Photo- and Thermodegradation of Anthocyanins from Grape and Purple Sweet Potato in Model Beverage Systems

Recently, interest in the application of natural pigments to replace synthetic dyes in beverages has grown. The present study investigates the stability of anthocyanin-rich grape and purple sweet potato (PSP) extracts to photo- and thermostresses in ready-to-drink (RTD) beverage models including hot fill beverages with various concentrations of ascorbic acid, a preserved beverage, and a vitamin-enriched water beverage. Thermo- and photostresses were induced at 40, 60, and 80 degrees C and 250, 500, and 750 W/m(2), respectively. Qualitative and quantitative data on anthocyanin content were collected by pH differential assay and LC-MS. Increasing concentration of ascorbic acid caused more rapid degradation through thermostress, but had a protective effect through photostress. Additionally, PSP was significantly less stable than grape extract in the vitamin-enriched water model beverage through photostress. Furthermore, photostress caused the formation of monoacylated peonidins from diacylated peonidins.