# Valorization of Carrot Pomace: UVC Induced Accumulation of Antioxidant Phenolic Compounds
## 3 Results and Discussion
### Phenolic Profile and Individual Phenolic Compounds  
A typical chromatogram showing the phenolic compound identified in carrot pomace that is treated with UVC radiation for 30 min and stored at 25 \({}^{\circ}\)C is shown in Figure 2. The compounds identified include protocatechuric acid, gallic acid derivative, 3,5-dicaffeoylquinic acid, chlorogenic acid, and ferulic acid. The phenolic profile obtained herein is similar to those previously reported for whole carrots [20; 24]. For the carrot pomace obtained immediately after juice extraction, CHA was the only phenolic compound identified (Figure 3). This result indicates that the other phenolic compounds usually detected in whole carrots (protocatechuric acid, gallic acid derivative, 3,5-dicaffeoylquinic acid, 3-hydroxy dihydro chlorogenic acid, 4,5-dicaffeoylquinic acid, \(p\)-coumaric acid, and ferulic acid) are extracted with the juice [16; 20]. Figure 3: Concentration of individual phenolic compounds in carrot pomace treated with UVC for 0 (control), 30, 60, or 120 min, and stored at 25 \({}^{\circ}\)C for 48 h. Data represent the mean of 3 repetitions \(\pm\) the standard error of the mean. Different letters among bars (a, b, c, d, e, and f) indicate a statistical difference between treatments using the LSD test (\(p<0.05\)). Individual phenolic compounds identified and quantified were: protocetchuic acid (**A**); gallic acid derivative (**B**); 3,5-dicaffeoylquinic acid (**C**); chlorogenic acid (**D**); ferulic acid (**E**). N.D. = not detected. Figure 2: Typical HPLD-DAD chromatogram (shown at 320 nm) of methanolic extracts from carrot pomace obtained as a by-product after juice extraction, treated with UVC radiation for 30 min, and stored at 25 \({}^{\circ}\)C for 48 h. Peak identification: 1. protocetchuic acid; 2. gallic acid derivative; 3.3,5-dicaffeoylquinic acid; 4. chlorogenic acid; 5. ferulic acid. Phenolic compounds were identified by comparing spectra characteristics of the chromatographic peaks with authentic chemical standards and previous reports [20,21]. Compared with the concentration of CHA previously reported for whole carrots (\(\sim\)500 mg/kg), the pomace retains around 12% of the content in whole carrots [24]. UVC did not induce the de novo biosynthesis of individual phenolics as an immediate stress response. However, the concentration of CHA decreased in carrot pomace that was irradiated for 30 and 60 min. These decreases could be attributed to the immediate increase in the concentration of ROS levels induced by UVC radiation, which could oxidize phenolic compounds [35]. Interestingly, the carrot pomace that was treated for 120 min with UVC light showed a slight increase (40.4%) in CHA content, suggesting that UVC radiation induces an immediate biosynthesis of the compound or that UVC radiation releases bound phenolics present in the carrot pomace [36]. The immediate increase in CHA content detected in the carrot pomace that was radiated for 120 min with UVC (Figure 3D) correlates with the higher AOXs identified in the tissue (Figure 1C). At 24 h of storage, additional phenolic compounds were detected in the carrot pomace (protocatechuric acid, gallic acid derivative, and 3,5-dicaffeoylquinic acid), confirming the wound-induced biosynthesis of individual phenolic compounds. Protocatechuric acid and 3,5-dicaffeoylquinic acid showed their highest accumulation at 24 h of storage in the irradiated tissue. For protocetachuic acid, the treatment that showed the highest accumulation (166.5 mg/kg, 50.6% higher than the control) was the carrot pomace that was irradiated for 120 min, where no significant difference was detected when compared with the 30 min UVC treatment (Figure 3A). On the other hand, the 3,5-dicaffeoylquinic acid showed its highest accumulation (169.4 mg/kg, 140.2% higher than the control) in the carrot pomace that was treated with 60 min of UVC radiation (Figure 3C).