Viability of two freeze-dried strains of Bifidobacterium and of commercial preparations at various temperatures during prolonged storage

Viability of bifidobacteria in freeze-dried probiotic products at various temperatures during prolonged storage was assessed. Bifidobacterium longum 1941 and B. longum 536 were freeze-dried and capsules were manufactured. Five commercial probiotic capsule products were also tested. The capsules were stored at 18 18degreesC, 4degreesC, and 20degreesC. Cell counts were enumerated using MRS-NNLP agar at 37degreesC for 72 h under anaerobic conditions at 0, 1, 2, 5, and 8 mo (commercial capsules) and at 0, 1, 2, 5, 8, 11, 14, 17, and 20 mo (laboratory capsules). Storage at 20degreesC showed the greatest decline in the viability of bifidobacteria, whereas that at -18degreesC showed the least decrease.