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Interactions between fat crystal networks and sodium caseinate at the sunflower oil‐water interface
Author(s) -
Ogden Leanne G.,
Rosenthal Andrew J.
Publication year - 1998
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11746-998-0290-6
Subject(s) - sunflower oil , crystal (programming language) , materials science , chemical engineering , viscometer , adsorption , surface tension , phase (matter) , pulmonary surfactant , crystallography , viscosity , chemistry , organic chemistry , composite material , thermodynamics , biochemistry , physics , computer science , engineering , programming language
A Couette‐type torsion wire surface shear viscometer was used to measure the apparent interfacial shear viscosity of pH 7 ( I =0.05 M) buffered solutions of sodium caseinate in contact with sunflower oil. The sunflower oil contained 1% fat crystals in either the β or β′ polymorphic form, or was crystal free. In all cases, the fat crystals increased the interfacial shear viscosity synergistically, with the β′ crystals causing the biggest increase. Substituting the protein for a small‐molecule surfactant (Tween‐40) showed that this was not simply due to the protein lowering the interfacial tension. Sedimentation studies of the different fat crystal slurries suggested that the extent of the interfacial shear viscosity increase was related to the strength of crystal‐crystal interactions in the oil phase. It seems likely that when protein is present at the interface, it fixes the adsorbed layer of fat crystals to the cross‐linked protein film at the interface. When this film was sheared, the strength of the crystal‐crystal interactions in the oil phase became important. However, when Tween‐40 was in the aqueous phase instead of the protein, the crystal‐crystal interactions were not relevant, presumably because the Tween‐40 interfacial film simply flowed around the adsorbed crystals