Antioxidant activity and free radicals of roasted herbal materials
Introduction: Novel raw materials are being constantly searched for chicory coffee, which thanks to their specific composition can influence human health, thus promoting properties and of course the attractive aroma. Prior to their addition herbs – sea buckthorn (Hippophaë rhamnoides L.), rowanberry (Sorbus aucuparia L.), lovage roots (Levisticum officinale Koch) and dandelion (Taraxacum officinale coll.) – are roasted, which may change their antioxidant properties and generate free radicals with pro-oxidative properties. Objective: The characteristic of antioxidant activity of roasted herbal raw materials (sea buckthorn fruits, rowanberry, lovage roots and dandelion roots) for the production of chicory coffee and to determine the level of free radicals formed under the influence of roasting. Methods: Total phenolic contents were determined before and after the roasting process using the Folin- Ciocalteu phenol reagent and antioxidant activity by ABTS and DPPH assays. Free radicals were examined using electron paramagnetic resonance (EPR) spectroscopy. Results: The roasted materials were good sources of bioactive compounds, estimated at the total phenolic levels from 23.9 to 38.8 mg GAE/g. The highest antioxidant activity by ABTS and DPPH at 109.6 and 71.0 mg Tx/g was determined in roasted sea buckthorn. Free radicals were present in both the raw and roasted herbal materials. Roasted materials were characterised by markedly higher free radical concentrations when compared with the corresponding samples. The lowest free radical concentrations were recorded for roasted sea buckthorn fruits (0.031 x 10^15 spin/g). Conclusion: Despite a high content of compounds with potent antioxidant activity, free radicals were present in novel roasted herbal materials. The formation of both antioxidant molecules and free radicals during the roasting process demonstrates that the two processes were not inversely related.