1. Centre for Water-Soluble Polymers, The North East Wales Institute, Plas Coch, Mold Road, Wrexham, LL11 2AW, U.K., Department of Biological and Chemical Engineering, Faculty of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan, Research Center, Denki Kagaku Kougyou Company, Ltd., Asahimachi, Machida, Tokyo 194-8560, Japan, Department of Food and Human Health Sciences, Graduate School of Human Life Science, Osaka City University, Sumiyoshi, Osaka 558-8585, Japan