Reversible adsorption of proteins at the oil/water interface I. Preferential adsorption of proteins at charged oil/water interfaces

The behaviour of positively and negatively charged oil-in-water emulsions, stabilized with hexadecyl trimethyl ammonium bromide and sodium hexadecyl sulphate respectively in the presence of protein solutions has been studied. Under certain conditions proteins will adsorb to a charged oil/water interface. When finely dispersed oil-in-water emulsion was used to provide this oil/water interface, adsorption of protein resulted in flocculation of the oil droplets. Flocculation of emulsion on the addition of protein is pH conditioned and occurred on the acid side of the isoelectric point of the protein with negatively charged and on the alkaline side with positively charged oil globules. No flocculation occurred on the alkaline side of the isoelectric point with a negative emulsion or the acid side with a positive emulsion. The amount of protein required to cause maximum clarification of the subnatant fluid corresponded with that needed to give a firmly gelled protein monolayer at the interface, namely, 2·5 mg. of protein/sq.m, of interfacial area. With that amount of protein the flocculated oil globules remained discrete and no coalescence or liberation of free oil occurred. If only 1 mg. of protein/sq.m, of interfacial area was added, flocculation was followed by rapid coalescence of oil globules and liberation of free oil. If smaller amounts still were used, no visible change in the dispersion of the oil droplets could be seen macroscopically. With greater amounts than 2·5 mg./sq.m, of interfacial area, up to ten times the monolayer concentration was adsorbed to the interface. Sodium chloride affected the flocculation range, and instead of the clear-cut change-over between the positive and negative interfaces at the isoelectric point of the protein, overlapping occurred. 5 % sodium chloride shifted the flocculation point about 1 unit of pH. The addition of sodium chloride also altered the point of maximum clarification. Thus with haemoglobin the maximum clarification point was shifted from 2·5 to 1·7 mg./sq.m. of interfacial area by the addition of 1 % sodium chloride. The adsorption of protein on to charged oil/water interfaces was reversible. This was best demonstrated with haemoglobin. Thus, haemoglobin was adsorbed at pH 5·0 to a negative emulsion— the red floccules were washed and transferred to a buffer at pH 10. The haemoglobin was released and the emulsion was redispersed. The effect of adsorption and desorption on the structure of the protein molecule has been studied with haemoglobin. By solubility and colour tests it was shown that the haemoglobin molecule was changed to parahaematin by adsorption and subsequent desorption from a charged oil/water interface. Molecular weight and shape determinations were carried out on the desorbed protein. Two proteins have been separated by this adsorption mechanism. This was demonstrated on a mixture of albumin and haemoglobin. Some applications of the flocculation technique are indicated and the significance of the phenomena described are discussed.

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Reversible adsorption of proteins at the oil/water interface I. Preferential adsorption of proteins at charged oil/water interfaces

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1946.0006 ◽

1946 ◽

Vol 133 (870) ◽

pp. 121-121

Keyword(s):

Sodium Chloride ◽

Isoelectric Point ◽

Interfacial Area ◽

Ammonium Bromide ◽

Water Interface ◽

Oil Droplets ◽

Water Emulsion ◽

Oil In Water ◽

Alkaline Side ◽

Oil Water

The behaviour of positively and negatively charged oil-in-water emulsions, stabilized with hexadecyl trimethyl ammonium bromide and sodium hexadecyl sulphate respectively in the presence of protein solutions has been studied. Under certain conditions proteins will adsorb to a charged oil/water interface. When finely dispersed oil-in-water emulsion was used to provide this oil/water interface, adsorption of protein resulted in flocculation of the oil droplets. Flocculation of emulsion on the addition of protein is pH conditioned and occurred on the acid side of the isoelectric point of the protein with negatively charged and on the alkaline side with positively charged oil globules. No flocculation occurred on the alkaline side of the isoelectric point with a negative emulsion or the acid side with a positive emulsion. The amount of protein required to cause maximum clarification of the subnatant fluid corresponded with that needed to give a firmly gelled protein monolayer at the interface, namely, 2∙5 mg. of protein/sq. m. of interfacial area. With that amount of protein the flocculated oil globules remained discrete and no coalescence or liberation of free oil occurred. If only 1 mg. of protein/sq. m. of interfacial area was added, flocculation was followed by rapid coalescence of oil globules and liberation of free oil. If smaller amounts still were used, no visible change in the dispersion of the oil droplets could be seen macroscopically. With greater amounts than 2∙5 mg. /sq. m. of interfacial area, up to ten times the monolayer concentration was adsorbed to the interface. Sodium chloride affected the flocculation range, and instead of the clear-cut change-over between the positive and negative interfaces at the isoelectric point of the protein, overlapping occurred. 5% sodium chloride shifted the flocculation point about 1 unit of pH . The addition of sodium chloride also altered the point of maximum clarification. Thus with haemoglobin the maximum clarification point was shifted from 2∙5 to 1∙7 mg. /sq. m. of interfacial area by the addition of 1% sodium chloride. The adsorption of protein on to charged oil/water interfaces was reversible. This was best demonstrated with haemoglobin. Thus, haemoglobin was adsorbed at pH 5∙0 to a negative emulsion—the red floccules were washed and transferred to a buffer at pH 10. The haemoglobin was released and the emulsion was redispersed. The effect of adsorption and desorption on the structure of the protein molecule has been studied with haemoglobin. By solubility and colour tests it was shown that the haemoglobin molecule was changed to parahaematin by adsorption and subsequent desorption from a charged oil /water interface. Molecular weight and shape determinations were carried out on the desorbed protein. Two proteins have been separated by this adsorption mechanism. This was demonstrated on a mixture of album in and haemoglobin. Some applications of the flocculation technique are indicated and the significance of the phenomena described are discussed.

