Anthocyanin changes in the Korean purple-fleshed sweet potato, Shinzami, as affected by steaming and baking

As hydrophilic pigments, anthocyanins reduce the incidence of cancer and cardiovascular diseases. In this study, the anthocyanin content and composition following steaming and baking of the roots of the Korean purple-fleshed sweet potato variety “Shinzami” were evaluated using liquid chromatography with diode array detection and electrospray ionisation/mass spectrometry (LC-DAD-ESI/MS). Anthocyanins of Shinzami were composed of mono- or di-acylated forms of p-hydroxybenzoic acid, caffeic acid and ferulic acid with the basic structure of cyanidin 3-sophoroside-5-glucoside or peonidin 3-sophoroside-5-glucoside. A total of 15 individual anthocyanins were isolated and confirmed, one of which was presumed to be a newly identified compound, peonidin 3-feruloyl-p-hydroxybenzoyl sophoroside-5-glucoside. Additionally, the amounts of di-acylated cyanidin 3-caffeoyl-p-hydroxybenzoyl sophoroside-5-glucoside and peonidin 3-caffeoyl-p-hydroxybenzoyl sophoroside-5-glucoside were the highest (137.0 and 565.9 mg/100 g DW, respectively) among cyanidin and peonidin compounds. After steaming, the total anthocyanin content was reduced by nearly a half, while roasting only slightly reduced the total anthocyanin content.