1. Department of Physiological Sciences, The Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, U.K.
2. Department of Food Research and Technology, Silsoe College, Silsoe, Bedford MK45 4DT, U.K.
3. Unilever Research, Colworth Laboratory, Sharnbrook, Bedford MK44 1LQ, U.K.