lauter tun

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Introduction The majority of brewers utilise six roller mills, mash tuns and lauter tuns as processing equipment for malted barley in the brewhouse. This paper describes the operation and objectives of this equipment and discusses the brewer’s raw material needs in order to optimise the process for cost efficiency and quality. Milling In practical terms, the milling operation is designed to reduce the malt to particle sizes suitable for rapid extraction and enzymic digestion, maximum extract yield and throughput. However, maximum extract yield is achieved with a fine grind while maximum throughput is achieved with a coarse grind, thus the brewer needs to find a balance. The objectives of milling are to: 1. Split the husk longitudinally, exposing and separating the endosperm, without tearing the hulls 2. Crush the endosperm allowing complete wetting and therefore rapid extraction and enzymic digestion. 3. Minimise the quantity of fine flour produced. Therefore the ideal grist for wort filtration in a lauter tun would contain: 1. No intact kernels 2. The majority of husks split end to end with no endosperm attached 3. The endosperm reduced to a uniform small particle size, called grits 4. A minimum of fine flour.

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Page 1: Lauter Tun

Introduction

The majority of brewers utilise six roller mills, mash tuns and lauter tuns as processing equipment for malted barley in the brewhouse. This paper describes the operation and objectives of this equipment and discusses the brewer’s raw material needs in order to optimise the process for cost efficiency and quality.

Milling

In practical terms, the milling operation is designed to reduce the malt to particle sizes suitable for rapid extraction and enzymic digestion, maximum extract yield and throughput. However, maximum extract yield is achieved with a fine grind while maximum throughput is achieved with a coarse grind, thus the brewer needs to find a balance.

The objectives of milling are to:

1. Split the husk longitudinally, exposing and separating the endosperm, without tearing the hulls

2. Crush the endosperm allowing complete wetting and therefore rapid extraction and enzymic digestion.

3. Minimise the quantity of fine flour produced.

Therefore the ideal grist for wort filtration in a lauter tun would contain:

1. No intact kernels

2. The majority of husks split end to end with no endosperm attached

3. The endosperm reduced to a uniform small particle size, called grits

4. A minimum of fine flour.

Figure 1. Six roll mill schematic F, flour; G, grits; H, husks; F.G, fine grits (Adapted from Briggs et al. 1981)

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When used in combination with lauter tuns, the majority of brewers use six roller dry mills, as shown in Figure 1. A fluted feed roller aligns the grain so they are presented in a lengthwise manner to the first pair of reduction rollers. The grain is split longitudinally and kept reasonably intact. The mixture is then separated through vibrating screens, with fine flour falling through to the grist case and small grits being screened to the third pair of rollers. Hard endosperms are separated from the husk in the second pair of rollers, along with coarse grits. The mixture is again separated through vibrating screens, with flour and husks falling to the grist case and remaining grits being delivered to the third pair of rollers.

For good lauter tun performance Briggs et al suggest that the grist should contain 15% husks, 23% coarse grits, 30% fine grits and 32% flour, while Kunze suggests that the grist should consist of 18% husk, 8% coarse grits, 56% fine grits and 18% flour. In fact, the optimum grist size distribution is dependent on a brewery’s specific requirements for extract yield and throughput, the modification of the malt and the loading on the lauter tun.

Mashing

The objective of mashing is to convert the malt into a fermentable extract suitable for yeast growth and beer production, in a controlled and predictable manner. The majority of Australian brewers use single temperature infusion mashing, where the grist is mixed with water at 65 - 70°C. At this temperature amylolytic conversion of starch to fermentable sugars and dextrins takes place as well as the enzymic and physical solubilisation of protein to give soluble polypeptides, peptides and assimilable amino acids. To control this complex range of biochemical reactions the brewer uses the simple control techniques of time, temperature and pH.

As the grist falls into the mashing vessel (mash tun) it is intimately mixed with water in a vessel, known as a Foremasher. This assures instantaneous and complete wetting of the grist and prevents starch from balling. The mash tun is a cylindrical dished bottom vessel with large slow rotating agitator. The mash must be treated gently as any shear during agitation or transfer will damage the husks, causing wort filtration difficulties. However a mash that is stirred too slowly can result in loss of extract and problems with heat transfer causing local hot spots.

Wort Recovery

Wort recovery or wort filtration is the process of separating the soluble material (wort) from the insoluble material (spent grain). The three objectives of wort recovery are:

1. To maximise extract yield.

2. To produce clear or non turbid quality wort.

3. To minimise wort filtration time, commonly called run off time.

Clear wort and maximum extract efficiency can be obtained by slow run offs however, considering that wort separation is often the rate determining process, this will be at the expense of brewhouse throughput. Therefore, as with milling, the brewer has to find a balance that will suit their specific requirements.

The most commonly used equipment for wort filtration is the lauter tun, Figure 2. The lauter tun is a cylindrical vessel of large diameter and comparatively shallow depth. Suspended approximately 10 cm from the true bottom is a false bottom of slotted stainless steel plates. These plates allow the wort to flow through, but retain the grain husks. Inside the lauter tun is a raking machine, this can

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be raised, lowered and rotated. Connected to the main shaft are radial arms that support the blades or rakes. While a brew is being run off the radial arms are rotated and the blades slice through and slightly lift the bed. This assists in preventing compaction, which can result in a slow or stalled run off and also provides access for the sparge water, thus increasing extract efficiency.

Figure 2. Lauter tun schematic

Malt requirements for milling, mashing and wort filtration

Essentially, malt provides all the ingredients necessary to make beer, including starch, nitrogen (foam proteins, amino acids, peptides), phosphates, silicates, polyphenols, vitamins (B1, B2, C, and E) and enzymes. However, the quality of the barley and how it is processed at both the maltings and in the brewhouse will have a significant impact on the quality and cost efficiency of the beer.

Impact of malt quality on beer quality

The reactions occurring during the mashing process determine the carbohydrate and protein profile of the wort and can be directly attributed to the malt.

