Inactivation of pre- and post-germinated mold spores by infrared radiation heating and ultraviolet irradiation

Inactivation effects of infrared radiation (IR) heating (1.87 μW/cm ²/nm) and ultraviolet (UV) irradiation (0.455 mW/cm ²) on two mold spores (Penicillium, Cladosporium) were investigated before and after germination on potato dextrose agar. Penicillium was more resistant to IR heating than Cladosporium both before and after germination. Over 90% of Cladosporium was inactivated by 120 sec of IR heating after germination for up to 36 hours. The inactivation ratio of Cladosporium was temporarily increased for periods of 6 to 12 hours after 60 sec of IR heating and decreased to < 10 % by 30 sec of UV irradiation at 18 hours. In contrast, about 75% of Penicillium was inactivated by 30 sec of UV irradiation at 36 hours. These findings indicate that the ability of IR heating and UV irradiation to inactivate germinated molds is affected by mold type and growth stage.