Abstract

Combined Calorimetric Gas- and Spore-based Biosensor for Aseptic Food Processing

Michael Schöning, Director of Institute of Nano- and Biotechnologies (INB), Aachen University of Applied Sciences

Gaseous H₂O₂ represents one of the most used sterilization agents in aseptic food processing. To validate this sterilization method under investigation, robust spores that are resistant against this sterilant are first exposed. Afterwards, the logarithmic kill rate (i.e., how many survived from them) is determined by time-consuming (48-72 h) and tedious microbiological count-plating methods (e.g., count reduction test, end point test). A novel sensing method is introduced, consisting of a spore-based biosensor, which is combined with a calorimetric H₂O₂ sensor onto a single chip to evaluate both the viability of the spores and to determine the gaseous H₂O₂ concentration. The calorimetric gas sensor responds to different concentrations of gaseous H₂O₂ via change of its initial resistance, whereas the spore-based biosensor monitors the spore degradation, depending on the H₂O₂ concentration detecting the impedance variation. Three different strains of spores were investigated with regard to the H₂O₂ durability, namely B. atrophaeus DSM 675, B. subtilis DSM 402 and G. stearothermophilus DSM 5934. The two sensor types were combined as sensor array enabling a considerably more specific multi-parameter experience in aseptic filling machines in comparison to isolated microbiological state-of-the-art- or hydrogen peroxide methods.