1. 1School of Biological and Chemical Sciences, Birkbeck College, University of London, Malet Street, London WC1E 7HX, UK
2. 2LGC Limited, Queens Road, Teddington Middlesex, TW11 0LY, UK
3. 3Food Standards Agency, c/o Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, UK