Co-pigmentation of anthocyanins extracted from sour cherry (Prunus cerasus L.) with some organic acids: Color intensity, thermal stability, and thermodynamic parameters

The co-pigmentation reactions involving anthocyanins of sour cherry (Prunus cerasus L.) were investigated with tannic, caffeic, 4-hydroxybenzoic, gallic, and malic acids at pH 3.5. The influence of the co-pigments with different concentrations (120, 240, 480, and 960 mg/L), and temperatures (20, 40, 60, 80 and 100 degrees C), on the co-pigmentation effects, stoichiometric ratio (n), the equilibrium constant (K) and thermodynamic parameters (Delta G degrees, Delta H degrees, and Delta S degrees) were determined. The strongest immediate co-pigmentation reactions were observed at 960 mg/L, being significantly highest using tannic acid; also, the greatest bathochromic and hyperchromic effects were reasonable for its n, K, and AG degrees values of 0.64, 56.55, and -10.00 kJ/mol, respectively. Furthermore, tannic and caffeic acids, with the highest negative values of Delta H degrees ( - 11.74 kJ/mol) and Delta S degrees ( - 8.08 J/K.mol) led to the most excellent stability at 100 degrees C. The presence of anthocyanins in the sour cherry extract was confirmed with the Fourier-transform infrared spectroscopy technique.

Automated summary

This study investigated the co-pigmentation reactions of anthocyanins in sour cherry with various acids at different concentrations and temperatures. It was found that the strongest co-pigmentation reactions occurred at 960 mg/L concentration of tannic acid, with the greatest stability observed at high temperatures for tannic and caffeic acids.