Anthocyanin changes in black currant juice and concentrates - Part 1: Kinetics of the decrease in anthocyanins during storage.

The loss of monomeric anthocyanins in blackcurrant 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; also total phenolics (Folin-Ciocalteu), antioxidant capacity (TEAC) and RSK values were determined. The total polyphenols of freshly produced products were in the range of 5011-5177 mg/l, the antioxidant capacity between 62-69 mmol/l Trolox equivalents, and the anthocyanin content (HPLC) between 2659-2786 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 reduction according to first order reactions. The half life of monomeric anthocyanins were between 690-816 days at 4 °C, 103-154 days at 20 °C, and 17-21 days at 37 °C; the reduction rate was faster in the concentrate compared to the juice. From the results, a storage temperature of 4 °C for blackcurrant juice and concentrate is recommended.