# Changes in Elderberry (_Sambucus nigra_ L.) Juice Concentrate Polyphenols during Storage
## 3 Results and Discussion  
### Characterization of the Initial Eldeberry Concentrates  
The concentrates were obtained by an industrial process that involved crushing, mash pressing, depeettinization, ultrafiltration, and concentration. The production of concentrate I, in addition to the steps described above, also involved a thermal treatment of the mash at 80 \({}^{\circ}\)C, prior to pressing. The main objective of this step is the inactivation of oxidoreductases such as polyphenol oxidase and peroxidase, which are assumed to be involved in the degradation of anthocyanins [24; 25]. Some chemical characteristics of the elderberry juice concentrates before storage are presented in Table 1.  
Concentrate I and concentrate II presented an average content of total soluble solids of 55.8 and 80.6 \({}^{\circ}\)Brix, respectively. Concentrate II contained 54.7 g GAE kg\({}^{-1}\) of total phenolic compounds, 15.8 g kg\({}^{-1}\) of total monomeric anthocyanins, 4.8 g QE kg\({}^{-1}\) of flavonoids, and 1.5 g EpiE kg\({}^{-1}\) of flavan-3-ols. The ratio between the concentrates in all these parameters was around 1.5, which indicates that concentrate II is 1.5-fold more concentrated compared to concentrate I. Therefore, for these analyzed parameters, the lower contents observed in concentrate I are explained by the concentration process, which results in different values of \({}^{\circ}\)Brix, and are not related to the heating treatment. The results obtained allow us to infer that the initial juices have similar phenolic characteristics. The percentage of polymeric color (%PC) was also similar; 26.2 \(\pm\) 1.6% and 28.3 \(\pm\) 1.2% for concentrate I and concentrate II, respectively. These values of %PC are within the expected values for fruit juices that have been subjected to industrial processing [20]. The concentrates I and II showed an ABTS\({}^{\bullet+}\) antioxidant activity equal to 352.3 and 455.0 mmol TE kg\({}^{-1}\) \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Concentrate I** & **Concentrate II** \\ \hline Thermal processing step & Heating of mash at 80 \({}^{\circ}\)C & No \\ \hline Total soluble solids (\({}^{\circ}\)Brix) & 55.8 \(\pm\) 0.8 & 80.6 \(\pm\) 1.0 \\ \hline Total phenolic content (g GAE kg\({}^{-1}\)) & 37.7 \(\pm\) 0.4 & 54.7 \(\pm\) 1.9 \\ \hline Total monomeric anthocyanins (g Cy3 gluE kg\({}^{-1}\)) & 10.6 \(\pm\) 0.1 & 15.8 \(\pm\) 0.4 \\ \hline Flavonols (g QE kg\({}^{-1}\)) & 3.1 \(\pm\) 0.04 & 4.8 \(\pm\) 0.2 \\ \hline Flavan-3-ols (g EpiE kg\({}^{-1}\)) & 1.0 \(\pm\) 0.6 & 1.5 \(\pm\) 0.3 \\ \hline Polymeric color (\%) & 26.2 \(\pm\) 1.6 & 28.3 \(\pm\) 1.2 \\ \hline Antioxidant activity (mmol TE kg\({}^{-1}\)) & 352.3 \(\pm\) 2.6 & 455.0 \(\pm\) 19.4 \\ \hline \hline \end{tabular} \({}^{\dagger}\) Results are expressed as mean values \(\pm\) standard deviation (\(n\) = 3). GAE—galtic acid equivalents, QE–quercetin equivalents, EpiE—epictechin equivalents, Cy3 gluE—cyanidin-3-O-glucose equivalents, TE–Trolox equivalents.  
\end{table} 
Table 1: Analytic data of the initial elderberry juice concentrates \({}^{\ddagger}\). respectively. The ratio between these values reveals the same trend observed for the content of phenolic compounds, where juice II is about 1.5 times more concentrated. Overall, the values presented in Table 1 are in agreement with those obtained by [PERSON] and [PERSON] [9] for elderberry concentrate. The most important phenolic compounds in the two concentrates were identified and quantified by HPLC-DAD. The concentrations of the phenolic compounds identified are presented in Table 2.  
The phenolic profile was similar in the two concentrates. As an example, the chromatograms of the concentrate I before storage are shown in Figure 2a,b. In the chromatogram at 325 nm, the peak at about 18.0 min (**1**) was identified as chlorogenic acid and the peaks at 24.8 (**5**) and 25.9 min (**6**) as rutin and quercetin-3-O-glucoside, respectively. In the chromatogram at 520 nm, three peaks corresponding to anthocyanins can be observed.