Lautering

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After mashing, wort (the liquid portion containing extract) must be separated from the spent grains in order to continue. This process is called lautering.[1][2]

The first runnings are generally returned to the top of the mash and the wort is recycled until it is completely clear and "runs bright".[3] Turbid worts should be clarified as soon as possible in the production process and certainly before they reach the fermentation vessels (Maule, 1986). In general, more turbid worts carry more lipids and techniques are usually adopted to minimize turbidity and the amounts of lipid remaining in the wort, even though their presence can increase the fermentation rate. Thus the wort is recirculated through the filter bed until it "runs bright". More lipids are also removed at later stages of the brewing process, for instance, during wort boiling and clarification, but it is sound practice to obtain the sweet worts as bright as possible. Using a traditional mash/lauter tun in combination with recirculation minimizes the amount of lipids in the wort.

Lautering speed is increased by keeping the malt husk as intact as possible during milling to give the mash bed a more "open" structure.[3] Flow speed is also increased by Low oxygen brewing, maintaining adequate levels of calcium ions (particularly in thick mashes), using well-modified malt, and collecting wort at elevated temperatures.

Lautering temperature is important. The viscosity of the liquid decreases as temperature increases, allowing lautering to proceed more rapidly. However, it's also important that the temperature doesn't get too high. Undissolved starch may be washed out of the grain during sparging, which may cause haze if it isn't converted. Therefore it's important for alpha-amylase to remain active during lautering, and so the temperature must not exceed 76-78°C.[1][2]

Starch can still go into solution during lautering and maybe broken down during the lautering process. However this requires active amylase which is increasingly inactivated at temperatures over 78°C.[1] Lautering at too high of a temperature may potentially cause a starch haze.

Two basic lautering methods exist for home brewers, and they are not mutually exclusive:

  • A traditional false bottom or screen in the mash tun
  • A porous bag holding the grains (brew in a bag, called BIAB)

Both of these methods are very effective and easy to use. However, removing the grain from the wort with a BIAB tends to introduce more often, and therefore a system with a false bottom is preferred for brewers wishing to avoid oxidation. In other words, aeration of the wort should be avoided.[2] Brewing systems are discussed separately.

The initial wort drained from the mash vessel is called "first wort".

Wort running into the kettle can range from clear to very hazy (turbid). The substances causing haze are fatty acids and proteins that are required by the yeast for growth. Turbid wort therefore often leads to a shorter fermentation time by 1 to 2 days. A more turbid wort has also been shown to produce beer that is somewhat fresher, fuller, more palatable, more floral, pure, softer, more pleasant, with a more clean bitterness, and generally has more character. A disadvantage however is that beers with more turbid are much more susceptible to oxidation (decreased flavor stability).[1] Therefore the ideal haze value during lautering with no cold break removal is 20 EBC. Clear worts impair fermentation and therefore reduce the quality of the beer. Moderate haze in conjunction with optional yeast treatment is therefore ideal.

Run-off from commercial mash tuns is typically no more than 10 EBC and averages 4 EBC.[3]

The process of low oxygen brewing reduces the formation of gel and therefore increases the wort flow rate during recirculation and lautering, reducing the likelihood of a stuck mash.[3][4]

Wort run off should be as clear as possible during lautering so that no particles that could disintegrate further during wort boiling and only small amounts of long-chain fatty acids (which destroy foam and contribute to staling) can get into the kettle.[3]

Squeezing the grains during lautering doesn't inherently cause any problems. However, depending on the system it can increase the turbidity, which is undesirable.[3]

Commercial literature sometimes claims that poor runoff may be due to an increase in viscosity because of a high level of undigested β-glucans in the wort. This is not true. Viscosity of β-glucan solutions at the concentration and high temperature of wort runoff is not significantly higher than that of wort from a very well-modified malt. Experimental investigation of the causes of poor wort filtration2 indicates that the presence of small particles, such as undigested starch granules and pieces of barley cell wall, which have not been broken down, are the main cause of poor wort separation. Addition of microbial enzymes to the mash capable of breaking down β-glucans and other hemicelluloses, such as xylans, arabinoxylans, and pentosans, has often been shown to improve runoff,3,4 especially with difficult malts or when barley is used as an adjunct.[5]

The lauter tun is similar to a mash tun, but the bed depth used is shallower (around 0.5 m). The vessel has a larger diameter and thus a greater surface area. This gives better filter performance and allows the use of finer grist, which results in higher extract rates. The false bottom consists of an open area comprising 10% to 22% of the total surface area, which is critical for lautering performance.[6] Recirculation is operated until the desired wort clarity is achieved (less than five European Brewery Convention [EBC] units) after which the wort is collected.

