Control of antioxidant beer activity by the mashing process

Abstract

Beer is considered to be a good source of antioxidants. The composition and the quantity of the antioxidant compounds depend not only on the qualities of the raw materials, but also on the technology processes. Barley and malt represent the main source of antioxidant compounds in beer and the contribution of the hop antioxidants is lower. The influence of he mashing process on the antioxidant activity and polyphenol concentration is crucial. The antioxidant state of the sweet wort and the hopped wort are dependent on the technology processes and the raw materials used. The spontaneous sorption of polyphenols onto wort dregs and the polymerization of catechin and epicatechin lead to decreasing concentrations of individual polyphenols in the final beer. Two methods, based on electron spin resonance were used todetermine antioxidant activity. These were the DPPH (2,2-diphenyl-1-picryl-hydrazyl) assay and the 'lag time' assay using free radical spin-trapping agent PBN (N-tert-butyl-α-phenylnitrone). HPLC with CoulArray detection was used to measure the concentration of the individual polyphenols. This study focused on the antioxidant compounds and on the correlation of their concentrations with the values of total antioxidant activity depending on the mashing process. A good correlation was found between the decline in the concentrations of DPPH (expressed as ARA2) and concentrations of catechin and epicatechin (in sweet wort samples R2 = 0.970, R2 = 0.961, respectively, and in hopped wort samples R2 = 0.949, R2 = 0.956 respectively). © 2012 The Institute of Brewing & Distilling.