Abstract: The interaction between anthocyanins and polyphenols can improve color properties of anthocyanins, while the color properties and stability of anthocyanins in solid and liquid systems containing polyphenols are not yet clear. In this paper, in order to clarify the effect and underlying mechanism of microwave and ultrasonic treatment on the color of anthocyanin-polyphenol complexes in the solid and liquid states, the changes in the apparent color, spectral characteristics and anthocyanin composition and contents were examined after the treatments. The results showed that after either treatment, L* value increased, b* value decreased, and a* value did not change remarkably in the solid system. The liquid system showed a remarkable red shift in the absorption spectra, indicating that molecular vibration and cavitation effect have a great impact on the spectral absorption. Meanwhile, in both systems, the content of total anthocyanins increased, together with a decrease in polyphenol content and the conversion of neochlorogenic acid to chlorogenic acid. Multivariate statistical analysis showed significant differences in color properties among the complex systems subjected to microwave and ultrasonic treatment under different conditions, which may be mainly caused by the differences in the contents of protocatechuic acid, catechins and total anthocyanins. For both liquid and solid systems, L*, a* and b* values, absorbance at the maximum absorption wavelength, the contents of total anthocyanins and polyphenols were higher after microwave treatment at 30 W or ultrasonic treatment for 90 min as compared to other treatment conditions, greatly contributing to the color stability of the systems. In summary, microwave and ultrasonic treatments are alternative techniques for improving the stability of anthocyanins.

Key words: anthocyanins; polyphenols; microwave; ultrasonic; color