Effects of UV Irradiation on Penicillium Strains Isolated from a Bread Plant and the Application to Bakery Products.

We tested treatement with UV irradiation for controlling the growth of bread mold. First, we analyzed the sterilizing effect of a dose of approximately 25 mJ/cm2 radiation on nine Penicillium and two Talaromyces strains that were isolated from a bread-manufacturing plant. The P. chermesinum and P. paneum strains were sterilized completely at that dose, while it was only partially effective against P. corylophilum. P. chrysogenum and P. decumbens were sterilized at a dose of approximately 120 mJ/cm2, while T. amestolkiae was sterilized at approximately 150 mJ/cm2. Sterilization of T. cecidicola and P. hispanicum required more than 200 mJ/cm2 of radiation. These results suggest that UV resistance varies depending on the species and the strains. We also carried out UV irradiation of bread at 70 mJ/cm2: a dose at which the taste of bread is not affected; we observed that mold growth was delayed visibly compared to the non-irradiated bread. These results suggest that UV irradiation at 70 mJ/cm2 is effective at delaying mold growth, though it does not cause complete sterilization. This method should prove useful for extending the shelf-life of bread.