abstract
Cyanidin 3-glucoside (Cy 3-glu) and cyanidin 3-sophoroside (Cy 3-soph) from red raspberry extracts
were selected as pigments, and five phenolic acids as copigments. The influences of pH, temperature,
structure of anthocyanins and copigments, and molar ratio of anthocyanins to copigments on the copigmentation
effect were analyzed with a UV–Visible spectrophotometer. The reaction was thermodynamically
defined in terms of DH0
, DG0 and DS0 values.
The maximum copigmentation effect for Cy 3-glu and Cy 3-soph with ferulic acid was observed around
pH 4. Sinapic acid and ferulic acid had stronger copigmentation effect than the other three phenolic acids
investigated. The strongest immediate copigmentation was observed at an anthocyanin/copigment molar
ratio of 1:100. Lower temperatures favoured the copigmentation reaction. Moreover, the calculated thermodynamic
data indicated that the copigmentation reaction was more favourable at pH 4.0 than at pH
3.2 for the same anthocyanin, and more favourable for Cy 3-glu than for Cy 3-soph at the same pH.