Optimization of Dehydration of Lactobacillus salivarius Using Radiant Energy Vacuum

Radiant energy under vacuum (REV) as a rapid dehydration method was employed to dehydrate Lactobacillus salivarius 417 along with different concentrations of skim milk powder as protective medium. Two optimization methods: response surface methodology and random centroid analysis (RCO) were applied and compared to optimize the dehydration parameters for maximum viability—microwave power, absolute pressure in the drying chamber, and protective agent concentration. The study showed that both methods were suitable for the process optimization. Microwave power, concentration of skim milk powder, and absolute pressure had a significant effect on final viability while the speed of sample rotation in vertical axis had no effect (P < 0.05). The result also indicated that a microwave power of <250 W, 10–15% concentration of skim milk powder, and <1 mmHg absolute pressure was needed to achieve viability of equal or greater than 80% in L. salivarius. The RCO-optimized REV process yielded higher viability than the reference freeze drying method and was completed in less than an hour as compared to 64 h for freeze drying.