Decoction mash

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Decoction mashing is a method of step mashing where part of the mash is withdrawn, boiled, and returned to the mash (which increases the overall mash temperature). This process is repeated for each additional step. With modern malts, decoction mashing generally is not recommended because it does not improve beer quality.[1] It was a historical process to compensate for poor quality malt, which necessitated lower rests to help degrade cell wall components (protein and beta-glucans).[1][2][3] Nowadays, decoction mashing methods are considered obsolete for various reasons.[4][5][6][7][8] Nevertheless, decoction mashing is believed to be important for the flavor profile of certain traditional beer styles, particularly when traditional less-modified malts are used.[3][8]

Buy your Maillard compounds don’t try to mash them! Many home brewers have some fantasy image of immense malty flavors emanating from a decoction, but the reality is that decoction imparts only a subtle flavor difference. A no sparge will outdo a decoction every time! Adding a little additional münich, vienna or melanoidin malt will do the same.[9]

A decoction mash is commonly suggested to cause numerous positive and negative effects such as reduced protein degradation, higher extraction, lower attenuation, improved foam, increased phenolic compounds, increased lipids, increased formation of melanoidins, increased removal of DMS, increased aeration leading to more oxidation, increased husk damage, more time & labor required, and higher energy consumption.[1][7][10][4][11][12][13][14][15][3][8] However, some of these claims may be exaggerated or misleading when comparing decoction to modern step mashing schedules with modern malts, and these effects may not be applicable to a smaller scale (e.g. home brewing). These studies certainly have their flaws. For example, the method commonly used in these studies to measure phenolic compounds is falsely increased by the presence of melanoidins, which also form during decoction. Also, the pumping action of the thick mash on an industrial scale produces a huge amount of agitation to the grain (like extreme stirring); this causes the release of a large amount of substances, such as arabinoxylans, which contain bound phenolic acids. This effect won't occur with home brew decoction methods because the grains are not typically moved by pumping. Interestingly, a recent study shows that decoction does not increase extraction, does not affect fermentability, and does not affect protein degradation.[16] It stands to reason that the modern Hoch-Kurz mash essentially provides all the benefits of decoction without the negative aspects, especially since it is a significant challenge to maintain low oxygen while decoction mashing.

Historical mashing process[edit]

Around 20–33% of the mash is drawn to be boiled. This portion should be very thick, containing a high concentration of solids/grain.[2][10] An infusion volume calculator can be used to determine the amount needed to be boiled, although in practice it will typically provide an underestimate. Normal boiling times are 10–15 minutes for pale beers and 20–30 minutes for dark beers.[1]

Historical decoction mash styles[2]

  • Single decoction - The first rest is 45°C. The boiled portion is returned slowly to increase the mash by 1°C/min up to 65–70°C.
  • Double decoction - The first rest is 45°C. The boiled portion is returned slowly to increase the mash by 1°C/min up to 65–70°C. A second portion is drawn off and returned to increase the mash to 76–78°C.
  • Triple decoction - The first rest is 35–37°C. The first decoction increases the mash to 45°C. The second decoction increases to 65°C, and the third to 76–78°C.

Modern implementations[edit]


A modern trick to produce decoction beers with higher degrees of attenuation is to hold the kettle portion of the mash at a dextrin rest (70–72°C) before proceeding to boiling. Also, for the sake of energy savings, it is sufficient in most cases to heat the mash in the mash kettle up to 96°C and hold it there for 5-10 minutes rather than heating all the way to boiling.[5]

See also[edit]

References[edit]

  1. ↑ a b c d Kunze W. Wort production. In: Hendel O, ed. Technology Brewing & Malting. 6th ed. VBL Berlin; 2019:219–265.
  2. ↑ a b c Evans E. Mashing. American Society of Brewing Chemists and Master Brewers Association of the Americas; 2021.
  3. ↑ a b c Enge J, Semik P, Korbel J, Srogl J, Sekora M. Technological aspects of infusion and decoction mashing. Kvasny Prumysl (Czech Republic). 2023;51(5):158–165.
  4. ↑ a b Briggs DE, Boulton CA, Brookes PA, Stevens R. Brewing Science and Practice. Woodhead Publishing Limited and CRC Press LLC; 2004.
  5. ↑ a b Sacher B, Becker T, Narziss L. Some reflections on mashing – Part 1. Brauwelt International. 2016;5:309-311.
  6. ↑ Sacher B, Becker T, Narziss L. Some reflections on mashing – Part 2. Brauwelt International. 2016;6:392-397.
  7. ↑ a b Krottenthaler M, Back W, Zarnkow M. Wort production. In: Esslinger HM, ed. Handbook of Brewing: Processes, Technology, Markets. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA; 2009.
  8. ↑ a b c Piper D, Jennings S, Zollo T. Pro-tips on lager decoction mashing, infusion mashing, yeast handling & sauergut (video). YouTube. Published 2022. Accessed 2024.
  9. ↑ Kallmeyer M. To mash or not to mash Kurz/Hoch. Drayman's Brewery website. 2016. Accessed online March 2024.
  10. ↑ a b Miedl-Appelbee M. Brewhouse technology. In: Stewart GG, Russell I, Anstruther A, eds. Handbook of Brewing. 3rd ed. CRC Press; 2017.
  11. ↑ Zhao H. Chapter 64: Effects of processing stages on the profile of phenolic compounds in beer. In: Preedy V, ed. Processing and Impact on Active Components in Food. Academic Press; 2015:533-539.
  12. ↑ Wannenmacher J, Gastl M, Becker T. Phenolic substances in beer: Structural diversity, reactive potential and relevance for brewing process and beer quality. Compr Rev Food Sci Food Saf. 2018;17(4):953–988.
  13. ↑ Habschied K, Košir IJ, Krstanović V, Kumrić G, Mastanjević K. Beer polyphenols—bitterness, astringency, and off-flavors. Beverages. 2021;7(2):38.
  14. ↑ Jurková M, Horák T, Hašková D, Čulík J, Čejka P, Kellner V. Control of antioxidant beer activity by the mashing process. J Inst Brew. 2012;118(2):230-235.
  15. ↑ Koren D, Kun S, Vecseri BH, Kun-Farkas G. Study of antioxidant activity during the malting and brewing process. J Food Sci Technol. 2019;56(8):3801–3809.
  16. ↑ Rübsam H, Gastl M, Becker T. Determination of the influence of starch sources and mashing procedures on the range of the molecular weight distribution of beer using field-flow fractionation. J Inst Brew. 2013;119(3):139–148.
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