Polimerização de proteínas do soro de leite por transglutaminase e propriedades físicas de iogurte elaborado após tratamento enzimático

Abstract

The aim of this study was to assess the optimal conditions for transglutaminase cross-linking of whey proteins from reconstituted Concentrated whey solutions, in regards to heat treatment effects on transglutaminase kinetics and protein polymerization effects on gel Temperature. The effects of this enzymatic assay on physical properties of yogurt were also determined. The polymerization of whey proteins by the effect of transglutaminase activities was determined by the consistency index obtained from rheological measurements in reconstituted concentrated whey solutions (50 %pv-1) at different temperature-time treatments and Enzyme concentrations. The effects of heat treatment on whey proteins flow behavior before the reaction were determined by using the Power Law Model. The gelation temperature and turbidity of whey solutions were Examined after treatment for 4#24 h at different pH values (6.0; 7.0; 8.0). Furthermore, the physical properties yogurt treated with transglutaminase (0.5 Ug-1 protein) were studied. It was determined that the reaction between â-lactoglobulin, á- lactalbumin and transglutaminase was improved when carried out at 36 °C for 4 hours, at the optimum enzyme concentration of 50 Ug-1. The samples submitted to this treatment showed a pseudoplastic behavior and had a higher consistency index. Heat treatment of solutions at 85, 90 e 95 °C prior to enzyme addiction seemed to improve the reaction; the consistency index was higher (p<0.05) on solutions submitted to this procedure. After the enzyme activity, the gelation temperatures of whey solutions were lower than in control samples. This reduction was intensified by increasing the time of reaction. The production of yogurt with previous enzymatic treatment of milk and whey conferred less syneresis and higher gel firmness in texture analysis. These results proof that transglutaminase could be applied in order to compensate for the changes on physical properties on yoghurt caused by the addition of milk whey.