饮用水中亚硝酸盐高通量检测微孔板法的研究

亚硝酸盐与间苯二胺在强酸性条件下发生重氮化偶联反应,生成橙红色偶联产物环偶氮亚氨基苯。本研究基于该原理,以微孔板为载体,确定最佳测定波长,通过单因素实验、正交实验优化工作条件,建立一种高通量检测饮用水中亚硝酸盐含量的方法。结果表明,最佳测定波长为451 nm,最佳工作条件:盐酸浓度为0.4 mol/L、间苯二胺浓度为30 g/L、反应时间为10 min。该方法的检出限为0.017 mg/L,线性范围为0~5 mg/L,线性相关系数r为0.9997,空白加标回收率在95.24%~103.98%之间,变异系数小于5%。该方法快速、灵敏,抗干扰能力强,操作简便,可进行高通量筛选,用于饮用水等食品样品中亚硝酸盐残留量的定量测定。     

婴儿配方食品中生物素测定

植物乳杆菌（ATCC No.8014)对生物素有很高的灵敏性，利用这种特异性，可以定量地测出奶基婴幼儿食品中的生物素的含量。为了达到定量测定的目的，在供繁殖试验菌株所用培养基中供给除生物素以外的所有营养成分，这样植物乳杆菌的生长就会同标准溶液及未知测定溶液的生物素的水平相对应。结果表明，本文法的重现性好，变异系数为3.34%，平均回收率为97%。     

Optimization of microbiological assay of folic acid and determination of folate content in spinach

The microbiological method for the determination of folate in plant foods uses the growth response of folate‐dependent Lactobacillus rhamnosus in extracts that have been enzymatically treated to release the bound vitamin. However, the use of cryoprotected cultures is hampered by low recovery of the microorganism after extended frozen storage times. In this study, growth of L. rhamnosus was enhanced using a microaerophilic enrichment procedure and optimal pH conditions and enzyme reaction times were determined for the release of bound folate in spinach. Optimum pH values for the release of bound folate in spinach samples treated with α‐amylase or protease were 3.0 and 4.0, respectively. Although treatment with α‐amylase had no significant (P > 0.05) effect on measured folate, addition of protease at pH 4.0 significantly (P 0.05) increased the release of folate at an optimum incubation time of 8 h. Therefore, a dual‐enzyme treatment (protease and conjugase) is sufficient to determine folate content in spinach.     

微生物法测定食品中的肌醇含量

目的建立微生物法测定食品中肌醇含量的分析方法。方法在含有除肌醇以外的所有营养成分的培养基中,通过实验过程细节改良使葡萄汁酵母菌(ATCC 9080)的生长程度与肌醇浓度呈正相关,且在一定浓度范围内具有线性关系,采用标准曲线法根据透光率(或吸光度)测定食品中肌醇的含量。结果通过本文的微生物法测定天然食品和强化食品中肌醇含量的线性浓度范围为1~10μg/m L,方法的精密度、重复性和回收率良好,实际样品检测结果均远小于国家食品安全方法学标准。结论微生物法具有快速、简便、检出限低、灵敏度高等优点,是测定食品中肌醇含量的有敁可靠方法。     

Folates in Asian noodles: I. Microbiological analysis and the use of enzyme treatments

ABSTRACT:  Asian noodles are a major end use of common wheat flour globally. A microbiological assay protocol for the folate contents of flour and Asian noodles has been developed. Different approaches were compared for enzymatic extraction and deconjugation of folate following the establishment of optimum inoculum concentration for analysis. The folate results obtained varied when samples were subjected to different preparation and extraction procedures. The use of trienzyme treatments gave significantly higher content values. The pH and specific conditions of enzyme treatment also influenced the results. In applying well-established methods for folate analysis, it is essential to consider extraction procedures effective for the specific food products being analyzed. A suitable, validated method was developed and is recommended for use in further studies of fortification of wheat flour for Asian noodle processing.     

The microplate reader: an efficient tool for the separate enzymatic analysis of sugars in plant tissues—validation of a micro‐method

An enzymatic assay method in 96‐well microplates (MP method) is proposed for non‐structural carbohydrates (NSC) in ligneous plants. Soluble sugars were extracted from 50 mg of finely ground plant powder, in the presence of water, methanol and chloroform. The glucose, fructose and sucrose contents were successively determined in each well, although sorbitol could not be assayed under these conditions. Whatever the sugar, the precision (reproducibility), linearity (addition of specific amounts of sugars) and accuracy (comparison with method using high‐performance liquid chromatography (HPLC)) were excellent. This method was more specific than with HPLC, so that the recovery rate of sugars was improved. In the absence of a significant matrix effect, purification of the extract was unnecessary, thus simplifying the procedure and contributing to its robustness. A micro‐method is thus proposed which can be applied to 5 mg of plant powder. This miniaturization affects neither the precision of the MP method nor sugar concentrations. The results of starch assays further demonstrated that this micro‐method was appropriate to the analysis of NSC in small samples of woody plant tissues. Reliable, rapid and simple to perform, this micro‐method is less expensive than HPLC or other classic enzymatic methods. Copyright © 2007 Society of Chemical Industry     

