Biological acidification
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Detailed studies have shown that biological acidification (BA) of mash and wort has resulted in improved mash and wort characteristics while ultimately resulting in a better beer (3,4,22,33,36,47,55). BA is the only direct method allowed by German regulations for pH adjustments of mashes and worts.[1]
An incubation temperature of 48°C for L. amylovorus is commonly used in the brewing industry to eliminate the growth of unwanted yeasts and spoilage organisms, especially the growth of butyric acid bacteria.[1]
biologically acidified beer may have better sensory characteristics compared to beer acidified with food-grade lactic acid — smooth taste with good mouthfeel rather than having a pronounced bitter after-taste.[1]
Biological acidification can be used both in the mash and in the boil.
Malt contains massive amounts of lactic acid bacteria on its surface. These naturally occurring bacteria can be cultivated and produce up to 2% lactic acid at 48°C.[2] A calculated amount of the acidified wort is added to the mash or boil in order to lower the pH to a specific value.
The biological acidification takes place with the help of the lactic acid rods found on the malt, from which specific species such as Lactobacillus amylovorus and L. amylolyticus prevail.[3]
The acid is produced in the following way: An approximately 10% light, unhopped wort is inoculated with a culture of these bacteria. After about 24 hours at 47–48 °C, the lactic acid content is 0.7–0.8%; after a further 8–12 hours, the limit value of 1%. With regard to the ability of the lactic acid sticks to multiply, it is beneficial to achieve an acid concentration of less than 0.4% after the amount required to acidify the wort has been removed.[3] Over a longer period, the lactic acid concentration will increase to around 1.3-2%.
For idle times, e.g. from the end of one brewing week to the beginning of the next, the culture must be lowered again to approx. 0.3% lactic acid concentration and cooled to below 30°C when it reaches 0.6–0.7%. In order to avoid contamination with Candida species and other wort pests, CO2 gassing is important during the entire biological souring process, also to protect against oxidation.[3]
In order not to drive the protein coagulation too far and to avoid a delay in the degradation of the dimethyl sulfide precursor, the sour wort is added completely or partially to the boil in the last 10 minutes. In general, biological acidification produces very light, soft and mild-tasting beers with good foam and improved taste stability.[3]
Malt contains a large population of lactic acid bacteria on its surface, which can be used to produce “natural” lactic acid by acidification of unhopped wort. Lactic acid produced in this way can be used in accordance with the Reinheitsgebot for mash or wort acidification and is often referred to as "biological acidification."[4]
Kunze suggests using a pure culture of Lactobacillus amylovorus or Lactobacillus amylolyticus because they are fast growing, produce lots of acid (up to 2%), are homofermentative, amylolytic, produce L-lactate, are hop sensitive, and do not grow below 30°C. They also do not produce off-flavors. Temperature of 48°C is maintained during acid production with these cultures.[2]
The acid wort culture is maintained by periodically mixing fresh wort with acidified wort, ideally at a ratio of 1:1. Therefore the process should ideally be regulated so that about half the acid wort is needed for a batch, and then it can be immediately refilled with fresh unhopped wort. Oxygen should be excluded as much as possible.[2]
The lactic acid content with the process described above is normally around 1-2%, and it will vary by culture and other factors. For example, higher gravity increases lactic acid yield.[2] The amount of lactic acid in the acidified wort must be determined by titration. See Titratable acidity.
Lactic acid produced by means of natural fermentation using bacteria introduces reductones, providing protection against oxidation.[5]
Biological acidification was originally proposed as a "natural" method for controlling mash pH.[6] However the benefits extend beyond simply controlling the pH. It provides a cleaner aftertaste as better defined malt and hop flavors.
German brewers (e.g. Weihenstephaner) add saurergut at the end of the boil to ~5.3 so as not to interfere with hop alpha acid utilization.[7] Low pH is needed for they lager yeast and a better taste from low pH in the final beer. Different bacteria strains produce different flavor. Bacteria from grain is used to comply with the Reinheitsgebot.
Cited by Fix
- Narziss L. Brauwelt. 1997;15(1).
- Oliver F, Dauman B. Brauwelt. 1988;6(3-4).
