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Title: MACROSTRUCTURE AND VISCOSITY OF AGGREGATING COLLOIDAL CASEIN MICELLES UNDER STRONG SHEARING FORCE

Author
item Konuklar, Gul
item Carriere, Craig
item OTAIGBE, JOSHUA - IOWA STATE UNIV

Submitted to: Biopolymers
Publication Type: Book / Chapter
Publication Acceptance Date: 4/17/2002
Publication Date: 1/1/2003
Citation: KONUKLAR, G., CARRIERE, C.J., OTAIGBE, J. MACROSTRUCTURE AND VISCOSITY OF AGGREGATING COLLOIDAL CASEIN MICELLES UNDER STRONG SHEARING FORCE. E.DICKINSON, T.VAN VLIET, EDITORS. FOOD COLLOIDS,BIOPOLYMERS AND MATERIALS. THE ROYAL SOCIETY OF CHEMISTRY, CAMBRIDGE, UNITED KINGDOM. BOOK CHAPTER. 2003. P. 93-99

Interpretive Summary:

Technical Abstract: Casein particle gels are the main constituents in many classes of soft food colloids. In this study, we examined the stability of casein micelles under strong hydrodynamic forces, and investigated the effect of continuous applied shear on the coagulation properties of rennet-induced milk. At the applied shear rates of 50 and 100 1/s, the recorded viscosities of rennet-induced coagulums at 3600 s were 27 times larger than the rennet-induced coagulums in the absence of shear. The observed macro structure at 20X magnification, indicated larger clusters and a directionality in domain growth for rennet-induced coagulums in the presence of shear flow. However, contrary to standard rennet concentrations, at lower rennet concentrations the system showed shear thinning behavior. Interestingly, as we applied shear rates from 400-1000 1/s to whole milk without rennet, we observed an increase in viscosities from 10-100 Pa.s, 3000 s after cessation of shear flow. The microscopic images of these samples depicted homogenized fat droplets with increased interactions and cross linking of the protein network. Moreover, at applied shear rates of 100 1/s, skim milk reconstituted to a total protein of 5%, 10%, and 15% had shear viscosities of 30, 100, 10**6 Pa.s, respectively, at about 900 s after shear ceased. However, these structures were also shear thinning. The results indicated the possibility of engineering a shear environment to induce aggregation of casein micelles with minimal physical alterations.