Effect of Lyophilization on the Mechanical Characteristics of a Large Particle and on the Behavior of Immobilized Bacterial Spores

The mechanical stability of the carrier and the behavior of the sensor element of a time-temperature integrator (TTI) after lyophilization and storage for 60 days at room temperature were studied. The results indicated that particles containing added starch at concentrations from 2 to 12% had good handling characteristics for use as TTI carriers, although mechanical resistance was lower by comparison with freshly prepared particles. Lyophilization reduced the number of viable microorganisms by 17 to 25%, depending on the length of the storage period. Variations were also observed in the count of surviving microorganisms after heating at 121°C for 12 min. These variations, expressed as decimal reductions in the number of microorganisms, might reflect an effect of lyophilization on the thermal resistance of the immobilized spores.