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New Ideas for Quantifying the Gushing Potential of Malt
M. Christian, V. Ilberg, J. Titze, H. Parlar and F. Jacob

In this work it was first shown how to quantify the gushing potential of malt with a modification of a common gushing test. Today there exist two acknowledged gushing tests for the brewing industry (Modified Carlsberg Test and Weihenstephaner Test). Both analytical methods use the overfoaming amount of a test-specific produced carbonated wort to determine the gushing potential of malt. Unfortunately the overfoaming amount can vary statistically in a way that this parameter can "only" be used for qualitative information if the malt has a potential for gushing or not and if one malt has a higher or lower gushing potential than another one; but a precise quantitative comparison for example between two malts which both have a gushing potential is difficult. This was the focus of this investigation. With two gushing-positive samples (malt?A and B) it could be shown that with an increase of the concentration of malt solutes a certain point is reached where gushing appears the first time determined by the overfoaming amount applied the Modified Carlsberg Test. For malt A a frequently higher gushing potential (f?≥?5) than for malt B was identified. These results were verified by determining the amount of a gushing suppressing hop product that led gushing to zero by having a constant concentration of malt solutes. The results demonstrated enhanced gushing analyses to quantify the gushing potential reproducibly, not by the overfoaming amount but by the "zero point" where gushing begins (concentration of malt solutes) or is neutralized (amount of hop product). The introduced methods enable the chance for the first time to quantify the gushing potential of malt more precisely. The brewing industry is furthermore faced with the problem of gushing which is characterized by the eruptive overfoaming of carbonated beverages directly after opening the bottle. As gushing is a complex phenomenon with a high diversity of causing factors, it is not yet completely under control despite of intensive investigations for a long time [1-7]. Therefore, risk analyzing for early gushing detection of the malt before the beer production gets more important as the brewers have the chance to react appropriately e.g. with technological measures. Malt is analyzed by two common used gushing tests according to MEBAK [8], the Weihenstephaner Test [8-10] and the Modified Carlsberg Test [8,11]. These tests determine the gushing potential of malt. The gushing potential is detected by the overfoaming amount of carbonated wort after shaking the bottles. The wort is produced according to test-specific mashing and boiling procedures. Experiments have shown that the overfoaming amount can fluctuate whilst efforts are made to improve the reproducibility [9,11] In this work the question is posed and answered if the overfoaming amount is really convenient for estimating the gushing potential. With present knowledge about the development and suppression of gushing it was possible to enhance an established gushing test (Modified Carlsberg Test) to characterize the gushing potentials of two malts more precisely. Hop is known for its gushing reducing characteristic [12?15]. A gushing suppressing hop product was applied purposefully to verify the first results.For the experiments two barley malt samples (malt A and B) from German malt houses were applied. Malt A had been investigated for gushing in a previous study [16]. The gushing suppressing hop product (CO2 hop extract) has been provided by Joh. Barth & Sohn GmbH & Co. KG. Information of the CO2 hop extract is given in the following [17]: The extract have been prepared from natural hops or hop pellets and contain α-acids, β-acids and essential oils. The content of α-acids for aroma hops is approx. 35 % and for high alpha hops (depending on variety) above 50 %. The extract was stored at 4??C and was homogenized by stirring shortly before starting the experiments. The hop extract was dissolved in ethanol (99 %).

Descriptors: gushing analysis, Modified Carlsberg Test, Weihenstephaner Test, quantification, gushing potential

BrewingScience Monatsschrift fr Brauwissenschaft, 62 (November/December 2009), pp. 164-171