锌粒还原法快速测定食品中的硝酸盐

目的：建立食品中硝酸盐的快速测定方法。方法：用锌粒作还原剂，在银离子催化下将食品中的硝酸盐还原成亚硝酸盐，然后按亚硝酸盐的测定方法测定。结果：该方法的相对标准差低于5％，平均回收率94．0％。结论：运用该方法能对食品中的硝酸盐进行准确而快速的测定。     

电流法快速测定鲜奶中蛋白质含量

采用电流法快速测定了鲜奶中蛋白质含量,该方法是利用Ｃｌａｒｋ氧电极监测在戊二醛与鲜奶中蛋白质或氨基酸的氨基反应中所消耗的氧来间接测定蛋白质含量。该方法快速、准确、便利,样品不同需要前处理。标准曲线线性范围为２．０＊１０＾－３－５．５＊１０＾－２ｍｏｌ／Ｌ。变异系数为５．７％。用本法与经典的凯氏定氮法对照测定市售３种鲜牛奶中蛋白质含量,对结果进行统计分析,得出Ｐ〉０．０１,说明两种方法无性区别。该方     

宽台栽培大豆叶面积动态及净光合生产率

采用小区试验测定了宽台栽培，７０ｃｍ行距垄作，３０ｃｍ行距平作大豆的叶面积指数和净光合生产率。结果表明，ＬＡＩ呈正态曲线变化，从大豆出苗至ＬＡＩ高峰时期，宽台栽培的最大ＬＡＩ出现时间比垄作和平作推迟３－６ｄ，ＬＡＩ提高０．２７５－０．４０４，ＬＡＩ〉４的天数延长５－１１ｄ。生育期平均ＮＡＲ比垄作和平作高０．３７－０．８２ｇ／ｍ２．ｄ     

啤酒酵母抽提制品的研究

啤酒压榨酵母是我厂啤酒生产中的主要副产品之一，营养丰富。通过洗涤、除去杂质。用正交试验选择酵母酶解抽提的最佳条件；控制ＰＨ６．０－７．０，温度５０－６０℃，盐１－１．２％，酶制剂０．５－１．０‰，自溶酶解８－１２小时，酵母氨基Ｎ抽出率增加一倍以上，达到先进的水平。酶解酵母抽出物，经离心后分别制成液膏状三种产品，液状产品含氨基，Ｎ１．５，膏状产品含氨基Ｎ２．５，粉状产品含蛋白质４０－５％，游离氨基酸     

柞蚕蛾配膳必需微量元素的营养评分研究

采用原子吸收光谱仪测得每１００ｇ柞蚕蛾中Ｚｎ、Ｃｕ、Ｆｅ、Ｍｎ含量分别为０．０３、０．０３、０．４４、０．０２ｍｇ，用２，３－二氨基萘荧光法测得Ｓｅ为０．７ｍｇ。并对蚕蛾、稻米等八种食物作了营养评分（ＮＳＦ），蚕蛾的ＮＳＦ值大于其它七种食物，有显著性差异（Ｐ＜０．０５）。又用蚕蛾和鸡蛋各５ｇ，分别与六种食物为儿童配膳并作ＮＳＦ，评得蚕蛾配膳的ＥＴ总ＮＳＦ值为４３６．４５，比鸡蛋膳４０８．３６高１．０７倍。因此认为蚕蛾的ＴＥ、ＮＳＦ值、蚕蛾配膳的ＮＳＦ值均比鸡蛋、鸡蛋膳要高。据此，建议推广食用蚕蛾。     

微乳液介质PAN光度法测定硬脂酸锌的含锌量

研究了在微乳液介质中，锌与１－（２－吡啶偶氮）－２－萘酚（ＰＡＮ）的显色反应，选择５５５ｎｍ处为测定波长，ε为４．５×１０４Ｌｍｏｌ－１ｃｍ－１，锌量在０～１．５２ｍｇ／Ｌ范围内符合朗伯－比耳定律，该法用于固体样品硬脂酸锌含量的直接测定     

ICP-AES法测定纺织品中的十种元素

采用微波消化产品预处理,以ＩＣＰ－ＡＥＳ法测定纺织品中Ａｓ、Ｃｄ、Ｃｒ、Ｃｕ、Ｍｎ、Ｎｉ、Ｐｂ、Ｓｅ、Ｚｎ、等十种元素的含量。该方法的相对标准偏差小于５％,各元素的加标回收率为８５．３％－１０３．０％,能简单、快速、准确地测定纺织品中的多种重金属含量。     

间接紫外检测离子色谱法同时测定食品中的无机阴离子

间接紫外检测离子色谱法同时测定食品中的无机阴离子袁建平（华南理工大学食品工程系，广州，５１０６４１）Ｃｌ－、ＮＯ２－、ＮＯ３－和Ｉ－是食品中常见的无机阴离子。硝酸盐和亚硝酸盐作为食品发色剂及防腐剂广泛用于肉制品加工工业，肉制品中总会含有一定量的对人体...     

