Comparison of Antioxidant Activity of Barley (Hordeum vulgare L.) and Malt Extracts with the Content of Free Phenolic Compounds Measured by High Performance Liquid Chromatography Coupled with CoulArray Detector

Abstract

J. Inst. Brew. 114(2), 150-159, 2008Hot water (45°C) extracts of ten barley varieties and their corresponding malts were analyzed in terms of antioxidant activity. The ferric reducing antioxidant power (FRAP) and radical scavenging activity (ABTS), ranged from 0.23-0.45 mg GAE/g dw for malt and 0.12-0.25 mg GAE/g dw for barley. The hull-less malt KM 1910 was the variety with the best antioxidant properties, whereas the highest antioxidant capacity for barley was detected for the variety Merlin. A significant positive correlation between the methods FRAP, ABTS and ITT was found (p < 0.01). The influence of fertilization (20 kg N/ha) on barley antioxidant capacity was studied. The results obtained suggest that the impact of fertilization was not evident and that it depends significantly on barley genotype. The total polyphenol content, as measured according to Folin-Ciocalteu's method, ranged from 0.6-2.9 mg GAE/g dw and correlated positively with all the antioxidant methods used (p < 0.01). Free phenolic compounds were measured by HPLC with a CoulArray detector. The dominant phenolic compound was ferulic acid and its content ranged from 12.5-21.9 and 7.8-56.1 μg/g dw for barley and malt, respectively. The content of catechin ranged from 11.0-17.0 μg/g dw in barley and 0.9-12.1 μg/g dw in malt.

Effect of Maillard reaction on reducing power of malts and beers

“…This is in a good agreement with the values of the DPPH • assay for pale malt found by Zhao and Zhao (2012), which ranged from 9.0 to 13.4 mmol Trolox equivalents (TE)/kg. Nevertheless, the methods used for the assessment of AOC can affect the investigation of extractable antioxidants in malts strongly, as shown in the comparison of a series of 10 barleys and corresponding pale malts (Dvořáková et al 2008a). While no significant differences were observed using DPPH…”

A comparison of Czech and Chinese varieties of barley with regards to technologically important polyphenolic substances.

“…Obsah ferulové kyseliny je oproti dříve publikovaným údajům (Ehrenbergerová et al, 2012;Běláková et al, 2010) nižší, je ovšem třeba zdůraznit, že zmiňované práce se lišily v použité metodice přípravy vzorku. Podíl dominantních kyselin vázané frakce naproti tomu poměrně přesně odpovídá dříve publikovaným výsledkům (Dvořáková, 2008b).…”

“…Proto je také izolace a purifikace ječných polyfenolů ve srovnání s chmelovými výrazně obtížnější. Celý proces je značně časově náročný, spočívá nejčastěji v alkalické hydrolýze nebo více-násobné extrakci organickými rozpouštědly, vyžaduje řadu násled-ných purifikačních kroků, které umožňují oddělení problematických látek, jako jsou polysacharidy, lipidy a bílkoviny (Ehrenbergerová et al, 2012;Dvořáková et al, 2008b). Na druhou stranu umožňují některé tyto postupy stanovení podílu konkrétních polyfenolů v jednotlivých dříve zmiňovaných frakcích (volné, vázané, esterifikované) a tím poskytují, ve srovnání s chmelovými, širší spektrum informací o této významné skupině látek.…”

“…Therefore, the separation and purification of barley polyphenols is more difficult when compared with hops polyphenols. The whole procedure is rather time consuming beginning with an alkali hydrolysis or multiple extractions with organic solvents followed by a number of purification steps which allow the removal of interfering substances such as polysaccharides, lipids and proteins (Ehrenbergerová et al, 2012;Dvořáková et al, 2008b). On the other hand, some of these procedures allow a quantitative determination of particular polyphenols in previously mentioned fractions (free, bound and esterified).…”

“…Lately, the antioxidation properties of polyphenols gained interest (Rice-Evans et al, 1996;Pietta, 2000;Dvořáková et al, 2008a), particularly with regard to the formation of sensory undesirable compounds (Vandehaegen et al, 2006;Mikyška et al, 2011) as well as anticancerogenic properties of polyphenols (Gerhäuser, 2005;Ramos, 2007). Moreover, the advanced analytical methods enabled the identification and a precise quantification of particular polyphenols (Dvořáková et al, 2008b). The development in this field caused a shift away from efforts to remove as much of the polyphenols as possible during the stabi-…”