Nondestructive testing of electron beam sterilization by means of an optically active marker material

Secure proof of sterilization processes on packaging materials is an important issue in many economic sectors. In this context, electron beam sterilization is a highly effective low temperature technique. However, verifying the application of a sufficient electron dose is still difficult - especially on products with complex geometry. Here we report on an optical, hence fast and contactless approach which gives reliable evidence of a successful e-beam treatment. The technique is based on placing a suitable marker material (rare-earth based particles) inside or as a coating on the packaging material. By electron irradiation these particles change their optical properties and thus indicate the successful application of the electron beam.