Abstract: Purple sweet potato pigment (PSPP) is a kind of natural pigment and has gained extensive concern in recent years. In this study, response surface methodology was employed to optimize the extraction conditions of PSPP. The results showed that the optimal extraction conditions were extraction temperature of 60 ℃, extraction time of 1 h, solid-to-liquid ratio 1:30, and acidic ethanol concentration of 80%. Under the optimal extraction conditions, the yield of PSPP was up to 12.4688 mg/g. In addition, the stability of PSPP was also investigated. Increasing temperature and extension of heating time could result in a decrease in PSPP stability. Similarly, the stability of PSPP revealed an obvious decrease in neutral and alkaline environments. Fe3+ and Al3+ could increase the stability of PSPP; on the other hand, Cu2+, Zn2+ and Pb2+ could lead to a decrease in PSPP stability. Moreover, ascorbic acid could significantly improve the stability of PSPP and Na2SO3 did harm to the stability of PSPP.

Key words: purple sweet potato pigment, response surface methodology, extraction, stability