1. Department of Food Chemistry, Friedrich-Schiller-University of Jena, Dornburger Strasse 25, and Department of Applied and Ecological Microbiology, Friedrich-Schiller-University of Jena, Philosophenweg 12, D-07743 Jena, Germany, Department of Technical Biology, University of Karlsruhe (TH), Engler Bunte Ring 1, D-76131 Karlsruhe, Germany, and Institute of Food Chemistry, University of Hohenheim, Garbenstrasse 28, D-70599 Stuttgart, Germany