Carrageenan Gels in Skim Milk: Formation and Rheological Properties

Phase behavior and mechanical properties of gels of three (kappa-, iota-, and lambda-) carrageenans in skim milk are thoroughly studied. The measurements were performed with the aid of a dynamic rheology in different regimes including determination of frequency dependences of rheological parameters, creep, and critical strain and stress at which the gelled systems are destroyed. Temperature dependences of the rheological parameters were also measured. A set of obtained data allowed to quantitatively characterize the mechanical properties of milk gels and compare the gel-forming properties of various carrageenans. In addition to gels of individual polysaccharides, their mixed gels were studied for the first time. It is shown that kappa-carrageenan formed the most stiff and brittle gels. Its mixing with iota- or lambda-carrageenans made gels softer. This effect is observed when the degree of substitution of kappa-carrageenan was higher than 50% that indicates its prevalent role in the mixed systems. The gelation is explained by the formation of crosslinked structure where the nodes are the casein micelles connected by polysaccharide chains. Their binding occurs due to electrostatic interactions between the sulfo groups of carrageenans and amino groups of kappa-casein. In the case of kappa- or iota-carrageenans, network structure is additionally stabilized due to crosslinking of segments of their molecular chains by the double helices at the gaps between casein micelles.     

High-Performance Gel-Permeation Chromatography of Bovine Skim Milk Proteins

Abstract

The separation of bovine skim milk proteins by gel-permeation high performance liquid chromatography was examined. Toya-Soda TSK-GEL (Type SW) columns were used with an eluent of .05 M phosphate buffer (pH 6.80) containing .1 M sodium sulfate at .5 ml/min. Bovine whole milk was centrifuged to remove lipids, and the resultant skim milk directly injected. A 2000SW column yielded three protein peaks: 1 = casein, IgG and BSA; 2 = 6-lactoglobulins and BSA; and 3 = α-lactalbumin and BSA. A 3000SW plus 2000SW column system with a 30 μl injection volume yielded four protein peaks: 1 = minor amounts of α - and β-casein; 2 = casein, BSA and IgG; 3 = β-lactoglobulins; and 4 = α¹-lactalbumin. A 3000SW plus 2000SW column system with a 10 μl injection volume yielded five protein peaks: 1 = casein; 2 = IgG; 3 = BSA; 4 = β-lactoglobulins; and 5 = α-lactalbumin. Both the single column and dual column applications yielded three nonprotein peaks, which were dialyzed from solution. Thus, a high speed analytical separation of milk proteins was achieved according to molecular size, but this application is highly dependent on sample size.     

紫外光度法间接测定脱脂乳中的芽孢数量

为了有效控制乳制品生产过程、保证质量,克服芽孢杆菌传统计数方法周期长的缺点,本实验通过分光光度法检测芽孢中特异性物质2,6-吡啶二羧酸(DPA)。根据DPA浓度与芽孢数量的关系,建立了快速检测脱脂乳中芽孢数量的方法。本研究对脱脂乳及其芽孢处理、DPA释放及采用紫外分光光度法检测做了研究。通过准确度和加标回收率检验,建立DPA含量与芽孢数的线性关系,回归方程为y=0.2084x-0.9363,r=0.6998,经验证可有效估测脱脂乳中芽孢数量(P<0.05)。     

Hydrodynamic Model for Plasmonics: A Macroscopic Approach to a Microscopic Problem

In this concept, we present the basic assumptions and techniques underlying the hydrodynamic model of electron response in metals and demonstrate that the model can be easily incorporated into computational models. We discuss the role of the additional boundary conditions that arise due to nonlocal terms in the modified equation of motion and the ultimate impact on nanoplasmonic systems. The hydrodynamic model captures much of the microscopic dynamics relating to the fundamental quantum mechanical nature of the electrons and reveals intrinsic limitations to the confinement and enhancement of light around nanoscale features. The presence of such limits is investigated numerically for different configurations of plasmonic nanostructures.     

A Method for Rapid Identification of Whey Powder and Milk Powder

In the inspection of diary products, it is frequently required to distinguish between whey powder and milk powder,but there is no standard test method for this work now. According to Nation Standards,the concentration of fat could be used as a criterion for distinguishing between whey powder and milk powder. Meanwhile, the method of fat analysis is sophistic and not suitable to be used as a quick analysis. In order to overcome this problem, a rapid test method in following have be developed.     

Qualitative Identification of Milk Fat from Chromatographic Data

The data on the amount of fatty acids in milk, animal, vegetable, and mixed fats were obtained by capillary gas–liquid chromatography. Statistical data on the concentrations of myristic, palmitic, stearic, oleic, linoleic, and linolenic acids in milk fat were considered as criteria of its natural origin. Concepts were formulated for the detection of a multicomponent adulterating additive of variable composition in a product containing variable amounts of the same components. A graphical interpretation of the results of the analysis was proposed based on the identification zone.     

