Abstract: In this study, high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was used to identify anthocyanins in tubers of the purple sweet potato cultivar ‘Eshu 12’. Changes in the contents of total and monomeric anthocyanins in purple sweet potato extract over 98 days of storage at 4, 20 and 35 ℃ were determined using the pH-differential method and HPLC. Additionally, the degradation kinetics of anthocyanins, and as well as the browning index and polymeric color index was investigated. Thirteen anthocyanins were identified majorinly including cyanidin and peonidin 3-sophoroside-5-glucosides acylated with p-hydroxybenzoic acid, ferulic acid, or caffeic acid. The contents of total and monomeric anthocyanins progressively decreased during storage, following first-order reaction kinetics. The half-life time of total anthocyanins were 228.8, 48.1 and 32.6 d at 4, 20 and 35 ℃, respectively. Moreover, the half-life of cyanidin glycosides was shorter than that of peonidin counterparts. The half-life of acylated anthocyanins was longer than that of non-acylated counterparts, and the half-life of diacyl anthocyanins was longer than that of monoacyl ones. Furthermore, the browning index and polymeric color index increased storage time and temperature. Our results suggested a strong negative exponential correlation between anthocyanin content and polymeric color index in purple sweet potatoas.

Key words: purple sweet potato, anthocyanins, storage stability, degradation characteristics, browning index, polymeric color index