The determination of the zeta potential of casein micelles

1979 ◽  
Vol 46 (2) ◽  
pp. 329-332 ◽  
Author(s):  
Donald F. Darling ◽  
John Dickson
Keyword(s):  
Zeta Potential ◽  
Electrostatic Interactions ◽  
Moving Boundary ◽  
Casein Micelles ◽  
Increase With Increase ◽  
Subsequent Calculation ◽  
90 C 30 ◽  
C 30 ◽  
C 50

SUMMARYThe principle of moving boundary electrophoresis has been employed for the measurement of the electrophoretic mobility and subsequent calculation of zeta potential of bovine casein micelles. The zeta potential of casein micelles was observed to increase with increase in temperature (from 10 to 50 °C) and to decrease with decrease in pH. Heat treatment of milk between 90 °C/30 min and 135 °C/50 min had no significant effect on zeta potential. The zeta potential of casein micelles during rennet action decreases until all the κ-casein has been cleaved by the enzyme.The results of this study indicate that electrostatic interactions alone are not sufficient for an understanding of the absolute stability of casein micelles.

Electroacoustic determination of size and zeta potential of casein micelles in skim milk

1996 ◽  
Vol 63 (3) ◽  
pp. 387-404 ◽  
Author(s):  
Theresa Wade ◽  
James K. Beattie ◽  
William N. Rowlands ◽  
Mary-Ann Augustin
Keyword(s):  
Particle Size ◽  
Zeta Potential ◽  
Skim Milk ◽  
Median Particle Size ◽  
Casein Micelles ◽  
Median Particle ◽  
Decreasing Ph ◽  
Good Agreement

SummaryMeasurements of the zeta potential and particle size of casein micelles in skim milk suspensions at natural and lower pH have been made using the technique of electroacoustics. This technique requires no dilution or change of environment of the casein micelles. The zeta potential obtained at natural pH for a commercial skim milk suspension was −18 mV; it became less negative with decreasing pH. The median particle size observed at natural pH for a commercial skim milk suspension was 0·2 εm, in good agreement with previously reported values. The particle size increased as the pH was decreased.

Electrophoretic mobility of casein micelles

1979 ◽  
Vol 46 (3) ◽  
pp. 441-451 ◽  
Author(s):  
Donald F. Darling ◽  
John Dickson
Keyword(s):  
Electrophoretic Mobility ◽  
Moving Boundary ◽  
Ionic Composition ◽  
Skim Milk ◽  
Casein Micelle ◽  
Casein Micelles ◽  
Zeta Potentials ◽  
Micelle Structure ◽  
Increase With Increase ◽  
Micelle Size

SummaryA simplified moving boundary electrophoresis technique has been developed for the measurement of the electrophoretic mobility of casein micelles. The zeta potentials of casein micelles from different skim-milk samples were calculated using Henry's equation and shown to decrease with decrease in pH between pH 6.9 and 5.3 and to increase with increase in temperature between 10 and 45 °C. Neither severe heat treatment (up to 135 °C for 51 min) nor centrifugal fractionation of micelles into different micelle size ranges had any significant effect on zeta potential. The ionic composition of the serum phase has been shown to be extremely important in determining the electrophoretic mobility. Casein micelles electrophoresed through milk ultrafiltrate consistently gave a lower mobilities than the same micelles centrifuged through milk centrifugate. The results are discussed in relation to present theories of casein micelle structure; these theories do not accommodate all of the observations.

scholarly journals Determination of the Zeta Potential of Planar Solids in Nonpolar Liquids

2021 ◽  
Author(s):  
Dennis C. Prieve ◽  
Benjamin A. Yezer ◽  
Keyi Xu ◽  
Aditya S. Khair ◽  
James W. Schneider ◽  
...  
Keyword(s):  
Zeta Potential ◽  
Nonpolar Liquids

scholarly journals Voltammetric sensor based on long alkyl chain tetraalkylammonium ionic liquids comprising ascorbate anion for determination of nitrite

