不同而存在差异.无论是高转化株还是非转化株,较低的晾制湿度均有利于降低叶片的烟碱转化率;晾制湿度对烟叶主脉中烟碱、降烟碱及烟碱转化率的影响,因试验品种的不同而异.因此,晾制过程中及时降低晾制湿度有利于降低烟叶的降烟碱含量.     

旺长期干旱胁迫对白肋烟烟碱向降烟碱转化的影响

通过控制旺长后期土壤水分含量,以研究干旱胁迫对白肋烟中烟碱向降烟碱转化的影响.结果表明,在晾制过程中,不同程度干旱处理导致B37高转化株烟碱转化率的变化存在差异,随烟叶着生叶位的升高烟碱转化率快速增长阶段向后延迟,B37非转化株烟碱转化率整体均维持在较低水平,处理问差异不明显;轻度干旱有利于降低高转化株的降烟碱含量和烟叶(包括转化株与非转化株)的烟碱转化率,提高非转化株烟碱转化性状的稳定性.     

基于烟茄嫁接的超低烟碱烟叶的感官质量和烟气特性

  背景和目的  本研究在烟茄嫁接（烤烟品种云烟87为接穗,茄子为砧木）的基础上,检测分析了所获得的超低烟碱含量烟叶TSNAs含量、中性香气物质含量,并对卷制的试验卷烟烟气参数和感官质量进行对比分析。  方法  试验共设烟/烟、烟/茄不培土、烟/茄培土等3个处理。  结果  （1）烟茄嫁接的超低烟碱含量烟叶,中性香气物质含量变化较小,但NNN、NNK、NAT和TSNAs含量显著降低,上部叶烟/茄不培土处理的NNN、NNK及TSNAs含量比烟/烟低82.71%、79.46%和68.78%,中部叶烟/茄不培土处理的NNN、NNK及TSNAs含量比烟/烟低79.68%、79.80%和68.63%。（2）卷烟烟气中烟碱含量大幅度降低,其中烟/茄不培土烟叶比常规烟叶低94.12%,焦油、CO、总粒相物、水分和抽吸口数无显著差异。（3）超低烟碱含量烟叶的香气质、浓度、刺激性和燃烧性无显著差异,香气量、杂气和余味与常规烟叶相比有不同程度的降低,劲头下降明显,消费者满足感、愉悦感、接受度显著降低。  结论  通过嫁接技术选择性降低烟碱含量对烟叶化学组成和感官质量产生不同程度的影响。      

碳酸氢钾和氯化钠对烟草转化株烟碱转化的诱导作用

以白肋烟TN90高转化株为材料研究了无机盐处理烟株早期叶片对烟碱转化的诱导作用及机理。结果表明,1.2%的碳酸氢钾水溶液和1.2%的氯化钠水溶液均具有显著的诱导转化株早期叶片烟碱转化作用,碳酸钠效果较差。比较碳酸氢钾处理、氯化钠处理分别对常规TN90品种烟株转化株的早期鉴定结果和自然晾制后烟叶的烟碱转化率发现,采用2种无机盐鉴别出的转化株均包括了所有在自然晾制后产生的转化株,且还可鉴别出一些在正常晾制条件下不能有效鉴别的低转化株;早期测定的烟碱转化率一般高于烟叶自然晾制后的烟碱转化率,有利于提高鉴定的准确性和有效性。碳酸氢钾可显著促进叶片内源乙烯的释放,在处理溶液中添加10-4mol/LAVG抑制乙烯的合成可逆转碳酸氢钾对烟碱转化的诱导。     

Ovarian structures and circulating steroids in heifers and lactating cows in summer and lactating and dry cows in winter

