Abstract: The effects of two factors,the temperature in water extraction and the temperature in dry process of raw material on polysaccharide determination were investegated.Four species,Dioscorea polystachya from Henan province(Tiegun yam),D.polystachya from Yunnan Province(Kunming yam),D.alata from Zhejiang Province and D.persimilis from Fujian Province,were took as samples in this experiment and their polysaccharide contents were determined by using sulphuric acid-phenol spectrophotometric method.The results showed that the temperature in dry process of raw material had little influence while the temperature in water extraction had significant influence.The suitable temperature in water extraction should be below 65 ℃.If the temperature was high enough,it would significantly affect the result of polysaccharide determination because of dissolved starch.

Key words: Dioscarea, D.polystachya, D.alata, D.persimilis, polysaccharide, determination