## 2 Phytochemicals Present in Beetroot
### Betalains
Some authors reported that the antioxidant properties of beetroot powder (DPPH scavenging activity) were improved with a temperature increase from 60 to 70 \({}^{\circ}\)C. However, with higher temperatures (80 \({}^{\circ}\)C), the same authors observed a significant reduction of the antioxidant activity [18]. The application and use of moderate temperatures during processing of beetroot increased the content of betalains and improved the antioxidant activity of beetroot powder. This could be related to facilitating the breakdown of cellular organelles and the release of these compounds. However, several studies \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Beetroot Material**} & \multicolumn{3}{c}{**Pigments**} & \multirow{2}{*}{**Ref.**} \\ \cline{2-2} \cline{4-5}  & **Betacyanins** & & **Betaxanthins** & **Total Betalains** \\ \hline \multirow{8}{*}{Beetroot extract} & 300 mg/L & 261 mg/L & 562 mg/L & [PERSON] et al. [9] \\ \cline{2-5}  & 16.3–20.7 mg/g & 19.0–30.78 mg/g & 39.7–47.1 mg/g & [PERSON] et al. [38] \\ \cline{2-5}  & 221–337 mg/L & 122–182 mg/L & - & [PERSON] et al. [36] \\ \cline{2-5}  & 3.46–4.20 mg/g & 2.59–2.80 mg/g & - & [PERSON] et al. [39] \\ \cline{2-5}  & 55.17 mg/100 g DM & 0.71 mg/100 g DM & - & [PERSON] et al. [40] \\ \hline Beetroot pulp & - & - & 370 mg/100g & [PERSON] et al. [41] \\ \hline Beetroot flour & - & - & 68–81 mg/g DM & [PERSON] et al. [18] \\ \hline Graded beetroot & 38–116 mg/kg & 13–19 mg/kg & - & \\ \hline Beetroot juice & 24–69 mg/L & 6–19 mg/L & - & [PERSON] et al. [28] \\ \cline{2-5}  & 2.81 mg/g DM & 1.27 mg/g DM & - & [PERSON] et al. [20] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Content of total betalains, betacyanins, and betaxanthins in different beetroot sources. reported contradictory effects of processing/extraction temperatures on the content of betalains. In this regard, it is well known that beetroot has several endogenous enzymes such as \(\beta\)-glucosidaseases, polyphenoloxidases, and peroxididases [43; 44], which have an important role in the degradation of betalains. Therefore, the application of moderate-high temperatures that effectively inactivate these enzymes ensures greater stability of the beetroot products (juice, powder, extract, etc. ), both during processing and storage. Nevertheless, it must be taken into account that the high temperatures also cause degradation of several bioactive compounds. However, more factors than just the use of moderate-high temperatures affect the amount of bioactive compounds, since other processes actively influence their content. In a recent research study, authors observed that vacuum treatment during processing favors the extractability of betalains from beetroot tissues [43]. These compounds are highly sensitive to oxidation, so therefore it seems clear that the application of high temperatures in vacuum-treated samples has a different effect on the degradation of betalains than the application of the same temperature in samples processed/stored in an atmosphere containing oxygen. Simply, low oxygen levels favor the pigment to be partially recovered after degradation [43]. Other authors reported that the application of a chlorination process to beetroot reduced the content of betalains and antioxidant activity when they are dehydrated at 80 \({}^{\circ}\)C, while this process did not affect the content of betalains at lower temperatures [18]. So, despite the fact that temperature plays a very important role in the degradation of betalains, other factors and treatments during processing also influence their degradation, and consequently, their antioxidant activity. In fact, a high correlation between the antioxidant activity of beetroots and content of betalains were reported by several authors [20; 33]. Additionally, it is important to note that this correlation is stronger with betacyanins than with betaxanthins, which indicates that the red pigments had greater antioxidant properties than yellow pigments [26].