Effect of storage on shelf life and viability of freeze-dried and microencapsulated Lactobacillus acidophilus and Bifidobacterium infantis cultures

Lactobacillus acidophilus CSCC 2409 and Bifidobacterium infantis CSCC 1912 were encapsulated with calcium alginate or whey protein, and the effect of freeze drying on their viability during storage and in yogurt was studied. The results showed that freeze-dried storage caused a substantial loss of viability in the free cells over an eight-week storage period at -20degreesC. The losses were, however, lower (p<0.05) for calcium alginate encapsulated and whey protein encapsulated cells. When the freeze-dried free and encapsulated Lb. acidophilus CSCC 2409 and B. infantis CSCC 1912 were incorporated into yogurt and stored at 4degreesC over a four-week period, the number of free cells of Lb. acidophilus CSCC 2409 and B. infantis CSCC 1912 were reduced by 2.7 and 3.7 log numbers, respectively, while the calcium alginate encapsulated Lb. acidophilus CSCC 2409 and B. infantis CSCC 1912 cells lost 1.7 and 2.3 log numbers, respectively, and whey protein encapsulated Lb. acidophilus CSCC 2409 and B. infantis CSCC 1912 lost 2.0 and 2.4 log numbers, respectively. The results showed that calcium-induced alginate encapsulation offered better protection to the viability of bacterial cells than whey protein encapsulation during freeze-dried storage and in yogurt. This study also showed that freeze-dried Lb. acidophilus and B. infantis cultures survived better in yogurt at 4degreesC than when stored as freeze-dried cultures at -20degreesC; that indicates that yogurt is a better vehicle as compared to freeze-dried cultures in delivering large numbers of viable cells to consumers.