Spray Drying, Freeze Drying, or Freezing of Three Different Lactic Acid Bacteria Species

Lactococcus lactis ssp. cremoris D11, Lactobacillus casei ssp. pseudo-plantarum UL137, and Streptococcus thermophilus CH3TH, were separately frozen, freeze dried or spray dried, and tested for survival and lactic acid production before and after processing. Virtually all cells survived freezing. Of the survivors, 60 to 70% survived the dehydration step of freeze drying. In contrast to freezing and freeze drying, spray drying caused considerable delay in lactic acid production and reduction in survival. After spray drying, survival was greatest for S. thermophilus and lowest for Lc. cremoris.     

Survival of Brevibacterium linens (ATCC 9174) after Spray Drying, Freeze Drying, or Freezing

The objectives of this work were to: (1) contrast spray drying, freeze drying and freezing for large-scale preservation of B. linens, (2) determine the thermal resistance curves, and (3) measure the storage stability. When B. linens was freeze-dried and frozen in feed suspensions containing 3% (w/v) cell paste and 25% (w/w) total solids, survival was 100%. During spray drying, lethal thermal injury was the main cause of loss of viability. Accordingly, by extrapolation, 100% viability would be possible at an outlet-air temperature of 57°C. Spray-dried and freeze-dried cells were stable during storage at 4°C in the absence of oxygen and moisture.