Thermal Food Processing

604 Thermal Food Processing: New Technologies and Quality Issues
The main advantage of a time–temperature integrator is its ability to quantify
the integrated impact of the time and the temperature in the target attribute without
the need for any information on the history of the product’s real temperature. 26
In accordance with the given definition, a time–temperature integrator should
fulfill some requirements for its structure, behavior, and use:
1. The integrator should contain a calibrated and resistant sensor element
for the thermal treatment, and it should experience the same evolution
of temperature as the real food.
2. The size of the integrator and its geometry should be similar to the real
food, with the sensor element homogeneously distributed in its interior.
3. The carrier should efficiently retain the sensor element so that losses
do not take place during the sterilization process.
4. The integrator should be incorporated in the product so that it does not
produce distortions during the heat transfer, neither should it modify
the time–temperature profile of the food.
5. The integrator should be cheap, easy, and quick in its preparation, and
easy to analyze and recover.
6. The integrator should be stable and capable of long-term storage without
any loss of functionality.
7. The integrator should be physically resistant enough to support the
heating process without disintegrating.
Besides these requirements, there are some kinetic aspects that an integrator
should satisfy. When the sterilizing value of the process is chosen as a concept
to express the integrated impact of the time and temperature, the TTI should
fulfill the following equation:
( Fz) =
( Fz)
Tref
indicator Tref
(19.1)
That is to say, the lethality reached in the integrator should be similar to the
response of lethality of the factor used as the indicator (microorganism, enzyme,
etc.). It is also easy to understand that a system will work as a TTI if its activation
energy (E a) or the z value is the same or similar to that of the factor considered
to be the indicator.
19.4 CLASSIFICATION OF THE TIME–TEMPERATURE
INTEGRATOR BY CONSIDERING THE SENSOR
ELEMENT
The time–temperature integrators can be divided into the following groups: 26 (1)
chemical systems, (2) physical systems, and (3) biological systems. The biological
systems are further divided into microbiological, enzymatic, and nonenzymatic
systems. In general, the sensor element of the TTI can be introduced in a carrier
TTI