Effects of high hydrostatic pressure-assisted organic acids on the copigmentation of Vitis amurensis Rupr anthocyanins

Natural anthocyanins are safer and nutritious as compared to synthetic pigments; however, their stability is poor. They can produce spontaneous copigmentation with organic acids, leading to the improvement of colour stability, albeit slowly. Box-Behnken experimental design was used to elucidate the mechanism of copigmentation between Vitis amurensis Rupr anthocyanins (0.1 mg/mL) and organic acids (0.87 mg/mL, ferulic acid:d-gluconic acid:caffeic acid:vanillic acid = 1.5:2.5:2.5:0.5, w/w/w/w) promoted by high hydrostatic pressure (HHP; 300 MPa, 2 min). The copigmentation effect and antioxidant activity of anthocyanins were also evaluated. The structure of anthocyanins was analysed using ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, high-performance liquid chromatography, and mass spectrometry. The results of HHP copigmentation showed that the following anthocyanins were newly formed-delphinidin-3-O-catechol, petunidin-3-O-catechol, delphinidin-4-vinyl-catechol, petunidin-3-O-guaiacol, malvidin-4-vinyl-guaiacol, cyanidin-3-O-(6″-O-caffeoyl)-glucoside, peonidin-3-O-(6″-O-caffeoyl)-glucoside, delphinidin-3-O-(6″-O-caffeoyl)-glucoside, malvidin-3-O-glucoside-4-vinyl-guaiacol, and malvidin-3-O-(6″-O-feruloyl)-glucoside-owing to appropriate modifications that increased the copigmentation rate (R = 42.12%), photo-thermal stability (R > 45%), and potential antioxidant activities expressed in vivo (p < 0.01 vs. Model Group).