考马斯亮蓝法测定奶粉真蛋白的研究

比较凯氏定氮法、考马斯亮蓝法和福林酚法测定奶粉蛋白含量的差异,研究了不同种类的非蛋白含氮物(尿素、三聚氰胺、甘氨酸和水解蛋白)、不同添加量(0%、0.5%、1%、2%和10%)对考马斯亮蓝法测定奶粉蛋白含量的影响。实验结果为,考马斯亮法所测蛋白含量与凯氏定氮法相近,福林酚法测定的结果显著高于凯氏定氮法;添加不同比例的4种非蛋白含氮物均对考马斯亮蓝法测定蛋白含量的结果没有影响,随着添加比例的增加,奶粉氮含量的理论值逐渐增大,而测定值没有显著变化。实验结果表明,考马斯亮法可排除添加非蛋白含氮物对奶粉真蛋白含量测定的影响,可以快速、准确的测定奶粉真蛋白含量。     

牛奶中泛酸含量测定

目的：对牛奶中泛酸的本底含量进行测定,为乳制品中泛酸的强化提供数据支持。方法：选取大量牛奶样本,通过微生物法和高效液相色谱法对泛酸含量进行测定。结果：牛奶中的泛酸含量大约为253～502μg/100mL,平均值为365.9μg/100mL。结论：乳制品中强化泛酸可以依据上述数值参考添加。     

4种蛋白质分析方法在液态乳中的适用性研究

分别利用凯氏定氮法、三氯乙酸-双缩脲比色法、考马斯亮蓝法和福林-酚法等4种方法,对液态乳中添加尿素、甘氨酸、硝酸铵、亚硝酸钠、水解蛋白、三聚氰胺等非蛋白含氮物后的蛋白质量浓度进行了测定,并与其理论值进行了比较.结果表明:凯氏定氮法和福林-酚法测定的液态乳蛋白质量浓度与其理论值存在显著差异,而考马斯亮蓝法和三氯乙酸-双缩脲比色法则能较好地反映其真实的蛋白含量.考马斯亮蓝法灵敏度高,适合测定蛋白含量较低的样品;而三氯乙酸-双缩脲比色法的测定结果与液态乳中真实蛋白质量浓度更加接近.     

UPLC-IDMS法测定配方奶粉中的生物素含量

建立一种超高效液相色谱-同位素稀释质谱法测定配方奶粉中生物素含量的方法。样品中加入生物素-D2作为同位素内标,经水超声提取后,以含体积分数0.1%甲酸的10 mmol/L乙酸铵溶液和乙腈作为流动相进行梯度洗脱,采用电喷雾正离子模式、多反应监测方式进行定性定量分析。结果表明：生物素在1～50 ng/mL范围内线性关系良好,线性范围内对已知生物素含量样品3 个标准添加水平的平均回收率为89.6%～93.1%,相对标准偏差为1.71%～4.33%。方法检出限为0.6 μg/100 g,定量限为1.5 μg/100 g,该方法具有灵敏度高、重复性好、分析时间短等优点,可以满足配方奶粉中生物素含量的测定要求。     

同位镀汞阳极溶出伏安法测定牛奶中镉、铅、铜

建立阳极溶出伏安法同时快速测定牛奶中的镉、铅和铜元素的方法。利用同位镀汞阳极溶出伏安法对 牛奶样品中镉、铅和铜元素含量进行同时测定,并对测试条件进行优化。镉、铅和铜元素峰电位分别为－0.70、 －0.52、－0.08 V;线性范围分别为0.1～40、1～80、0.5～100 μg/L;检测限为0.06、0.3、0.1 μg/L。采用该方法测 定了牛奶样品中的镉、铅和铜含量,加标回收率分别为99.57%、101.3%、98.00%,相对标准偏差（n=5）分别为 4.0%、2.9%、2.7%,将测定结果与原子吸收光谱法检测结果对比,两者无显著性差异(P＞0.05）。结果表明该方法 快速、简单、准确,可用于牛奶中镉、铅和铜元素的同时检测。     

