1. Food Research Center, Niigata Agricultural Research Institute, Kamo, Niigata 959-1381, Japan, Department of Biotechnology, Niigata Agricultural Research Institute, Nagaoka, Niigata 940-0826, Japan, Department of Material Science and Technology, Niigata University, Niigata, Niigata 950-2181, Japan, and Department of Biochemistry, Nippon Dental University School of Dentistry at Niigata, Niigata, Niigata 951-8580, Japan