Abstract
High performance liquid chromatographic (HPLC/UV) method was adapted for simultaneous determination of seven polyphenols, including derivatives of benzoic (gallic and vanillic acids) and cinnamic acids (p-coumaric, ferulic and sinapic acids), flavan-3-ols (catechin) and flavonols (rutin) in worts and beers at the various stages of the brewing process. Based on the semi-quantitative HPLC analysis, total polyphenols chromatographic index (TPCI) was in the ranges of5.18 - 19.4 mg/L and 7.37 - 20.7 mg/L for all worts and beers, respectively. The HPLC analyses showed that relatively high levels of (+)-catechin and gallic acid were in all the worts and the beers, while the values were much lower for ferulic acid, rutin, vanillic acid, sinapic acid and p-coumaric acid. Polyphenols with relatively high concentrations, that were detected in all tested worts and beers, were gallic acid (1.29 - 4.75 mg/L resp. 2.59 - 4.97 mg/L), (+)-catechin (1.66 - 7.95 mg/L resp. 4.70 - 10.0 mg/L) and ferulic acid (0.41 - 4.53 mg/L resp. 1.05 - 2.87 mg/L). On the other side, the sinapic acid(0.72 - 1.59 mg/L resp. 0.72 - 2.5 mg/L), rutin (1.17 - 2.03 mg/L resp. 1.16 - 2.85 mg/L), p-coumaric acid(ND - 4.73 mg/L resp. ND - 1.44 mg/L) and vanillic acid (ND - 1.52 mg/L resp. 0.75 - 1.81 mg/L) were detected in lowest concentrations. In both, worts and beers investigated in this study, the changes in the contents of individual polyphenols were not uniform. In the case of some polyphenols, a decrease in the content was observed after boiling the worts with hops or after the main fermentation until maturation and filtration, but with some polyphenols, the concentrations were constant until the end of the process or even increased.
Highlights
Beer polyphenols have been mostly investigated in the light of their potential antioxidant activity claimed to enhance beer flavor and stability or even human health (Cortacero–Ramırez et al, 2003; Kondo, 2004; Nardini and Natella, 2006)
Analysis of individual polyphenols by analytical HPLC To remedy the limitation of spectrophotometric methods (Chunsriimyatav et al, 2010a–c) for total polyphenols polyphenols including derivatives of benzoic and cinnamic, flavan–3–ols and flavonols were identified and quantified by HPLC analysis in six kinds of “Czech brews” and their corresponding worts and beers from various stages during the brewing process
HPLC analysis coupled with UV–VIS diode array detection allows separation of polyphenols in worts and beers during the brewing process
Summary
Beer polyphenols have been mostly investigated in the light of their potential antioxidant activity claimed to enhance beer flavor and stability or even human health (Cortacero–Ramırez et al, 2003; Kondo, 2004; Nardini and Natella, 2006). Polymerization of phenolics and formation of polyphenols, and their chemical changes can occur during wort boiling and possibly during fermentation and storage of beer. Minimizing the formation and reducing activity of reactive oxygen species (O2–, HOO, H2O2 and HO) in beer and wort, must be the first step for improving beer flavor stability. There are many endogenous antioxidants such as polyphenols, Maillard reaction products, and sulfite present in beer. Among these antioxidants, polyphenols are of particular interest to brewers because they play a key role in the brewing process by delaying, retarding, or preventing oxidation processes (Lugasi and Hovari, 2003; Lu et al, 2007; Zhao et al, 2010)
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