Thermal Food Processing

598 Thermal Food Processing: New Technologies and Quality Issues
19.6.3 Recovering of Sensor Element and Calculating
Impact of the Process ............................................................. 612
19.7 Application Examples of TTI .............................................................. 614
19.8 Conclusions .......................................................................................... 616
References ........................................................................................................ 617
19.1 INTRODUCTION
Consumer demand for new and higher-quality foods has forced the food industry
to develop new sterilization and pasteurization systems and to optimize current
practices so that such demands can be satisfied without any negative impact on
food safety. One of the main areas of current investigation is related to the use
of heat in food preservation; the main objective is the application of the minimum
heat levels to destroy or inhibit the development of the pathogen and spoiling
microorganisms and to provide food with a longer shelf life. Technological
developments such as treatment with high temperatures for short times (HTST)
(or ultrahigh temperature (UHT)) and the aseptic processing of food containing
particles are very interesting because of the potential advantages that they offer
from the point of view of nutritive and organoleptic food quality. With the
objective of guaranteeing the microbiological safety of food preserved by heat,
a strict evaluation of the thermal process is necessary. However, the conventional
validation methods of these preservation processes are not always appropriate
due to the way in which the food is produced and thermally processed. The
time–temperature integrators (TTIs) offer an alternative to the thermocouples and
the conventional microbiological methods used to quantify the impact of thermal
treatment on the microorganisms and other food components, such as vitamins
or enzymes. In this chapter a historical perspective is given on the systems used
in the evaluation of the thermal processes, and the development and use of TTI
as a tool for ensuring the safety of thermally processed foods is described.
19.2 CALCULATION AND EVALUATION
OF STERILIZATION PROCESSES
The thermal treatment of foods is one of the oldest and most used industrial
methods to prolong the shelf life of foodstuffs. Today, its use as a preservation
technology in its different applications represents a very significant percentage
of all processed or manufactured foods. Apart from the heating system used and
the way in which the heat is generated, an evaluation of the impact of the heat
on the safety (inactivation of microorganisms and analysis of risks) and on the
quality (nutritive value and acceptability for the consumer) is essential. Although
there is no universal model system to predict the exact number of surviving spores
after thermal treatment, the impact of the thermal processes has traditionally been
evaluated in four different ways: (1) the method in situ, (2) the physicomathematics
approach, (3) the inoculated experimental packs, and (4) the use
of time–temperature integrators. Traditionally, the first three methods have