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46 2007

Journal of Food and Nutrition Research
Súhrny čísla 2 / 2007

POLOVKA, M. - BREZOVÁ, V. - ŠIMKO, P.
EPR spectroscopy: A tool to characterize gamma-irradiated foods
Journal of Food and Nutrition Research, 46, 2007, č. 2, s. 75-83

Martin Polovka, VÚP Food Research Institute, Priemyselná 4, P. O. Box 25, SK - 824 75 Bratislava, Slovakia. Tel: 00421 2 50237 174, fax: 00421 2 55571 417. E-mail: polovka@vup.sk

Súhrn: The g-radiation induced changes in ground black pepper (Piper nigrum L.), allspice berries (Pimenta officinalis L.), ginger root (Zingiber officinale Rosc.), dried clove buds (Caryophyllus aromaticus L.) and dry oregano leaves (Origanum vulgare L.) exposed to doses from 2.5 to 30 kGy using 60Co source were studied by EPR spectroscopy. Influence of the dose on the character of generated paramagnetic structures, as well as their thermal stability and life-time were investigated. EPR spectrum of all reference (non-irradiated) samples consists of a broad singlet line with unresolved hyperfine splitting, attributable to Mn(II) ions, upon which an additional narrow EPR signal (g = 2.0022; DBpp ~ 1 mT) is superimposed, assigned to stable semiquinone radicals produced by the oxidation of polyphenolics in plants. The analysis of individual EPR spectra of g-radiation treated spice showed the formation of new paramagnetic structures of different origin (mostly cellulose and carbohydrate), which exhibited diverse thermal stability and life-time. Ethanolic extracts of reference spice samples showed considerable radical scavenging ability using the 1,1‑diphenyl-2-picrylhydrazyl (DPPH) free radical as an oxidant. The influence of g-radiation dose on the ability of spice extracts to terminate DPPH was also investigated. The results indicated that the antioxidant capacity was only slightly affected by the radiation treatment.

Kľúčové slová: EPR; g-irradiation; spice; free radicals; thermal stability; life-time; DPPH scavenging ability

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