Developing and testing novel time-temperature indicators (TTIs) which will help to quantify the "impact" of the thermal processes on food quality and safety is the topic of an ongoing EU project in the AAIR programme. The sensors are essential in the introduction of new technologies which improve safety and quality of heat preserved foods and reduce production costs. Current active tasks include theoretical modelling and the development of microbiological, protein-based and chemical TTIs.
Microbiological TTIs for pasteurisation are being developed based on fungal ascospores and the inactivation temperatures for Talaromyces flavus ascospores (free and immobilised in alginate gels) are in the range 80-90 °C; a mean z-value of 18.4 °C was obtained for the free ascospores.
The work on microbiological TTI's for sterilisation is using both Bacillus stearothermophilus and Clostridium sporogenes strains covering the temperature domain from 110-145 °C. It has been shown that pH and the composition of the inactivation medium has a pronounced effect on the decimal reduction time and to a lesser extent on the z-value.
Both enzymic and non-enzymic proteins are being studied as potential TTI's. The degree of denaturation is analysed using enzyme activity, differential scanning calorimetry and immunochemical response. The thermostability of peroxidase and different bacterial amylases has been studied and systems with different z-values (6-30 °C) applicable in different temperature domains can be generated. The work on chemical TTI's has been initiated by analysing commercially available indicators showing integration properties and the z-values of these chemical indicators are in the range 25-30 °C which makes them useful for quality assessment.
The TTIs under test in this project are full history indicators and quantify the thermal impact of sterilisation or pasteurisation processes in terms of product safety and quality.

For more information:
Contact: Prof. Dr. Ir. M. Hendrickx or Ir. A. Van Loey, Katholieke Universiteit Leuven, Dept. of Food and Microbial Technology, Lab. of Food Technology, Kardinaal Mercierlaan 92, B3001 Heverlee, Belgium, tel. +32-16-220931; Fax: +32-16-293805