Growth, activity and mean doubling time (T d ) of five Bifidobacterium species in the presence of four types of prebiotics, and concentrations of acetic and lactic acids were determinted during fermentation and after 4 weeks of refrigerated storage. The T d was lowest for B. animalis with raftilose and inulin. Retention of viability of bifidobacteria was greatest with hi-amylose corn starch (hi-maize). The average pH of skim milk at the end of 4 wks storage averaged 4.34 (for B. animalis with raftilose) to 4.07 (for B. longum with inulin). The highest levels of acetic acid and lactic acid were produced by B. pseudolongum with lactulose and B. infantis with lactulose, respectively.

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 °C, 4 °C, and 20 °C. Cell counts were enumerated using MRS-NNLP agar at 37 °C 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 20 °C showed the greatest decline in the viability of bifidobacteria, whereas that at -18 °C showed the least decrease.

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