Improving the color stability and antioxidation activity of blueberry anthocyanins by enzymatic acylation with p-coumaric acid and caffeic acid

In this work, p-coumaric acid and caffeic acid were grafted on blueberry anthocyanins through enzyme catalysis method to improve their colour stability and antioxidant activity. The acylation degrees of p-coumaric acylated anthocyanins (Co-An) and caffeic acid anthocyanins (Ca-An) reached 5.38% and 5.68%, respectively. The results from Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, ultraviolet visible spectroscopy and hydrogen nuclear magnetic resonance implied that p-coumaric acid and caffeic acid grafted on the 6-OH of glucoside and galactoside and the 5-OH of arabinose through esterification reaction. As revealed in the in vitro experiment on antioxidation activity and the experiment on colour stability, Co-An and Ca-An showed stronger antioxidant activity in DPPH assay and beta-carotene bleaching assay and higher colour stability during storage at 25 degrees C, 40 degrees C and 60 degrees C than native blueberry anthocyanins.