The carbohydrate profile of the wort is adjusted by controlling the time and temperature of the malt in the mash tun. It can take three days before a change in the trend of the carbohydrate profile is known and then, if required, subsequent process adjustments can be made. This long feedback loop can possibly result in three days of beer production that is out of specification and therefore require blending.

The goal of brewhouse is to produce wort that is “right first time”, this will result in beer that doesn’t require blending. To achieve this goal the brewer needs consistent diastatic power in the malt or a very good indicator that could be used to predict the required stand time. Since neither is available the brewer must continually adjust stand times or temperatures to meet the carbohydrate profile target for his beer.

Australian brewers add sugar adjuncts directly to the kettle and therefore do not require high levels of diastase to convert starch adjuncts. In fact, high levels of diastase convert starch too quickly and controlling the process becomes difficult if not impossible. Ideally, the malt would contain a level of diastase that resulted in a stand time of thirty minutes. This allows enough time for amylolytic conversion of the starch to maximise extract yield, shorter times can result in low extract yields,

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while longer stand times can result in damage to the husks due to shear and subsequent problems with wort filtration.

The protein profile of the wort determines the foam quality and to some extent the shelf life of the final beer it also has to be suitable for yeast growth. While there have been reports on some specific proteins that affect foam quality (Evans et al., 2000) and beer stability, such as protein Z4, LTP1 and hordein derived polypeptides respectively, these are not routinely analysed, so the brewer relies on a soluble and total nitrogen specification that will provide enough protein for foam quality and yeast nutrition, while not adversely affecting beer stability.

Impact of malt quality on cost efficiency

Obviously, the available hot water extract of the malt has the greatest impact on cost. As mentioned previously cost efficient beer production requires a balance between extract yield and throughput. When using dry mills, which have a tendency to damage the grain, in combination with lauter tuns, which need the husk to be intact, consistency of grain size (grain plumpness) has a large impact on extract yield and throughput. During the milling process variable grain size can result in the following:

1. Small grains may not be effectively crushed. Wetting of large grain particles or grain with the husk still intact is slow, and often incomplete. Therefore the access of enzymes to starch is restricted. This leads to lower extract yield and higher extract cost.

2. Large grains tend to be crushed too severely. This causes the grain to shatter resulting in too much fine flour and shredded or torn husks. Fine flour can ball in the mash leaving unconverted starch, which can cause irreversible carbohydrate hazes in the beer. Fine flour also blocks the lauter tun resulting in slow run offs and further problems during diatomaceous earth filtration. Torn husks are not effective in forming a filtration bed for wort separation and so also result in slower run offs. Inefficient filtration will also result in “dirty” wort, with an increase in polyphenols, which contribute to a harsh palate in the beer and increase the potential of the beer to form polyphenol – protein hazes.

For grain size which follows a normal distribution, a greater standard deviation will result in a greater proportion of grain either being to small or too large, with the resulting problems mentioned above. For example, normal distributions with standard deviations of 1 and 1.5 will result in 5% and 19.4% of grain falling outside 1.96 standard deviations from the mean respectively, Figure 3. Screening alleviates problems with small grain however, it does not provide a solution for malt batches with a large grain size distribution.

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Figure 3. Schematic of the effect of variable grain size on mill performance.

The moisture content, husk adherence, husk thickness and friability of the malt will also have an impact on how the grain performs in the mill and subsequently in the lauter tun. The brewer prefers not to pay for water, however if the grain is too dry it will have a much greater propensity to shatter. If a grain has poor husk adherence, harvesting, storage and handling, malting and milling may also be affected. There are also issues with the potential of dust to cause explosions.

Apart from the physical characteristics of the malt, mentioned above, the biochemical attributes of the malt also can have an impact on cost. High concentrations of beta glucans, particularly those with high molecular weight, can impede:

wort filtration, resulting in long turn around times

diatomaceous earth filtration, resulting in short filter runs and therefore greater DE usage

micro filtration, resulting in short filter runs with the need for more regenerations, thus increased use of cleaning chemicals and reduced filter life.

Considering Australian brewers mash in at 65-70°C the natural beta glucanases and proteases, which are heat labile, will be inactivated and have little effect. Therefore, it is imperative that the malt is well modified. Exogenous heat stable enzymes can be added to the mash, but at a cost.

Hazes that result from protein / polyphenol complexes have been well documented (Siebert 1999). Polyphenols originate from malt and hops, however the levels in the malt are not specified or routinely measured. It has been reported that grain with a thick husk contains more polyphenol. Never the less, to ensure good shelf life, the use of expensive treatments, such as polyvinylpolypyrrolidone (PVPP) may be required. Proteins are equally important in the formation of haze. High protein malts contain relatively more hordein protein and it is the fragments derived from hordein proteins that have been reported to be “haze active”. So, while the brewer specifies an upper protein limit, to ensure good final product stability, haze active proteins may still require treatment with silica gel. Higher protein malts require larger doses of silica gel. High protein barleys also consist of more small starch granules relative to large starch granules. Examination of

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spent grain, reveals that unconverted starch is mainly small starch granules, which unlike large starch granules are not fully gelatinised during mashing. Therefore high protein barleys may result in lower extract yield. Small starch granules have also been implicated in haze and particle formation in the final beer.

Conclusion

In this paper the operation and the objective of six roller mills, mash tuns and lauter tuns has been described. To optimise cost efficiency the brewer needs to find a balance between extract yield and throughput. Hot water extract has the largest impact on cost however, consistency of grain size, beta glucan, polyphenol and haze active protein levels will also affect the cost of production. In order to optimise the process for quality the brewer needs malt where the starch conversion is easily and consistently controllable, a nitrogen profile that provides enough nutrition for yeast growth, fermentation, and foam quality while not adversely impacting on product stability. Currently these needs are met with broad parameters such as diastatic power and total and soluble nitrogen. More research leading to a greater fundamental understanding of the biochemistry of malting and brewing is needed to define the raw material needs more closely.

