Abstract: In order to obtain the determination wavelength of blue pigment from Ophiopogon japonicus Fruit,its water extract was scanned in the range of 200 to 650 nm,and then the effects of pH,carbohytrates,temperature and metal ions on the stability of the pigment were probed. The pigment is found to has three absorption wavelengths,380,574 and 617 nm. In this study,the two visible wavelengths,574nm and 617 nm,were selected to determine the pigment. The carbohydrates such as glucose and sucrose etc can improve the stability of the blue pigment. When temperature is lower than 60 ℃,the blue pigment has no change in color,but when temperature is higher than 30 ℃,some precipitates appear in the pigment solution. The pigment is greatly affected by pH. Most metal ions can enhance its absorbance,and few metal ions have obvious effects on it,such as Cu2+,Fe3+,Na+ and K+ and so on.

Key words: Ophiopogogon japonicus, fruit, blue pigment, stability