kappa-carrageenan interaction with bovine and caprine caseins as shown by sedimentation and nuclear magnetic resonance spectroscopic techniques

The solubility and hydration characteristics of kappa-carrageenan-casein sy stems from bovine and caprine milk with incorporated salt (NaCl) were deter mined by means of sedimentation and O-17 nuclear magnetic resonance (NMR) e xperiments. Relative salt interaction parameters for both caseins alone and caseins in mixtures with kappa-carrageenan were assessed by nonlinear regr ession analysis from the characteristics of solubilization of the systems. The kappa-carrageenan-casein interactions appear to depend largely on the r atios of kappa- to alpha(s1)-casein and possibly alpha(s2)-casein. Second v irial coefficients (B-0 values) and hydration products derived from O-17 NM R data suggest that while soluble at high salt, the caprine casein mixtures exhibit strong interactions, whereas the bovine counterparts do not. At lo wer salt concentrations the solubility data and the O-17 NMR data are in ag reement. Thus, a structural dependence upon protein components in salt-cont aining kappa-carrageenan-casein solutions from bovine and caprine milk has been demonstrated.