2021 ◽  
Vol 188 (2) ◽  
Author(s):  
Tomasz Rębiś ◽  
Michał Niemczak ◽  
Patrycja Płócienniczak ◽  
Juliusz Pernak ◽  
Grzegorz Milczarek
Keyword(s):  
Ionic Liquids ◽  
Electrostatic Interactions ◽  
Film Surface ◽  
Modified Electrodes ◽  
Voltammetric Sensor ◽  
Nitrite Oxidation ◽  
Alkyl Chains ◽  
Modified Surface ◽  
Influence Of Ph

AbstractAn electrochemical sensor was fabricated utilizing ionic liquids possessing cations with long alkyl chains such as trimethyl octadecylammonium and behenyl trimethylammonium and ascorbate anion. The ionic liquids were drop-coated onto the electrode. Thin modifying layers were prepared. Cyclic voltammetric investigations revealed electrostatic interactions between the electrochemical probes and the modified surface, proving that a positive charge was established at the film surface. Hence, negatively charged species such as nitrite can be pre-concentrated on the surface of presented modified electrodes. The fabricated electrodes have been used as a voltammetric sensor for nitrite. Due to the electrostatic accumulation properties of long alkyl cation, the assay exhibits a remarkable improvement in the voltammetric response toward nitrite oxidation. The influence of pH on the electrode response was thoroughly investigated, and the mechanism of the electrode was established. The developed sensor showed a linear electrochemical response in the range 1.0–50 μM with a detection limit of 0.1 μM. The electrode revealed good storage stability, reproducibility, and anti-interference ability. The determination of nitrite performed in curing salts brought satisfactory results. Graphical abstract

scholarly journals Dispersive evaluation and surface chemistry of advanced, multifunctional silica/lignin hybrid biomaterials

2013 ◽  
Vol 11 (11) ◽  
pp. 1860-1873 ◽  
Author(s):  
Magdalena Nowacka ◽  
Łukasz Klapiszewski ◽  
Małgorzata Norman ◽  
Teofil Jesionowski
Keyword(s):  
Zeta Potential ◽  
Surface Charge ◽  
Electrochemical Sensors ◽  
Relevant Information ◽  
Structural Features ◽  
Kraft Lignin ◽  
Morphological Properties ◽  
Wide Range ◽  
Hybrid Biomaterials

AbstractAdvanced silica/lignin hybrid biomaterials were obtained using hydrated or fumed silicas (Aerosil®200) and Kraft lignin as precursors, which is a cheap and biodegradable natural polymer. To extend the possible range of applications, the silicas were first modified with N-2-(aminoethyl)-3-aminopropyltrimethoxsysilane, and then with Kraft lignin, which had been oxidized with sodium periodate. The SiO2/lignin hybrids and precursors were characterised by means of determination of their physicochemical and dispersive-morphological properties. The effectiveness of silica binding to lignin was verified by FT-IR spectroscopy. The zeta potential value provides relevant information regarding interactions between colloid particles. Measurement of the zeta potential values enabled an indirect assessment of stability for the studied hybrid systems. Determination of zeta potential and density of surface charge also permitted the quantitative analysis of changes in surface charge, and indirectly confirmed the effectiveness of the proposed method for synthesis of SiO2/lignin hybrid materials. A particularly attractive feature for practical use is their stability, especially electrokinetic stability. It is expected that silica/lignin hybrids will find a wide range of applications (polymer fillers, biosorbents, electrochemical sensors), as they combine the unique properties of silica with the specific structural features of lignin. This makes these hybrids biomaterials advanced and multifunctional.

scholarly journals Volume Texture of a Deformed Quartzite Observed With U-Stage Microscopy and Neutron Diffractometry

