
70
ssf for foods and beverages
the pores and uptake by the micro organ ism. However, due to the dif-
ferent ways in which the system was visualized, the equations appear
differently. e equation used by Smits et al. (1999) to describe the O
2
balance within the bed is relatively simple:
∂
=
∂
−
C
D
C
ro
b
O
O
O
2
2
2
2
, (3.1)
where t is the time,
b
the concentration of O
2
per unit volume of the
bed, z the vertical coordinate, and ro
2
is the rate of O
2
uptake by the
micro organ ism (Smits et al., 1999). e first term on the right- hand
side describes the diffusion of O
2
within the pores, the diffusivity
being an effective diffusivity that accounts for ...