Stilbenes
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Resveratrol a stilbenoid phenolic compound found in hops, has received attention due to its benficial health effects. With a free trans-resveratrol content of around 0.5 to 8 mg/L, red wine is the main dietary source of this stilbenoid. Due to the relatively low amount of hops added during the brewing process, low resveratrol contents are expected in beer when using a classical hopping regimen. Total resveratrol content in commercial beers generally ranges between 2 to 81 μg/L, which represents a much lower level than is usually found in red wine (2 to 12 mg/L). Therefore, beer is not considered a major dietary source of resveratrol.[1]
At least three stilbenes are present in hops: trans-resveratrol, trans-piceid, and cis-piceid.(43,72) Concentrations ranging from 0.7 to 11 mg/kg trans-piceid and from 0.03 to 2.3 mg/kg trans-resveratrol have been reported in hop cones (Table 8).(73) In grapes, these compounds are known as phytoalexins because they are synthesized in response to injury or fungal attack.(74,75) A strong influence of geographic origin and harvest year has been shown,(73) but American aroma cultivars like Willamette and Cascade emerge in all cases as the best sources of stilbenes. Resveratrol is very sensitive to heat and light.(43) Even during hop storage, a significant loss occurs, especially in highly oxygen-sensitive varieties, leading to new analogs like cis-resveratrol and dimers.(76) Likewise, hop pelletization induces strong degradation.(76,77) trans-Resveratrol and glycosides are absent from malt,(78) so one should not be surprised to find only traces of stilbenes in beer. In order to increase the stilbene level, stilbene-enriched hop products and brewery process modifications are needed.[2]
At least three stilbenes are present in hop: trans-resveratrol, transpiceid, and cis-piceid [4, 109]. Concentrations ranging from 0.7 to 11 ppm transpiceid and from 0.03 to 2.3 ppm trans-resveratrol have been reported in hop cones [110]. A strong influence of geographic origin and harvest year has been shown [110], but American aromatic cultivars like Willamette and Cascade emerge in all cases as the best sources of stilbenes. Resveratrol is very sensitive to heat and light [110]. Even during hop storage, a significant loss occurs, especially in highly oxygen-sensitive varieties, leading to new analogs like cis-resveratrol and dimers [111]. Likewise, hop pelletization induces strong degradation [111, 112]. transResveratrol and glycosides are absent from malt [113], so one should not be surprised to find only traces of stilbenes in beer (Fig. 75.7). Up to 5 mg/L trans-resveratrol was detected in Belgian commercial beers [114].[3]
References[edit]
- ↑ Wannenmacher J, Gastl M, Becker T. Phenolic substances in beer: Structural diversity, reactive potential and relevance for brewing process and beer quality. Compr Rev Food Sci Food Saf. 2018;17(4):953–988.
- ↑ Callemien D, Collin S. Structure, organoleptic properties, quantification methods, and stability of phenolic compounds in beer—a review. Food Rev Int. 2009;26(1):1–84.
- ↑ Collin S, Jerković V, Bröhan M, Callemien D. Polyphenols and beer quality. In: Ramawat KG, Mérillon J-M, eds. Natural Products. 1st ed. Springer; 2013:2334–2353.