Transglutaminaz enziminin kazeinomakropeptidin emülsiyon özelliklerine etkisi

Caseinomacropeptide (CMP) is a polypeptide with biological activity which is released from casein during cheese production. In recent years, CMP is investigated because of its physiological, nutritional and technological functions. In the present study, effect of transglutaminase (Tgase) on emulsifying properties of CMP was investigated. In addition, emulsifying properties of enzyme treated and untreated CMP were compared with those of Na-caseinate and whey protein isolate. Firstly, influencing factors on emulsifying properties of CMP were studied. Emulsions were formed with sunflower oil and CMP solution at different concentration (0.25-5%), ionic strenght (0-500 mM NaCl) and pH (2.5-10). Emulsion activity index (EAI), emulsion stability index (ESI) and creaming index of emulsions were measured. No significant effect of concentration of CMP was observed on emulsion stability. Increase in CMP concentration caused decrease in emulsion activity and creaming index values. Change in ionic strength did not affect emulsion activity and creaming index values. But it increased emulsion stability at 10 mM NaCl, while higher salt concentrations negatively affected stability. Emulsion activity and stability of CMP were found to show a minimum around pH 4.0. In the second part of the study, effect of transglutaminase enzyme on emulsifying properties of CMP was studied at concentration of 0.5%, ionic strength of 10 mM NaCl and pH 3.5, 4.5 and 6.5. CMP solutions were treated with 1, 5 and 20 U Tgase/g CMP and then heat treated at 80°C for enzyme inactivation. EAI of CMP was increased as the activity of the enzyme was incresed. ESI of CMP was highest at the highest enzyme concentration at pH of 3.5 and 4.5, while there was no effect of enzyme on ESI at pH 6.5. Creaming index of CMP decreased with enzyme treatment at pH 3.5 and 4.5. To determine the effect of inactivation heat treatment on the emulsion properties of CMP, CMP emulsions were prepared with or without enzyme (20 U Tgase/g CMP) and heat treatments. Both enzyme and heat treatment were found to increase the emulsion activity and stability of CMP. CMP was found to have similar emulsion activity and stability with Na-caseinate and whey protein isolate. Enzyme treatment of CMP with 20 U Tgase/g CMP significantly improved emulsion properties.