AimsTo investigate the influence of surface hydrophobicity of carrier material (CM) and bacterial spores of Bacillus subtilis SA 22 and Bacillus atrophaeus (DSM 675) on spore inactivation with condensing hydrogen peroxide (H2O2) gas. Methods and ResultsSurface hydrophobicity of bacterial spores and CM was determined by means of contact angle measurement. Spores of B. subtilis showed water contact angles of 90 degrees, spores of B. atrophaeus showed water contact angles of 42 degrees. Above that, a resistance test against liquid H2O2 at room temperature was conducted with resulting DH2O2 values of 101s (B. subtilis) and 906s (B. atrophaeus). The spores were deposited on CMs of different wettability (water contact angles of 115-30 degrees). The spores were applied either individually or as an 1:1 mixture of both spore species. Exposure of biological indicators (BI) with 5200ppm of gaseous H2O2 at 70 degrees C treatment temperature for defined times up to 10s led to inactivation kinetics. Surfaces with high hydrophobicity showed faster spore inactivation than surfaces with lower hydrophobicity for single-spore species. Regarding the mixed BI, better survival of hydrophobic spores was expected. However, this effect can only be seen as a slight trend and is not significant after 10s. ConclusionsSurface hydrophobicity of CMs does influence the decontamination with gaseous, condensing H2O2. However, surface hydrophobicity of spores in a mixed population does only have a small influence on inactivation results. Significance and Impact of the StudyThe intensity of spore inactivation depends more on other factors than on the wettability of the bacterial spores. However, hydrophobic surfaces lead to faster inactivation effects and should thus be preferred for aseptic packaging technology.