Effect of Transglutaminase Addition on the Physicochemical Properties of Sodium Caseinate and Whey Proteins

In this study, several factors were analyzed in an effort to determine the effects of transglutaminase (TGase) treatment on sodium caseinate (NaCN), ${\alpha}--lactalbumin$ (${\alpha}-La$), and ${\beta}-lactoglobulin$ (${\beta}-Lg$) polymerization reactions. The results of SDSPAGE showed that NaCN was slightly hydrolyzed to molecular weights of 50-400 kDa according to activation time. ${\alpha}-La$ formed high-molecular polymers of 30-300 kDa, whereas ${\beta}-Lg$ remained almost completely unhydrolyzed. Melting temperatures of NaCN, ${\alpha}-La$ with and without TGase were all in the range of $100{\pm}10^{\circ}C$ under the endothermic curve, and the melting temperature of ${\beta}-Lg$ with TGase was lower than that with TGase. When the proteins were incubated for 3 h with TGase, the micrographic structures showed a small quantity of sediment and broad layers. The final ${\alpha}-La$ residues remained at a level of 21.38%, and the TGase-treated ${\alpha}-La$ was confirmed to have undergone a profound loss of mass, to 18.25%. The DPPH-radical scavenging activity of NaCN and ${\beta}-Lg$ with TGase treatment was higher than that observed in the untreated sample, while those of ${\alpha}-La$ increased with concentration.