1. Federal Center for Meat Research, Institute of Microbiology and Toxicology, E. C. Baumann Strasse 20, D-95326 Kulmbach, Germany; Technical Analytical Research Group of the Hungarian Academy of Sciences, Institute for General and Analytical Chemistry, Budapest University of Technology and Economics, Szent Gellért tér 4, H-1111 Budapest, Hungary; and Department of Food Chemistry, University of Würzburg, D-97074 Würzburg, Germany