Multihyperspectral Microscopic Imaging for the Precise Identification of Pollen

We report a method for precisely identifying and locating the pollen of different species in a microscope based on multihyperspectral imaging. Since pollen species are complicated and difficult to identify by one feature, both fluorescence and transmission spectral images of the samples were obtained and used for the identification together with their morphologic features. Three different species of pollens were used as test samples for investigation. The results showed that the accuracy reached 99.5%, which was a significant improvement comparing with the single spectral detection. Because more information was taken into consideration, this method has great potential for the precise identification of biological specimens.     

推荐一个与生命科学有关的综合化学实验——牛奶中酪蛋白和乳糖的分离与鉴定

通过调节牛奶的pH分离出酪蛋白和乳糖,并采用醋酸纤维薄膜电泳、颜色反应、TLC和旋光性测定等方法鉴定酪蛋白和乳糖。使学生掌握分离纯化生物大分子物质的一些方法和手段,为参加生命科学研究打下基础。     

人奶样品中蛋白质种类的FT-MS鉴定

奶制品主要由蛋白质、脂肪、碳水化合物、维生素、矿物质组成,其中,蛋白质是生命活动的基础物质,也是构成人体新生组织、维持人体健康的重要成分,其含量直接决定奶制品的营养价值和质量.因此,研究奶制品中蛋白质的成分成为食品领域中的一个热门课题.     

中性人乳寡糖的分离及结构鉴定

以脱脂、除蛋白后的人乳为原料,联合运用阴离子交换色谱(AEC)、凝胶渗透色谱(GPC)和多孔石墨化碳色谱(PGC)等多种分离纯化技术制备了18种中性人乳寡糖,并采用电喷雾碰撞诱导串联质谱(ESI-CIDMS/MS)技术对其结构进行了鉴定.结果表明,所制备的中性人乳寡糖主要为三至九糖,含有半乳糖(Gal)、葡萄糖(Glc)、N-乙酰葡萄糖胺(GlcNAc)和岩藻糖(Fuc).所有寡糖的还原端均含有乳糖核心(Galβ1-4Glc),非还原端均含有乳糖胺(Galβ1-3/4GlcNAc),并且Fuc以α1-2,α1-3和α1-4连接于主链的Gal,Glc和GlcNAc上.     

Membrane Pretreatment: A Method for Reducing Fouling by Natural Organic Matter

The prevention of fouling of polysulphone ultrafiltration membranes, used for the purification of natural brown water, was investigated by pretreating the membranes prior to filtration. Polysulfone membranes were pretreated by commercial nonionic surfactants Triton X-100 and Pluronic F108. Specific characterisation techniques, developed by Maartens et al. (1998) and Jucker and Clarke, (1994), were used to determine and compare the effects induced by the adsorption of natural organic matter on the permeability of untreated as well as surfactant treated capillary ultrafiltration membranes. The extent of foulant adsorption and the quality of the resultant permeate solutions were determined by ultraviolet visible-light spectroscopy. The findings of this investigation provides information of importance for the operation of future natural brown water ultrafiltration plants. Copyright 2000 Academic Press.     

BHC Residues in Milk: A Gas Chromatographic Investigation

Abstract

BHC residues were determined in milk samples of cows and buffaloes (Indore, M.P., India), α-, β- and γ-BHC were identified in samples from four different localities using gas chromatography. All samples were contaminated with BHC, with the toxic gamma isomer appearing in the largest concentration. Buffalo milk was more contaminated than cow milk, with maximum values of 17 and 12 μg/l, respectively.     

A Reverse Vaccinology Approach for the Identification of Potential Vaccine Candidates from Leishmania spp

Leishmaniasis is a group of diseases with a spectrum of clinical manifestations ranging from cutaneous ulcers to visceral leishmaniasis, which results from the bite of an infected sandfly to human. Attempts to develop an effective vaccine have been shown to be feasible but no vaccine is in active clinical use. This study adopts a Reverse Vaccinology approach to identify common vaccine candidates from both highly pathogenic species Leishmania major and Leishmania infantum. Total proteome of both species were compared to identify common proteins, which are further taken for sub-cellular localization and transmembrane helices prediction. Plasma membrane proteins having only one transmembrane helix were first identified and analyzed which are non-homologous in human and mouse in order to avoid molecular mimicry with other proteins. Selected proteins were analyzed for their binding efficiency to both major histocompatibility complex (MHC) class I and class II alleles. As a result, 19 potential epitopes are screened in this study using different approaches, which can be further verified through in vivo experiments in MHC compatible animal models. This study demonstrates that Reverse Vaccinology approach has potential in discovering various immunogenic antigens from in silico analysis of pathogen??s genome or proteome instead of culturing the whole organism by conventional methods.     

