DSC and protein-based time-temperature integrators: Case study of alpha-amylase stabilized by polyols and/or sugar

Differential scanning calorimetry (DSC) was used as a tool for rapid assay of the thermostability of two Bacillus sp. alpha-amylases and horseradish peroxidase as a function of the concentration of glycerol, sorbitol, and sucrose. In this screening study, the DSC peak temperature proved to be a good measure of protein thermostability. By means of isothermal heating experiments, the kinetics of heat decay of B. amyloliquefaciens alpha-amylase were studied by following the course of the DSC peak area (heat exchange (DeltaH/wt)) as a function of time. The high stability of this enzyme in the presence of polyolic alcohols or carbohydrates allowed working at temperatures as high as 127 degrees C. The results of this study can have particular relevance with regard to research on and development of protein-based time-temperature integrators (TTls) for evaluating heat pasteurization or sterilization treatments of foods or pharmaceutical products. The use of the DSC peak area (DeltaH.wt) as TTI-response was validated in experiments with a time-variable temperature profile. Finally, it was shown how the results of such non-isothermal experiments can even be used for (re-) estimation of the protein decay kinetic parameters (k, E(A)). (c) 1994 John Wiley & Sons, Inc.