• Title, Summary, Keyword: orthokinetic stability

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Orthokinetic Stability of $\beta$-Lactoglubulin-Stabilized Emulsions : Effects of Protein Heat Treatment and Surfactant Addition

  • Hong, Soon-Taek
    • Preventive Nutrition and Food Science
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    • v.3 no.2
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    • pp.133-142
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    • 1998
  • Effects of protein heat treatment and surfactant additionoo the orthokindetic stability of $\beta$-lactoglobulin-stabilized emulsions have been investigated under turbulent flow conditions. In studies on protein-stabilized emulsions, samples which had been subjected to heat treatment(i.e. the protein solution orthe emulsion) have been found to be more prone to orthokinetic coalescene than the untreated ones. The emulsions stabilized with protein heated above the denaturation temperature(i.e. 7$0^{\circ}C$) showed the bigger initial average droplet size, which resulted in an increased orthokinetic coalescenece rate. The storage of the protein-stabilized emulsion at high temperature prior to the shearing experiment also made the emulsion less stable in the shear field. Interestingly. the addition of DATEM has been found to produce a substantial increase in orthokinetic stability of the heat-denatured protein-stabilized emulsion system, although Tween 20 is the opposite case.

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Changes in the Stability Properties of Methylcellulose Emulsions as Affected by Competitive Adsorption Between Methylcellulose and Tween 20 (메칠셀룰로오스/Tween 20 경쟁 흡착이 메칠셀룰로오스 유화액의 안정도 특성에 미치는 영향)

  • Hong, Soon-Taek
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.37 no.10
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    • pp.1278-1286
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    • 2008
  • The effect of Tween 20 addition on changes in the stability of methylcellulose (MC) emulsions (1 wt% MC, 10 wt% n-tetradecane, 20 mM bis-tris buffer, pH 7) was investigated by creaming stability and orthokinetic stability measurements. In the case of MC emulsions containing varying amounts of oil (1$\sim$30 wt%) and no Tween 20 added, creaming stability, judged by mean migration velocity of fat globules ($V_m$), was found to depend on droplet size: the larger the droplet size, the worse the stability [$V_m$: 0.326 $\mu$m $min^{-1}$ ($d_{32}$: 0.32 $\mu$m) ${\rightarrow}V_m$: 0.551 $\mu$m $min^{-1}$ ($d_{32}$: 0.53 $\mu$m)]. With Tween 20, creaming stability was found to be worse than the one without Tween 20, except for MC emulsion containing 0.2 wt% Tween 20. In addition, cream stability was the lowest with the lowest concentration of Tween 20 and a tendency to recover with increasing Tween 20 concentration [$V_m$: 0.598 $\mu$m $min^{-1}$ (0.01 wt%)${\rightarrow}V_m$: 0.389 $\mu$m $min^{-1}$ (0.2 wt%)] was found. From viscosity measurement for aqueous bulk phase of MC emulsions, such a change in the creaming stability was found to coincide well with the results of viscosity measurement. Therefore, it was reasonable to say that creaming stability of MC emulsions containing Tween 20 depended on MC concentration in aqueous bulk phase, which was in turn varied by competitive adsorption between MC and Tween 20 at the oil droplet surface. In case of orthokinetic stability, judged by destabilization time ($t_d$), it was found that the addition of Tween 20 resulted in lowered stability with more pronounce tendency at higher concentrations [$t_d$: 160 min (0.03 wt%)${\rightarrow}t_d$: 100 min (0.2 wt%)]. Moreover, combined with previous results, the orthokinetic stability of MC emulsions containing Tween 20 was found to be exponentially proportional to MC load. In conclusion, competitive adsorption between MC and Tween 20 may affect the stability properties of MC emulsion to varying extents, depending on the concentration of Tween 20.

Flocculation kinetics and hydrodynamic interactions in natural and engineered flow systems: A review

  • Oyegbile, Benjamin;Ay, Peter;Narra, Satyanarayana
    • Environmental Engineering Research
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    • v.21 no.1
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    • pp.1-14
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    • 2016
  • Flocculation is a widely used phase separation technique in industrial unit processes and is typically observed in many natural flow systems. Advances in colloidal chemistry over the past decades has vastly improved our understanding of this phenomenon. However, in many practical applications, process engineering still lags developments in colloidal science thereby creating a gap in knowledge. While significant progress has been made in environmental process engineering research over the past decades, there is still a need to align these two inter-dependent fields of research more closely. This paper provides a comprehensive review of the flocculation mechanism from empirical and theoretical perspective, discuss its practical applications, and examines the need and direction of future research.