关于肉类灌制品中淀粉含量测定方法的探讨

用ＧＢ５００９．７－８５“真接滴定法”代替ＧＢ９６９５．１４－８８“碘量法”测定肉类灌制品中淀粉的还原糖，简化了操作，提高工作效率和准确度，回收率在９３．０％－９６．０％之 间，通过对５个样品的４次平行测定，标准偏差在０．３３－０．５５之间，精密度符合标准要求，实验证实：应用氧化还原原理测定，测定结果准确可靠。     

用固定化酶流动注射法同时测定葡萄酒中的丙三醇和乙醇

叙述了一种同时测定葡萄酒中丙三醇和乙醇的自动分光荧光法。该法使用流动注射岐管，脱氢酶固定在控制孔玻璃上，可同时测定丙三醇和乙醇，丙三醇的线性范围为１－１０μｇ／ｍｌ，γ＝０．９９８９，Ｓｒ〈１％，乙醇的线性范围为１０－１００μｇ／ｍｌ，γ＝０．９９９８，Ｓｒ〈０．９％，该法用于不同酒的测定，丙三醇和乙醇的回收率分别为９７％和１０５％，进样频率为６０个样／小时，将８个酒样的分析结果与传统方法作了比较     

硝酸盐二元混合溶剂体系相平衡的研究

测定了硝酸钾、硝酸铵和硝酸钠在甲醇-水、氨-水二元混合溶剂体系的相平衡数据,查明了甲醇和氨对三种硝酸盐溶解度的影响规律。研究结果表明,随着甲醇浓度的增加,硝酸钾、硝酸铵和硝酸钠的溶解度均随之降低,其中硝酸钾的溶解度变化更为明显;随着氨浓度的上升,硝酸钾和硝酸钠的溶解度随之减少,而硝酸铵的溶解度却显著增加。氨对硝酸钾的选择分离结晶效果较好。     

硝酸盐二元混合溶剂体系相平衡的研究

测定了硝酸钾、硝酸铵和硝酸钠在甲醇-水、氨-水二元混合溶剂体系的相平衡数据，查明了甲醇和氨对三种硝酸盐溶解度的影响规律。研究结果表明，随着甲醇浓度的增加，硝酸钾、硝酸铵和硝酸钠的溶解度均随之降低，其中硝酸钾的溶解度变化更为明显；随着氨浓度的上升，硝酸钾和硝酸钠的溶解度随之减少，而硝酸铵的溶解度却显著增加。氨对硝酸钾的选择分离结晶效果较好。     

烤烟中硝酸盐和亚硝酸盐的测定

本文提出了一种使用紫外分光光度计测定硝酸盐和亚硝酸盐的方法。主要过程包括将烟样在弱碱性条件下热水中萃取,亚硝酸盐标准曲线的绘制,亚硝酸盐含量的测定,硝酸盐的还原,硝酸盐含量的测定,回收率的测定。该方法具有简单、高效、重复性好、不需专用仪器设备等特点,适用于各种烟草样品中硝酸盐和亚硝酸盐含量的测定。      

Effect of nitrate reduction on the microbial reductive transformation of pentachloronitrobenzene