Two experiments compared follicular and luteal development and circulating steroid concentrations from induced luteolysis to ovulation in lactating Holstein cows (n = 27; 40.0 +/- 1.5 kg milk/day) vs. nulliparous heifers (n = 28; 11 to 17 mo-old) during summer (Experiment 1), and in lactating (n = 27; 45.9 +/- 1.4 kg milk/d) vs. dry cows (n = 26) during winter (experiment 2). All females received PGF2,, 6 d after ovulation and were monitored until next ovulation by daily ultrasound and assay of serum progesterone (P4) and estradiol (E2). Every female was used two or three times. In Experiment 1, lactating cows had high incidence of multiple ovulation (63.5%) compared with heifers (1.3%). Among single ovulators, there was no difference in maximal size of ovulatory follicles between lactating cows and heifers (15.8 vs. 16.5 mm, respectively). However, lactating cows had lower peak serum E2 (8.6 vs. 12.1 pg/ml), took longer to ovulate after luteolysis (4.6 vs. 3.8 d), developed more luteal tissue volume (7,293.6 vs. 5,515.2 mm3), and had lower serum P4 on d 6 after ovulation (2.0 vs. 3.0 ng/ml) than heifers (data included multiple ovulators). In experiment 2, multiple ovulations were similar between lactating and dry cows (17.9 vs. 17.2%, respectively). Peak serum E2 was also similar between lactating and dry cows (7.6 vs. 8.5 pg/ml) although lactating cows had larger ovulatory follicles (18.6 vs. 16.2 +/- 0.4 mm). Lactating cows took longer to ovulate (4.8 vs. 4.2 d), developed more luteal tissue (7,599 vs. 5,139 +/- 468 mm3), but had similar serum P4 (2.2 vs. 1.9 ng/ ml) compared with dry cows. Therefore, lactating cows had similar or lower circulating steroid concentrations than dry cows or heifers, respectively, despite having larger ovarian structures.     

Fertilization and early embryonic development in heifers and lactating cows in summer and lactating and dry cows in winter

Two experiments in two seasons evaluated fertilization rate and embryonic development in dairy cattle. Experiment 1 (summer) compared lactating Holstein cows (n = 27; 97.3 +/- 4.1 d postpartum [dppl; 40.0 +/- 1.5 kg milk/d) to nulliparous heifers (n = 28; 11 to 17 mo old). Experiment 2 (winter) compared lactating cows (n = 27; 46.4 +/- 1.6 dpp; 45.9 +/- 1.4 kg milk/d) to dry cows (n = 26). Inseminations based on estrus included combined semen from four high-fertility bulls. Embryos and oocytes recovered 5 d after ovulation were evaluated for fertilization, embryo quality (1 = excellent to 5 = degenerate), nuclei/embryo, and accessory sperm. In experiment 1, 21 embryos and 17 unfertilized oocytes (UFO) were recovered from lactating cows versus 32 embryos and no UFO from heifers (55% vs. 100% fertilization). Embryos from lactating cows had inferior quality scores (3.8 +/- 0.4 vs. 2.2 +/- 0.3), fewer nuclei/embryo (19.3 +/- 3.7 vs. 36.8 +/- 3.0) but more accessory sperm (37.3 +/- 5.8 vs. 22.4 +/- 5.5/embryo) than embryos from heifers. Sperm were attached to 80% of UFO (17.8 +/- 12.1 sperm/UFO). In experiment 2, lactating cows yielded 36 embryos and 5 UFO versus 34 embryos and 4 UFO from dry cows (87.8 vs. 89.5% fertilization). Embryo quality from lactating cows was inferior to dry cows (3.1 +/- 0.3 vs. 2.2 +/- 0.3), but embryos had similar numbers of nuclei (27.2 +/- 2.7 vs. 30.6 +/- 2.1) and accessory sperm (42.0 +/- 9.4 vs. 36.5 +/- 6.3). From 53% of the flushings from lactating cows and 28% from dry cows, only nonviable embryos were collected. Thus, embryos of lactating dairy cows were detectably inferior to embryos from nonlactating females as early as 5 d after ovulation, with a surprisingly high percentage of nonviable embryos. In addition, fertilization rate was reduced only in summer, apparently due to an effect of heat stress on the oocyte.     

