1. College of Chemistry and Chemical Engineering Qingdao University Qingdao 266071 P. R. China
2. College of Chemistry and Chemical Engineering Ocean University of China Qingdao 266100 P. R. China
3. Department of Food and Medicine Weifang Vocational College Weifang 262737 P. R. China
4. Faculty of Production Engineering University of Bremen Bremen 28359 Germany