Malt: its role in oxidation.

Cantrell, I.C. and Griggs, D.L.

Abstract
The influence of the composition and properties of malt on the flavour stability of the beer brewed from it is discussed. Topics covered include the enzymic oxidation of malt lipid precursors, leading to the formation of flavour active substances (e.g. the "cardboard" off flavour compound trans-2-nonenal), the possible influence of sulphur compounds in barley on malt and wort quality, the conflicting evidence on the effects of malt polyphenols, the contribution of dimethyl sulphoxide (formed from dimethyl sulphide during malt kilning and turned back into dimethyl sulphide during fermentation) to the total dimethyl sulphide content of the beer, and the formation of reducing agents (which help to delay the onset of the oxidative reactions by which various beer off flavour compounds are formed) during the kilning and/or roasting of different types of malt, especially the darker coloured types.
Keywords : beer composition flavour malt off flavour oxidation properties stability