快速滴定法测定原料乳蛋白质的条件控制

目的:实验快速滴定法直接测定原料奶中蛋白质含量的可行性及掺杂物对该法的干扰程度,为原料奶验收和大批量样品检测提供快速有效的测定方法。方法:分别对快速滴定法的测定条件、操作步骤、终点判定进行反复实验,采用干燥法和凯氏定氮法对结果准确性进行验证。结果:样品取样量为1.00mL,用1.00mL 0.1mol/L盐酸控制酸度时,采用2次滴定法,消耗4.50mL 0.2%SDS,得到理想结果;与凯氏定氮法和仪器法所得结果相比,无显著差异(p0.05)。以凯氏定氮法为标准,得到两种方法之间的数量关系,即消耗1.00mL 0.2%SDS相当于含蛋白质7.53×10-3g。一定浓度范围内的非蛋白氮掺杂物对快速滴定法测定原料奶中蛋白质的含量也无明显影响。结论:本法操作简便、结果准确,可满足原料奶验收、大批样品测定和实时掌控牛奶品质状况的要求,在奶业生产领域具有非常明显的推广应用价值。     

Bradford法测定牛奶中蛋白质含量

采用Bradford法与传统的凯氏定氮法测定牛奶中蛋白质含量并进行比较,Bradford法方便快捷,成本低廉。通过试验对比验证,添加的尿素或者三聚氰胺对测定无影响,与微量凯氏定氮法比较,两者的结果有相关性。     

采用蛋白质定量方法检测掺假牛乳比较研究

研究非蛋白质掺假牛乳样品中的乳蛋白质检测方法。样品用15%三氯乙酸溶液处理牛乳样品,沉淀分离乳蛋白质,通过凯氏定氮法和四种分光光度法对液态乳中添加尿素和三聚氰胺常见掺假物进行检测比较研究。结果表明,凯氏定氮法、双缩脲比色法、Folin-酚试剂法、BCA法检测牛乳中掺入不同比例尿素溶液蛋白质含量,结果不受尿素溶液的影响,准确度高。对于牛乳中掺入三聚氰胺溶液,三氯乙酸结合凯氏定氮法检测相对误差较大,而三氯乙酸结合双缩脲比色法、Folin-酚试剂法、BCA法检测结果不受三聚氰胺溶液影响,准确度高。考马斯亮蓝法测定牛乳中掺入尿素溶液和三聚氰胺溶液相对误差均很大。     

在线双毛细管火焰原子吸收法测定海带中的微量锶

研究在线双毛细管快速测定海带中微量锶的方法,使用相同管径的双毛细管对酸度和干扰离子进行探讨。采用湿法溶样对样品进行前处理,通过在线加入十二烷基磺酸钠抑制干扰,采用10.0 L/min空气流量和1.2 L/min乙炔流量进行了实验,结果显示：海带中Sr含量在700 μg/g左右。方法检出限为0.1 μg/g,样品回收率在97.8%～107.4%,精密度小于5%。方法准确快速、成本低廉,适合样品中微量锶的测定。经实际样品验证获得较为满意的结果。     

微波密闭消解-ICP-AES同时测定贼小豆中18 种矿物质元素

为探讨郑州地区野生贼小豆中微量元素的组成、含量和分布特性,充分开发利用贼小豆自然资源,用微波 密闭消解-电感耦合等离子体发射光谱法同时测定了贼小豆样品中Al、Ba、Ca、Cd、Co、Cr、Cu、Fe、Hg等18 种 微量元素。结果表明：在优化条件下,待测各元素间相互干扰较小,18种元素在一定范围具有良好的线性关系,相 关系数（r）均不小于0.995 0,检出限范围为0.000 1～0.035 μg/mL,定量限范围为0.000 17～0.058 μg/mL,平均回收率 为97.08%～113.06%,相对标准偏差为0.14%～3.2%（n=6）。该法所用样品和消解剂量少,消解完全、快速省时,待 测元素不易挥发损失,可同时测定18 种矿物质元素,工作效率较高,用于贼小豆样品的测定,结果令人满意。     

BCA法在反胶束萃取大豆蛋白中的应用

本文建立了用一种新的方法测定反胶束（如AOT）体系中所萃取大豆蛋白质的方法，即BCA（二辛可宁酸）法，经过对照实验，证明该方法的测定结果可靠，与半微量凯式定氮法相比无显著差异，该方法操作简便，结果准确可靠，可替代半微量凯式定氮法。     

