engleski

Free radical detection ​in water and herb extracts after processing ​by high voltage electrical discharges and high power ultrasound​

Formation of radicals by nonthermal processing can be good in order to inactivate microorganisms, for wastewater treatments, for dyes destruction, for oxidative processes, chemical synthesis, formation of plasma activated air (PAA) or water (PAW), but on the other hand it can deteriorate quality of some food products, extracts etc. In this study, the influence of sonification of water on the formation and stabilization of hydroxyl radicals has been investigated by Electron spin resonance (ESR) spectroscopy and spin-trapping method. Sonication was done using ultrasonic processor (S-4000, Misonix Sonicators, Newtown, Connecticut, USA), set at 600 W, 20 kHz, 12–260 µm with different probes. Probes of 1.6 mm and 6.4 mm were used in order to observe influence of different ultrasound power on formation of hydroxyl radicals. Ultrasonication was carried out with 50, 75 and 100 % amplitude, for 1, 3 and 5 min. High voltage electrical discharge- plasma (HVED) is one of new promising green techniques for extractions. Plasma generator IMP-SSPG-1200 (Impel group, Zagreb, Croatia) was used for extractions of bioactive compounds from herbs in different solvents. Optimization of processing extraction parameters (argon and nitrogen gases for generation of plasma, voltage – 15kV, 20kV and/or 25kV), frequency (100Hz), pulse duration (400 ms) and treatment times (3 and 9 min) was done using software STATGRAPHICS. Results showed that number of radicals is increasing with treatment time and increase in amplitude, and the reduction in their number is smaller at samples stored at 4°C after treatments, than for those stored at room temperature after treatments. For extracts, radical scavenging activity of extract was monitored. The remaining DPPH radicals, expressed as a percentage, showed that is some treatment runs, especially with nitrogen there was less % of left DPPH radicals in samples that means that phenolic compound form extracts chemical bonded with DPPH.

Free radicals ; high voltage electrical discharges ; high power ultrasound​

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