Determination of free radicals and flavan-3-ols content in fermented and unfermented teas and properties of their infusions

Robert Socha , Małgorzata Bączkowicz , Teresa Fortuna , Agnieszka Kura , Maria Łabanowska , Małgorzata Kurdziel

Abstract

The objective of this study was to analyse selected brands of fermented (red and black) and unfermented (white and green) teas for free radical content with the use of electron paramagnetic resonance (EPR) spectroscopy and for contents of flavan-3-ols by means of high-performance liquid chromatography. Analyses were also conducted for the polyphenolic profile of infusions of the analysed teas (with the Folin–Ciocalteu’s method) and their antioxidant activity (in reaction with a DPPH radical) at three brewing times (5, 10 and 15 min). The obtained results showed the possibility of using rapid spectroscopic method EPR to evaluate the oxidative changes in tea leaves caused by enzymatic fermentation. The number of free radicals in teas was negatively correlated with contents of flavan-3-ols, (−)-EGCG in particular. The main signals observed in EPR spectra of teas were attributed to semiquinone radicals; however, also signals attributed to carbohydrate radicals were detected. Regarding unfermented teas, it was ascertained that teas with the highest content of flavan-3-ols, (−)-EGCG in particular, were characterised by the lowest content of semiquinone radicals and a high content of carbohydrate radicals. The group of fermented teas demonstrated to contain mainly semiquinone radicals. The total phenolic content and antioxidant activity of the tea infusions were strongly diversified depending on the kind and brand of tea as well as on the extraction time. The predominating flavan-3-ol in the analysed teas was epigallocatechin gallate (−)-EGCG, the content of which was additionally highly correlated with the antioxidant activity of the tea infusions.
Author Robert Socha (FoFT / DoAaEFQ)
Robert Socha,,
- Department of Analysis and Evaluation Food Quality
, Małgorzata Bączkowicz (FoFT / DoAaEFQ)
Małgorzata Bączkowicz,,
- Department of Analysis and Evaluation Food Quality
, Teresa Fortuna (FoFT / DoAaEFQ)
Teresa Fortuna,,
- Department of Analysis and Evaluation Food Quality
, Agnieszka Kura (FoFT / DoAaEFQ)
Agnieszka Kura,,
- Department of Analysis and Evaluation Food Quality
, Maria Łabanowska
Maria Łabanowska,,
-
, Małgorzata Kurdziel
Małgorzata Kurdziel,,
-
Journal seriesEuropean Food Research and Technology, ISSN 1438-2377, (A 25 pkt)
Issue year2013
Vol237
No2
Pages167-177
Publication size in sheets0.5
Keywords in Englishfree radicals, EPR spectroscopy, teas, flavan-3-ols, antioxidant activity
DOIDOI:10.1007/s00217-013-1975-0
URL http://link.springer.com/article/10.1007%2Fs00217-013-1975-0#page-1
Internal identifierWTŻ/2013/99
Languageen angielski
LicenseJournal (articles only); author's original; Uznanie Autorstwa (CC-BY); after publication
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Determination of free radicals and flavan-3-ols content in fermented and unfermented teas and properties of their infusions of 17-04-2019
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Determination of free radicals and flavan-3-ols content in fermented and unfermented teas and properties of their infusions
Score (nominal)30
ScoreMinisterial score = 30.0, 26-07-2017, ArticleFromJournal
Ministerial score (2013-2016) = 30.0, 26-07-2017, ArticleFromJournal
Publication indicators WoS Citations = 6
Citation count*5 (2016-07-06)
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