Development of a package-sterilization process for aseptic filling machines: a numerical approach and validation for surface treatment with hydrogen peroxide

Abstract Within the present work a sterilization process by a heated gas mixture that contains hydrogen peroxide (H2O2) is validated by experiments and numerical modeling techniques. The operational parameters that affect the sterilization efficacy are described alongside the two modes of sterilization: gaseous and condensed H2O2. Measurements with a previously developed H2O2 gas sensor are carried out to validate the applied H2O2 gas concentration during sterilization. We performed microbiological tests at different H2O2 gas concentrations by applying an end-point method to carrier strips, which contain different inoculation loads of Geobacillus stearothermophilus spores. The analysis of the sterilization process of a pharmaceutical glass vial is performed by numerical modeling. The numerical model combines heat- and advection-diffusion mass transfer with vapor-pressure equations to predict the location of condensate formation and the concentration of H2O2 at the packaging surfaces by changing the gas temperature. For a sterilization process of 0.7 s, a H2O2 gas concentration above 4% v/v is required to reach a log-count reduction above six. The numerical results showed the location of H2O2 condensate formation, which decreases with increasing sterilant-gas temperature. The model can be transferred to different gas nozzle- and packaging geometries to assure the absence of H2O2 residues.