# Changes in Elderberry (_Sambucus nigra_ L.) Juice Concentrate Polyphenols during Storage
## 3 Results and Discussion
### Characterization of the Initial Eldeberry Concentrates
The peaks at 20.1 (**3**) and 20.3 min (**4**) were identified as cyanidin-3-O-sambubioside and cyanidin-3-O-glucoside, respectively. Cyanidin-3-O-sambubioside and cyanidin-3-O-glucose corresponded, respectively, to around 33% and 20% of the total individual anthocyanins in both concentrates. Cyanidin-3-O-sambubioside-5-O-glucose and cyanidin-3,5-O-diglucoside are other anthocyanins described to be present in high amounts in elderberries and elderberry products [3; 8; 9; 12; 26]. The peak at 18.2 min (**2**) was attributed to these two anthocyanins that eluted at the same retention time and appeared overlaid. Therefore, they were quantified together, the result being expressed in g of cyanidin-3-O-sambubioside-5-O-glucose equivalents per kg. The sum of cyanidin-3-O-sambubioside-5-O-glucose and cyanidin-3,5-O-diglucoside accounted for 45% of the total analyzed anthocyanins. The total anthocyanins content determined by HPLC was 9.68 and 14.04 g kg\({}^{-1}\), for concentrate I and II, respectively, which is slightly lower than the total monomeric anthocyanins obtained using the pH differential method (Table 1). These differences may be explained by the presence of some compounds that were not quantified by HPLC. \begin{table}
\begin{tabular}{l c c} \hline \hline
**Compounds** & **Concentrate I** & **Concentrate II** \\ \hline Cyanidin-3-O-sambubioside & 3.30 \(\pm\) 0.06 & 4.69 \(\pm\) 0.04 \\ \hline Cyanidin-3-O-glucose & 1.99 \(\pm\) 0.07 & 2.86 \(\pm\) 0.02 \\ \hline Cyanidin-3-5-diglucoside + cyanidin-3-O-sambubioside-5-O-glucose & 4.39 \(\pm\) 0.15 & 6.49 \(\pm\) 0.08 \\ \hline Rutin & 2.51 \(\pm\) 0.04 & 3.70 \(\pm\) 0.04 \\ \hline Quercentin-3-O-glucose & 0.79 \(\pm\) 0.01 & 0.96 \(\pm\) 0.01 \\ \hline Chlorogenic acid & 0.78 \(\pm\) 0.02 & 1.11 \(\pm\) 0.01 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Contents of individual phenolic compounds in the initial elderberry concentrates quantified by HPLC in g kg\({}^{-1}\). Effect of Storage on Total Phenolic Content, Total Monomeric Anthocyanins, Percent Polymeric Color, and Antioxidant Activity  
The changes in total phenolic content (TPC), total monomeric anthocyanins (TMA), percentage of polymeric color (%PC), and antioxidant activity (AA) were evaluated during storage at 5 \({}^{\circ}\)C and at room temperature (Figure 3). Figure 2: HPLC chromatograms of concentrate I (**a**) before storage with detection at 325 nm, (**b**) before storage with detection at 520 nm, (**c**) after 7 months of storage at 5 \({}^{\circ}\)C with detection at 325 nm, (**d**) after 7 months of storage at 5 \({}^{\circ}\)C with detection at 520 nm, (**e**) after 7 months of storage at room temperature with detection at 325 nm, and (**f**) after 7 months of storage at room temperature with detection at 520 nm. (**1**) Chlorogenic acid, (**2**) cyanidin-3-O-sambubioside-5-O-glucoside + cyanidin-3,5-O-diglucoside, (**3**) cyanidin-3-O-sambubioside, (**4**) cyanidin-3-O-glucose, (**5**) rutin, and (**6**) quercetin-3-O-glucose. After seven months of storage at 5 \({}^{\circ}\)C, the content of total monomeric anthocyanins decreased from 10.6 to 8.2 g cy3 gluE kg\({}^{-1}\) in concentrate I and from 15.8 to 13.5 g cy3 gluE kg\({}^{-1}\) in concentrate II, representing losses of 22% and 14%, respectively. Moreover, storage at room temperature resulted in a strong reduction in total monomeric anthocyanins in both concentrates. After the same seven months, their content was 3.5 g cy3 gluE kg\({}^{-1}\) in concentrate I and 4.6 g cy3 gluE kg\({}^{-1}\) in concentrate II, corresponding to losses of 67% and 71%. These results demonstrate the greater stability of monomeric anthocyanins at lower temperatures, which is in accordance with studies conducted by [PERSON] et al. [27] in which they observed that degradation of anthocyanins in blueberry juices was significantly accelerated with increasing storage temperatures.