Efect of Heat Processing on Monomeric Anthocyanin of Purple Sweet Potato (Ipomoea batatas L)

Anthocyanin is a natural pigment found in plants, such as leaves, flowers, roots, fruits or vegetables. Purple sweet potato (PSP) is one source of antocyanin consisting of 98% acylated anthocyanin of the total anthocyanin content in tuber. Anthocyanin color varies from red, purple, blue to yellow. The color and amount of anthocyanin may change due to heating processings. The purpose of this research was to observe the changes in color and anthocyanin monomeric content in PSP during heat processing of flakes. The other purpose of this reseach was to observe the order kinetics model of effect temperature and time baking on total anthocyanin monomeric of fresh PSP and rehydration PSP flakes. The experimental applied a completely randomized design with three replications. The color and amount of anthocyanin from fresh PSP, after steaming process and processed into a flake were compared. Fresh PSP had browny purple color (L * = 23.38 +/- 0.71, C = 9.84 +/- 0.98, Hue = 12.25 +/- 1.61). Total monomeric anthocyanin in fresh PSP was 1.45 +/- 0.00 mg cyanidin equivalent (CyE)/g dry basis (db). In general, the color and the amount of PSP anthocyanin changed during the flakes processing. Steamed PSP for 7 minutes turned its color into a bright purple (L * = 25.88 +/- 0.47, C = 24.64 +/- 0.25, Hue = 348.83 +/- 0.33) with the amount of monomeric anthocyanin increased to 3.76 +/- 0.01 CyE mg/g db. Flakes PSP was very bright purple (L * = 36.12 +/- 0.11, C = 9.97 +/- 0.18, Hue = 359.29 +/- 0.31) and the amount of monomeric anthocyanin was slightly lower than that of steamed sweet potato (3.19 +/- 0.12 mg CyE / g db). Total monomeric anthocyanin of fresh PSP and rehydration flakes PSP decrease during baking time.