Krahl, M.; Muller, S.; Zarnkow, M.; Back, W.; Becker, T.
Arabinoxylan and fructan in the malting and brewing process
Introduction Soluble dietary fibre is of interest in the malting and brewing process for at least two reasons. In the past, brewers feared them because of possible lautering and filtration problems, and thus a prolonged production time of wort and beer. On the other hand, they have beneficial attributes for colonic and consumer's overall health and are a fermentable part of dietary fibre in the human diet. As diseases caused by poor diet or malnutrition are becoming a severe problem in Western countries, interest in health-beneficial compounds like dietary fibre are of growing interest in the diet. Objectives In this work, the influence of the malting and brewing process on the content of soluble dietary fibre in malt, wort and beer derived from it was investigated. Methods Arabinoxylan was measured by HPAEC/PAD after acidic hydrolisis. Fructan was determined subsequent to enzymatic digestion beta-glucan was analysed using calcoflour. Malt and beer analysis were carried out following the methods outlined in MEBAK and EBC. The amount of water-extractable arabinoxylan (WEAX) rapidly increased during malting whereas the brewing and fermentation process showed no influence on the WEAX content in the finished beer. The amount of fructan in most of the investigated cereals was not affected by malting and wort production but decreased to < 10% of the initial amount during fermentation. An analysis of 40 German wheat beer samples from different breweries showed arabinoxylan contents ranging from 0.87 up to 2.88 g l(-1). The arabinoxylan content correlated very well with the original gravity. Conclusion The amount of malt used in beer production and the grist load seems to be the key factors for the arabinoxylan content of the bottled beer. Only negligible amounts of fructans were found in beer, although fructans were present in wort. Higher arabinoxylan contents did not result in increased viscosity of wort and beer.