Fluorescence Spectrum Characteristics of Melanoidins From Yunnan Arabica Coffee

The melanoidins was prepared from Yunnan Arabica coffee. The 3D-EEMs were used to study the fluorescence characteristics of coffee melanoidins at different temperatures, pH, lighting conditions and at different concentrations. The results showed that the fluorescence intensity of aqueous solution of melanoidins was inversely proportional to the temperature in the range of 10～80 ℃. The fluorescence intensity of aqueous solutions of melanoidins with pH between 5 and 10 was stable. The fluorescence intensity of the melanoidins solution stored in dark did not change significantly within 60 min (P>0.05), while the increase of light time would lead to a significant decrease in fluorescence intensity (P<0.05). The fluorescence intensity of aqueous solutions of melanoidins was proportional to the concentration, and the correlation coefficient was 0.9846 when the concentration was less than 0.5 mg/mL. Fluorescence quenching occurs when the concentration was higher than 10 mg/mL, and the fluorescence intensity of aqueous solutions of melanoidins was not correlated with the concentration. This study would provide some data support for the further study of the spectral characteristics of coffee melanoidins.