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Electrochemical, photometric, and chromatographic methods for the evaluation of organic matter and bioactive compounds in coffee brews

Grigoriou, Constantina, Karavoltsos, Sotirios, Kaliora, Andriana C., Sakellari, Aikaterini, Plavšić, Marta, Dassenakis, Manos, Kalogeropoulos, Nick
European food research & technology 2018 v.244 no.11 pp. 1953-1961
Maillard reaction products, active ingredients, antioxidant activity, bioactive compounds, blood lipids, blood serum, caffeine, chlorogenic acid, chromatography, copper, electrochemistry, humans, instant coffee, ligands, lipid peroxidation, lipoproteins, organic carbon, oxidation, phenolic compounds, photometry, surfactants
Sensitive electrochemical techniques were combined with photometric and chromatographic assays to characterize the organic matter, determine selected bioactive compounds, and evaluate antioxidant properties of popular coffee brews. Physicochemical properties of organic material released in Greek/Turkish, espresso, filter, and instant coffee brews were investigated measuring copper-complexing ligands (LT), surface active substances (SAS), and catalytically active compounds (CAC). In addition, organic carbon, total and individual phenolics, and caffeine were measured. The content of Maillard reaction products was estimated. Antioxidant potential was primarily assessed measuring DPPH-radical scavenging capacity and ferric-reducing antioxidant power. The potential inhibition of human serum lipoprotein oxidation in vitro was also investigated. The effect of fast or slow sipping of Greek/Turkish coffee was investigated as regards organic matter release and antioxidant activity. Coffee brews release Cu complexing ligands at different concentrations (74.6 and 364 mM in filter and Greek/Turkish coffees, respectively). Coffee brews contained 50.1–445 mg caffeoylquinic acids (CQAs) per 100 mL, the 47–53% being chlorogenic acid. Among coffee brews, espresso contained more CAC, SAS, copper-complexing ligands, caffeine, browned compounds, and phenolics. In addition, espresso exhibited higher antiradical activity and reducing power, while Greek/Turkish coffees higher resistance to serum lipid oxidation.