Title
Orthokinetic flocculation of caseinate-stabilized emulsions: Influence of calcium concentration, shear rate and protein content
Author
Schokker, E.P.
Dalgleish, D.G.
Centraal Instituut voor Voedingsonderzoek TNO
Publication year
2000
Abstract
Calcium-induced flocculation of caseinate-stabilized soybean oil-in- water emulsions in conditions of Couette flow was studied. A concentrated emulsion (20% oil, 0.5-2.0% sodium caseinate in 20 mM imidazole, pH 7) was diluted 20 times in buffer containing concentrations of CaCl2 between 9 and 17 mM and sheared at rates between 335 and 1340 s-1. The average particle size (d43), measured by integrated light scattering, increased in a sigmoidal manner with shearing time. An increased shear rate resulted in an increased flocculation rate, because of the increased number of collisions between particles, but a decreased value of the maximum d43, because higher shear rates increasingly disrupted the flocs. The flocculation rate was increased by increasing the calcium concentration, indicating an increased collision efficiency. The orthokinetic stability of the emulsions was increased with increased protein content, and it is postulated that the increased surface coverage and hydrodynamic thickness of the adsorbed protein layer increased steric repulsion between droplets, so that higher calcium concentrations were necessary to induce sufficient conformational change of the proteins to allow flocculation. At high caseinate concentrations, calcium may also induce precipitation of unadsorbed caseins from the serum to the oil-water interface, thereby in increasing steric repulsion and hence increasing orthokinetic stability. Chemicals/CAS: Calcium, 7440-70-2; Caseins; Chelating Agents; Emulsions; Proteins
Subject
Calcium-induced flocculation
Caseinate-stabilized emulsions
Orthokinetic flocculation
Shear
Calcium
Casein
Chelating agent
Protein
Emulsion
Flocculation
Kinetics
Molecular dynamics
Molecular stability
Protein content
Shear rate
Soybean
Calcium
Caseins
Chelating Agents
Emulsions
Flocculation
Kinetics
Proteins
Soybeans
Glycine max
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http://resolver.tudelft.nl/uuid:a84a51ce-d921-49e1-9e77-f0c7d8c8e553
DOI
https://doi.org/10.1021/jf9904113
TNO identifier
56537
ISSN
0021-8561
Source
Journal of Agriculture and Food Chemistry, 48 (2), 198-203
Document type
article