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Abstract

Brewing apparatus and a method of brewing in which mash cooking and wort boiling are carried out in a single vessel (2), the vessel having an agitator (202), a heater preferably formed as a steam jacket (220, 224) and as an external through flow heater (8), the wort being circulated through the heater and back into the vessel by means of a tangential feed inlet (56) which causes the vessel's

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contents to whirl whilst the wort is boiling. The apparatus and method reduces the requirement for separate mash cooking and wort boiling vessels.

Images(3)

Claims(10)

1. Brewing apparatus comprising an at least part cylindrical vessel mash agitation means within the vessel, means for raising the temperature of the vessel contents and means for causing a rapid circulation of the contents of the vessel by whirling the contents.

2. Apparatus as claimed in Claim 1 further comprising a lauter tun connected to an outlet of said vessel, the tun having an outlet connected to an inlet of the vessel whereby wort from the tun can be fed back into the vessel.

3. Apparatus as claimed in Claim 1 or 2 wherein said means for raising the temperature of the vessel contents comprises a steam jacket at least partially surrounding said vessel, said jacket connected to a source of steam.

4. Apparatus as claimed in any one of claims 1 to 3 wherein said means for raising the temperature of the vessel contents comprises an external through flow wort boiler, the wort boiler connected to a tangential input into a cylindrical side of said vessel and wherein a pump is provided to pump the contents through the boiler and input, said input and pump comprising said circulation means.

5. Apparatus as claimed in any one of claims 1 to 4 wherein said mash agitation means comprises blade means having at least one blade mounted to a vertical shaft connected for rotating to a motor, said blade means being connectable with raising means to raise blade means from a lower position engageable with vessel contents to an upper position disengaged with said vessel contents.

6. Apparatus as claimed in any one of claims 1 to 5 wherein said agitation means is mounted to a vertical shaft the axis of which is offset to the axis of the vessel, the shaft being connected for rotating to a motor and wherein further blade means are provided at a lower extremity of said shaft, said further blade means being rotatable in an area surrounded by a sump of said vessel provided in an outwardly dished bottom.

7. Apparatus as claimed in any one of claims 1 to 6 wherein said vessel is dimensioned so that its height without a sump is related to its diameter and so that H:D is about 1:1, a lowest point of said height defining a reference point R, and wherein a tangential input is provided for said circulation means at an input level above point R where said input level relates to D as about 55 to 230 and to H as about 55 to 235.

8. A method of brewing comprising using a single vessel with agitation means to agitate mash whilst cooking said mash, to boil the wort and to circulate said wort through said vessel whilst boiling, and including the steps of:

(a) filling said vessel with a mash charge of grist and hot water whilst activating said agitation means,

(b) raising said mash temperature to cook said mash,

(c) emptying said vessel into a lauter tun,

(d) cleaning said vessel,

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(e) running off wort from said tun into said vessel to a level,

(f) raising said agitation means above said level,

(g) circulating said wort through said vessel by pumping,

(h) boiling said wort,

(i) ceasing pumping and allowing circulation to continue for a period,

(j) transferring said boiled and clarifying wort through cooling means to fermentation vessel means.

9. A method according to claim 8 wherein after step (a) said charge is allowed to stand for about 15 minutes, in step (b) said mash is raised to about 650C in about 20 minutes after which said mash is allowed to stand for about 30 minutes.

10. A method according to claim 8 or 9 wherein in step (b) said mash is raised to about 650C in about 20 minutes after which said mash is allowed to stand for about 30 minutes and with said agitation means still running said mash is raised to about 760C in about 11 minutes prior to step (c) and wherein step (g) is continuous with step (e) after about 50% of the final wort volume is reached and step (g) continues after the final wort volume is reached, step (h) continuing after said final wort volume is reached for about an hour.

Description

[0001]

Advantages of the invention over known apparatus and methods are reduction in construction costs, space utilization and heat losses, heat losses being quite considerable in known apparatus between individual vessels. Energy conservation is utilized to the maximum since the structural heat requirements of the vessel are combined plant utilization for prime movers, that is pumps, and ancillary equipment, that is valves, is maximised since components may be used for multiple functions.

[0002]

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which:-

o Figure 1 is a flow diagram of the brewing apparatus according to the invention,

o Figure 2 is a side view in partial cross section of a combined mash mixer, kettle, whirlpool vessel for the apparatus of Figure 1, and

o Figure 3 is a plan view of the vessel of Figure 2.

[0003]

A brewing apparatus is qhowp generally in Figure 1 which comprises two main vessels namely a combined mash mixer, kettle and whirlpool vessel 2 and a lauter tun 4. Associated with these vessels are grist feed means 6, a flow through wort boiler 8, a combined transfer and circulation pump 10 (shown as two separate pumps 12 and 14 in Figures 2 and 3), a wort run-off or transfer pump.16,

[0004]

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The present invention relates to brewing apparatus and 3 method of brewing using such an apparatus.

[0005]

Traditionally the process of mash cooking, wort boiling and whirlpool separation have been carried out in separate vessels. Recently we have successfully combined the wort boiling process and whirlpool separation in a single vessel, this has resulted in heat savings whilst there has been some saving in plant cost.

[0006]

Brewing apparatus according to the present invention comprises an at-least part cylindrical vessel, mash agitation means within the vessel, means for raising the temperature of the vessel contents, means for causing a rapid circulation of the contents of the vessel by whirling the contents.

[0007]

A method of brewing according to the present invention comprises in a single vessel agitating mash whilst cooking the mash, boiling the wort, and circulating the wort through the vessel whilst boiling.

[0008]

Preferably the apparatus also comprises a lauter tun into which the mash may be run off and from which wort is returned to the vessel.

[0009]

The means for raising the temperature of the contents preferably comprises a steam jacket at least partially surrounding the vessel and an external through flow wort boiler, the wort boiler having a tangential input into a cylindrical side of the vessel.

[0010]

a lauter tun spent grain removal device 18 and wort cooling means 20.

[0011]

The lauter tun 4 with associated device 18 are conventional and need no further description.

