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Enzymatic pressure temperature time indicator


Key words pressure temperature time indicator, pTTI, uniformity, pressure, temperature, enzyme inactivation, enzyme activity, amylase, Bacillus, process impact, non-uniformity, heterogeneity, high pressure processing, high hydrostatic pressure, pasteurization, sterilization, heat transfer, adiabatic heating, kinetics, enzymatic sensor
Latest version 2010/12/13
Completed by KU Leuven LFT

How does it work?

Primary objective A pressure temperature time indicator (pTTI) allows detection of temperature non-uniformity in a high-pressure vessel, during high pressure processing (stabilizing operation). This temperature non-uniformity is caused by heat transfer of adiabatic heat during compression. This temperature non-uniformity can result in process impact non-uniformity. This tool allows detection of the point of lowest temperature or even lowest impact, in case the temperature dependence of its kinetics match that of the target attributes (quality or safety). (3,8)
Working principle The enzyme shows a pressure and temperature sensitive inactivation. The isolated enzyme is positioned at different locations in the high pressure vessel. After the process, the residual activity of the enzyme is read out. The lower the residual activity, the higher the temperature at the given location.

Temperature and pressure dependence of the pTTI can be adapted to the window of processing conditions by

  • selecting a different enzyme (for instance, enzymes originating from thermophilic micro-organisms are useful for detection of temperature non-uniformity in HP/HT conditions)
  • selecting different solvent conditions for the enzyme = solvent engineering (pH, additives, type of buffer …)

Example: alpha-amylase from Bacillus species (1,5-7)

Additional effects Once the non-uniformity of the vessel is determined, process parameters can be changed to minimize this non-uniformity. The pTTI can be used to validate this optimization.
Important process parameters pressure, temperature, time
Important product parameters none, as the integrator is isolated from the product

What can it be used for?

Products Packaged foods (meat, fish, shellfish, chicken, juices, ...)
Operations Pasteurisation through high pressure processing
Solutions for short comings Process non-uniformity in high pressure processing

What can it NOT be used for?

Products Non-packed liquid products
Operations High pressure thermal sterilisation (batch). No enzymatic pTTIs have been described yet that can be used under conditions of high pressure, high temperature (HPHT) processing.
Other limitations To asses process impact, the kinetics of the pTTI should match that of the target attribute (safety or quality)
Risks or hazards Integrators should be isolated. Food labelled with the integrator should not be used for consumption.


Maturity Lab scale
Modularity /Implementation This tool can be placed between packed foods or in a labeled (not to be sold) packed food.
Consumer aspects No information. No problems expected.
Legal aspects This tool offers a solution for legislation with regard to process control, as direct temperature measurement is difficult in high pressure vessels.
Environmental aspects No information. No problems expected.

Further Information

Institutes KU Leuven LFT
References 1. Grauwet, T. et al. (2009) Investigating the Potential of Bacillus subtilis alpha-amylase as a Pressure-Temperature-Time Indicator for High Hydrostatic Pressure Pasteurization Processes. Biotechnology Progress 25, 1184-1193.

2. Rauh, C. et al. (2009) Uniformity of enzyme inactivation in a short-time high-pressure process. Journal of Food Engineering 91, 154-163.

3. Hartmann, C. & Delgado, A. (2003) The influence of transport phenomena during high-pressure processing of packed food on the uniformity of enzyme inactivation. Biotechnology and Bioengineering 82, 725-735.

4. Hartmann, C. & Delgado, A. (2002) Numerical simulation of convective and diffusive transport effects on a high-pressure-induced inactivation process. Biotechnology and Bioengineering 79, 94-104.

5. Grauwet, T. et al. (2010) Protein-based indicator system for detection of temperature differences in high pressure high temperature processing. Food Research International 43, 862-871.

6. Grauwet, T. et al. (2010) Mapping temperature uniformity in industrial scale HP equipment using enzymatic pressure-temperature-time indicators. Journal of Food Engineering 98, 93-102.

7. Grauwet, T. et al. (2010) Solvent engineering as a tool in enzymatic indicator development for mild high pressure pasteurization processing. Journal of Food Engineering 97, 301-310.

8. Van der Plancken, I. et al. (2008) Impact evaluation of high pressure treatment on foods: considerations on the development of pressure-temperature-time integrators (pTTIs). Trends in Food Science & Technology 19, 337-348.

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Created by LiesbethV on 28 January 2011, at 02:01