Deamidation Kinetics of Casein Precipitated by Carbon Dioxide Compared with Commercial Caseinates

The authors are with the U.S. Dept. of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 E. Mermaid Lane, Wyndmoor, PA 19038. Direct inquiries to Dr. C.V. Santos. ABSTRACT Casein precipitated by carbon dioxide (CO2-casein), and commercial sodium and calcium caseinates (1% w/v in water) were thermally deamidated at pH 8 for up to 96h at 85, 100, and 1158C. CO2-casein displayed the highest overall extent of deamidation at 100 and 1158C after 32 and 24h, respectively, while there was no difference at 858C. Structural differences between CO2-casein and the commercial caseinates may account for the difference in deamidation. Deamidation kinetics were apparent first-order with respect to concentrations of the amides, asparagine and glutamine. Reaction rate constants and Arrhenius parameters were comparable from regression modeling.