Submitted to: American Chemical Society Symposium Series
Publication Type: Proceedings
Publication Acceptance Date: 11/6/2005
Publication Date: 7/10/2006
Citation: Farrell, H.M., Gutierrez, A. 2006. K-carrageenan interaction with bovine and caprine caseins:as shown by sedimentation and NMR spectroscopic techniques: Implication of surface charge by a homologous three-dimension model for as2-casein:K-carregeenan-casein interaction American Chemical Society Book Symposium Series. 935:93-114.
Technical Abstract: The solubility and hydration characteristics of kappa-carrageenan-casein systems from bovine and caprine milk with incorporated salt (NaCl) were determined by means of sedimentation and 17O nuclear magnetic resonance (NMR) experiments. Relative salt interaction parameters both for caseins alone and in mixtures with kappa carrageenan were assessed by nonlinear regression analysis from the characteristics of solubilization of the systems. The kappa-carrageenan-casein interactions appear to depend largely on the ratios of kappa- to alpha-s1-casein and surprisingly to alpha-s2-casein. Second virial coefficients (BO values) and hydration products derived from 17O NMR data suggest that while soluble at high salt, the caprine casein mixtures exhibit strong interactions, whereas the bovine counterparts do not. At lower salt concentrations the solubility data and the 17O NMR data are in agreement. Thus, a structural dependence upon protein components in salt containing kappa carrageenan-casein solutions from bovine and caprine milk has been demonstrated. The evidence suggested a role for alpha-s2-casein in the interactions observed. A homologous three-dimensional model for alpha-s2-casein was developed to test this hypothesis. The model was produced by the use of a template model derived from a crystal structure of a human chloride intracellular channel protein (CLIC-1) and demonstrates a large unique positively charged surface potential for interactions with kappa-carrageenan.