# Antioxidant Activity of Coffee Components Influenced by Roast Degree and Preparation Method
## 3 Results and Discussion
### Antioxidant Activity of Coffee Extracts  
The antioxidant properties of coffee were investigated using four methods that differ in the reaction mechanism. All methods used in this study reflect the ability to break the chain of oxidation reactions by scavenging or inhibiting the creation of free radicals but through different mechanisms. Antioxidant compounds react with active radicals to stabilize them by single electron transfer (SET) or hydrogen atom transfer (HAT) mechanisms. In both cases, the antioxidant compounds react more rapidly with the oxidative agent, thus, protecting the potentially exposed molecules. The antioxidant activity based entirely on the SET mechanism is tested with the use of the complex of neocuproine with copper(II) ions. As a result of the tested compound's reducing power, the electron is transferred to the complex and the copper ion is being reduced. In the case of the method based entirely on the HAT mechanism, crocin was used in our study as a molecular probe. Crocin is a carotenoid that undergoes decomposition (and discoloration) only in the presence of free radicals, losing hydrogen atoms upon the reaction. Most oxidation reactions, however, follow a mixed mechanism, and to investigate them, different methods are used, i.e., the ABTS method (advantage of SET mechanism) and the most complex method based on autoxidation of linoleic acid (advantage of HAT mechanism) [38]. The results per 100 g DM show that espresso was much less active than moka brews, and both brews were less active than bean extracts (Table 3). In the CUPRAC method, the activity of espresso in relation to the total activity of the beans was 71.6% and 57.8%, while the activity of moka brews was 81.7% and 82.4% for medium and dark roasted beans, respectively. In the ABTS method, the statistical analysis showed no significant effect of the roasting degree on the antioxidant activity, as well as no significant differences between the activity of moka brews and bean extracts, which indicates a high extraction of compounds \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Brew Type** & \multicolumn{2}{c}{**Beans**} & \multicolumn{2}{c}{**Epresso**} & \multicolumn{2}{c}{**Moka Brew**} \\ \hline
**Roast Degree** & **Medium** & **Dark** & **Medium** & **Dark** & **Medium** & **Dark** \\ \hline \begin{tabular}{c} Phenolic compounds \\ [mg GA/100 g DM] \\ \end{tabular} & 2438.82 \(\pm\) 98.14 bc & 2538.84 \(\pm\) 116.20 c & 1800.65 \(\pm\) 27.6 a & 1640.95 \(\pm\) 37.31 a & 2642.69 \(\pm\) 99.33 c & 2273.70 \(\pm\) 155.00 b \\ \hline \begin{tabular}{c} Phenolic compounds \\ [mg GA/portion] \\ \end{tabular} & – & – & 282.76 \(\pm\) 4.34 d & 260.260 \(\pm\) 5.92 c & 142.78 \(\pm\) 5.37 b & 103.40 \(\pm\) 7.05 a \\ \hline \begin{tabular}{c} Antioxidant \\ activity \\ [mg Trolox/100 g DM] \\ \end{tabular} & \begin{tabular}{c} CUPRAC \\ \end{tabular} & 10,015.74 \(\pm\) 518.66 & 9612.67 \(\pm\) 458.53 d & 7175.03 \(\pm\) 148.55 b & 5559.92 \(\pm\) 194.20 a & 8190.50 \(\pm\) 338.24 c & 7930.01 \(\pm\) 287.30 \\ \hline \begin{tabular}{c} Antioxidant \\ activity \\ [mg Trolox/100 g DM] \\ \end{tabular} & \begin{tabular}{c} AISTS \\ \end{tabular} & 7380.07 \(\pm\) 403.65 b & 7687.40 \(\pm\) 518.66 b & 4560.03 \(\pm\) 311.10 a & 4508.23 \(\pm\) 310.36 a & 6628.27 \(\pm\) 268.25 b & 6636.83 \(\pm\) 364.25 b \\ \hline \begin{tabular}{c} Antioxidant \\ activity \\ [mg Trolox/portion] \\ \end{tabular} & \begin{tabular}{c} CUPRAC \\ \end{tabular} & – & – & 1126.71 \(\pm\) 2333 d & 891.66 \(\pm\) 29.03 c & 482.74 \(\pm\) 19.94 b & 393.42 \(\pm\) 14.23 a \\ \hline \
\begin{tabular}{c} Activator \\ activity \\ [mg Trolox/portion] \\ \end{tabular} &
\begin{tabular}{c} AISTS \\ \end{tabular} & – & – & 691.39 \(\pm\) 33.42 & 715.02 \(\pm\) 49.22 & 358.11 \(\pm\) 14.49 & 301.83 \(\pm\) 16.57 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Content of phenolic compounds and antioxidant activity measured by SET-based methods. active against ABTS**+** in this preparation method.