The effect of nitrate reduction onthe reductive biotransformation of pentachloronitrobenzene (PCNB), an organochlorine fungicide, was assessed with a mixed fermentative/methanogenic culture enriched from a contaminated estuarine sediment. Glucose and methanol served asthe electron and carbon source. PCNB at an initial concentration of 3 microM was transformed to pentachloroaniline (PCA) simultaneously with nitrate reduction in cultures amended with 10 to 200 mg N/L nitrate. PCA sequentially dechlorinated to dichlorinated anilines (mainly 2,5-DCA) in the nitrate-free control culture, and the culture which was amended with 10 mg N/L nitrate. PCA partially dechlorinated to tetrachloroanilines (TeCAs), and methanogenesis was completely inhibited in the cultures amended with 50-200 mg N/L nitrate, whereas fermentation was only inhibited in the cultures amended with 200 mg N/L nitrate. The impact of nitrate reduction on the sequential dechlorination of PCA was attributed to the production of nitric oxide (NO) and nitrous oxide (N2O). Partial nitrate reduction to ammonia was observed in the cultures amended with 50, 100, or 200 mg N/L nitrate and PCNB (3 microM). Therefore, nitrate concentrations at or above 50 mg N/L lead to accumulation of toxic compounds such as highly chlorinated anilines (i.e., PCA, TeCAs) and denitrification intermediates (i.e., NO, N2O). These findings have significant environmental implications in terms of the fate and transformation of PCNB in subsurface environments where nitrate is present.     

Simultaneous Determination of Nitrite and Nitrate in Milk Samples by Ion Chromatography Method and Estimation of Dietary Intake

The presence of nitrate and nitrite in foods may be considered hazardous after ingestion in the gastrointestinal tract due to their reaction with naturally occurred secondary amines to form potentially carcinogenic nitrosamines. Due to this fact, a new method was developed in this study for the simultaneous determination of nitrite and nitrate in milk samples using by ion chromatography. Proposed mobile phase composed of sodium hydrogen carbonate and sodium carbonate (1.0 and 3.2 mmol/L) with a flow rate of 0.7 ml/min. The average recoveries for nitrate and nitrite were higher than 86 and 88%, respectively. The limit of detection for nitrate and nitrite were 0.24 and 0.09 mg/L, respectively. The results of 102 real milk samples showed nitrate was found in all of the samples (100%) with a mean of 34 ± 11 mg/L, while nitrite was found in none of the samples. The mean intake of nitrate in all age groups was lower than World Health Organization guideline. The present assessment concludes that the maximum contaminant level was equal to 82.8 mg/L nitrate. This method was fast, sensitive and accurate and is capable of being an alternative method in food control laboratories for investigation of nitrite and nitrate content. This is the first study of the determination and survey of nitrite and nitrate and exposure assessment of the Iranian population to nitrite and nitrate level in milk, which was widely used in infants and adolescents as one of the basic food components.     

Nitrate and sulfate: Effective alternative hydrogen sinks for mitigation of ruminal methane production in sheep

Twenty male crossbred Texel lambs were used in a 2 × 2 factorial design experiment to assess the effect of dietary addition of nitrate (2.6% of dry matter) and sulfate (2.6% of dry matter) on enteric methane emissions, rumen volatile fatty acid concentrations, rumen microbial composition, and the occurrence of methemoglobinemia. Lambs were gradually introduced to nitrate and sulfate in a corn silage-based diet over a period of 4 wk, and methane production was subsequently determined in respiration chambers. Diets were given at 95% of the lowest ad libitum intake observed within one block in the week before methane yield was measured to ensure equal feed intake of animals between treatments. All diets were formulated to be isonitrogenous. Methane production decreased with both supplements (nitrate: -32%, sulfate: -16%, and nitrate+sulfate: -47% relative to control). The decrease in methane production due to nitrate feeding was most pronounced in the period immediately after feeding, whereas the decrease in methane yield due to sulfate feeding was observed during the entire day. Methane-suppressing effects of nitrate and sulfate were independent and additive. The highest methemoglobin value observed in the blood of the nitrate-fed animals was 7% of hemoglobin. When nitrate was fed in combination with sulfate, methemoglobin remained below the detection limit of 2% of hemoglobin. Dietary nitrate decreased heat production (-7%), whereas supplementation with sulfate increased heat production (+3%). Feeding nitrate or sulfate had no effects on volatile fatty acid concentrations in rumen fluid samples taken 24h after feeding, except for the molar proportion of branched-chain volatile fatty acids, which was higher when sulfate was fed and lower when nitrate was fed, but not different when both products were included in the diet. The total number of rumen bacteria increased as a result of sulfate inclusion in the diet. The number of methanogens was reduced when nitrate was fed. Enhanced levels of sulfate in the diet increased the number of sulfate-reducing bacteria. The number of protozoa was not affected by nitrate or sulfate addition. Supplementation of a diet with nitrate and sulfate is an effective means for mitigating enteric methane emissions from sheep.     

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。     

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.