Spectral alteration and degradation of cyanidin-3-glucoside exposed to pulsed electric field.

Anthocyanins are polyphenol antioxidants that have been shown to prevent many chronic diseases. The compounds are not stable, so they tend to be decolorized or degraded during processing and storage. In this study, the spectral characteristics alteration and degradation products of cyanidin-3-glucoside (Cyd-3-glc) exposed to pulsed electric field (PEF) were investigated, and the reaction kinetics was discussed. The intensity of the UV-vis spectra decreased noticeably upon PEF treatment without modification of the spectral pattern. Protocatechuic acid and 2,4,6-trihydroxybenzoic acid were identified as degradation products of both PEF and thermally treated Cyd-3-glc, but cyanidin present in thermally treated Cyd-3-glc was absent in PEF-treated Cyd-3-glc, indicating that the first step of Cyd-3-glc degradation induced by PEF was not the hydrolysis of glycosidic bonds, which was different from that of thermal degradation. With increased electric field intensity or treatment time, the degradation of Cyd-3-glc and the formation of protocatechuic acid were enhanced; their kinetics (except 7 kV/cm for protocatechuic acid formation) were well fitted to a first-order reaction. Meanwhile, a good correlation was present between Cyd-3-glc degradation and protocatechuic acid formation.