酶联免疫吸附法与二喹啉甲酸法检测核桃蛋白浓度的比较研究

目的 探究间接酶联免疫吸附法(enzyme-linked immunosorbent assay, ELISA)和二喹啉甲酸 (bicinchoninic acid, BCA)试剂盒2种方法在核桃蛋白浓度检测中的优缺点和适用范围。方法 对本实验室提取的核桃蛋白进行烘烤、高温高压以及微波加热处理后, 用ELISA法和BCA法2种方法分别检测其蛋白质浓度。结果 在不同的热加工处理条件下, ELISA对蛋白浓度测定结果存在显著性差异, 高度依赖热处理的类型。与之相比, 使用BCA法测定蛋白浓度时, 受到热加工处理影响较小。结果提示, 在食物加工中的一些剧烈条件下, 蛋白质的高级结构很容易遭到破坏, 蛋白质结构的改变会干扰其与抗体结合部位的作用, 导致ELISA法测定的结果不准确。BCA法测定蛋白质浓度的准确性较高, 且受加热影响较小。结论 在剧烈的食品加工条件下, 尤其当这种条件引起蛋白结构发生改变后, 对其蛋白质浓度进行测定时, 可选用BCA法进行测定。     

Applicability of protein estimation methods for assaying glycomacropeptide

Glycomacropeptide (GMP) is a nutraceutical additive, which is released during cheese preparation. In this study, the protein content in a laboratory GMP preparation and two commercial GMP samples, which was estimated by the Bradford, biuret, Lowry and bicinchoninic acid (BCA) assays, were compared using the Kjeldahl method. There were apparent differences in the values of estimated proteins using the different methods. An absence of dose response in the Bradford method and a low dose response using the Lowry method indicated the unsuitability of both these methods. Absorbance in the biuret and BCA methods linearly increased with increasing GMP content. The BCA method was the most sensitive of these methods.     

β-葡聚糖酶活力测定方法的研究进展

本文综述了β-葡聚糖酶活力的测定方法,如黏度法、生色底物法、琼脂糖扩散法、酶联免疫吸附分析法(ELISA)和目前使用较多的还原端基法,如3,5-二硝基水杨酸(DNS)法、Somogyi-Nelson法、二金鸡纳酸(BCA)法和最新涌现的用于微量测定的3-甲基-2-苯并噻唑酮腙(MBTH)法,并就还原端基法介绍了其具体实验手段,如试管法、罐法、微孔板法、流动注射法(FIA)。分析了方法中存在的问题并展望了β-葡聚糖酶活力测定方法研究的发展趋势,如安培法和等温滴定量热法等。     

蛋白质定量检测方法的探讨

综述了凯氏定氮法、考马斯亮蓝法、双缩脲法、Folin-酚法、紫外吸收法、BCA法、近红外光谱技术、电泳法及数字图像法等主要的蛋白质定量检测方法,分别介绍了各方法的原理、特点及应用,说明了其优缺点和适用范围,并通过实例对各种蛋白质的检测方法进行了探讨。     

Development of a Method for Evaluating Floor Dry‐Cleanability from Wheat Flour in the Food Industry

Many productive processes are characterized by inadequate protocols of sanitation that increase the possibility of proliferation of microbial contaminants, especially on surfaces. The use of this method for evaluating the degree of floor cleanability in agri‐food companies is important not only to reduce the risk of contamination of products, but also to provide companies with a tool to identify critical issues. The method is based on the usage of bicinchoninic acid assay (BCA) in a solution at a 1:50 ratio of Cu²⁺/BCA, which is ideal for detecting the amount of proteins contained in wheat flour residues on industrial flooring. Spectrophotometric analysis allowed identifying maximum absorbance values at 562 nm for different protein concentrations, although the construction of a regression function led to the definition of the intervals of evaluation corresponding to different degrees of cleanliness from residues of wheat flour. The results of the absorbance curves, obtained by applying the proposed evaluation method to 6 tiles commonly used in agri‐food buildings, showed the clear persistence of food material on 2 tiles with surface relief. In particular, such tiles showed a higher presence of proteins, with a level of contamination 440% higher. Furthermore, a robotic system was designed to standardize the cleaning method commonly employed in agri‐food companies to remove solid particles from flooring.     