Sweetness and aroma perceptions in dairy desserts varying in sucrose and aroma levels and in textural agent

Sweetness–aroma interactions were investigated in model dairy desserts varying in sucrose concentration, aroma concentration and in textural characteristics using different textural agents (κ-, ι-, λ-carrageenans and an equal-mix of the three). Overall intensities of sweetness and aroma perceptions were evaluated by sensory analysis and apparent partition coefficients of aroma compounds were measured by static headspace—GC.Sweetness–aroma interaction was characterised by a non-reciprocal relationship. Concentration of aroma had no impact on sweetness intensity, whatever be the sucrose concentration or textural characteristics of desserts, whereas varying texture or sucrose concentration modified aroma intensity. However, effects on aroma assessment were effective only when aroma concentration was the highest. In this condition, use of λ-carrageenan or increasing sucrose concentration from 25 to 50 g kg⁻¹ enhanced aroma intensity, but no extra enhancement was observed when sucrose concentration was 100 g kg⁻¹. As the air–dessert partition coefficient remained constant, impact of textural characteristics and sweetness variation on aroma perception did not result from physico-chemical interaction.     

2018年深圳市售蔬菜和鸡蛋中氟虫腈及其代谢物的检测分析

目的 建立超高效液相色谱-串联质谱法同时测定蔬菜和鸡蛋中氟虫腈及其代谢物(氟甲腈、氟虫腈砜和氟虫腈亚砜), 并对深圳市售的蔬菜和鸡蛋中氟虫腈及其代谢物残留状况进行抽样检测。方法 采用QuEChERS前处理方法, 以C18色谱柱为分离柱, 以乙腈和10 mmol甲酸+6 mmol甲酸铵水溶液为流动相进行梯度洗脱, 用超高效液相色谱-串联质谱(ultra performance liquid chromatography-mass spectrometry/mass spectrometry, UPLC-MS/MS), 电喷雾电离(electrospray ionization, ESI), 多反应监测(multiple reaction monitoring, MRM)模式检测, 外标法同时定量测定氟虫腈及其代谢物。结果 方法的线性范围为0.1~2.0 μg/L, 线性相关系数均大于0.9994, 检出限0.0005 mg/kg, 定量限0.001 mg/kg; 蔬菜中3个水平的平均加标回收率88.0%~101.2%, 相对标准偏差(relative standard deviation, RSD)均小于8.5%; 鸡蛋中3个水平的平均加标回收率86.1%~104.8%, 相对标准偏差(RSD)均小于9.2%。结论 该方法具有操作简单、干扰少、快速、准确可靠等特点, 可适用于蔬菜鸡蛋中氟虫腈及其代谢物的检测。     

Aluminium and fluoride in hospital daily diets and in teas

The levels of aluminium and fluoride have been determined in hospital daily diets including breakfast, dinner and supper, as well as in black teas and herbal teas purchased from the local market. In tea, aluminium was determined directly in a sample solution by atomic absorption spectroscopy using nitrous oxide and an acetylene flame. For analysis of the hospital diet, samples containing lower levels of aluminium were analysed using a spectrophotometric method which measured aluminium in the form of a 8-hydroxyquinoline complex. Decomposition of the samples was achieved using a mixture of concentrated acids [nitric (HNO₃), perchloric (HClO₄) and sulphuric (H₂SO₄)] in platinum dishes. Fluoride was assayed by spectrophotometry using a microdiffusion procedure with a mixture of concentrated HClO₄ and silver sulphate, trace amounts of the released fluoride [as hydrogen fluoride (HF)] were trapped on the alkaline surface of a Petri dish and then determined in the form of an alizarin-fluoride complex. The mean level of aluminium found in hospital daily diets amounted to 21.3±12.3 mg and the mean level of fluoride was 1.38±1.12 mg per adult person. In the 16 samples of commercially available brands of black teas, the levels of aluminium and fluroide ranged from 445 to 1552 ppm (mean=897±264 ppm) and from 30 to 340 ppm (mean 141±85 ppm), respectively. In six herbal teas, the mean levels of aluminium and fluoride were lower, and amounted to 218.9±150.7 ppm and 6.0±6.9 ppm, respectively. This study has shown that concern about a high intake of aluminium and fluoride from these foods is unfounded.     

