1. Akita Research Institute of Food and Brewing, 4-26, Sanuki, Arayamachi, Akita City, Akita, 010-1623, Japan.
2. Corresponding author. Phone: +81-18-888-2004. Fax: +81-18-888-2008. E-mail: toru@arif.pref.akita.jp
3. Faculty of Agriculture, Iwate University, 3-18-8, Ueda, Morioka City, Iwate, 020-8551, Japan.