Screening test for rapid food safety evaluation by menadione-catalysed chemiluminescent assay

The chemiluminescent assay of menadione-catalysed H₂O₂ production by living mammalian cells was proposed to be useful for rapid food safety evaluation. The tested foods were extracted with water, ethanol and dimethylsulfoxide, and each extract was incubated with NIH3T3, Neuro-2a and HepG2 cells for 4 h. Menadione-catalysed H₂O₂ production by living mammalian cells exposed to each extract was determined by the chemiluminescent assay requiring only 10 min, and the viability of the cells was estimated as percentage based on H₂O₂ production by intact cells. In this study the cytotoxicity of food was rated in order of inhibitory effect on H₂O₂ production by intact cells. The well known natural toxins such as Fusarium mycotoxin, tomato toxin tomatine, potato toxin solanine and marine toxins terodotoxin and brevetoxin could be detected by the above chemiluminescent assay.     

食品风味物质的提取与分析方法研究进展

介绍了目前使用较广泛的风味物质提取及分析鉴定方法,阐述了各技术的原理,并指出了它们的优点及不足。     

浅谈实验室检测方法的验证与确认

检验方法是实验室用于实施检测工作所依据的标准方法和技术规范, 方法及检测步骤的不同直接导致了检验结果的不同。本文从检验方法的选择及原则、方法验证和确认的定义、技术要求、开展方式等方面展开论述二者的区别, 以阐述化学分析实验室如何做好方法的选择、验证和确认, 从而保证检验结果的准确性。     

植物源食品中叶酸的生物合成与调控及其提取与检测技术研究进展

叶酸作为一碳代谢时的辅因子,是生物体的必需物质,对人体健康至关重要。本文综述了植物源食品中叶酸的类型与结构、叶酸合成途径及相关酶、叶酸代谢调控、发芽富集技术、叶酸提取与检测技术,并对开发快速而准确的叶酸测定方法、研发植物性食品中叶酸的富集与提取技术进行了展望。     

Folates in Asian noodles: II. A comparison of commercial samples and the impact of cooking

ABSTRACT:  The folate contents of 26 commercial noodle samples were investigated. The impact of ingredients, pH, and cooking on folate content was studied for the 3 predominant styles of noodles: white salted, yellow alkaline, and instant. Some variability was found in the proportion of folate present in the free form and the noodles generally had low total folate contents. The pH values of the samples covered a wide range, varying from 3.7 to 10.3; however, the results did not provide strong evidence for a relationship between pH and folate content for any of the noodle styles studied. Higher folate levels were typically found in yellow alkaline samples compared to white salted and instant noodles. The storage of noodles in dry or moist forms did not appear to influence total folate contents, and subsequent losses during cooking depended upon the time of exposure to elevated temperatures. The enzymatic treatment of samples was particularly important for cooked noodles, indicating that folates were bound or entrapped during this process.     

微生物法测定发酵食品中维生素B12含量的研究

为明确发酵食品中维生素B12的含量及分布,利用微生物法对大豆发酵食品（3种类型腐乳、韩国大酱、纳豆、豆汁）及奶酪中维生素B12的含量进行了测定。结果表明,在3种腐乳中,臭腐乳维生素B12含量最高,达到（3.57±1.08） μg/100 g,红腐乳和白腐乳分别为（0.48±0.21） μg/100 g和（0.41±0.16） μg/100 g;除腐乳外,纳豆（0.50 μg/100 g、0.20 μg/100 g）、韩国大酱（0.97 μg/100 g、0.10 μg/100 g）、豆汁（熟）（0.52 μg/100 g）的维生素B12含量均低于臭腐乳。虽然个别奶酪样品中维生素B12含量最高可达1.54 μg/100 g,但其总体维生素B12的分布及含量也均低于臭腐乳。     

对含中药成分保健食品微生物检验方法的探讨

目的分析含中药成分的保健食品进行微生物检验时所采用的菌落计数和控制菌检查方法的合理性。方法根据GB16740-2014《保健食品》中的微生物限量要求,结合《中国药典》附录中微生物限度检查法和GB4789《食品微生物学检验》,对固态茶类和液态口服液类10批次含中药成分的保健食品进行了抑菌性筛查及消除的方法学验证。结果对菌落计数采用常规法进行方法学验证时,筛查出3批供试品存在抑菌性:供试品对菌落计数的抑菌性通过培养基稀释法不能完全消除,但可通过中和法消除;对控制菌检查采用常规法进行方法学验证时,筛查出4批供试品存在抑菌性,供试品对控制菌金黄色葡萄球菌的抑菌性通过培养基稀释法和中和法等均未能消除。结论建议采用含中和剂的琼脂培养基进行计数,并在试验中增加阳性对照菌株进行监控,含中药成分保健食品的检验方法应参照《中国药典》进行方法学验证。     

Comparison of folate losses in soybean during the preparation of tempeh and soymilk