Evaluation of a rapid protein analyzer for determination of protein in milk and cream

Accurate and rapid measurement of the protein content of milk is important from both a product quality and an economic standpoint. The Sprint rapid protein analyzer (CEM Corporation, Matthews, NC) is a commercial system based on a dye-binding technique and can be used for rapid measurement of protein in foods. The objective of the present study was to compare the Sprint method with the reference method (Kjeldahl method). Milk and cream samples were analyzed in duplicate for true protein and crude protein (CP) using the reference method as well as the rapid method. Method comparison statistics (regression analysis, graphical representation, standard deviation of residuals, repeatability, and so on) were used to evaluate the agreement between the 2 methods. Regression coefficients and the intercepts were not significantly different from 1 and zero for CP measurement in milk and cream, respectively. The average coefficient of variance between the duplicate CP measurements for the Sprint method was found to be 0.40, 0.49, and 0.76 for milk, light cream, and heavy cream, respectively. True protein measurement in milk and cream also followed a similar trend. Overall, there exists a sufficient level of agreement between the Sprint rapid protein analyzer and Kjeldahl method for true protein and CP measurement of milk and cream samples.     

Effect of biocontrol agents Candida sake and Pantoea agglomerans on Penicillium expansum growth and patulin accumulation in apples

Penicillium expansum is the major responsible of fruit pome decaying in cold storage. Apples spoiled by P. expansum are expected to contain patulin, a mycotoxin which is proven to affect human health. The use of chemicals is the most common procedure to prevent rots in postharvest but legislation is becoming more and more restrictive. The use of biocontrol agents (BCA) as an alternative tool is currently being proposed. The aim of this study was to evaluate the effect of two BCA (Candida sake CPA-2 and Pantoea agglomerans CPA-1) on P. expansum growth and patulin accumulation in cold storage and further deck (ambient) storage. Wounded apples were inoculated with a cell suspension of either C. sake or P. agglomerans and with a P. expansum conidial suspension. Apples were cold stored at 1 degrees C until lesion diameter reached 2 or 4 cm. Half the apples of each treatment were further stored at 20 degrees C for three days before patulin analyses. Both BCA tested controlled blue rot and patulin accumulation during cold storage. The control of P. expansum growth was enhanced in C. sake treated apples. On the other side, control of patulin accumulation in P. agglomerans treated apples seemed to be more efficient. BCA treatment could not control blue rot and patulin accumulation during further storage at room temperature and in some cases, an increase in P. expansum aggressiveness was observed.     

重金属汞螯合物人工抗原的合成与鉴定

以重金属汞为起始物质,将其离子化为二价汞,与双功能螯合剂谷胱甘肽(GSH)螯合后,获得半抗原,然后将半抗原与载体蛋白牛血清白蛋白(BSA)、卵清蛋白(OVA)进行偶联,获得完全抗原。实验对各步骤的反应条件进行优化,采用紫外光谱、凝胶电泳对产物进行表征,成功制备了汞-GSH-BSA完全抗原。为计算完全抗原中重金属和载体蛋白的偶联比,采用石墨炉原子吸收法测定产物中重金属汞的含量,采用二喹啉甲酸(BCA)法测定抗原中载体蛋白的含量,所制备的免疫原中汞和蛋白的偶联比是9:1。Hg-GSH-BSA的成功合成是制备可识别重金属汞螯合物抗体的基础。     

油菜蜂花粉蛋白水解度测定方法比较

采用Alcalase 2.4L FG 水解油菜蜂花粉蛋白,比较pH stat 法、OPA 法和TNBS 法测定蜂花粉蛋白水解度的差异。水解118min 后,pH stat 法、OPA 法和TNBS 法测得的水解度分别为24.7% ﹑ 13.4% ﹑ 6.6%。由于OPA试剂和甘氨酸﹑半胱氨酸﹑赖氨酸反应生成的化合物在340nm 波长处的吸光度较低,致使OPA 法测得的水解度低。TNBS 试剂和ε-NH2 的作用不稳定,也可能是由于TNBS 试剂产生的发光物使测定结果降低。在水解度较低的情况下,α-NH2 平均解离度的变化可以忽略,pH stat 法测得的水解度比较准确。