At the beginning of the lautering step, it is common to recirculate wort over the top of the mash bed in a process called vorlaufing. The purpose of this step is twofold. One is to ‘set’ the grain bed and establish a workable differential pressure across the mash bed that will lead to a smooth and efficient run-off without crashing the grain bed, or sticking it against the false bottom, leading to an increasingly difficult run-off. The other main reason for the vorlauf is to establish the grain bed in the vessel as a filter bed for the wort to be collected. Clarifying wort will help reduce the amount of trub formed (and subsequently need to be removed) during the boiling process.[7]

As wort is collected into the wort kettle, the process of heating the wort can begin as soon as the heating element in the kettle is fully covered with wort, whether this is the bottom of a direct fired kettle, the elements of an electric kettle, or the bottom steam jackets (see also Section 3.4, Wort Boiling). As run-off continues, it will be important to keep an eye on the top of the mash bed. To ensure that oxygen ingress into the mash bed is minimized, it is advisable not to run the extract rich first wort down below the surface of the mash bed.[7]

Ensuring a specific and proper sparge liquor temperature range of 71–78 °C will help prevent the extraction of unwanted polyphenolic compounds from spent grains that can lead to harsh and astringent mouthfeel characteristics in beer (Ockert, 2006).[7]

The finer the grain is crushed, the denser the spent grains cake is, the more difficult it is for the wort to drain off and the longer it takes to lautering. The coarser it is crushed, the looser the spent grains are and the faster it can be purged. [8]

If your MLT has a pressure gauge or a sight gauge at the bottom, you want to keep the pressure differential under 8 inches water during recirc, lautering, and sparging. Lower differential is better.[9]

Darcy's Law is often referenced with regard to lautering, but this law really doesn't apply to grain beds.[9]

The rate of wort separation is reduced by the presence of inadequately degraded "gel proteins" in the mash contributing to the fine particles and the Oberteig which impede the flow of the wort through the goods.[3]

Minimizing bed disruptions during lautering with the goal of Low wort turbidity is helpful to avoid negative impact of lipids.[10] It is essential to minimize exposure to oxygen when transferring the mash (9). This can be accomplished by purging transfer lines and pipes with deaerated water and underletting the lauter tun false bottom with hot water prior to filling (10). Both lauter tuns and mash filters should be filled from the bottom to minimize oxygen pick-up. Efforts should be made to minimize the bed disruptions (deep cuts, intense raking, etc.) during the wort filtration cycle, as lower wort turbidity has been shown to decrease lipid carryover into the kettle (31).[10]

with mash-in temperatures greater than 65°C, the rate of wort run-off progressively declined and the wort became more visually turbid.[11]

Wort turbidity is a well known indicator associated with the quality of the resulting wort and therefore is of outstanding importance.[12] Wort turbidity is correlated with lipid content, notably long-chain fatty acids. The lauter step is assumed to be the most important step in the reduction of total long-chain fatty acids throughout the brewing process, whereby a reduction of more than 90% related to the total content in mash can be achieved.

Besides lipids and fatty acids, turbid worts contain more high molecular protein complexes, or protein-polyphenol complexes, which cause a lower bitter substance yield during wort boiling and an intensified precipitation of colloids which adsorb bitter substances.[12]

insufficient starch conversion (iodine test) can be observed in turbid worts.[12]

