Cyclic Voltammetric Determination of Antioxidant Capacity of Cocoa Powder, Dark Chocolate and Milk Chocolate Samples: Correlation with Spectrophotometric Assays and Individual Phenolic Compounds
Jelena M. Brcanović1, Aleksandra N. Pavlović1*, Snežana S. Mitić1, Gordana S. Stojanović1, Dragan D. Manojlović2, Biljana M. Kaličanin3 and Jovana N. Veljković1
1University of Niš, Faculty of Sciences and Mathematics, Department of Chemistry, Višegradska 33, RS-18000 Niš, Serbia
2University of Belgrade, Faculty of Chemistry, Department of Analytical Chemistry, Studentski trg 12–16, RS-11000 Belgrade, Serbia
3University of Niš, Faculty of Medicine, Department of Pharmacy, Blvd. Dr Zorana Đinđića 81, RS-18000 Niš, Serbia
Article history:
Received February 11, 2013
Accepted July 22, 2013
Key words:
cocoa powder and chocolates, cyclic voltammetry, antioxidant capacity, spectrophotometric assays, catechins, procyanidins
Summary:
Phenolic antioxidants in cocoa powder, dark chocolate and milk chocolate samples are quantified electrochemically using cyclic voltammetry with a glassy carbon electrode. Cyclic voltammograms were recorded from 0 to 800 mV at a scan rate of 100 mV/s. Phenolics with an ortho-diphenol group show the first oxidation peak in the potential range between 370 and 460 mV (vs. Ag/AgCl) in 0.1 mol/L of the acetate buffer, pH=4. The first and third anodic current peaks, close to 670 mV, can be ascribed to the first and second oxidation of the catechin-type flavonoids that are present at a high concentration in samples. The second peak at around 560 mV can be ascribed to phenolic acids. Procyanidins B1, B2, B3 and B4 did not have any visible waves. Strong positive correlation was established between antioxidant activities deduced from cyclic voltammograms with those determined using spectrophotometric assays. HPLC method was used for the quantification of individual phenolic compounds.
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