Changes in Elderberry (Sambucus nigra L.) Juice Concentrate Polyphenols during Storage

Elderberry (Sambucus nigra L.) juice concentrate is highly rich in polyphenols, particularly anthocyanins and flavonols, which have been associated with a wide range of health-promoting properties. Phenolic compounds, in particular anthocyanins, are unstable and may change during storage, which might influence the product color quality and its potential health effects. The aim of this study was to evaluate the changes in the polyphenols profile of elderberry juice concentrate produced at an industrial scale during seven months of storage at 5 degrees C and at room temperature. The total phenolic content, the total monomeric anthocyanins, the percent polymeric color, and the ABTS(center dot+) scavenging activity were monitored over time. In addition, the profile and content of the main individual phenolic compounds were also assessed by HPLC-DAD. The results show that cyanidin-3-O-sambubioside, cyanidin-3-O-glucoside, cyanidin-3-O-sambubioside-5-O-glucoside, cyanidin-3,5-O-diglucoside, chlorogenic acid, rutin, and quercetin-3-O-glucoside were the main phenolic compounds identified. Storage at room temperature resulted in a strong reduction in total monomeric anthocyanin content accompanied by an increase in percent polymeric color values. Cyanidin-3-O-sambubioside and cyanidin-3-O-glucoside degraded faster than cyanidin-3,5-O-diglucoside and cyanidin-3-O-sambubioside-5-O-glucoside. Concentration of chlorogenic acid also decreased over storage, whereas rutin and quercetin-3-O-glucoside were quite stable. Storage at 5 degrees C caused a lower impact on the contents of anthocyanins and chlorogenic acid and the percent polymeric color was not affected. The total phenolic content and the in vitro antioxidant activity remained quite similar over the time, for both temperatures, suggesting that elderberry concentrates still preserve their health benefits of antioxidant capacity after seven months of storage.