Impact of hop raw material type on antioxidant behaviour beer
2010
Mikyska, A.,Vyzkumny Ustav Pivovarsky a Sladarsky, Prague (Czech Republic) | Haskova, D.,Vyzkumny Ustav Pivovarsky a Sladarsky, Prague (Czech Republic) | Horak, T.,Vyzkumny Ustav Pivovarsky a Sladarsky, Prague (Czech Republic) | Jurkova, M.,Vyzkumny Ustav Pivovarsky a Sladarsky, Prague (Czech Republic)
Experimental all malt decoction brews (200 L) of 12% pale lager beer were hopped by a series of five hops ranging from the fine aromatic variety Saaz hops to the high-alpha variety Magnum and CO2 hop extract. Antioxidant properties were assessed by three methods as follows: RC-DCPI, ESR-DPPH a ESR-T150 (lag time). Sensorial stability was assessed after heat aging and three months' storage. The amount of hop antioxidants, polyphenols and free phenol compounds strongly decreased from the aromatic to the high-alpha variety. An important factor was the bitter acids/polyphenols ratio in hops. Beer hopped by Saaz hops contained 60 % more total polyphenols and 80 % more free phenolics, flavonoids and flavanoids in comparison with the zero variant, i.e.hop extract. ESR-DPPH reducing power of worts and both ESRDPPH and RC-DCPI reducing power of beers significantly depended on hopping, decreasing from beers hopped by aromatic hops to beers hopped by bitter varieties. In comparison with beers hopped by hop extract, beers hopped by Saaz hops showed a 38 % higher value, those hopped with Sladek a 27 % higher value. Antiradical activity ESR-T150 value of worts depended partially on hopping, and was comparable in worts hopped by Saaz hops, Sladek, Premiant and Agnus varieties (T150 = 6.5-6.7). The value for brews hopped by Magnum (T150 = 7.5) and by hop extract (T150 = 9.5) was less satisfactory. The content of a group of markers of carbonyl compounds formed from amino acids and higher alcohols, as well as 2-furfuraldehyde content in aged beer depended on hopping, i.e. on reducing activity (ESR-DPPH, RC-DCPI), and decreased from beers hopped by hop extract to beers hopped by aroma varieties Saaz hops and Sladek. Explicit influence of hopping on a group of carbonyl markers formed from fatty acids was not proved. Sensory aging of beers, rated either by deterioration of the overall impression or by intensity of oxidized, moldy (musty) and stale flavour, was faster for beers hopped by bitter hop varieties Agnus and Magnum or hop extract than for beers hopped by Saaz hops, Sladek and Premiant. The experiments proved a significant effect of the type of hop and amounts of hop antioxidants on antioxidant properties and a slowing down of beer sensory aging.
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