Rapid Direct Extraction Derivatization Method for the Determination of Acylglycerol Lipids in Selected Sample Matrices

Acylglycerol lipids as total fatty acid methylesters (FAME) were rapidly determined by direct extraction derivatization from sample matrices utilizing 0.4N methanolic sodium methoxide in hexane solution and quantitated using gas chromatography. FAME values determined by the direct extraction derivatization (DED) method and standard AOAC ether extraction saponification method were similar for all samples. The DED method was reproducible and required less than 35 min total sample preparation and analysis time compared to a minimum of 6 hr needed for the standard AOAC method. The DED method yielded FAME derivatives of acylglycerol lipids which were free from interfering compounds when analyzed by gas chromatography. Identity and purity of isolated FAME were positively confirmed by mass spectrometry by comparison with authentic standards.     

手工分解定量方法探讨

本文在对纺织品采用手工分解法进行含量分析时,采取经纬纱根数比取样的方式进行试验并计算,所得数据与常规方法所得数据基本一致,该方法大大缩短试验时间,提高了工作效率。     

乳与乳制品中主要营养成分快速分离与测定

介绍一种适用于绝大多数食品乳液及也制品中主要营养成分的简便,快速分离测定方法,并与标准法对照进行实际样品分析。     

Effects of Lactic Fermentation of Milk on Milk Lipids

Fermentation of whole milk by Lactobacillus acidophilus, Lactobacillus bulguricus and Streptococcus thermophilus resulted in moderate but significant increase in the levels of saturated fatty acids and oleic acid with a concomitant decrease in the levels of linoleic and linolenic acids in the glyceride fraction. Similarly, the increase in the levels of free fatty acids was moderate. There were significant increases in the levels of stearic and oleic acids. Unusual fatty acids of bacterial origin were not detected, and monoglycerides disappeared completely upon fermentation. Changes in cholesterol levels were also not significant. Acid degree value and free fatty acid levels were correlated significantly (r = 0.711). Results indicate that previously reported hypocholestermic effect of fermented milk is not due to changes in the composition of lipid classes investigated.     

重楼中薯蓣皂苷元的分离提取及含量检测

目的 研究重楼中薯蓣皂苷元的分离提取和含量测定方法.方法 以薯蓣皂苷元的提取量为参考指标,采用超声提取法提取薯蓣皂苷,正交试验法优选重楼中薯蓣皂苷元的酸解条件,分光光度法测定其含量.结果 影响提取含量的因素的主次顺序为:反应温度＞超声时间＞硫酸量;选择优化条件为:反应温度90℃,超声2.5 h,5％硫酸10 mL.结论 此法处理简单,准确度高,精密度好,适合于重楼中薯蓣皂苷元的提取分离和含量测定.     

A Rapid Immunoturbidimetric Method for Whey Proteins in Nonfat Dry Milk and Buttermilk

An immunoturbidimetric assay, using antibodies to whole bovine whey, was developed for the rapid screening of whey proteins in nonfat dry milk and buttermilk. Milk samples are heat-treated prior to analysis to denature the whey proteins for a more uniform response to antibodies. Of the whey proteins tested, the assay is most sensitive to bovine serum albumin and the least sensitive to β-lactoglobulin. Precision of the method is about 4% coefficient of variation with a minimum detectable level of 3% whey protein concentrate added to nonfat dry milk. Results are compared with electrophoretic analysis of whey proteins and high performance size exclusion chromatography of the glycomacropeptide from rennet whey.     

A Rapid Method for Separation and Quantitation of D-Malic Acid in Fruit Juice

A HPLC method using an aqueous mobile phase containing the chiral ligand-exchanger Cu II-L-valine complex at pH 5.5 with a polystyrene divinyl-benzene copolymer column was used to resolve D-malic acid in apple, pear, and Concord grape juices. D-malic acid was detected and quantitated at 330 nm in less than 15 min per sample. The detection limit appeared to be 2 mg/100 mL D-malic acid in 12 Brix juice, or 0.33% total malic acid in a typical apple juice containing 0.6 g/100 mL using the described procedure.     