The changes in undeconjugated and total folate content of soybean during various stages of tempeh and soymilk preparation were studied. Total folate was extracted by the tri‐enzyme technique. The ratio of total folate to undeconjugated folate was compared in all samples. Raw soybeans used for tempeh and soymilk preparation contained 4.04 and 4.50 mg total folate kg^?1 respectively. Soaking and boiling soybean caused a significant loss of folate during tempeh and soymilk preparation. Leaching was identified as the major cause of folate loss, as soaking and cooking waters were found to contain a large amount of folate. Rhizopus fermentation of boiled soybean caused an increase of 68 and 100% in undeconjugated and total folate contents respectively. Frying reduced the folate content of tempeh significantly. Milling of boiled soybean in soymilk preparation significantly reduced the undeconjugated folate content of blanched soybean but increased the total folate. UHT treatment of soymilk caused a loss of 9 and 14% of undeconjugated and total folates respectively. The total folate content of deep‐fried tempeh and soymilk was 2.35 and 2.76 mg kg^?1 respectively. Analysed values are expressed on a dry weight basis. © 2002 Society of Chemical Industry     

一种测定食用菌中总糖含量的新方法

总糖含量是食用菌的一项重要质量指标,国标方法中采用分光光度计比色法。本实验采用多微孔板检测仪检测食用菌中的总糖含量,并与国标方法进行比较。结果表明,采用多微孔板检测仪测得的结果与国标方法测得的结果相符,而且新方法消耗试剂少,检测速度快,结果重现性好。多微孔板检测仪可以在1min对90个样品进行检测。      

动态显色法鲎试验用于果汁细菌内毒素活性检测及干扰分析

目的建立一种定量检测果汁细菌内毒素活性的方法,准确评估果汁潜在的内毒素污染风险。方法采用动态显色法东方鲎(Tachypleus amebocyte lysate, TAL)试验对常见的4种果汁(橙汁、桃汁、苹果汁和葡萄汁)细菌内毒素活性进行检测,对果汁样品中的干扰因素进行识别与排除,最后使用抗增液排除β-葡聚糖等类似物质带来的假阳性结果。结果市售果汁(n=36)的细菌内毒素活性范围为0.2～209.5 EU/mL,自榨果汁(n=12)的细菌内毒素活性范围为0.4～4.2EU/mL,加标回收率范围均在50%～200%之间,符合药典要求。结论动态显色法TAL试验适用于常见的4种果汁(橙汁、桃汁、苹果汁和葡萄汁)细菌内毒素活性的检测,为果汁的健康风险评价和卫生监管提供参考。     

酶联免疫吸附技术在食品检测分析中的研究进展

酶联免疫吸附技术(ELISA)是酶免疫测定技术中应用最广泛的技术,是将已知的抗原或抗体吸附在固相载体表面,使酶标记的抗原抗体反应在固相表面进行,通过酶与底物产生颜色反应,用洗涤法将液相中的游离成分除去后再进行定量测定。主要分为夹心法、间接法和竞争法。本文简要介绍了几种常用方法及其基本作用机制,详述了ELISA检测技术在食品检测中具体应用及发展历史与现状,对其在食品中农药残留、病原微生物、生物毒素、转基因食品、重金属残留、过敏性残留物及违规添加成分检测等方面的应用情况进行系统总结,并对其发展前景进行了分析。     

离心管微生物法优化食品中的烟酸检测

目的 简化GB 5009.89—2016微生物法检测食品中烟酸的步骤和操作,提高可操作性。方法 在国标微生物法的基础上,将试管改进为一次性离心管,将移液管改进为微量移液器,优化校准曲线,再通过分析校准曲线线性、定量限、精密度和加标回收率验证方法的适用性。结果 离心管微生物法根除了试管残留的培养基和试样等造成的污染,节省准备时间,配制测定系列管的时间缩短为国标法的56.8%;培养体积优化为2 mL,称量精密度得到提高;将烟酸拟合曲线确定为对数曲线方便样品含量的计算,相关系数r2达到0.997。离心管法的定量限是0.17 mg/100 g,加标回收率是93.52%~107.95%,相对标准偏差为4.60%（n=7）。实测16种不同类型的样品,烟酸含量在0.913~5.539 mg/100 g之间。结论 离心管微生物法改善了微生物法的培养体系,缩短了检测周期,操作简便,适合检测使用。     

微生物法测定婴幼儿乳粉中维生素B12含量的不确定度评定

目的建立微生物法测定婴幼儿乳粉中维生素B₁₂含量的不确定评定方法。方法依据JJF1059.1—2012《测量不确定度评定与表示》及GB 5413.14—2010《食品安全国家标准婴幼儿食品和乳品中维生素B₁₂的测定》分析微生物法测定婴幼儿乳粉中维生素B₁₂含量过程中产生的各测量不确定度分量,计算测量结果的合成标准不确定度和扩展不确定度。结果当样品中维生素B₁₂含量为3.97μg/100 g时,其扩展不确定度为0.53μg/100 g(k=2)。结论标准溶液配制和标准曲线拟合计算待测溶液含量产生的不确定度对检测结果影响较大。