[0012]

Grist feed means 6 comprising a feed in device 30, a grist case 32, an outlet valve 34, a vortex feed unit 36 with mash liquor input line 38 controlled by valve 40, a mono pump 42 and a static in line mixer 44 feeds line 46 into the combined vessel 2. The liquor is normally fed from a separate guaged liquor tank where the liquor can be treated to 65 - 750C. The cooling.means 20 comprising a two stage cooler 50 is fed from wort run-off line 52 controlled by valve 54.

[0013]

The wort boiler 8 which may be either steam heated (suitable for larger installations e.g.1000 barrel output) or gas fired for smaller installations e.g. 30 barrel output is coupled to the combined vessel 2 by a vessel input 56 which feeds tangentially into a cylindrical

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wall 58 of the vessel and is fed by vessel outlet line 60 having valve 62, common line 64, pump line 66 having valve 68, pump inlet line 70, pump 10, pump outlet line 72 having valve 74 and boiler inlet line 76. A bypass valve 78 separates lines 76 and 64. Line 80 joins line 82 having valve 84 for feeding mash from the vessel 2 to tun 4.

[0014]

Wort is run-off from the lauter tun 4 through run-off line 90 through valve 92 in line 94, line 96 in which is valve 100. Lines 96 and 90 are connected also by by-pass valve 98. Line 96 is connected to wort run-off pump inlet line. Wort run-off pump 16 then pumps through outlet line 104, line 106 (which is connected to underlet line 108 through underlet line valve 110),wort run-off 112 in which are valves 114 and 116 and thence back through line 66 or 70 into vessel 2.

[0015]

Within vessel 2 is an off-centrally mounted shaft 200 on which are mounted agitator blades 202 and trub sump blades 204. The off-centred mounting of the shaft improves agitation. Shaft 200 is arranged to be raised from the firm line position A shown in Figure 2 either by attaching a tackle or chain hoist to eye 201 or when fully raised the blades 204 are at the broken line position B of Figure 2. An external motor and gearing 206 is provided on the vessel top to drive shaft 200 to rotate the blades.

[0016]

Around the cylindrical wall 58 at its lower part is a steam jacket 220 and on the outside of the dished bottom wall 222 is a second steam jacket 224. Jackets 220 and 224 are fed by a main steam line 226.

[0017]

Trub sump 228 is fitted with a drain line 230 closed by valve 232 and isolation from line 64 by its valve 234.

[0018]

A typical operating cycle using the above apparatus ; would be as follows:-

[0019]

Starting with a vessel 2 being clean, agitator blades 202 are at position A and running whilst malted grist and liquor (hot water) are pumped in through line 46. The hot water is normally at about 65-750C and is a preset quantity gauged at a liquor tank (not shown).

[0020]

When the charge of grist and water is complete in vessel 2, the charge is allowed to stand at 45°C for 15 minutes.

[0021]

With the agitator blades still running the charge, that is the mash, is raised to 65°C in 20 minutes by means of jackets 220 and 224.

[0022]

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The mash is allowed to stand for 30 minutes.

[0023]

With the agitator running the mash is then raised to 760C in 11 minutes by means of jackets 220, 224. On reaching 76°C the mash is pumped by means of pump 10 or 12 to lauter tun 4. On emptying vessel 2, the vessel is flushed clean - suitable cleaning fluid can be pumped into the vessel 2 through lines 250 and 252 using pump 16.

[0024]

Within 15 or 20 minutes wort run-off from the lauter tun 4 is commenced returning the wort back to vessel 2 by means of pump 16, this will continue for about 120 minutes.

[0025]

When 50% of the wort volume is reached in vessel 2 the agitator blades 202 are raised from lower position A to the upper position B so that they disengage from the contents of the vessel.

[0026]

Wort circulation is now commenced by running pump 10 or 14 and heat is applied to the wort by means of boiler 8 to commence pre-heating the wort from 76°C to 100°C.

[0027]

When the full wort volume is reached, the adjuncts -e.g. sugar and hops are added and the whole volume is boiled for about 60 minutes whilst continuously circulating through the boiler 8.

[0028]

On completion of the boiling phase, the heater and circulating pump 10 or 14 are isolated and the wort continues to rotate due to inertia for about 15 minutes.

[0029]

The clarified wort is then transferred through the cooling means 20 to fermentation vessels (not shown).

[0030]

The trub.residue collected in the trub sump 228 is then discharged through drain valve 232 and the system flushed clean ready for the next batch of mash.

[0031]

It will be appreciated that the cylindrical diameter D of vessel 2 is dimensioned so as to provide optimum flow characteristics when whirling the wort. Taking the effective bottom the vessel at a calculated point approximately where the dishing of the bottom wall 222 would indicate a reference point or bottom level R can be determined. The optimum wort level L is then at a height above R where

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In Figure 2 vessel 2 is dimensioned so that L /D (34 barrel wort level) is about 0.65 and L"/D (30 barrel wort level) is about 0.60. A lower level L"'(for a-half charge of 15 barrels) is such that L"'/D is about 0.33. At this lower level of optimum wort level may not be achieved.

[0032]

On initial trials L/D may preferably be about 0.73.

[0033]

In the example given in Figure 2 D is 2300 mm. The height of the whirlpool inlet above R is about 550 mm whilst L' is 1485 mm.

A Practical Guide to LauteringAuthor:  Randy WhistlerIssue: March 1998

Considering how important it is to the brewing process, lautering doesn’t get much respect. Many brewers see it as simply the process

of rinsing grains. They give it little thought, rush through it, and curse it when it causes problems such as a stuck lauter.

But a successful lauter plays an important role in getting the most from your grains, avoiding astringent flavors, and making your

brewing more consistent.

Lautering, by definition, is simply the separation of mash solids from mash liquids. The act of lautering gives the brewer the wort

needed for making beer.