仪器法快速检测鲜乳微生物的可靠性研究

本文通过乳制品微生物活性快速检测仪对鲜乳中微生物酶活性的测定,快速检测鲜乳中微生物数量的变化,判定鲜乳品质的优劣。试验结果表明:仪器法可以在30min内完成一个鲜乳样品的微生物含量的检测。利用鲜乳微生物快速检测仪和国标平板菌落计数法分别检测大肠杆菌、蜡样芽胞杆菌、变形杆菌、灰绿曲霉、黑曲霉、球拟酵母菌、金黄色葡萄球菌、伤寒沙门氏菌和志贺氏菌等主要危害鲜乳品质的菌落数量,两种方法的测定结果相关系数均在0.98以上,这表明两种方法间有很好的线性相关性,同样用两种方法监测鲜乳贮藏过程中的微生物活动情况,其检测结果 R2=0.991,属于显著相关。     

白酒中两种常见塑化剂快速定量方法的研究

根据2011年6月卫生部签发的551号文件《卫生部办公厅官员通报食品及食品添加剂中邻苯二甲酸酯类物质最大残留量的函》[1]规定,建立了气相色谱-质谱同时测定白酒中相关塑化剂含量的检测方法。特别对影响白酒样品中塑化剂提取的各种因素和多种前处理方法进行比较,并进行优化处理,最终使本方法能够快速准确测定白酒中的塑化剂含量,具有准确度高、操作简便、成本低等优点。试验结果显示,在S/N=10条件下,DBP、DEHP的定量下限分别为0.04mg/L、0.03mg/L,平均加标回收率为94.4%~108.3%,精密度试验R SD均小于6%,满足常规定量分析要求。     

阻抗法快速分析牛奶中的菌落总数

以电导、总阻抗、双电层电容、培养介质电容、阻抗角作为检测参数,比较含初始菌数不同的阻抗测试管的阻抗变化率曲线,结果阻抗角不适于作为阻抗法快速分析牛奶中菌落总数的检测参数。将检出时间DT值和平板计数法得到的菌落总数的对数值lgC用SAS做线性回归,结果电导、总阻抗、双电层电容之间存在线性相关。用Δ=lg(C0/CSPC)=lg(C0)-lg(CSPC)值分析阻抗法的检测误差,结果由电导、总阻抗作为检测参数得到的菌落总数值符合实际情况。用阻抗法快速分析牛奶中的菌落总数时,分析FPR、FNR随DTTH的变化趋势,DTTH值分别选440min(电导和总阻抗)和410min(双电层电容)。     

Interactions Between Lipids and Milk Proteins in Emulsion

The interactions between nitroxide homologs of fatty acids and purified components of milk proteins in a model food emulsion were studied using electron spin resonance. The importance of the interactions in emulsions decreased in the order α_s1-casein > β-lacto-globulin > β-casein β whole casein. α_s1-Casein resulted in a better organization of the lipid monolayer. Neither the flexibility nor the tertiary structure of the proteins explained this result. It appeared that the interactions occurred through lipid polar heads and protein polar side chains due to hydrogen bonds and/or electrostatic interactions.     

Composition and Distribution of Lipids of Goats’ Milk

Fresh commercial goats’ milks were examined for their lipid contents and distribution of these lipids among milk fractions. Whole milk, skim milk (produced by centrifugation at 330 and 2,000 × g), and cream were studied. Petroleum ether (free lipids) and chloroform methanol (2:1) (bound lipids) were used successively to extract the lipids from all milk fractions. Average total lipid content for five bulk milk samples was 5.0 ± 1.2%. Lipid fractions of whole milk and cream contained 97 to 99% free lipid and 1 to 3% bound lipid, respectively. Free lipid was 96.8% triglyceride, whereas bound lipids contained neutral lipid, glycolipid, and phospholipid. In this respect, goats’ milk resembled cows’ milk. However, goats’ skim milk fractions contained significantly more free lipid than did cows’ milk. This free lipid, investigated in detail by gas chromatography, was shown similar in triglyceride distribution and fatty acid content to whole goats’ milk triglyceride. Quantitative data for the triglyceride distribution in all fractions are given and differ from published data for fresh goats’ milk.     

Simple and Rapid Method for Measuring Turbidity in Gels and Sols from Milk Whey Protein

Protein isolates prepared from acid whey concentrate and cheese whey concentrate, and β-lactoglobulin were studied. Turbidity of samples was measured using a 96-well microplate and a microreader. This method allowed many (>100) small samples (< 250 μL) to be treated at the same time. At low ionic strength and at neutral to alkaline pH, samples were transparent after heating. Transparent gels could also be prepared in this region with a small amount of NaCl.     