- Bach J, Fersing F. Brauwelt. 1997;15(3).
- Narziss L. Brauwelt. 1998;16(1).
Acidify unhopped first wort by incubating it with thermophilic lactic acid bacteria (Lactobacillus delbruÈckii, L. amylolyticus) at 45–47°C (113–116.6°F) for 8–71 h (Oliver-Daumen, 1988).[8]
Biologically (naturally) produced lactic acid results in better flavor stability in the finished beer than does artificially produced lactic acid.[9]
Perhaps biological acidification may improve beer flavor stability compared to other methods, although the evidence is somewhat poor.[10]
The natural microflora on malt is very diverse, and includes viable LAB, wild yeasts, molds and a plethora of other bacteria (9–11) that are responsible for the production of a range of metabolites, the most important of which are ethanol and lactic, succinic and acetic acids. Because of the diversity of the microbial population, souring at different temperatures can favor the growth of different organisms (12,13) and alter the flavor of the finished product. At higher temperatures, LAB have a much higher survivability, and thus make up a much larger proportion of the microbial population (9), although LAB make up only a small fraction of the population of raw barley malt (11).[11] In this study, 49°C was found to be the optimum fermentation condition for wild cultures because it produces the highest amount of lactic acid relative to other fermentation products such as acetic acid.
- Sour wort - Biological acidification made easy
- Sour wort - Biological acidification made easy same as above?
- Identification of Microflora in a Biological Brewer’s Wort Acidification Process Run Continuously for 20 Years
- Biological acidification and beer quality: addition of lactic acid bacteria isolated from malt
- Impact of buffering capacity on the acidification of wort by brewing-relevant lactic acid bacteria
- A Sauergut Reactor
- My wife “gets” sauergut now. Low Oxygen Brewing forum. 2020.
- http://www.themodernbrewhouse.com/wp-content/uploads/2016/11/hefebank-weihenstephan-biologicalacidification-englisch.pdf Biological Acidification
See also[edit]
References[edit]
- ↑ a b c Lowe DP, Ulmer HM, Barta RC, Goode DL, Arendt EK. Biological acidification of a mash containing 20% barley using Lactobacillus amylovorus FST 1.1: Its effects on wort and beer quality. J Am Soc Brew Chem. 2005;63(3):96–106.
- ↑ a b c d Kunze W. Wort production. In: Hendel O, ed. Technology Brewing & Malting. 6th ed. VLB Berlin; 2019:219–265.
- ↑ a b c d Narziss L, Back W, Gastl M, Zarnkow M. Abriss der Bierbrauerei. 8th ed. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA; 2017.
- ↑ Miedl-Appelbee M. Brewhouse technology. In: Stewart GG, Russell I, Anstruther A, eds. Handbook of Brewing. 3rd ed. CRC Press; 2017.
- ↑ Sacher B, Becker T, Narziss L. Some reflections on mashing – Part 2. Brauwelt International. 2016;6:392-397.
- ↑ Fix G. Principles of Brewing Science. 2nd ed. Brewers Publications; 1999.
- ↑ Piper D, Jennings S, Zollo T. Pro-tips on lager decoction mashing, infusion mashing, yeast handling & sauergut (video). YouTube. Published 2022. Accessed 2024.
- ↑ Briggs DE, Boulton CA, Brookes PA, Stevens R. Brewing Science and Practice. Woodhead Publishing Limited and CRC Press LLC; 2004.
- ↑ Kraus-Weyermann T. pH in the Brewery: A Much Underestimated Brewing Variable (slides). Weyermann Malting Company. Bamberg, Germany. Accessed online April 2025.
- ↑ Titze J, Beermann M, Blieninger S, Kaltenbrunner A. Sour wort concentrate as an efficient alternative to traditional biological acidification or the use of acidified malt. In: American Society of Brewing Chemists, Annual Meeting, Chicago 2014. Accessed online April 2025.
- ↑ DiCaprio A, Edwards J. Application of quantitative nuclear magnetic resonance spectroscopy to biological acidification of barley mashes. J Inst Brew. 2014;120(3):207–211.