Abstract:Five polyphenolic compounds (catechin, gallic acid, vanillin, quercetin, and kaempferol) were selected as co-pigments of purple cabbage anthocyanins. Results indicated that the co-pigmentation effects of catechin and gallic acid strengthened with increased concentration; however, a slow increase rate was observed when the concentration reached 0.01 mol/L. The co-pigmentation effect of vanillin was strongest at 0.004 mol/L but declined when the concentration was further increased. Quercetin and kaempferol exhibited poor co-pigmentation effects and accelerated the degradation of purple cabbage anthocyanin when the concentration of 0.002 mol/L was reached. These results showed that catechin was the most effective co-pigment among the five polyphenolic compounds, followed by gallic acid. Moreover, the thermal stability of purple cabbage anthocyanin was increased significantly by catechin, gallic acid, and vanillin. Gallic acid showed the best enhancement effects on thermal stability, with the degradation rate decreasing from 34.02% to 22.88%, while quercetin and kaempferol had little effects on thermal stability. Thermodynamic analysis revealed that co-pigmentation of purple cabbage anthocyanin with catechin, gallic acid, and vanillin was a spontaneous exothermic process, which suggests that the co-pigmentation effects were caused by noncovalent bonding. Therefore, catechin, gallic acid, and vanillin can be used to enhance the thermal stability of purple cabbage anthocyanins during production, with catechin showing the most promising effect.
