Accurate determination of thermal resistance of microorganisms
in liquid egg is important for designing thermal
processes to ensure food safety and shelf-life. Pflug (2003)
has reported procedures and methods that can be used to
minimize the effect of potential test-system errors on microbial
resistance data, and also listed heating and cooling lagcorrection
values for several commonly-used testing
systems including glass TDT tubes and aluminium TDT
tubes. Pflug (2003) showed that glass TDT tubes have
longer temperature-response times, equivalent-times, and
heating times for test units to reach 0.1 F below test temperature
than aluminium TDT tubes when 1 ml of water is
heated in steam or oil to 121.1 C. Therefore a new design
of TDT device based on an aluminium TDT tube should be
interesting to researchers in this area.
When using a surrogate microorganism for process validation,
its thermal tolerance must be equivalent to or
higher than the targeted pathogen. Its use, as opposed
to using an actual pathogen, derives from the need to prevent
the introduction of harmful organisms into the production
facility. The safety and liability resulting from
mishandling a pathogen to worker safety, food safety
and safety of the processing environment could be devastating.
Therefore, the use of surrogates by processing
companies is of great value to validate a thermal process
(FDA, 2000).