The estimate of Salmonella cells surviving
pasteurization (L) described aslog10( p), where
p is the probability of an individual Salmonella
cell surviving pasteurization, was used with
information collected from 31 egg processing
plants for pasteurization times and temperatures
used in processing egg products (see pp.
54–59 in Annex G of the full-length risk assessment
report at http:==www.fsis.usda.gov=PDF=
SE_Risk_Assess_Annex_G_Oct2005.pdf.). Predicted
values of p for given temperatures and
times were made using lethality models developed
by FSIS from data generated by Froning
et al. (2002). Because, in practice, pasteurization
of liquid egg products is done by passing
product through heated pipes, we needed to
account for variability in the velocity of individual
egg product particles as they moved
through the pipe. We assumed a laminar flow
of liquid egg products through the pipes. Distribution
of particle velocity was then estimated
by assuming the amount of pasteurized product
proportional to the cross section circumference
of the pipe and the particle velocity. In particular,
particle velocity was assumed proportional
to 1x2, where x is the relative distance from
the center of the pipe (x¼1 means that the particle
is at the interior edge of the pipe). Because
current USDA regulations are specified for
fastest particle speeds, for the calculations for
net lethalities, the maximum velocity was assumed
known (an input variable).