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Switchable superlyophobic zeolitic imidazolate framework-8 film-coated stainless-steel meshes for selective oil–water emulsion separation with high flux

New Journal of Chemistry ◽

10.1039/d0nj02517h ◽

2020 ◽

Vol 44 (32) ◽

pp. 13534-13541

Author(s):

Xin Gao ◽

Qiang Ma ◽

Zhengwei Jin ◽

Pei Nian ◽

Zheng Wang

Keyword(s):

Stainless Steel ◽

High Flux ◽

Water Droplets ◽

Oil Droplets ◽

Zeolitic Imidazolate Framework ◽

Water Emulsion ◽

Oil In Water ◽

Emulsion Separation ◽

Oil Water ◽

Oil Emulsions

A switchable superlyophobic ZIF-8 membrane can selectively remove oil droplets in oil-in-water emulsions via superoleophobicity and water droplets in water-in-oil emulsions via superhydrophobicity.

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OIL SPILL DISPERSION STABILITY AND OIL RE-SURFACING

International Oil Spill Conference Proceedings ◽

10.7901/2169-3358-2008-1-661 ◽

2008 ◽

Vol 2008 (1) ◽

pp. 661-665 ◽

Cited By ~ 3

Author(s):

Merv Fingas

Keyword(s):

Water Column ◽

Oil Spill ◽

Emulsion Stability ◽

Dispersed Phase ◽

Water Interface ◽

Water Emulsion ◽

Stabilization Process ◽

Oil In Water ◽

Oil Water ◽

Oil In Water Emulsion

ABSTRACT This paper summarizes the data and the theory of oil-in-water emulsion stability resulting in oil spill dispersion re-surfacing. There is an extensive body of literature on surfactants and interfacial chemistry, including experimental data on emulsion stability. The phenomenon of resurfacing oil is the result of two separate processes: de stabilization of an oil-in-water emulsion and desorption of surfactant from the oil-water interface which leads to further de stabilization. The de stabilization of oil-in-water emulsions such as chemical oil dispersions is a consequence of the fact that no emulsions are thermodynamically stable. Ultimately, natural forces move the emulsions to a stable state, which consists of separated oil and water. What is important is the rate at which this occurs. An emulsion is said to be kinetically stable when significant separation (usually considered to be half or 50% of the dispersed phase) occurs outside of the usable time. There are several forces and processes that result in the destabilization and resurfacing of oil-in-water emulsions such as chemically dispersed oils. These include gravitational forces, surfactant interchange with water and subsequent loss of surfactant to the water column, creaming, coalescence, flocculation, Ostwald ripening, and sedimentation. Gravitational separation is the most important force in the resurfacing of oil droplets from crude oil-in-water emulsions such as dispersions. Droplets in an emulsion tend to move upwards when their density is lower than that of water. Creaming is the de stabilization process that is simply described by the appearance of the starting dispersed phase at the surface. Coalescence is another important de stabilization process. Two droplets that interact as a result of close proximity or collision can form a new larger droplet. The result is to increase the droplet size and the rise rate, resulting in accelerated de stabilization of the emulsion. Studies show that coalescence increases with increasing turbidity as collisions between particles become more frequent. Another important phenomenon when considering the stability of dispersed oil, is the absorption/desorption of surfactant from the oil/water interface. In dilute solutions, much of the surfactant in the dispersed droplets ultimately partitions to the water column and thus is lost to the dispersion process. This paper provides a summary of the processes and data from some experiments relevant to oil spill dispersions.

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Sodium caseinate/flaxseed gum interactions at oil–water interface: Effect on protein adsorption and functions in oil-in-water emulsion

Food Hydrocolloids ◽

10.1016/j.foodhyd.2014.05.009 ◽

2015 ◽

Vol 43 ◽

pp. 137-145 ◽

Cited By ~ 44

Author(s):

Qiangzhong Zhao ◽

Zhao Long ◽

Jing Kong ◽

Tongxun Liu ◽

Dongxiao Sun-Waterhouse ◽

...

