葡萄酒中还原糖含量测定方法的研究

比较测定葡萄酒中还原糖含量的两种方法－直接滴定法和改进后的碘量法,研究结果表明,改进后的碘量法比直接滴定法的终点易于分辨,测定数据重复性强,精密度和准确度高,易于操作。     

3种测定乳制品中乳糖含量方法的比较

为确定一种快速、简易、灵敏的测定乳糖的方法,比较了直接滴定法、蒽酮法和碘量法3种方法测定乳制品中乳糖含量的差异.结果表明:平行试验直接滴定法精度最低,但其乳糖回收率的最大相对误差最小;蒽酮法精度高,但其乳糖回收率的最大相对误差最大,而且蒽酮试剂腐蚀性强,操作不安全;碘量法的精度与乳糖回收率的最大相对误差均介于直接滴定与蒽酮比色法之间,综合而言,碘量法的重复操作性强,结果准确,测定乳制品中乳糖含量可优选碘量法.     

两种测定食品添加剂硫酸铜主含量的方法比较研究

比较GB 29210-2012《食品安全国家标准食品添加剂硫酸铜》和GB 34459-2017《饲料添加剂硫酸铜》对食品添加剂硫酸铜和含杂质硫酸铜主含量测定结果的差异性.采用GB 29210-2012和GB 34459-2017分别对食品添加剂硫酸铜和含杂质硫酸亚铁的硫酸铜进行主含量检测,使用电位滴定法与两种国标方法做...     

电位滴定法测定食盐中NaCl含量

本文讨论用电位滴定法测定食盐中主成分NaCl的含量，用于精制盐和加碘盐中NaCl含量的测定，操作简便，结果准确。     

螯合铁离子能力测定方法比较

采用三种方法[EDTA滴定法(用磺基水杨酸显色)、Fe3+滴定法(用磺基水杨酸显色)和碘量法]测定螯合剂TF-510、TF-133A、TF-133B的螯合能力,并比较其测定结果.结果表明:3种测定方法各有优缺点,其中,Fe3+滴定法(用磺基水杨酸显色)相对标准偏差最小,操作简单、方便且不受放置日寸间、样品本身颜色的影响,故测定螯合剂螯合能力时选择此法为宜.     

植物油过氧化值检测方法的研究

本文采用国家标准检验方法,对菜籽油、茶籽油、大豆油、花生油、调和油、玉米油中过氧化值进行测定,研究不同方法对过氧化值检测的影响。结果表明:过氧化值高的植物油采用滴定法检测,测定结果稳定,误差小。过氧化值低的植物油采用电位滴定法,滴定结果误差满足标准要求,滴定速度快,结果准确、误差小。     

食品中游离氨基酸的电位滴定法测定

氨基酸是衡量食品营养价值的重要指标之一。食品中游离氨基酸的测定方法很多,如滴定法、茚三酮比色法、硝旋光法、氨基酸分析仪法、液相色谱法等。在这些方法中,有的准确性差,有的操作繁琐,有的则因为仪器设备昂贵而难以普及应用。本文采用仪器设备简单,操作方便的电位滴定法则定食品中游离氨基酸的含量,作为电位滴定法应用于食品中游离氨基酸测定的可靠性和可行性的初步探讨。     

电位滴定法测定食用油中过氧化值不确定度的评定

根据测量不确定度评定与表示理论,对电位滴定法测定食用植物油的过氧化值进行不确定度评定,对影响测量过程的不确定度来源进行了分析.结果表明,该方法测定食用植物油中过氧化值的扩展不确定度为Ux=0.004 g/100g,提出通过精确配制标准溶液及多次重复测量的方法能够降低该分析方法的不确定度.     

两种方法标定盐酸标准溶液的结果比较

利用自动电位滴定法与人工滴定法分别标定盐酸标准溶液,对标定的结果进行比较,以确定两种方法标定结果的差异.采用自动电位滴定法与GB/T601-2002和GB/T 5009.1-2003中盐酸标准溶液的标定的规定方法,以无水碳酸钠为基准物质,标定盐酸的浓度.结果表明:两种方法标定高浓度和低浓度的盐酸溶液,最终结果没有差别.计算标准偏差和相对标准偏差,自动滴定法在标定高浓度盐酸标准溶液中精密度显著优于人工滴定法.     

电位滴定法测定葡萄酒中还原糖含量的研究

根据直接滴定法的原理，应用电位滴定法测定了葡萄酒中的还原糖含量。结果表明，该法检测灵敏度高，方便快捷，测定结果符合葡萄酒中糖含量标准。检测结果的标准偏差为0．09，RSD为4．09％，回收率在92．8％～113.2％之间，平均回收率为102．16％。     

索氏提取法测定黏红酵母含油量的改进

研究分别用索氏提取的传统法和改进法测定了黏红酵母菌体含油量,并利用SPSS统计软件比较分析了两种测定方法的准确性。结果表明,按照传统增重法测定废水培养基和基础培养基发酵黏红酵母菌体的含油量分别为16.2%和9.3%,而用改进后减重法测得其含油量分别为20.6%和15.3%;SPSS分析表明,传统索氏增重法计算平行试验的标准误差分别为0.002 9和0.008 1,改进减重法计算平行试验的标准误差分别为0.000 8和0.004 6。可见,传统增重法测定黏红酵母菌体含油量数据偏小,而利用改进后的减重法测定准确度较高,餐厨固体垃圾含油量的测定结果进一步验证了改进后的减重法优于传统增重法。     

