# Effect of Cooking Methods on Bioactive Pigments in Purple Carrots (_Daucus carota_ L.)
## 3 Results and Discussion
Whereas polyphenols including anthocyanins are basically polar compounds and, therefore, removable by water, carotenoids are non-polar and, therefore, stable in an aqueous environment. In order to evaluate the loss of polyphenols in general and anthocyanins in particular, the water resulting from the cooking was analyzed for TPC and TAC. As a result, values of TPC and TAC of 10.30 \(\pm\) 0.14 mg GA g\({}^{-1}\) DW and 1.60 \(\pm\) 0.15 mg C3G g\({}^{-1}\) DW, respectively, were obtained in the cooking water. This con \begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{4}{c}{**TOTAL CONTENT OF BIOACTIVE PIGMENTS**} \\ \hline \multirow{2}{*}{**UNCOOKED**} & **TCC** & **TPC** & **TAC** \\  & (\(\upmu\)g\(\upbeta\)-carotene g\({}^{-1}\) DW) & (\(\upmu\)g GA g\({}^{-1}\) DW) & (\(\upmu\)g C3G g\({}^{-1}\) DW) \\ \hline
**Fresh** & **1136.66 \(\pm\) 0.08 a** & **66.71 \(\pm\) 0.08 a** & **4.83 \(\pm\) 0.16 a** \\ \hline
**COOKING METHOD** & & & \\ \hline Freeze-drying & 554.90 \(\pm\) 0.02 b & 2919.02 \(\pm\) 0.03 b & 364.78 \(\pm\) 0.11 b \\ \hline Boiling & 3245.61 \(\pm\) 0.07 b & 15.71 \(\pm\) 0.11 b & 1.41 \(\pm\) 0.06 b \\ \hline Steaming & 2061.95 \(\pm\) 0.01 b & 82.49 \(\pm\) 0.05 a & 7.79 \(\pm\) 0.14 b \\ \hline Roasting (10 min) & 1596.76 \(\pm\) 0.04 b & 99.65 \(\pm\) 0.01 b & 4.73 \(\pm\) 0.12 a \\ \hline Roasting (20 min) & 1292.47 \(\pm\) 0.05 a & 199.40 \(\pm\) 0.01 b & 10.99 \(\pm\) 0.18 b \\ \hline Roasting (30 min) & 1247.22 \(\pm\) 0.03 a & 317.82 \(\pm\) 0.01 b & 18.72 \(\pm\) 0.11 b \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Effect of cooking on the antioxidant pigments of purple carrots. Different lowercase letters between the sample subjected to each cooking method and fresh carrots (used as a reference) indicate differences at \(p<0.05\). firms the major transference of polyphenols including anthocyanins from the samples to the aqueous medium. Both the increase of carotenoids and the reduction of polyphenols after boiling have been described in both orange [26] and purple [15; 27] carrots. Actually, maximum concentrations of \(\alpha\)- and \(\beta\)-carotene have been found after 20-30 min boiling as compared with fresh vegetables. Although there are also a few studies that describe opposite results (i.e., decrease of carotenoids [28] and increase of TPC values after boiling [29]), the values shown here support the substantial loss of water-soluble bioactive compounds as a consequence of boiling. It is interesting that steaming, despite also resulting in an increase of TCC (from 1136.66 \(\upmu\)g\(\cdot\)g\({}^{-1}\) to 2061.95 \(\upmu\)g\(\cdot\)g\({}^{-1}\)), did not bring about the loss of either TPC (from 66.71 \(\upmu\)g\(\cdot\)g\({}^{-1}\) to 82.49 \(\upmu\)g\(\cdot\)g\({}^{-1}\)) or TAC (from 4.83 \(\upmu\)g\(\cdot\)g\({}^{-1}\) to 7.79 \(\upmu\)g\({}^{-1}\)). This suggests that steaming is a less aggressive cooking method than boiling. As far as roasting is concerned, it not only preserved naturally occurring carotenoids in uncooked purple carrots, but also led to a significant (\(p<0.05\)) increase of all bioactive pigments. This increase was higher for carotenoids when the roasting time was as short as 10 min. However, TPC and TAC exhibited even higher values when the roasting times were longer than 10 min. It is known that the heat treatment of vegetables can cause two opposite effects. On the one hand, it can induce the thermal degradation of phytochemicals, and on the other hand, it can increase the extractability of the compounds as a result of matrix softening [30]. Our results evidenced that, under the roasting conditions here applied, all studied pigments, including carotenoids and anthocyanins, not only were not degraded, but their formation was slightly stimulated. This phenomenon has also been observed in previous studies on purple-corn-derived products [31]. Although the heating temperature applied was 100 \({}^{\circ}\)C, it is believed that the slight formation of non-enzymatic browning compounds might occur during the roasting.