1. Institute of Food Technology, University of Agriculture, Peter Jordan-Strasse 82, A-1190 Vienna, Austria
2. Institute of Biotechnology, Technical University of Graz, Petersgasse 12/1, A-8010 Graz, Austria
3. Laboratory of Biochemistry, State University of Gent, K.L.-Ledeganckstraat 35, B-9000 Gent, Belgium