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Title: MACROSTRUCTURE AND VISCOSITY OF AGGREGATING COLLOIDAL CASEIN MICELLES UNDER SHEAR

Author
item Byars, Jeffrey
item KONUKLAR, G - ABBOTT LABORATORIES
item Carriere, Craig
item OTAIGBE, J - IOWA STATE UNIVERSITY

Submitted to: Annual Meeting of the Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: 7/16/2004
Publication Date: 7/16/2004
Citation: Byars, J.A., Konuklar, G., Carriere, C.J., Otaigbe, J. 2004. Macrostructure and viscosity of aggregating colloidal casein micelles under shear. (Abstract) Annual Meeting of the Institute of Food Technologists. Paper No. 99C-7.

Interpretive Summary:

Technical Abstract: Applying shear to solutions is known to align and orient the systems in the direction of flow, resulting in increased molecular interaction. However, despite its industrial importance, there is still very little experimental information on particle-particle interactions in colloidal milk suspensions in the presence of applied shear fields. This work studies the effect of applied shear on the rheological properties and macrostructure of rennet-induced milk coagulation. A Rheometrics ARES controlled-strain rheometer with a Couette cell was used to measure the viscosity of skim milk during rennet-induced coagulation. A Cambridge Shearing Stage CSS450 connected to a microscope was used to visualize the orientation during shearing. As the shear rate was increased from 6×10-5 s-1 to 6×10-4 s-1, the lag time before rapid viscosity growth decreased, and the rate of viscosity growth during coagulation increased. Measurements of the linear viscoelastic properties of the coagula showed that the higher applied shear rates formed stronger gels more quickly than the lower rates. Experiments in the Cambridge Shearing Stage confirmed the importance of applied shear, by showing larger domain sizes for coagulation under shear. These results demonstrate that applied shear can result in a faster build-up of structure during rennet-induced coagulation of skim milk.