芝麻饼粕及其在烟草上应用研究现状

概述了芝麻饼粕的有效营养成分及其作为有机肥的加工方法,介绍了芝麻饼粕在烟草生产上的应用效果。并就进一步促进芝麻饼粕在烟草上的应用提出了建议,以期为烟叶生产过程中科学使用芝麻饼粕提供参考资料。     

Characterization of limestones and their effects in vitro and in vivo in dairy cattle

Capacities of limestones of differing particle size to neutralize acid in vitro and to modify pH and utilization of feedstuffs in vivo were compared. Acid neutralization during pH-stat titrations was faster for fine than for coarse limestone, and mixed microbial cultures were more resistant to pH change when they contained fine calcium carbonate. Diets containing 25:75 corn silage to concentrates and .95% calcium from either coarse or fine limestone were fed to rumen-fistulated heifers. Total ruminal volatile fatty acid concentrations were higher for the fine limestone treatment. Ruminal volumes, dry matter disappearance, and ruminal fluid pH and dilution rate did not differ between fine and coarse limestone treatments. Ruminal fluid volume, osmolality, ratios of acetate to propionate, and concentrations of total volatile fatty acids were unaffected in rumen-fistulated Holstein cows fed 60:40 corn silage to concentrates and either .5% calcium (control) or 1.0% calcium from either coarse or fine limestone. Ruminal pH increased .07 to .10 units with limestone supplementation. Ruminal fluid dilution and particulate turnover rates were slower for the coarse limestone than the control treatment. Differences between coarse and fine limestones in vitro were observed under some conditions in vivo, but they were not consistent.     

Flavour and vitamin stability in pasteurized milk in polyethylene-coated cartons and in polyethylene bottles

Commercially pasteurized, non-homogenized full cream milk in 2-pt white polyethylene (PE)-coated cartons overprinted with blue, and in 4-pt PE bottles was stored for 4 d in the dark or under white fluorescent light of 4000 1x, at a temperature of 7°C. The flavour of milks kept in the dark remained good, but exposure to light resulted in early off-flavour development: cartoned milk was disliked by a flavour panel after about 17.5 h exposure and milk in the PE bottles after 9 h. Vitamins A and B₂ were stable in the milk during 4 d storage in the dark in both bottles and cartons, and in cartons exposed to light. In the bottled milks, light-induced losses of these vitamins after 4 d were, respectively, 15% and 35%. but there was little or no loss before the development of light-induced flavour. Loss of total vitamin C by day 4 was about 50% in the dark, irrespective of container. In the cartons exposed to light, 66% of the vitamin C was lost, while virtually none remained in the exposed, bottled milk. There was also a markedly greater loss of vitamin C in the bottled milk than in the cartoned milk at the time the flavour became unacceptable. The dissolved O₂ concentration dropped considerably in the bottled milk exposed to light, but only marginally in the cartons. There were small increases in dissolved O₂ in the dark in both types of container.     

Heavy metals in vegetables grown in the Netherlands and in domestic and imported fruits

Summary The contents of cadmium, lead mercury, copper, manganese and zinc in 242 samples of 37 different species of domestic and imported fruits have been determined. Also contents of the same heavy metals, except mercury, have been determined in 205 samples of 7 species of domestic vegetables (lettuce, spinach, endive, beetroots, onions, celeriac and Swedish turnips). The median contents (in mg/kg fresh mass of the edible part) found for fruits are: Cd 0.002; Pb 0.017; Hg 0.002; Cu 0.61; Mn 0.52 and Zn 0.99. In the vegetables median levels have been found (mg/kg) of 0.009–0.073 for Cd, 0.01–0.03 for Pb, <0.2–0.3 for Cu, 0.69–1.41 for Mn and 0.95–5.5 for Zn. The contribution of fruits to the tolerable daily intakes of Cd, Pb and Hg is, for an average consumption pattern, less than 1%. On the other hand, the contribution to the recommended amounts of the essential elements Cu, Mn, and Zn is no more than 1%–3%. From the vegetables an average portion of spinach contains 19% and 2.6% of the tolerable daily amounts of Cd and Pb, respectively. For the other species of vegetables these figures are less than 5% for Cd (except for endive, 6.8%) and for lead less than 1%. Spinach contributes considerably to the need for Cu, Mn and Zn, in general more than 10% of the recommended daily amounts. The other species of vegetables contribute only from less than 1% to less than few percents.

