1. Malvern Instruments Limited, Enigma Business Park, Grovewood Road, Malvern, Worcestershire WR14 1XZ, U.K., Zeneca Pharmaceuticals, Silk Road Business Park, Macclesfield, Cheshire SK10 4TG, U.K., and Biopolymers and Colloids Research Laboratory, Department of Food Science, University of Massachusetts, Amherst, Massachusetts 01003