破囊壶菌(Thraustochytrium)脂质的提取与分析

研究了超声波破碎破囊壶菌细胞及其脂质提取的方法 ,并对脂质脂肪酸组成进行了分析。实验结果表明 :超声波能有效破碎破囊壶菌细胞 ,从而可使脂质得率提高 6 0 % ;脂质脂肪酸组成以DHA为主 ,含量高达 6 0 %以上 ,其他多不饱和脂肪酸含量均不到 10 %。     

腈纶基牛奶蛋白纤维混纺织物的纤维含量测定方法探讨

根据牛奶蛋白复合纤维的特点,借助纤维细度分析仪对含牛奶蛋白复合纤维的混纺织物进行准确定性;通过大量溶解试验,探索出了一种比较理想的由腈纶基牛奶蛋白复合纤维、羊绒、桑蚕丝和莱赛尔纤维组成的四组分混纺织物的纤维含量定量分析方法。     

Rapid Separation and Quantification of Major Caseins and Whey Proteins of Bovine Milk by Polyacrylamide Gel Electrophoresis

A rapid polyacrylamide gel electrophoretic method was developed for separating and quantifying major proteins in casein and whey protein fractions of bovine milk. For casein separation, best results were achieved by an 8% polyacrylamide gel containing 4 M urea and a top layer of large pore sample gel; for whey protein the most satisfactory separation was with 12% polyacrylamide gel in the absence of urea and a large pore gel. Electrophoretic conditions for separation of whey protein were also applicable for identifying genetic variants of β-lactoglobulin. Densitometric tracings were used to resolve and quantify protein peaks from stained bands in the gels. Casein was resolved into three major fractions with relative proportions of 50:30:15 for α_s1- and α_s2-casein, β-casein, and κ-casein. Whey protein was resolved into four major fractions with relative proportions of approximately 60:20:7:13 for β-lactoglobulin, α-lactalbumin, serum albumin, and immunoglobulin.     

黄胫小车蝗脂类的提取分离和组成研究

据有关资料显示,蝗虫脂质无论在量上还是在质上都有其可资研究和利用的特点.文章探讨了黄胫小车蝗脂质的提取方法,确定了分离其混合脂的最佳工艺条件,研究了其油脂的组成.结果表明,不饱和脂肪酸含量较高,其中以亚麻酸为典型代表,含量高达29.8%.     

Simple and Rapid Method for the Simultaneous Determination of Cholesterol and Retinol in Meat Using Normal-Phase HPLC Technique

A direct saponification and normal-phase high-performance liquid chromatography (NP-HPLC) procedure was developed for simultaneous determination of cholesterol and retinol in meat. A normal-phase silica column fitted with diode array detection at 208 nm for cholesterol and fluorescence detection (λ-excitation 344 nm/λ-emission 472 nm) for retinol, with mobile phase consisting of 2% (v/v) 2-propanol in n-hexane was used. Cholesterol was eluted at 10 min and retinol at 12.66 min. High linearity (R ² > 0.9996 for both compounds) in calibration range was obtained. The LOD and LOQ values show the high sensitivity of the developed methodology for simultaneous determination of cholesterol and retinol in meat. Recovery results obtained in this study (98.67–102.14% for cholesterol and 91.72–98.27% for retinol) were between AOAC recommendations to validated method and were comparable to most recent studies in precision and accuracy. In addition, the present method showed high repeatability and reproducibility. As a general conclusion, the results indicate that the direct saponification, extraction, and HPLC analysis is an adequate method for cholesterol and retinol analysis in meat samples.     

多糖的提取、分离与纯化

介绍了动物,植物和菌类多糖的提取方法,并针对粗多糖中所含的杂质不同,采用不同的方法加以去除,以达到多糖与杂质的分离。     

液体乳和乳饮料中β-内酰胺酶检测方法的研究

利用杯碟法检测液体乳和乳饮料中β-内酰胺酶,确定了检测方法的各项参数。研究表明,选择LB营养琼脂作为上层培养基,用量为5 mL,以藤黄微球菌作为指示菌,菌悬液浓度达到1×109cfu/mL,青霉素G的使用浓度为0.5μg/mL时,0.05 IU/mL的β-内酰胺酶可以分解0.5μg/mL青霉素G,此方法的最低检测限为0.005 IU/mL,重复性较好,准确度高。