Technological influence on sensory stability and antioxidant activity of beers measured by ORAC and FRAP

BACKGROUND Many studies have confirmed a wide variation in the phenolic content and antioxidant activity of beers. However, when commercial beers are studied, there is usually no information available on the brewing technology applied. In this study, technological parameters were varied systematically to influence the antioxidant content of beer with a view to improving its flavor stability. High-throughput assays, ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC) were investigated as fast analytical methods to evaluate the influence of brewing technology on antioxidant activity. RESULTS Beers (n = 12) were brewed with systematic technological variations (malt modification, hopping regime) to influence the antioxidant potential. A late hop addition resulted in significantly higher phenolic content (high-performance liquid chromatography with diode-array detection - HPLC-DAD) and antioxidant activity. Raw protein content and malt modification significantly influenced phenolic content and the antioxidant activity of beers hopped at the beginning of wort boiling. Samples were stored under forced and natural conditions and were evaluated by a sensory panel. The decline of bitter iso-alpha-acids as an analytical marker for oxidative aging was significantly lower in beers brewed from malts with high raw protein content. These samples also had higher antioxidant activity values. Panelists gave higher ratings for beer quality to aged beers with a late hop addition. However, late hopping resulted in enhanced hoppy aroma attributes and therefore an altered aroma profile. CONCLUSIONS Both antioxidant capacity methods were well suited as fast methods to evaluate brewing raw material and technological influence on antioxidant activity. The appropriate choice of barley malt and the malting regime could be promising tools to enhance the antioxidant activity of traditionally hopped beers. (c) 2019 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.