Affiliation: | (1) Department of Food Hygiene, Faculty of Veterinary Medicine, Swedish University of Agricultural Sciences, Box 7009, S-750 07 Uppsala, Sweden;(2) Present address: Department of Botany, The University, BS8 1UG Bristol, UK;(3) Present address: Department of Biochemistry, Biomedical Centre, University of Uppsala, P.O. Box 576, S-751 23 Uppsala, Sweden |