Steffen Reisert

Calorimetric Gas Sensors for Hydrogen Peroxide Monitoring in Aseptic Food Processes

For the sterilisation of aseptic food packages it is taken advantage of the microbicidal properties of hydrogen peroxide (H2O2). Especially, when applied in vapour phase, it has shown high potential of microbial inactivation. In addition, it offers a high environmental compatibility compared to other chemical sterilisation agents, as it decomposes into oxygen and water, respectively. Due to a lack in sensory detection possibilities, a continuous monitoring of the H2O2 concentration was recently not available. Instead, the sterilisation efficacy is validated using microbiological tests. However, progresses in the development of calorimetric gas sensors during the last 7 years have made it possible to monitor the H2O2 concentration during operation. This chapter deals with the fundamentals of calorimetric gas sensing with special focus on the detection of gaseous hydrogen peroxide. A sensor principle based on a calorimetric differential set-up is described. Special emphasis is given to the sensor design with respect to the operational requirements under field conditions. The state-of-the-art regarding a sensor set-up for the on-line monitoring and secondly, a miniaturised sensor for in-line monitoring are summarised. Furthermore, alternative detection methods and a novel multi-sensor system for the characterisation of aseptic sterilisation processes are described.

Controlling aseptic sterilization processes by means of a multi-sensor system

In this work, a metal-oxide-semiconductor gas sensor has been investigated on sensitivity towards hydrogen peroxide and other influencing factors of the aseptic sterilization process employing hydrogen peroxide vapor. Microbiological reduction tests of Bacillus atrophaeus spores have been carried out in order to characterize the influencing factors of the sterilization by hydrogen peroxide vapor. A parallelism between the sensor behavior and the results of microbiological tests was drawn.

Characterisation of aseptic sterilisation processes using an electronic nose

The present work describes the development of a multi–sensor system for the evaluation of aseptic sterilisation processes employing hydrogen peroxide vapour by means of an electronic nose. Microbiological count reduction tests with Bacillus atrophaeus spores have been carried out in order to characterise influencing factors of the sterilisation by hydrogen peroxide vapour, namely the hydrogen peroxide concentration, humidity, gas temperature and gas flow. In parallel, three different types of gas sensors have been investigated on sensitivity towards the same parameters. A correlation between the results of the microbiological tests and the response of the gas sensors is drawn.