Thermal Food Processing

616 Thermal Food Processing: New Technologies and Quality Issues
central part and the corners of each crate or within jars. These data allowed an
efficient establishment of the variability of inactivation within the product, the
coldest spot of each crate, and the coldest spot of the whole retort.
19.8 CONCLUSIONS
Thermal processing of food remains one of the most widely used methods of
food preservation. Consumer pressure for more convenient and nutritional foods
and the need of saving energy in the industry has been the engine driving the
development of new heating and filling systems (heat exchangers, heaters, and
aseptic processing). The main inconvenience that arises with the development of
these new heating technologies for low-acid particulated foods is the difficulty
to establish a sterilization process that ensures food safety against pathogenic
organisms, e.g., C. botulinum. Time–temperature integrators can help in developing
safe sterilization or pasteurization processes and are essential for their
validation. Those systems allow a fast, easy, and correct quantification of the
thermal processes’ impacts in terms of food safety without knowing the actual
temperature history of the product. Time–temperature integrators (chemical,
enzymatic, and microbiological) have also demonstrated their ability to validate
processes that are carried out in conventional still retorts. In those cases, their
usages overcome the need of performing heavy and expensive inoculated experimental
packs. Nevertheless, a good knowledge of the heat resistance of the sensor
element under isothermal and nonisothermal conditions is required, and a study
to assess the mechanical properties of the carrier is advisable in order to ensure
that the TTI behaves as the real food under the same treatment conditions.
NOMENCLATURE
AW Water activity
DT Decimal reduction coefficient at temperature T
Ea Activation energy
Fo Treatment time at 121.1°C needed to reach a preestablished
number of decimal reductions in a microbial population
with z = 10°C
FT, CT Time at a given reference temperature that produces the same
reduction in the thermolabile element (microorganism or chemical)
during the temperature evolution that the food undergoes
F z
Tref
Treatment time at reference temperature needed to reach a
preestablished number of decimal reductions in a microbial
population with a particular z value
kT First-order reaction constant at temperature T
TTI Time–temperature integrator
z Inverse negative of the slope of the thermal destruction curve