Interaction of vitamin C and flavonoids in elderberry (Sambucus nigra L.) during juice processing.

A field experiment and two oxidation experiments in the laboratory were carried out. The content of the major anthocyanins, cyanidin-3-glucoside (Cy-3-G) and cyanidin-3-sambubioside (Cy-3-Sa), in the fresh fruits from the 13 cultivars were from 361 to 1266 and from 269 to 656 mg/100 g, respectively. The two minor anthocyanins, cyanidin-3-sambubioside-5-glucoside (Cy-3-Sa-5-G) and cyanidin-3.5-diglucoside (Cy-3.5-dG), occurred in concentrations between 5 and 47 mg/100 g. The content of ascorbic acid and quercetin in the fresh fruits of the cultivars varied from 6 to 25, and from 29 to 60 mg/100 g, respectively. Purging of the elderberry juice with N2 and/or addition of ascorbic acid reduced the oxidative degradation rate of the two major anthocyanins and quercetin. Ascorbic acid protected the anthocyanins, but not quercetin from oxidative degradation. Mixing of fruits with air during processing and even a low content of oxygen in the juice before tapping must be avoided by appropriate steps during processing. Improvement of the nutritional value of the elderberry juice and increased protection of anthocyanins against oxidative degradation may potentially be obtained by selection of cultivars with a high content of ascorbic acid.