1. Matforsk ASNorwegian Food Research Institute, 1430 Ås, Norway, Department of Food Science, The Royal Veterinary and Agricultural University, DK-1958, Frederiksberg, Denmark, Norwegian University of Life Sciences, Department of Chemistry, Biotechnology, and Food Science, P. O. Box 5003, 1432 Ås, Norway, and The Norwegian Radium Hospital, Institute for Cancer Research, Department of Biophysics, Montebello, 0310 Oslo, Norway