Lautering begins after the mash. Mashing means that grains are immersed into water warm enough (149° to 158° F) to convert starch

into small sugars, among other processes that take place. Most of these particles that are broken down into smaller parts become

soluble (they become a liquid solution). These small parts are required by the yeast to convert wort to beer. However, the yeast doesn’t

really need all the solid stuff, and not even the most hearty homebrewers want that much body to their beer. Plus if you boiled the gruel

at this point, you would end up with excessive tannins in your beer. Therefore, lautering was invented.

The basic principles of lautering involve putting the mashed grain into a vessel with a sieved bottom. Using the most standard setup,

you will mash and lauter in the same (sieved-bottom) vessel. The sieve can be anything from a leg out of a pair of nylons (usually large

and preferably never before worn) to a V-plate stainless steel false bottom installed in one of those large, round water coolers. The

sieved vessel then allows the liquids of the mash to flow out of the mash tun into another vessel.

However, there is a small problem here. This initial juice that escapes from the lauter vessel has a very high initial gravity, which is not

always preferred by the brewer, and a brewer who just drained the lauter without adding more water would lose a bunch of sugar that

the yeast could otherwise eat. So unless you want really small batches of high-alcohol beer, you have to add more water back into the

lauter. 

The Process

The details of the lautering process depend to some extent on the equipment you use and the type of beer you are brewing. For this

example we’ll look at a beer of medium starting gravity, lautered in the most standard of homebrew lauters, the five-gallon bucket with

umpteen zillion holes drilled into the bottom of it, stuffed into another five-gallon bucket with a spigot near the bottom.

At the point when you are just completing your mash and are ready to lauter, the mash water will serve as foundation water.

Foundation water allows the mash to float rather than become wedged into the sieve. If you were lautering in a separate vessel, you

would fill the bottom with 175° F water and add the mash.

Hot water is preferred to cold water for lautering. Hot water extracts more sugar than cold water. There are many chemical/physical

principles at work here, but they can all be boiled down into a maple-syrup example. If you have ever tried to pour maple syrup straight

from the refrigerator onto your waffles, you know the syrup does not pour very fast. But if it is heated, it pours much more quickly.

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The same is true for the sugars in the mash. If you add cold water to them, they will move very slowly through the lauter. But if you add

hot water, the sugar molecules move around much faster and are therefore extracted much faster. Another reason for using hot water

is that you will be able to bring the wort to a boil faster once lautering is completed.

Once the mash is complete, let it settle for about five minutes. This allows the grain bed to sort of settle out. At the end of the five

minutes, open the spigot and start running off slowly. The lautering process should take about an hour; it’s not a race. A common

mistake made in lautering is to zip the water through the lauter and into the boil as fast as possible.

At the start of the lautering process, you should use a quart container to catch the first runnings. These will be cloudy and have bits of

husk in them. Pour the cloudy, husky material back into the top of the lauter. This process is called vorlauf, a German word that means

temporary. The mash materials will act like a filter and clear the runnings.

Repeat this process until you are satisfied with the clarity of your wort. Some worts never become totally clear, while others can

become almost crystal clear. It depends on your lauter tun design and the type of malt and adjuncts you are using. However, as a

general rule you should at least vorlauf long enough to get the husky material out of the runoff. Fifteen minutes is a reasonable time for

the vorlauf.

Once you have reached the desired clarity, you can start running off into the brew kettle. Again, this is not a race. You should take at

least 45 minutes to run the rest of the water through the lauter vessel. You will notice that the water level in the lauter tun will begin to

get low as you drain off the bottom liquid.

At this point you should be adding hot water back into the top of the lauter. One of the simplest methods is to put boiling or near-

boiling water into your quart vorlauf jug and add the water as needed to the lauter vessel. It is a good idea to keep the water level in

the lauter about an inch above the grain bed.

This is one simple method for adding water to the lauter tun. There are many tools available to help the brewer add water evenly over

the top of the lauter bed. Some are as complicated as another bucket attached to a tube that runs into a second, T-shaped tube. When

water is added to the bucket, the T-tube spins around like a lawn sprinkler. For the most part these devices work well.

You can also use an ordinary gardening water can, plastic not galvanized. If you use this method, the water will cool down significantly

between the time it’s on the stove and it gets to the lauter, so overshoot your target temperature a bit.  

The important thing is to evenly distribute the water over the top of the lauter. This allows the water to flow evenly through the grain

bed. The whole purpose of adding the extra water is to extract more sugar. Therefore, it makes sense to evenly distribute the water. If

the water does not get to a certain spot in the lauter bed, you will get what are called sweet spots. Sweet spots represent lost extract.

One way to prevent sweet spots is to stir up the top of the grain bed with a fork. You can go as far as halfway down the bed and not

disturb it too much. But it’s important to move gently. Some people might be afraid that this will disturb the bed too much. If you feel

that way, this is by no means a necessary procedure. It just helps you get the most out of your extraction. Also, only do this early,

during the vorlauf. Doing it later may cause setting of the disturbed layers, leaving you with a stuck lauter.

Finishing Up

So when do you stop lautering? You have been adding water for quite some time now. How can you tell when it is time to stop? There

are two schools of thought on when to stop: when you reach a certain volume or when you reach a certain gravity. Of course if all goes

well, you’d like to hit both at the same time. However, this takes a lot of practice.

If you decide to aim for volume, the question becomes: Which volume is correct? This depends on how much energy you can stuff into

your boiling kettle. If you are using a five-gallon fermenter, you need 5.5 to eight gallons of starting wort. Generally if you are boiling

on a stove top, you won’t need much more than 5.5 gallons. That’s because the boil on most stoves is fairly weak. However, if you’re

cooking on a propane burner, especially one of those 150,000-BTU flame throwers, and you have a large enough kettle to contain the

boil, you can easily extract eight gallons of wort and boil it down to five in an hour. You will also get good hop extraction this way.

If you decide to aim for a specific gravity, you won’t know in advance, especially when you first try this, how much volume you’ll end up

with. With time, as you get more used to yoursystem, you may become successful at predicting the volume.

However, aiming for specific gravity will make your results more consistent with the recipe, if you’re using one. It will also make it

easier to repeat your results the next time you brew the same beer.   

