Anthocyanalterung in Säften und Konzentraten der Aroniabeere (Aronia melanocarpa)

The loss of monomeric anthocyanins in aronia juice and concentrate was investigated. The products were stored in the dark for 12 months at 4 °C, 20 °C, and 37 °C in glas bottles. Anthocyanins were analysed with HPLC-DAD and spectrophotometrically; in addition total phenolics (Folin-Ciocalteu), antioxidant capacity (TEAC) and RSK values were determined. The total polyphenols of freshly produced products were in the range of 6144-6188 mg/l, the antioxidant capacity between 66-72 mmol/l trolox equivalents, and the anthocyanin content (HPLC) between 1035- 1160 mg/l. Total polyphenols and TEAC values were found to be rather stable during storage at 4 °C and 20 °C and are therefore not suited for the description of ageing processes. In contrast, strong decreases were found for the monomeric anthocyanins showing a decrease according to first order reactions. In the case of the concentrate the very long half-lives between 1158 (cyanidin-3-arabinoside) and 1390 days (cyanidin-3-galactoside) at 4 °C are noticeable, whereas the half-lives were 726-920 days for the aronia juice. The better anthocyanin stability in concentrate may be related to the high viscosity and the lower water activity at 4 °C. In contrast, the anthocyanin stability of the concentrate and the half-lives at 20 °C and 37 °C were lower than that of the aronia juice. The relative concentrations of cyanidin-3-galactoside :c y anidin- 3- g l ucoside :c y ani d in-3-arabinoside :c y anidin- 3 -x y loside of about 55:4:33:5 remained rather constant during the storage of juice and concentrate at 4 °C but at the end of the storage time at 20 °C and particularly 37 °C, the relations of the anthocyanins were shifted towards cyanidin-3-galactoside. From the results, a storage temperature of 4 °C for aronia juice and concentrate is recommended. The high contents of phenolic acids result mainly from the presence of neochlorogenic acid (> 500 mg/l) and chlorogenic acid (> 350 mg/l). Those show only minor changes during storage at 4 °C, whereas strong decreases were found at 20 °C and 37 °C. A broad spectru.m of flavonol glycosides is characteristic for the phenolic profile of aronia. Besides quercetin-3-galactoside, quercetin-3-rutinoside, and quercetin-3-glucoside, also quercetin-3-vicianoside und quercetin-3-robinobioside described by Slimestad et al. (2005) could be detected in aronia juice.