title: Free radical generation induced by ultrasound in red wine and model wine: An EPR spin-trapping study.
abstract: Direct evidence for the formation of 1-hydroxylethyl radicals by ultrasound in red wine and air-saturated model wine is presented in this paper. Free radicals are thought to be the key intermediates in the ultrasound processing of wine, but their nature has not been established yet. Electron paramagnetic resonance (EPR) spin trapping with 5,5-dimethyl-l-pyrrolin N-oxide (DMPO) was used for the detection of hydroxyl free radicals and 1-hydroxylethyl free radicals. Spin adducts of hydroxyl free radicals were detected in DMPO aqueous solution after sonication while 1-hydroxylethyl free radical adducts were observed in ultrasound-processed red wine and model wine. The latter radical arose from ethanol oxidation via the hydroxyl radical generated by ultrasound in water, thus providing the first direct evidence of the formation of 1-hydroxylethyl free radical in red wine exposed to ultrasound. Finally, the effects of ultrasound frequency, ultrasound power, temperature and ultrasound exposure time were assessed on the intensity of 1-hydroxylethyl radical spin adducts in model wine.
authors.affiliation: School of Food Engineering and Nutrition Science, Shaanxi Normal University, Xi'an 710062, PR China. Electronic address: qinganzhang@snnu.edu.cn.
authors.forename: Qing-An
authors.initials: QA
authors.lastname: Zhang
authors.affiliation: School of Food Engineering and Nutrition Science, Shaanxi Normal University, Xi'an 710062, PR China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Shen
authors.affiliation: School of Food Engineering and Nutrition Science, Shaanxi Normal University, Xi'an 710062, PR China.
authors.forename: Xue-Hui
authors.initials: XH
authors.lastname: Fan
authors.affiliation: Department of Chemical Engineering, University of Malaga, Campus Teatinos, 29071 Malaga, Spain; Instituto de la Grasa, Spanish National Research Council, Avda. Padre García Tejero 4, 41012 Seville, Spain.
authors.forename: Juan Francisco García
authors.initials: JFG
authors.lastname: Martín
authors.affiliation: School of Food Engineering and Nutrition Science, Shaanxi Normal University, Xi'an 710062, PR China.
authors.forename: Xi
authors.initials: X
authors.lastname: Wang
authors.affiliation: School of Food Engineering and Nutrition Science, Shaanxi Normal University, Xi'an 710062, PR China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Song
mesh_terms: D003497:Cyclic N-Oxides / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000737:chemistry; D013010:Sonication; D019097:Spin Trapping; D013696:Temperature; D013997:Time Factors; D014920:Wine
chemical_list: D003497:Cyclic N-Oxides; D005609:Free Radicals; C017245:5,5-dimethyl-1-pyrroline-1-oxide
keywords: EPR; Free radical; Model wine; Spin trapping; Ultrasound; Wine