Brindzová L., Čertík M., Rapta P., Zalibera M., Mikulajová A., Takácsová M. (2008): Antioxidant activity, β-glucan and lipid contents of oat varieties. Czech J. Food Sci., 26: 163-173.The antioxidant activity, total phenolic and β-glucans contents, and the fatty acid profile of total lipids in covered (black and yellow) and naked oats were studied. Oats with black hulls showed a significantly higher antioxidant activity in 2,2'-azino-di-[3-ethylbenzthiazoline sulphonate] (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) based tests in comparison to the grains with yellow hulls and those of the naked varieties. Radical scavenging activity of oats determined by electron paramagnetic resonance (EPR)/spin-trapping test did not depend on the colour of the grain hulls, but the naked grains showed a lower ability in scavenging reactive radicals. A positive correlation between the content of β-glucans in covered oat grains and the amount of reactive radicals scavenged was observed. Total phenolic content in the black oats was significantly higher than in the yellow and naked oat varieties. However, no significant differences in the fatty acid profile between the naked and covered oats were found, and the common fatty acids being linoleic, oleic, and palmitic acids.

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In the available literary sources there are many works concerned with the antioxidative effects of spices involving mainly rosemary, sage, majoran, pepper, peppermint, ginger, etc. [l -61. To extend the knowledge of the antioxidative effects of spices some changes of lipids occuring in the model sample of the low-erucic rapeseed oil "Vitol" with addition of extracts of thyme, sage, juniper and oregano were studied by defining the acid, peroxide, thiobarbituric acid numbers and the composition of fatty acids.

Flavonoids are a large group of secondary plant metabolites with hydroxyl groups. The flavonol quercetin is commonly found in onions. In the edible fleshy scales of yellow onions quercetin mono- and diglucosides are present. The aim of this work was to study quercetin glucosides during technological processing of yellow onion bulb. Onion was boiled in water under reflux for 30 min. The cooking was performed at three different onion/water ratios (1/5, 1/10, 1/20; w/w). The resulting soup, boiled onion solids and the control raw onion samples were lyophilised, extracted with ac. methanol and analysed for quercetin and its derivatives (3-β-D-glucoside, 4’-β-D-glucoside, 3,4’-β-D-glucoside) using HPLC-UV. Major flavonoid components identified in yellow onion were quercetin-4’-β-D-glucoside<br />and 3,4’-β-D-glucoside with a decreasing concentration from outer toward inner rings of the raw bulb. These substances were rapidly transferred into cooking water during thirty minutes boiling making the resulting soup a good source of flavonoids. The effect of water amount added on flavonoid concentration was followed.

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