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The specific gravity method entails taking periodic gravity readings in the boiling kettle. The general method for this is to take a sample

of wort, put it in the measuring device, and immerse the measuring device in ice or ice water until the temperature is correct. Then,

take a gravity reading and throw the wort back into the boiling kettle. Continue to take gravity readings until you have reached the

desired gravity. Keep in mind that the gravity after boiling will be higher than the gravity at the start of the boil. This is due to

evaporation of water during the boil.  

As the measuring device, it’s helpful to use a copper tube with one closed end. Copper has a tremendous heat-exchange capacity, which

allows the wort inside it to cool much more rapidly than wort cools in plastic. Also, stirring helps greatly. Convective heat exchange,

heat passed by a current or flow, is much faster than conductive heat exchange, the passive process of giving off heat without the aid of

a current.

There is also a third method that is used to decide when to quit lautering. It involves neither volume nor gravity of the extracted wort.

This one is practiced by those fearful of tannin being in their beer. This method involves either tasting or taking a gravity reading of the

wort as it exits the lauter tun. It is generally accepted that when the readings get down to a specific gravity of 1.008, there are more

tannins and other unwanted material flowing from the lauter vessel.

If you are tasting the wort, at the point when you can no longer perceive a sweet flavor the gravity ranges from 1.012 to 1.006,

depending on your ability to perceive sweetness. If you fear tannin, stop the lauter at this point.

If you still need more water to reach the volume you desire, then you can make up that amount of water by using hot tap water, or take

the excess sparge water and pour it directly into the brew kettle. The important point is that you are not losing too much fermentable

sugar at this point. It is completely acceptable to use this practice. Many professional brewers use this method. 

Nothing But Time

What if the lauter is taking too long? First, it’s important to emphasize that a lauter that goes too fast is a more common problem than

one that goes too slow. If you lauter for 15 minutes, you’re going to leave a lot of sugar behind, and your extraction efficiency will be

closer to 50 percent than 60 or 70 percent.

The two most likely reasons for a slow lauter are: 

1. The grain was milled too small.

2. The protein layer that forms on top of the grain bed has set thick and is restricting the flow of wort through the grain bed, thus

leaving Lake Lauter in its flood stage.    

Both of these problems are easily rectified. If your milling size is too small, simply make it larger. Many people try a small milling size

because they are dissatisfied with their yield and want to get more extract out of their grain. But a larger mill setting (the actual setting

varies based on the type of mill and grain) combined with a slow lauter will result in substantial extraction.

The second problem of the protein layer on top of the lauter is easily remedied by taking a fork and periodically stirring the top of the

grain bed. A side note on this problem: Wheat is notorious for gumming up lauters, so expect some delays in lautering a wheat mash.

Also, grind the grain a bit larger than normal for wheat beers.   

There is yet one more way that you can slow your lauter down, and that is by sticking your lauter bed. This basically means that the

wort is removed too fast from the bottom of the lauter, causing the top of the lauter bed to push down on the sieve. This stops all flow

through the lauter.    

The most common way that this happens is that people take a long tube from their lauter spigot and put it into their brew kettle on the

floor. Then they open the lauter spigot. The wort in the tube creates a great suction and,whammo, a stuck bed is formed.    

To get rid of a stuck bed, underlet the lauter by pushing water back up through the spigot. This helps clear the sieve holes. After

underletting you should wait about five minutes, then resume lautering.   

Here’s one last suggestion to make the lautering process easier. As soon as you are done using your lauter tun, clean it. Procrastination

about cleaning the lauter tun will almost inevitably cost you more time next time you brew. Also, there tends to be a fascinating array of

molds that are willing to spring up in as little time as a day or two if the lauter tun is left even partially dirty.   

Finally, if you still have trouble going slowly through the lautering process, try drinking some of your previous work during this time

and making it a social event. Most all social events are known to cause time to elongate. 

 

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Randy Whisler is a brewer and microbiologist at Smuttynose Brewing Co., Portsmouth, N.H. He holds an M.S. in brewing from the

University of California, Davis.     

Lautering: malt factors and their use in barley breeding

Chris Ford1, Doug Stewart2, Peter Healy3 and Evan Evans1

1Department of Plant Science, Adelaide University, Waite Campus PMB1, Glen Osmond, SA 50642Adelaide Malting Company, Cavan, SA 50943Lion-Nathan Australia, Milton, QLD 4007

Abstract

Lautering remains a bottleneck in brewery operations. The malt factors contributing to reduced performance in the lauter tun have been incompletely characterised, and breeding of barleys with improved brew-house performance largely overlooked. By gaining a complete understanding of the processes involved, malt characteristics that promote or retard lautering can be targeted within existing breeding programs to produce barleys more closely attuned to the needs of brewers. A laboratory-scale lautering device with a capacity of 1 kg malt has been built, which replicates the grain bed depth and run-off rates of commercial lauter tuns. Lautering performance is assessed by recording differential pressure across the grain bed. The effects of barley variety, malting, milling and mashing conditions, and parameters of lauter tun operation are being assessed for their contributions to lautering performance. Preliminary results have shown that it is possible to discriminate the lautering performance of malts using the small-scale device developed. A number of Australian malts have been examined, and the outcomes of these trials will be presented. By operating the device at temperatures used commercially, it has been possible to minimise interference from β-glucans, and thereby more accurately examine those malt factors of importance to lautering in the brewery.

Introduction

The common thread linking each new malting variety released by barley breeders is an improvement in levels of extract or diastase activity when compared with the variety to be replaced. Traditionally this is achieved through selection specifically for these factors, with little or no emphasis placed on the likely performance of the variety when it is malted and passes into the brew-house. Modern-day brew-houses may operate at up to 10-12 brews per day, and it is generally accepted that the rate-limiting step of the processes from ‘milling to chilling’ lies with the separation of sweet wort and spent grains following mashing. The means by which this is achieved has varied with brewing styles and the advent of hydraulically actuated press-filters, but in each case there is a premium to be had by recovering the maximum extract in the minimal cycle time.