According to Schur and Pfenninger90 lauter turbidity had only minor influence on wort composition in terms of metals such as calcium, iron, copper and zinc. In contrast to this, Eils32 observed increased zinc concentrations in more turbid kettle-up and pitching worts. Indeed, most of the zinc originally derived from malt45 was removed during lautering or precipitates with trub during wort boiling and cooling later on.53,55 In particular, zinc was found in mash at mashing-in in a concentration of 1.2–1.5 ppm, after mashing-in at a concentration of 0.37–0.56 ppm, while after lautering only 0.07–0.16 ppm was found in kettle-up wort, due to absorption to spent grains as well as dilution due to sparging.19,53[12]

if a false bottom with gaps of greater than 0.8 mm and a larger free flow area was applied, worts of higher turbidity were obtained.[12]

turbid lauter wort caused a significantly faster fermentation than clear worts, and this was also observed for trub rich worts. On the other hand, a high wort turbidity might make yeast stay in suspension longer.[12]

Some studies show little negative impact from turbid wort, in contrast to many other reports.[13]

on a commercial scale, use of a lauter tun potentially causes a much greater loss of phenolic compounds compared to a mash filter.[14]

Lautering time can be significantly reduced by using antioxidants such as phenolic compounds.[15]

oxidation slows down lautering.[16]

Undegraded starch in the wort can be elimated by recirculating the first running back to the top of the mash.[17]

References[edit]

  1. ↑ a b c d Kunze W. Wort production. In: Hendel O, ed. Technology Brewing & Malting. 6th ed. VBL Berlin; 2019.
  2. ↑ a b c 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.
  3. ↑ a b c d e f g Briggs DE, Boulton CA, Brookes PA, Stevens R. Brewing Science and Practice. Woodhead Publishing Limited and CRC Press LLC; 2004.
  4. ↑ De Rouck G, Jaskula-Goiris B, De Causmaecker B, et al. The impact of wort production on the flavour quality and stability of pale lager beer. BrewingScience. 2013;66(1/2):1–11.
  5. ↑ Ryder DS. Processing aids in brewing. In: Stewart GG, Russell I, Anstruther A, eds. Handbook of Brewing. 3rd ed. CRC Press; 2017.
  6. ↑ Miedl-Appelbee M. Brewhouse technology. In: Stewart GG, Russell I, Anstruther A, eds. Handbook of Brewing. 3rd ed. CRC Press; 2017.
  7. ↑ a b c Holbrook CJ. Brewhouse operations. In: Smart C, ed. The Craft Brewing Handbook. Woodhead Publishing; 2019.
  8. ↑ Narziss L, Back W, Gastl M, Zarnkow M. Abriss der Bierbrauerei. 8th ed. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA; 2017.
  9. ↑ a b http://brewlikeapro.net/lautering.html
  10. ↑ a b Golston AM. The impact of barley lipids on the brewing process and final beer quality: A mini-review. Tech Q Master Brew Assoc Am. 2021;58(1):43–51.
  11. ↑ Evans DE, Goldsmith M, Redd KS, Nischwitz R, Lentini A. Impact of mashing conditions on extract, its fermentability, and the levels of wort free amino nitrogen (FAN), β-glucan, and lipids. J Am Soc Brew Chem. 2012;70(1):39–49.
  12. ↑ a b c d e f Kühbeck F, Back W, Krottenthaler M. Influence of lauter turbidity on wort composition, fermentation performance and beer quality – a review. J Inst Brew. 2006;112(3):215–221.
  13. ↑ Kühbeck F, Back W, Krottenthaler M. Influence of lauter turbidity on wort composition, fermentation performance and beer quality in large-scale trials. J Inst Brew. 2006;112(3):222–231.
  14. ↑ Fumi MD, Galli R, Lambri M, Donadini G, De Faveri DM. Effect of full-scale brewing process on polyphenols in Italian all-malt and maize adjunct lager beers. J Food Compos Anal. 2011;24(4–5):568–573.
  15. ↑ Karabín M, Hanko V, Nešpor J, Jelínek L, Dostálek P. Hop tannin extract: a promising tool for acceleration of lautering. J Inst Brew. 2018;124(4):374–380.
  16. ↑ Araki S, Kimura T, Shimizu C, Furusho S, Takashio M, Shinotsuka K. Estimation of antioxidative activity and its relationship to beer flavor stability. J Am Soc Brew Chem.] 1999;57(1):34–37.
  17. ↑ Muller R. The effects of mashing temperature and mash thickness on wort carbohydrate composition. J Inst Brew. 1991;97(2):85–92.
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