Calorimetric Studies on Dry Pectinlyase Préparations: Impact of Glass Transition on Inactivation Kinetics

The glass transition température (Tg) of a dry ultrafiltrated pectinlyase (PL) préparation decreased from 56 to 24 °C when water content increased to 20%. The thermal transition temperature (7p) for protein denaturation decreased greatly up to 40% moisture; above 40% no further changes in Tp were observed. In the glassy state, a lag period of approximately 7 days with no PL activity loss was observed; after that, PL activity was lost. Above Tg, the rates of PL inactivation greatly increased. In the glassy state Ea was 16.6 kJ/mol. When the system was in a higher mobility state (rubbery), Ea increased to 66.5 kJ/mol.