Keyword(s):

Protein Adsorption ◽

Sodium Caseinate ◽

Interface Effect ◽

Water Interface ◽

Water Emulsion ◽

Oil In Water ◽

Oil Water ◽

Oil In Water Emulsion ◽

Flaxseed Gum

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Nature of the oil/water interface and equilibrium surfactant aggregates in systems exhibiting low tensions

Canadian Journal of Chemistry ◽

10.1139/v88-469 ◽

1988 ◽

Vol 66 (12) ◽

pp. 3031-3037 ◽

Cited By ~ 20

Author(s):

Robert Aveyard ◽

Bernard P. Binks ◽

Thomas A. Lawless ◽

Jeremy Mead

Keyword(s):

Molecular Structure ◽

Sodium Chloride ◽

Water Interface ◽

Rich Phase ◽

Aqueous Sodium ◽

Interfacial Tensions ◽

Aerosol Ot ◽

Surfactant Aggregates ◽

Monolayer Adsorption ◽

Oil Water

Oil/water interfacial tensions are reported for systems containing pure alkane, aqueous sodium chloride, and a pure anionic surfactant, either Aerosol OT or p-dihexylbenzene sodium sulphonate (DHBS). Evidence is produced to support the claim that monolayer adsorption at the oil/water interface can produce ultralow tensions (~ 1 µN m−1), and that the presence at the interface of a third, surfactant-rich phase is not necessary. The aggregation of DHBS and its distribution between oil and aqueous phases of various salinities have been investigated. It has been confirmed that the behaviour of DHBS in these respects is similar to that of Aerosol OT, as might be expected from its molecular structure. The sizes of microemulsion droplets in equilibrium with planar adsorbed monolayers have been determined, and related to the tensions of the plane oil/aqueous phase interfaces using simple existing theory.

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Enabling single-molecule localization microscopy in turbid food emulsions

10.1101/2021.03.03.433739 ◽

2021 ◽

Author(s):

Abbas Jabermoradi ◽

Suyeon Yang ◽

Martijn Gobes ◽

John P.M. van Duynhoven ◽

Johannes Hohlbein

Keyword(s):

Adaptive Optics ◽

Single Molecule ◽

Optical Resolution ◽

Three Dimensions ◽

Water Interface ◽

Water Emulsion ◽

Food Emulsions ◽

Localization Microscopy ◽

Oil Water ◽

Single Molecule Localization Microscopy

Turbidity poses a major challenge for the microscopic characterization of many food systems. In these systems, local mismatches in refractive indices can cause reflection, absorption and scattering of incoming as well as outgoing light leading to significant image deterioration along sample depth. To mitigate the issue of turbidity and to increase the achievable optical resolution, we combined adaptive optics (AO) with single-molecule localization microscopy (SMLM). Building on our previously published open hardware microscopy framework, the miCube, we first added a deformable mirror to the detection path. This element enables both the compensation of aberrations directly from single-molecule data and, by further modulating the emission wavefront, the introduction of various point spread functions (PSFs) to enable SMLM in three dimensions. We further added a top hat beam shaper to the excitation path to obtain an even illumination profile across the field of view (FOV). As a model system for a non-transparent food colloid in which imaging in depth is challenging, we designed an oil-in-water emulsion in which phosvitin, a ferric ion binding protein present in from egg yolk, resides at the oil water interface. We targeted phosvitin with fluorescently labelled primary antibodies and used PSF engineering to obtain 2D and 3D images of phosvitin covered oil droplets with sub 100 nm resolution. Droplets with radii as low as 200 nm can be discerned, which is beyond the range of conventional confocal light microscopy. Our data indicated that in the model emulsion phosvitin is homogeneously distributed at the oil-water interface. With the possibility to obtain super-resolved images in depth of nontransparent colloids, our work paves the way for localizing biomacromolecules at colloidal interfaces in heterogeneous food emulsions.

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Janus membrane decorated via a versatile immersion-spray route: controllable stabilized oil/water emulsion separation satisfying industrial emission and purification criteria

Journal of Materials Chemistry A ◽

10.1039/c8ta11452h ◽

2019 ◽

Vol 7 (9) ◽

pp. 4941-4949 ◽

Cited By ~ 33

Author(s):

Weifeng Zhang ◽

Xiangyu Li ◽

Ruixiang Qu ◽

Yanan Liu ◽

Yen Wei ◽

...

Keyword(s):

Water Emulsion ◽

Industrial Emission ◽

Oil Emulsion ◽

Highly Efficient ◽

Oil In Water ◽

Emulsion Separation ◽

Oil Water ◽

Water In Oil Emulsion

A PANI–SiNP-decorated Janus membrane was fabricated for highly efficient stabilized oil-in-water and water-in-oil emulsion separation, meeting industrial purification standards.

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