Enzyme inactivation kinetics: Coupled effects of temperature and moisture content

Enzymes are often dried for stability reasons and to facilitate handling. However, they are often susceptible to inactivation during drying. It is generally known that temperature and moisturecontent influence the enzymeinactivation kinetics. However, the coupledeffect of both variables on enzymeinactivation over a broad temperature–moisturecontent range is still not well understood. Therefore, the inactivation of ß-galactosidase in maltodextrin matrix is investigated using a newly developed method. An improved kinetic modelling approach is introduced, to predict the inactivation over a large range of temperature–moisture values. The model assumes a two-step inactivation mechanism involving reversible unfolding and irreversible inactivation. The model is able to describe the inactivation kinetics of ß-galactosidase accurately, showing the temperature-dependent kinetic transition from reversible unfolding to irreversible inactivation limited. Application of this approach can provide immediate understanding of the effect of processing on enzymeinactivation and indicates the processes’ critical points, which offers the possibility for optimisation.