茶多糖不同提取工艺的比较研究

用醇沉淀法、超滤法和CTAB沉淀法分别制备了茶多糖粗提物,对粗提物的组成进行了分析,并对多糖的清除羟基自由基的能力进行了比较。结果表明,超滤法所得多糖纯度高,且活性也最高,对羟基自由基抑制率可分别比CTAB沉淀法、醇沉淀法提高23.5％、37.1％。通过纸层析和气相色谱分析,三种工艺所提取的茶多糖均由阿拉伯糖、木糖、核糖、葡萄糖、半乳糖及半乳糖醛酸组成,但组成比不同。     

A preprocessing method for inferring genetic interaction from gene expression data using Boolean algorithm

Unknown genetic regulation mechanisms are expected to be discovered by information technology using large amount of biological data especially for gene expression data. In this study, we propose a novel inferring method for genetic interactions that combines our original preprocessing method and the Boolean algorithm. First, the performance of our method was evaluated using artificial data. The results showed that our method was able to infer genetic interactions with high specificity (specificity=0.629). Then, using our method, the genetic interaction was inferred from the experimental time course data collected using microarray on 69 genes of cell cycle for Saccharomyces cerevisiae. Our method estimated about 80% of all genetic interactions in Kyoto Encyclopedia Genes and Genomes (KEGG) for these genes. Furthermore, our method was able to infer several other genetic interactions that are not included in KEGG but whose existence is supported by other biological reports.     

韩国的"药念"调料

该文介绍了韩式泡菜的原料处理方法、腌制方法;韩式辣酱的原料及制作方法;生姜、大蒜在其中的作用及使用方法;韩式火锅的“药念”使用方法及其构成;韩式牛尾汤的“药念”构成和制作方法。     

紫外分光光度法测定面粉中的巯基含量

本文利用：琉基还原重铬酸钾生成铬酸钾，最大吸收波长发生改变，建立了利用紫外分光光度法测定面粉中巯基的新方法；同时针对该法对样品的处理进行了研究，结果表明：采用醇提法不仅可以有效的提取样品中巯基组分而且测定过程不受其他杂质的干扰。利用该法测定不同用途面粉中巯基的含量，与Ellman的比色法测定结果无显著性差异。     

基于图像处理的纱线捻度测定

用适当方法对纱线图像作二值化处理,提取表面纤维图像,并根据图像分析技术中的傅里叶变换原理,对有关像素坐标进行线性回归确定纱线捻度,与手工测试相比,用图像处理测试纱线捻度的方法是可靠、准确、快捷的。     

Gravimetric determination of soil carbon using the LECO induction furnace

A gravimetric method of determining soil carbon using a LECO high-frequency induction furnace is described. The results obtained using this method were compared with those obtained using two other gravimetric procedures: a wetoxidation method and a dry-combustion (680 °C) method which was taken as the standard. The results showed that the induction furnace method is satisfactory for the determination of soil carbon within the range covered by the 22 soils studied. The method is relatively simple and an operator can perform about 12 determinations/hour.     

超临界CO_2萃取鹰嘴豆工艺研究及应用

采用超临界CO_2对鹰嘴豆中脂溶性成分进行萃取,对提取物进行高效气相色谱和高效液相色谱分析;并对萃余物采用酸碱法从中分离出蛋白质、淀粉和纤维,进而对鹰嘴豆这一特色食品进行全面评价。     

Comparison of gas chromatographic methods for analysis of butyric acid in milk fat and fats containing milk fat

 The analysis of butyric acid (C4) is of importance for the determination of the proportion of milk fat in mixed fats. Three gas chromatographic methods were compared with regard to their precision for the measurement of C4, i.e. analysis of butyric acid methyl ester after trans-esterification of fat by sodium methylate (method A) or trimethyl sulphonium hydroxide (method B), as well as analysis of free butyric acid (method C), using an internal standard with each method. The examination of 30 milk fats which varied greatly in terms of their C4 content, using methods A, B and C, resulted in mean values of C4 of 3.42 g/100 g fat, 3.71 g/100 g fat and 3.06 g/100 g fat, respectively. The value determined using method B seemed too high, and this may have been due to the presence of co-eluting artefacts, whereas the value determined using method C was clearly too low, and can probably be attributed to losses during sample preparation. The standard deviation (SD) of 0.015 obtained from repeated analyses using method A was quite good. Results obtained using methods B and C had SDs of 0.029 and 0.074, respectively. Different levels of free fatty acids did not affect the results obtained using method A. When method A was checked by analysis of the reference fat, CRM 164, the C4 level determined was found to deviate from the certified C4 content of 3.49 (± 0.06) g/100 g fat by only 0.05 g C4/fat 100 g. Thus method A proved the most suitable for the determination of the proportion of milk fat in mixed fats by analysis of butyric acid. Received: 1 October 1997     

Short communication: Separation and quantification of caseins and casein macropeptide using ion-exchange chromatography

The aim of this work was to improve an existing method to separate and quantify the 4 major caseins from milk samples (i.e., containing whey proteins) using ion-exchange chromatography. The separation process was carried out using a mini-preparative cation exchange column (1 or 5 mL of column volume), using urea acetate as elution buffer at pH 3.5 with a NaCl gradient. All 4 major caseins were separated, and the purity of each peak was assessed using sodium dodecyl sulfate-PAGE. Purified casein fractions were also added to raw milk to confirm their elution volumes. The quantification was carried out using purified caseins in buffer as well as added directly to fresh skim milk. This method can also be employed to determine the decrease in κ-casein and the release of the casein-macropeptide during enzymatic hydrolysis using rennet. In this case, the main advantage of using this method is the lack of organic solvents compared with the conventional method for separation of macropeptide (using reversed phase HPLC).