In the unending quest for improved malting barley varieties, there has to the best of our knowledge been no attempt made to select directly for improved performance during the wort separation process. We have recently started a research project that aims for the first time to provide barley breeders with a measurable parameter for the prediction of potential efficiency in the wort separation process. This will be achieved by developing an operational understanding of the most common form of wort separation, namely lautering, and determining the role of individual barley and malt factors in the process. Subsequently, tests to detect the presence or absence of desirable or deleterious components will be developed or adopted from existing analytical protocols, and applied to barley lines undergoing evaluation within our breeding programs.

Lautering research and development – a brief historical perspective

The heyday for lautering research on a laboratory scale seems to have been the period of 20 years or so between about 1970 and 1990. Both before and since that time, few if any reports of new developments or understandings in lautering have appeared. During the 1970s, several papers were published that described the development of increasingly sophisticated laboratory-scale lautering vessels. These were often of all-glass construction, and were designed to allow the assessment of a number of factors in apparatus that mimicked the salient features of brewery lauter vessels. For instance, Crabb and Bathgate (1973) and Bathgate et al (1975) reported the construction and operation of a combined mash and lauter vessel with a capacity of 1 kg malt. The equipment incorporated a host of control units and measurement devices to allow monitoring of wort run-off rates and differential pressure across the bed of spent grains, and was capable of discriminating between two malts with quite similar specifications. Similar, although less complex designs were reported also by Huite and Westermann, (1974), Webster (1981), Armitt et al, (1984) and Laing and Taylor (1984).

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It is interesting to note that 20 years ago, Webster and Portno (1981) stated that ‘the lautering performance of malt is a factor of increasing economic significance...any incidence of poor lautering will inevitably …lead to loss of valuable extract and low brew-house yield’; yet it remains largely a matter of serendipity if a new barley variety performs well during the wort separation process. The outcome of their work was the derivation of an expression that allowed the prediction of wort run-off times from a set of malt parameters, namely the grist mean particle size, the sedimentation value, wort viscosity and the volume of fine particles.

The control of lautering

The outcome of the research summarised in the previous section has been the determination of a list of factors that in various ways have an impact on lautering efficiency. The measurement of lautering efficiency has been achieved by several means, including time to achieve the run-off of a pre-determined wort volume (Webster and Portno, 1981), differential pressure across the grain bed (Laing and Taylor, 1984) and integration under the curve of differential pressure against filtration time (Armitt et al, 1984).

In most cases, the parameters controlling lautering efficiency can be split into physical factors and those derived from barley and malt. The purely physical parameters include the effects of grain bed geometry (shallow beds filter more quickly than deep ones), temperature (higher temperature equates to faster run-off, but at the cost of extraction of lipids and, from the husks, tannins), flow rate (lautering is a combination of filtering of first worts from spent grain and leaching of soluble sugars into the sparge water; at excessive flow rates there is insufficient time for adequate leaching to occur) and the size of the particles that make up the grain bed (smaller particles give better extraction but a lower flow rate). Successful lautering is therefore a compromise between these and other factors, superimposed on which are the effects arising from the mash that is to be separated.

Lautering research for the new millennium

It is clear that although no consensus exists by which effective and efficient behaviour of malt during lautering may be completely predicted, a considerable body of knowledge exists that describes specific factors important in the process. Our research will focus first on gaining an understanding of the particular barley or malt factors that are associated with efficient lautering. When this has been achieved, we will be able to provide to the Australian barley breeding community tools by which new varieties may be selected with improved performance in the brew-house.

Materials and Methods

Design of the laboratory-scale lauter tun used in this study was based on several devices reported in the literature. The main design considerations were the need to mimic brewery conditions of malt loading, grain column dimensions and run-off flow rates, while simultaneously measuring meaningful parameters of malt performance during lautering. It was decided to work with approximately 1 kg malt per trial, using both free-flow and pumped run-off of worts to determine the best set of experimental lautering conditions.

Similarly, a number of parameters for measuring grain bed performance were chosen. These included differential pressure across the grain bed, the volume of wort collected and the decrease in depth of the grain bed. A glass column 900 mm long with an internal diameter of 80 mm was cut and fitted with Perspex ends. A false bottom of commercial manufacture (a kind gift from Briggs of Burton Ltd.) with an aperture of ca 10% was fitted into a 100 mm diameter Quickfit flask lid and the entire lower assembly was fastened to the column using wing nuts and bolts. An attemperating glass jacket was sealed in place and tested for water tightness. Attemperating water was pumped from a thermostatically controlled water bath, and the complete small-scale lauter tun (SSLT) mounted onto a trolley to allow secure and easy access. Malt was milled using a Valley 2-roll home-brew mill, with roll diameters of 31.75 mm, driven by a cordless electric drill running at 350 rpm. Conditions for mashing were based on the Small Scale Brewing protocol developed previously in the laboratory (Stewart et al, 1998), and a grist:liquor ratio of 3:1 was chosen accordingly. Lautering performance was assessed by measuring the differential pressure across the bed of spent grains by way of a water manometer connected beneath the false bottom; in later developments was supplemented with an electronic pressure transducer connected via an analogue-to-digital converter to a laptop computer. The height of water in the manometer was compared to the height of liquid within the lauter vessel at regular intervals following mash transfer and the recirculation and run-off that follows. The differential pressure was plotted against time, or when comparing lautering trials at different run-off rates, against the volume of wort passed through the grain bed. The use of rakes or knives was decided against in the design of the SSLT; the proportion of the grain bed surface area cut would be much larger than that occurring in a commercial lauter, thereby causing disproportionate increases in bed channel to grain bed ratio.

