Research Watch: Wetlands nitrate

Groundwater.     

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。     

Research Watch: Detecting nitrate radicals

Air.     

Effect of nitrate and incubation conditions on the production of catalase and nitrate reductase by staphylococci

The objective of this work was to study the production of catalase and nitrate reductase by staphylococci in order to understand their role in lipid oxidation during sausage manufacturing. Catalase and nitrate reductase were measured in resting cells and supernatants of staphylococci grown in different conditions. All staphylococci (except S. warneri) synthetized nitrate reductase. In static condition, the synthesis was maximal during exponential growth phase, whereas in shaking condition, the synthesis was maximal at the beginning of stationary phase. The production of nitrate reductase was increased in presence of nitrate, this effect was particularly important for the two S. carnosus strains which exhibited the highest activity. For all staphylococci, the production of catalase was maximal at the end of the exponential growth phase. The lowest amount of catalase was produced by S. warneri and the highest by S. carnosus. Only S. xylosus 873 and S. saprophyticus 852 released high amounts of catalase in the supernatant growth. Staphylococci produced higher amounts of catalase in shaking conditions. Addition of nitrate in the growth media favoured the synthesis of catalase, with a pronounced effect for S. carnosus. Nitrate also favoured the release of catalase.     

制硝生产中结垢处理方法综述

论述了制硝生产中的结垢处理的方法，并对各种处理方法进行了利弊分析。     

Analysis of nitrate and nitrite in feed. 2. Potentiometric nitrate determination with ion sensitive electrodes]

Nitrate-sensitive PVC matrix membrane electrodes produced in the German Democratic Republic are suited for determining nitrates in feeds and plants if the different causative parameters are taken into account. A rational determining method is presented. Comparisons with the o-cresol method showed statistically confirmed agreement.     

分光光度法测定烟草中的硝酸盐

采用醋酸溶液提取烟丝中的ＮＯ３,锌粉作还原剂,硝酸盐试剂作显色剂,建立了一种测定烟草中硝酸盐的分光光度法。该法简便、灵敏、准确、准确,线性范围为０ ．１－０．６μｇ／ｍＬ,平均回收率为９５．５％,用该方法测定了９种卷烟烟丝中的硝酸盐含量,将测定结果与相应烟气焦油中的Ｎ－亚硝胺量作比较,发现二者呈正相关。     

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。     

The microbiological role of nitrite and nitrate

In unheated products nitrite, together with sodium chloride and the pH value, contributes to the selection of the bacteria which grow during storage. Nitrate per se is generally believed to serve only as a reservoir for nitrite, but the commercial use of nitrate-free cover brines in the Wiltshire bacon industry shows that such a reservoir is not always essential. Nitrate sometimes reduced the growth rate of bacteria in experimental Wiltshire collar bacon, but was of no benefit in back bacon. The clostridia occurring naturally in the bacon grew to higher numbers in collar cured without nitrate than that cured with nitrate. Clostridium botlinum (types A and B) was detected in these bacons, but did not grow in the bacon. In heated products the growth of surviving bacteria is controlled by the interaction of several factors including pH, sodium chloride, storage temperature and sodium nitrite or a substance derived from it upon heating. Further experiments are warranted to investigate the effects of dextrose, nitrate, ascorbate and polyphosphate.