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Electrochemical determination of antioxidant capacity of fruit tea infusions

Piljac-Žegarac, Jasenka, Valek, Lidija, Stipčević, Tamara, Martinez, Sanja
Food chemistry 2010 v.121 no.3 pp. 820-825
tea (beverage), antioxidant activity, food analysis, food composition, electrochemistry, electrical properties, physicochemical properties, fruit drinks, phenol, gallic acid, rose hips, phytochemicals
Cyclic voltammograms (CV) taken to 800mV at a scan rate 100mVs⁻¹ were used to quantify electrochemical properties of antioxidants present in 10 fruit tea infusions as well as to deduce antioxidant capacity from the Q₆₀₀ parameter (charge passed to 600mV). A pronounced anodic current peak observed at 440mV in all analysed fruit teas indicated that ortho-dihydroxy-phenol and gallate groups are the major contributors to the antioxidant capacity of investigated teas. Antioxidant composite index (ACI) was determined for each tea employing antioxidant capacity values from previous spectrophotometric determinations as well as the Q₆₀₀ parameter derived from CV. A ranking of the most potent teas was obtained: the fruit tea containing a large portion of rose hip fruit exhibited the highest ACI and a CV with the most pronounced anodic current peak at 440mV pointing to the presence of ortho-dihydroxy-phenol and gallate group containing compounds. Strong positive correlation was established between antioxidant capacities deduced from CVs with those previously determined using established spectrophotometric techniques (FRAP, ABTS and DPPH assays).