Technological approach to improve flavour stability.

Narziss, L., Miedaner, H., Graf, H., Eichhorn, P. and Lustig, S.

Abstract
The chemistry of off flavour formation in aging beer is briefly described with particular reference to the oxidative reactions which cause staling. An experimental demonstration of the influence of the dissolved oxygen content of freshly packaged beer on its shelf life expectancy is described. Investigations into beer flavour stability were carried out in which the analytical and sensory profiles of 44 beer brands (from 28 German breweries and 6 in other countries) immediately after packaging were compared with those of the same beers just prior to the "best before" date declared on the label. A number of substances involved in the production of off flavours were found to have significantly increased their concentrations in the beer between the day of packaging and the "best before" date. The influences of the gas (carbon dioxide or nitrogen) used to exclude air from containers during filling, oxygen uptake in the brewhouse, the turbidity and fatty acid content of wort, and thermal reactions during mashing and wort boiling (which continue, with especially detrimental consequences, if the wort remains at a temperature close to boiling for too long a period after the actual boiling process is over) are discussed together with the possibility of increasing the natural sulphur dioxide content of the beer, either by using Burtonized liquor (which is rich in calcium sulphate) or by using yeast strains which naturally produce more sulphur dioxide than is normal among brewers' yeasts, to bind the carbonyl compounds released during the aging process and thereby prevent these compounds from causing stale flavours.
Keywords : aging beer carbonyl compound chemistry flavour off flavour oxidation oxygen stabilisation stability staling