PROTECTIVE ROLE OF TREHALOSE ON THERMAL-STABILITY OF LACTASE IN RELATION TO ITS GLASS AND CRYSTAL FORMING PROPERTIES AND EFFECT OF DELAYINGCRYSTALLIZATION

Thermal inactivation of beta-galactosidase was investigated in dried m atrices of poly (vinyl) pyrrolidone (PVP), maltodextrin and trehalose. Significant lactase inactivation was observed in the polymeric matric es kept well below their glass transition temperature (T-g). The stabi lity of the enzyme in the anhydrous glassy matrices of maltodextrin an d PVPs heated at 70 degrees C was directly related to their T-g; i.e. systems with higher glass transition temperature afforded better therm al protection of lactase. However, the stability of lactase in the hea ted trehalose matrix deviated from this behaviour since enzyme stabili ty was higher than expected on the basis of the results obtained with polymeric matrices. In systems in which the trehalose matrix was rehum idified to conditions which allowed a high proportion of trehalose to crystallize, the enzyme was rapidly inactivated upon heating. Addition of maltodextrin to trehalose matrix provided enhanced protection to t he enzyme, and this was probably due to delayed trehalose crystal form ation.