The influence of malt quality and malting technology on the flavour stability of beer

Brewing trials of different produced malts were carried out to investigate the influence of malt quality and malting technology on flavour stability of beer. All interpretations of the results of these malting and brewing trials are done in consideration of malting technology and in matters of flavour stability. An evaluation of the barley variety is not possible due to the number of trials for each variety and was not intention of this work. The trials comprised nine commercial and one pilot plant (200 kg) malts of the varieties Annabell, Auriga, Braemar (grown in Baden-Wurttemberg), Barke (grown in Franconia) and Scarlett (grown and malted in France). The malting conditions of the German malts were similar, i. e. seven vegetation days (steeping and germination), the kilning procedures varied with respect to the cycle length and the final temperatures between 78 and 90 °C. The beers were processed in a pilot plant (scale: 60 l cast out wort). The resulting data point out, that lipids and their degradation products show a negative impact on beer flavour and flavour stability, but they are mostly not dominant in the flavour profile of fresh and forced aged beer. They can be used as analytical indicators, but the Strecker aldehydes exercise the main influence on the formation of stale flavours. The thiobarbituric acid index (TBI) in malt, unboiled wort and fresh beer was found to correlate highly with the sum of Strecker aldehydes and the tasting results of the aged beer.