1999 ◽  
Vol 31 (4) ◽  
pp. 239-248 ◽  
Author(s):  
H. Ghildiyal ◽  
E. Jansen ◽  
A. Kirfel
Keyword(s):  
Neutron Diffraction ◽  
Pole Figure ◽  
North West ◽  
Pole Figures ◽  
Slip Planes ◽  
Subsequent Calculation ◽  
Kaoko Belt ◽  
Universal Stage ◽  
Active Slip

The volume texture of a naturally deformed quartzite from the Kaoko belt, North-West Namibia, has been analysed by both universal stage microscopy and neutron diffraction. Universal stage microscopy is restricted to the determination of the base pinacoid preferred orientation in quartzite. For a more complete description of the texture, the orientations of additional crystal planes, such as first and second order prisms as well as positive and negative rhombs, must be known. Neutron methods allow the evaluation of pole figures of all Bragg reflecting planes, of which those of the first order prisms being considered to be the most active slip planes, are of particular interest. Drawbacks of neutron diffraction, i.e. the faking of an eventually absent inversion centre and lack of resolution, can be overcome by pole figure inversion and subsequent calculation of desired pole figures. Both, universal stage microscopy and neutron diffraction yield well comparable results, of course only with respect to the pole figure of the c-axis.

The Determination of Electrokinetic Coupling-Coefficient and Zeta Potential of Rock Samples by Electrokinetic Measurements

2012 ◽  
Vol 516-517 ◽  
pp. 1870-1873 ◽  
Author(s):  
Jun Wang ◽  
Heng Shan Hu
Keyword(s):  
Zeta Potential ◽  
Coupling Coefficient ◽  
Streaming Potential ◽  
Potential Method ◽  
Surface Conductivity ◽  
Reliable Estimate ◽  
Surface Conductance ◽  
Streaming Current ◽  
Low Concentrations

The electrokinetic effects are important in the understanding of electric properties in porous medium. In this study, the streaming potential and streaming current of saturated samples are measured at different concentrations, then three methods are applied to obtain the zeta-potential and electrokinetic coupling coefficient. The study shows that the results obtained from streaming potential and streaming current methods agree well with each other, but the results obtained from simplified streaming potential method become seriously inaccurate at low concentrations due to the influence of surface conductance. This experimental study also provides a reliable estimate of the surface conductivity and its contribution to zeta-potential at given concentrations.

scholarly journals Development and Validation of Optical Methods for Zeta Potential Determination of Silica and Polystyrene Particles in Aqueous Suspensions

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 290
Author(s):  
Yannic Ramaye ◽  
Marta Dabrio ◽  
Gert Roebben ◽  
Vikram Kestens
Keyword(s):  
Zeta Potential ◽  
Particle Tracking ◽  
Colloidal Stability ◽  
Optical Methods ◽  
Intermediate Precision ◽  
Electrophoretic Light Scattering ◽  
Measurement Uncertainties ◽  
Development And Validation ◽  
Direct Implementation

Zeta potential is frequently used to examine the colloidal stability of particles and macromolecules in liquids. Recently, it has been suggested that zeta potential can also play an important role for grouping and read-across of nanoforms in a regulatory context. Although the measurement of zeta potential is well established, only little information is reported on key metrological principles such as validation and measurement uncertainties. This contribution presents the results of an in-house validation of the commonly used electrophoretic light scattering (ELS) and the relatively new particle tracking analysis (PTA) methods. The performance characteristics were assessed by analyzing silica and polystyrene reference materials. The ELS and PTA methods are robust and have particle mass working ranges of 0.003 mg/kg to 30 g/kg and 0.03 mg/kg to 1.5 mg/kg, respectively. Despite different measurement principles, both methods exhibit similar uncertainties for repeatability (2%), intermediate precision (3%) and trueness (4%). These results confirm that the developed methods can accurately measure the zeta potential of silica and polystyrene particles and can be transferred to other laboratories that analyze similar types of samples. If direct implementation is impossible, the elaborated methodologies may serve as a guide to help laboratories validating their own methods.

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