Effect of peracetic acid on ascospore-forming molds and test microorganisms used for bio-validations of sanitizing processes in food plants.

Industrial sterilization of packaging and filling machineries by peracetic acid (PAA) is a widespread practice. In our study we assessed the resistance to PAA of three ascospore-forming molds (Chaetomium globosum ATCC 6205; Talaromyces bacillisporus SSICA 10915; Aspergillus hiratsukae SSICA 3913) compared to that of Aspergillus brasiliensis ATCC 16404 and Bacillus atrophaeus DSM 675, that are currently used as test microorganisms during industrial bio-validations of food packaging and machineries. Tests were carried out at 40 °C using 1,000 mg/l of PAA, with or without a supporting material (aluminium, tin-plate, PET). At all conditions tested, a greater resistance to PAA was registered for C. globosum, followed by T. bacillisporus, A. hiratsukae, A. brasiliensis and B. atrophaeus. D-values of C. globosum varied from 23 to 68 min, whereas T. bacillisporus showed D-values from 83 to 352 s and A. hiratsukae showed D-values from 32 to 65 s. Surprisingly, both test microorganisms (A. brasiliensis and B. atrophaeus) proved less resistant than ascospore-forming molds tested, their D-values being always lower than 30 s. Cells treated without a supporting material proved more resistant than those deposited on plastic or metallic strips, with the exception of tin-plate, where results approaching those obtained without a supporting materials were obtained. Based on the results obtained in this paper, test microorganisms currently used for bio-validations in industrial plants and also heat-resistant strains proved sensibly less resistant to PAA than C. globosum. Therefore, for practical purposes C. globosum should be furtherly studied to understand if its use during bio-validations of sanitizing processes could lead to more performing results.