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Schwermetalle in niederländischen Gemüsen und in inländischem und importiertem Obst

Zusammenfassung Es wurde der Gehalt an Cadmium, Blei, Quecksilber, Kupfer, Mangan und Zink in 242 Proben von 37 verschiedenen Fruchtarten, landeseigenen und importierten, bestimmt. Darüber hinaus wurde der Gehalt der gleichen Schwermetalle, außer Qeucksilber, in 205 Proben von 7 Sorten landeseigenen Gemüsen, Kopfsalat, Spinat, Endivie, rote Rüben, Zwiebeln, Sellerie und Kohlrüben ermittelt. Die Medianwerte (in mg/kg Frischsubstanz des eßbaren Anteils) für die Fruchtproben sind: Cd 0,002; Pb 0,017; Hg 0,002; Cu 0,61; Mn 0,52; Zn 0,99. In den Gemüsen betrugen die Medianwerte (mg/kg) für Cd 0,009–0,073, für Pb 0,01–0,03, für Cu <0,2–1,3, für Mn 0,69–1,41 und für Zn 0,95–5,5. Der Anteil an den duldbaren täglichen Aufnahmemengen für Cd, Pb und Hg liegt bei durchschnittlichem Verzehr von Früchten unterhalb 1%. Andererseits ist der Anteil der Früchte an den empfohlenen Mengen für die essentiellen Spurenelemente Cu, Mn und Zn bei normalem Verzehr auch nur 1%–3%. Bei den Gemüsen liefert eine Tagesportion Spinat im Durchschnitt 19% bzw. 2,6% der duldbaren täglichen Menge an Cd bzw. an Pb; bei den übrigen Gemüsearten macht das Cd weniger als 5% (außer Endivie 6,8%) und das Pb weniger als 1% aus. Spinat liefert einen wesentlichen Anteil des Bedarfs an Cu, Mn und Zn von über 10%. Der Beitrag der übrigen Gemüsearten ist im Durchschnitt nur einige Prozent.

     

Heavy metals in vegetables grown in The Netherlands and in domestic and imported fruits

The contents of cadmium, lead mercury, copper, manganese and zinc in 242 samples of 37 different species of domestic and imported fruits have been determined. Also contents of the same heavy metals, except mercury, have been determined in 205 samples of 7 species of domestic vegetables (lettuce, spinach, endive, beetroots, onions, celeriac and Swedish turnips). The median contents (in mg/kg fresh mass of the edible part) found for fruits are: Cd 0.002; Pb 0.017; Hg 0.002; Cu 0.61; Mn 0.52 and Zn 0.99. In the vegetables median levels have been found (mg/kg) of 0.009-0.073 for Cd, 0.01-0.03 for Pb, less than 0.2-0.3 for Cu, 0.69-1.41 for Mn and 0.95-5.5 for Zn. The contribution of fruits to the tolerable daily intakes of Cd, Pb and Hg is, for an average consumption pattern, less than 1%. On the other hand, the contribution to the recommended amounts of the essential elements Cu, Mn, and Zn is no more than 1%-3%. From the vegetables an average portion of spinach contains 19% and 2.6% of the tolerable daily amounts of Cd and Pb, respectively. For the other species of vegetables these figures are less than 5% for Cd (except for endive, 6.8%) and for lead less than 1%. Spinach contributes considerably to the need for Cu, Mn and Zn, in general more than 10% of the recommended daily amounts. The other species of vegetables contribute only from less than 1% to less than few percents.