## 3 Results and Discussion
### Individual Polyphenolic Compounds Determined by HPLC
They could either by quenched by nucleophiles, such as the A-ring  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Samples** & **(+)-Catechin** & **(–)-Epicatechin** & **(–)-Epigallocatechin-3-0-Gallate** \\ \hline \hline \multicolumn{4}{c}{**Samples at 35 \({}^{\circ}\)C**} \\ \hline M & 7.34 \({}^{\text{ab}}\)\(\pm\) 0.01 & 2.56 \({}^{\text{a}}\)\(\pm\) 0.01 & 1.34 \({}^{\text{ab}}\)\(\pm\) 0.06 \\ Fe min & 8.42 \({}^{\text{a}}\)\(\pm\) 0.45 & 2.25 \({}^{\text{a}}\)\(\pm\) 0.12 & 1.26 \({}^{\text{ab}}\)\(\pm\) 0.04 \\ Fe max & 7.87 \({}^{\text{a}}\)\(\pm\) 0.27 & 1.90 \({}^{\text{ab}}\)\(\pm\) 0.02 & 0.91 \({}^{\text{b}}\)\(\pm\) 0.01 \\ Se min & 8.84 \({}^{\text{a}}\)\(\pm\) 0.42 & 2.12 \({}^{\text{a}}\)\(\pm\) 0.02 & 1.41 \({}^{\text{a}}\)\(\pm\) 0.01 \\ Se max & 7.80 \({}^{\text{a}}\)\(\pm\) 0.58 & 2.17 \({}^{\text{a}}\)\(\pm\) 0.10 & 1.39 \({}^{\text{a}}\)\(\pm\) 0.03 \\ All min & 8.58 \({}^{\text{a}}\)\(\pm\) 0.00 & 1.81 \({}^{\text{ab}}\)\(\pm\) 0.02 & 1.30 \({}^{\text{a}}\)\(\pm\) 0.03 \\ All max & 5.29 \({}^{\text{b}}\)\(\pm\) 0.01 & 1.69 \({}^{\text{b}}\)\(\pm\) 0.06 & 0.88 \({}^{\text{b}}\)\(\pm\) 0.02 \\ \hline \hline \multicolumn{4}{c}{**Samples at 50 \({}^{\circ}\)C**} \\ \hline M & 7.81 \({}^{\text{a}}\)\(\pm\) 0.16 & 1.96 \({}^{\text{a}}\)\(\pm\) 0.01 & 1.24 \({}^{\text{a}}\)\(\pm\) 0.01 \\ Fe min & 5.30 \({}^{\text{b}}\)\(\pm\) 0.37 & 1.81 \({}^{\text{ab}}\)\(\pm\) 0.07 & 1.38 \({}^{\text{a}}\)\(\pm\) 0.01 \\ Fe max & 5.27 \({}^{\text{b}}\)\(\pm\) 0.16 & 1.36 \({}^{\text{b}}\)\(\pm\) 0.03 & 0.71 \({}^{\text{b}}\)\(\pm\) 0.02 \\ Se min & 7.02 \({}^{\text{a}}\)\(\pm\) 0.58 & 1.56 \({}^{\text{ab}}\)\(\pm\) 0.05 & 1.34 \({}^{\text{a}}\)\(\pm\) 0.01 \\ Se max & 6.88 \({}^{\text{ab}}\)\(\pm\) 0.02 & 1.56 \({}^{\text{ab}}\)\(\pm\) 0.01 & 1.29 \({}^{\text{a}}\)\(\pm\) 0.00 \\ All min & 4.39 \({}^{\text{c}}\)\(\pm\) 0.03 & 1.34 \({}^{\of flavonoids, and prevent oxidation and browning development, or oxidize the B-ring (catechol ring) of flavanols though electron transfer, leading to flavonoid quinones, substrates of browning development. [PERSON] and [PERSON] [40] observed a much faster electron transfer than nucleophilic reaction between (+)-catechin and caffeic acid quinone in a model solution, explaining the reason why flavanols in wine contribute to browning rather than delay it. In this study, EGCG was the most affected compound at 35 \({}^{\circ}\)C, probably due to the higher number of ortho -OH groups in its B-ring, compared with the other two flavanols studied. Since the B-ring is mainly responsible for browning development, the observed reduction of this compound was probably connected with increased formation of quinones and hence more intense browning appearance. However, at 50 \({}^{\circ}\)C, all three flavanols studied showed a similar trend probably due to the higher temperature at which the samples were subjected and the acceleration of their oxidation reactions and browning rate. Previous studies have shown that (\(-\))-epicatechin content decreases faster than (+)-catechin concentration under oxidizing conditions [26, 51], while others [52] reported that (+)-catechin is most sensitive to oxidation. This trend was not observed in the present study, since the amount of both compounds showed a similar reduction in the presence of oxidants. Gallic acid content at 35 \({}^{\circ}\)C was also reduced significantly in samples containing high amounts of Fe\({}^{2+}\) and H\({}_{2}\)O\({}_{2}\), while at 50 \({}^{\circ}\)C, both contents of the oxidants resulted in significant differences compared with those of the control (Table 4). Since this compound contains three -OH groups in its phenol ring, it participates in oxidation reactions by similar mechanisms with flavanols [5]. Regarding the hydroxycinnamic content of the samples (Table 4), the following compounds were determined: trans-cafratic, coutaric, ferratic, trans-caffeic, ferulic, and p-coumaric acid.