Results and Discussion

Two laboratory lautering protocols were devised to reflect the different strategies by which Australian brewers manage wort run-off:

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(i) A constant-rate recirculation, run-off and sparge at relatively low (30-40 ml min-1 for 50 cm2 false bottom, equivalent to ca 3.6 to 4.8 hl m-

2 hr-1) or higher, 80-100 ml min-1 (equivalent to 9.6 to 100 hl m-2 hr-1) flow rates

(ii) ii) An initial free-flow run-off (ca 600 ml min-1, equivalent to 72 hl m-2 hr-1) for 15-30 secs followed by recirculation, run-off and sparge at 80-100 ml min-1 (equivalent to 9.6 to 100 hl m-2 hr-1) (see Figure 2)

Using a constant run-off rate, a clear difference in differential pressure was seen for the two rates, but a ca 20% increase in the final depth of spent grains occurred at the lower rate. The difference in maximum differential pressure across the spent grains bed between the two run-off rates was only 0.35 psi, suggesting that accurate discrimination of malts by this protocol would be very difficult

An initial free-flow run-off with the outlet tube placed 35 cm above the false bottom gave a higher differential pressure for the same malt than with constant-rate run-offs. Additionally, the final height of the spent grains bed was lower, suggesting that bed formation was more complete using this protocol than with a constant-rate run-off.

At constant run-off rates, differential pressure (DP) across the spent grain bed varied with flow rate. Maximum DP across the spent grain beds differed by only 0.35 psi between the two run-off rates (Figure 1)

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Figure 1 Lautering performance of Sloop malt at two run-off rates.

An initial free-flow run-off gave a higher DP than with constant rate run-offs (Figure 3). Also, the final height of the spent grain bed was lower, suggesting that bed formation was more complete than by constant rate run-off.

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Figure 2. Lautering performance of Harrington malt using a 30-second free-flow run-off to initiate grain bed formation

.

Reproducibility between duplicate runs using either protocol was low, with unacceptably high variation in differential pressure and spent grain bed formation. Further trials are underway in an attempt to improve the reproducibility of the SSLT.

Conclusion

Experimental lautering protocols have been developed that reflect those used in Australian breweries. Only very small differences were seen in the experimental lautering performance of a number of commercial Australian malts. We are currently addressing the remaining technical shortcomings with the experimental lautering apparatus and parameters needed to ensure reliable and consistent data. Our research efforts will now be directed towards the precise determination of malt factors influencing lautering efficiency, and developing assays for their rapid and accurate measurement, thereby providing breeding programs with a valuable tool in the search for improved malting barley varieties.

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Acknowledgments

This work is supported by the Grains Research and Development Corporation of Australia.

The Lauter Tun

ObjectiveIdentify the construction and operation of a Lauter Tun

Design

ConstructionIt is usually built of stainless steel or copper. It is insulated to prevent heat loss of the mash. There is a vent to discharge vapour. It has a false bottom.

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PlatesThe false bottom is built up of interlocking plates. These may have either milled slots or they may be built up of wedge wire.The advantage of wedge wire over cut slots is that wear on the wire does not produce an " opening" of the gap.The plates are made in sections so that they can be lifted. This enables them to be thoroughly cleaned if required.

SpargeIt has a sparging system. This is used to spray water over the mash to wash out the worts.

RakesIt has a raking system. These are knives which can “cut” the bed. This, when used properly, helps the filtrationprocess.

 

There is a CIP system installed. There are spray balls or jets which clean the internal surface and under the plates.Raking can be continuous or using a number of discrete steps. The sparge can be added continuously or as a batch addition.

CleaningThe vessel is normally thoroughly cleaned and descaled once a week with “Caustic”

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Draw offAll Lauter tuns are fitted with a draw off device. This enables the operator to balance run off to the differential pressure of the bed over the plates. Too much differential pressure will pull the bed onto the plates. This will cause a set mash. Modern Lauter Tuns are computer controlled.

Mash inletThere is an inlet for the mash. This is normally through the bottom. This cuts down on oxidation during the transfer from the mash tun.

OperationThe mash is transferred from the Mash tun  into the Lauter Tun. The filter bed in the lauter tun is shallow and has a large surface area. A fine grind increases the resistance to flow and this is compensated for by the use of rakes. These open the bed to allow faster filtration. The rakes must operate in such a way that sparge is not channelled and the filter bed is not totally disrupted. A slight increase in wort viscosity Ability of a liquid to flow freely. Water has a high viscosity, porridge has a lower viscosity. can have a dramatic effect on run off performance.Most lauter tuns are fully automated. The wort run off rate is controlled. Also the differential pressure above and below the lauter plates is measured and controlled. When this pressure falls below a set pressure it has reached a "set bed” condition. The run off is stopped and the rakes are lowered to the bottom of the bed and used to break up the bed for 5 to 10 minutes before normal filtration is resumed.The typical run off sequences and control are shown below.Another measurement often used to control run off is haze Cloudy particles sometimes seen in beer or other products, caused by long protein chains that have not been removed at filtration.. The wort turbidity is measured. The contents of the lauter tun are re-circulated to ensure that only bright (haze less than 5 to 12 EBC) wort runs to the kettle.A typical lauter tun cycle to collect 1000 hl is described below. Event Duration Volume  HI

UnderlettingThis covers the false bottom. It stops the mash settling into the slots and blocking them.

3 minutes 23

FillingThe mash is pumped from the mashing vessel.

11 minutes  

Re-circulationWort is recirculated until it is bright.

4 minutes 20

First worts   The strong worts are run off

41 minutes 200

Second wortsWeaker worts are run off. Sparge water starts to wash out the wort.

74 minutes 475

Last wortsThe last weak runnings are collected

10 minutes 141

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Weak wortsWeak worts are sent to drain. They may be collected and used for mashing the next brew. This saves extract The amount of fermentable matter derived from the brewing process.. However they must be kept hot and thereforesterile Free from microbial/micro-organism contaminationcontamination.

16 minutes 179

Drain downThe remaining liquid goes to drain.

8 minutes 93

Grain removalSpent grains are removed

25 minutes  

Under plate flushThe space under the plates is cleaned. This removes any bits of grain which may have got through the slots. If it was left it would get infected very quickly.

5 minutes  

Total 197 minutes 1000