1. Graduate School of Life Sciences and Biotechnology, Korea University, 5-1 Anam-dong, Sungbuk-ku, Seoul 136-701, Korea.
2. Korea Food Research Institute, Seongnam, Gyeonggi 463-746, Korea.
3. Corresponding author. Phone: 82-2-3290-3435. Fax: 82-2-921-0557. E-mail: limst@korea.ac.kr