Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 15, 2008
Publication Date: N/A
Technical Abstract: At the heart of the skim milk system are the colloidal casein–calcium–transport complexes termed the casein micelles. The application of physical chemical techniques such as light, neutron, and X-ray scattering and electron microscopy, has yielded a wealth of experimental data concerning the structure of the casein micelle. Despite extensive research, the molecular interactions involved in the casein micelles remain elusive and controversial. In this work, we investigate casein precipitated by pressurized carbon dioxide (CO2) using TEM, SEM and AFM techniques. Native casein micelles prepared from skim milk and calcium caseinate derived from acid casein precipitation were also studied in comparison. Microscopic images showed significant difference in average particle sizes and distribution among various caseins. To elucidate the mechanism of the formation of CO2-induced casein aggregates, experiments at various concentrations of NaCl were also conducted to examine pH and ionic effects. Results showed that inter-molecular protein-protein interactions on two distinctive levels may be the driving forces for the dissociation of casein micelles by pressurized CO2, leading to the formation of casein aggregates. We speculate that electrostatic interactions among caseins may be the dominating force though hydrophobic interactions are also important in this dissociation-aggregation process. This work not only provides insights on the nature of molecular forces attributable to casein aggregates formed by pressurized CO2 but sheds light on the role of caseins in the formation and stabilization of the casein micelles.