1. Institute of Chemistry, Department of Organic Chemistry, Uppsala University, P.O. Box 531, SE-751 21 Uppsala, Sweden; Department of Food Science, Swedish University of Agricultural Sciences (SLU), P.O. Box 7051, SE-750 07 Uppsala, Sweden; and Department of Chemistry, Swedish University of Agricultural Sciences (SLU), P.O. Box 7015, SE-750 07 Uppsala, Sweden