THE EFFICACY OF A BOILING WATER BLANCH ON THE INACTIVATION OF LISTERIA MONOCYTOGENES IN DICED CELERY
THE EFFICACY OF A BOILING WATER BLANCH ON THE INACTIVATION OF LISTERIA MONOCYTOGENES IN DICED CELERY
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Date
1990
Authors
Losikoff, Mary Bohrer
Advisor
Westhoff, Dennis C.
Citation
DRUM DOI
Abstract
The effect of a boiling water blanch on the thermal
inactivation of Listeria monocytogenes in raw diced
celery was investigated. L. monocytogenes, Scott A was
heated in Tryptic Soy Broth with 0.6% yeast extract, pH
5.3, at 52, 54, 56, 58, and 59°C. D values were 13.33,
7.75, 1.29, 0.792, and 0.701 min, respectively. A
predicted D value at 60°C = 0.36 min was obtained using
a z value of 5. These thermal inactivation
characteristics were subsequently used to evaluate the
L. monocytogenes was recovered from inoculated (1 X
10^7 cells/g) diced raw celery after heating for 0.25 min
in a laboratory boiling water blanch. Viable cells were
not recovered after 0.5 min of heating.
Heat penetration data for diced raw celery during a
boiling water blanch were obtained in a commercial setting. These data were analyzed by the general method
to determine the cumulative lethality at reference
temperatures of 60°C using a z of 5 and, 70 and 71.7°C
using a z of 10. It was determined that a recommended
process of 2 min at 70 °C was reached in 80 sec during
the blanch. Based on the findings of this study, a
boiling water blanch could be used as part of the
hurdles approach to eliminate L. monocytogenes from raw
diced celery.