代谢组学方法研究奶牛注射氯霉素后牛奶中的生物标志物

建立了高效液相色谱-质谱(HPLC-MS)技术研究牛奶代谢组学的方法.样品用乙腈提取,经浓缩富集,采用HPLC-MS技术研究了注射氯霉素后牛奶中内源性代谢物随时间的变化情况.结果表明,注射氯霉素后,牛奶的代谢指纹图谱中8个谱峰的变化随给药及休药时间呈现一定升降规律;采用偏最小二乘判别分析法(PLS-DA)可将给药组与空白组样品完全分开;鉴定了对组间差异贡献较大的化合物为单羟基十八碳二烯酸(HODE),HODE可以作为注射氯霉素后奶牛体内代谢应激产生的内源性生物标志物.     

有特色的选修课教材——《色彩与微观世界》

颜色是物质的基本属性之一,是物质微观结构的宏观表现。围绕颜色这一广泛而生动的话题,化学工业出版社于2004年9月出版的《色彩与微观世界》一书较系统地论述了颜色与物质微观结构理论之间的关系。本书是编著者金增瑗在首都师范大学开设色彩与物质结构选修课9年后精心完成的。全书共9章:第1章,颜色的基本理论。第2章,物质的结构状态与光学颜色。以露珠彩虹、蓝天白云以及多种宝石的彩晕为例,剖析了色散、散射、干涉、衍射等物理效应产生的颜色与物质的微观结构的特有关系。第3章,原子的结构状态与简单激发产生的颜色。介绍了黑体辐射与彩色…     

Fluorescence Analysis: A New Approach

Abstract

The Video Fluorometer is a new instrument for fluorescence analysis which offers significant advantages for the study of complex systems. This instrument can acquire 241 fluorescence spectra, taken at 241 different exciting wavelengths in 16.7 milliseconds. These results are displayed in a three-dimensional graphical format in real time. Coupled with a laboratory computer, this instrument should provide new algorithms for the analysis of luminescence spectra of multi-component systems.     

X-ray Diffraction: A Practical Approach

X-ray Diffraction: A Practical Approach, C. Suryanarayana and M. Grant Norton, 1998. Plenum Press, New York and London. xiii + 273 pages. (hardback, $49.50, U.S. and Canada; $59.40, elsewhere).It is the aim of this text to teach undergraduates majoring in materials science the use of powder X-ray diffraction for materials characterization. Since it does not treat X-ray diffraction and crystallography in a general way, it would have been better if it were given a more specific title, such as X-Ray Powder Diffraction for Metallurgical Characterization. A Primer and Workbook. As a laboratory course with work pages to be filled out by the student, it might have been spiral-bound to facilitate such use.     

显微分光光度法与显微红外光谱综合方法在黑色中性笔字迹鉴定中的应用

以黑色中性笔字迹为研究对象,共收集10个不同厂家不同型号的样本56份,结合化学计量学的方法对黑色字迹样本的显微红外谱图和显微分光谱图进行处理.对显微红外谱图进行聚类分析和相似度比较,以区分不同成分的字迹;利用聚类分析,可将56份样本中的47份按成分不同分为6大类;利用相似度的概念,可对谱图的差异性进行量化;显微分光谱图主要进行色差计算,以区分不同色度的字迹;利用色差计算公式,计算两样品间的色差,共得1 596份色差数据,色差小于1的数据为31份,占全部比对样品的1.9%;将显微红外和显微分光分析结果进一步结合比对,可发现红外谱图聚为一类的样本之间有较大的色差,而色差很小的样本其红外谱图有较大差异,从而可将56份黑色字迹区分,为字迹的鉴定提供了新思路和新方法.     

Skim and cream natural rubber particles: colloidal properties, coalescence and film formation

Cream and skim fractions of freshly tapped natural rubber latex have been studied using atomic force microscopy and scanning electric potential microscopy to elucidate the topology and charge properties in film formation. Elemental distribution maps of the particles have also been obtained using electron energy-loss imaging in a low-energy transmission electron microscope. The two rubber fractions are obtained by centrifugation. The cream fraction is stable while rapid coagulation occurs in the skim fraction. After removal of the coagulum, no further coagulation occurs and the remaining skim rubber particles are stable. The rubber particles from the cream rubber particles contain higher amount of adsorbed protein-phospholipid materials compared to those in the "self-cleaned" skim fraction. This difference in membrane property has a significant impact on the spreading of the cis-1,4-polyisoprene cores, their coalescence and film formation behavior. Coalescence of cream particles appears to be hindered by the membrane materials, forming a rough film that retains the topology of individual particles. Skim particles coalesce more readily, forming relatively smooth films.