The formation of the pH gradient in

The formation of the pH gradient in beads was dependent on the bead size and the exposure time of the beads in simulated gastric juice.

When placed into simulated gastric juice,

free cells were exposed to the extreme low pH immediately,

while the cells in the core and the surface of the beads were subjected to a different pH.

In this study,

about 5×106 CFU / ml of bifidobacterial cells would be alive,

when 1×109 CFU / ml of cells in beads were kept in simulated gastric juice (pH 2.5) for 120 min. Generally,

the average time to empty half of the stomach contents is 90 min,

and the pH of the human stomach is 1–3 (Giannella et al., 1972)