What's the point of separate mash and lauter tuns (vessels)?

[perfection]

My understanding is
mashing = saccharification of the starch in the malt (and other adjuncts) involving hot water and amylase that may be a single step infusion or multi step infusion (with rests for proteins, beta amylase and alpha amylase) or a decoction mash. This means the mash tun (and i include mash ketles in this term) could be
(i) traditionally shaped with no heating facility, just a covered insulated tank with or without stirring paddles to cater to single step infusion mashes and decoction mashes by connecting the mash tun to and from a kettle or
(ii) with heating facility to accommodate the periodic increase in temperature in the case of a multi infusion mashes

Lautering = separation of the sweet wort from the spent grain by a mashout, then the drain off initiated by recirculation and followed by sparging all of which is aimed at maximizing the volume of and obtaining a clearer wort (ready for brewing with hops). Equipment that specialize in lautering are called lauter tuns which are wider and shallower than typical mash tuns and without the facility to heat with capacities that would line balance the incoming mash

In i got something wrong above - please correct me

My query is why cannot manufacturers fabricate a SINGLE equipment for both for large scale breweries - something covered and insulated that can conduct the mash in, allow for heating in the case of multistep infusions to ready the mash and proceed with the mashout, recirculation, the drain off through the slotted or perforated false bottom assisted by rakes within the tun? What is the idea of having separate mash tuns and lauter tuns and have the mash pumped out to the lauter tuns only for extraction of wort? Is the pump out so clean, efficient and cost efficient that it is worth. this trouble for the additional amount of wort? Simple why cannot the whole f the two processes be done in a single equipment ?

I am also curious to know how a mashout is done by raising the temperature in a lauter tun when lauter tuns do not have heating facility

Thanks

Stay Safe

[dick murton]

There are three principal methods of mashing in and sparging

• Isothermal (single temperature – typically around 65 C) mashing, taking place in a mash tun
• Rising temperature infusion mashing, which takes place in a mash mixing vessel, with separation taking place in a separate vessel, normally known as a lauter tun, more commonly recently, a mash filter, and very recently, a cascade of centrifuges. Here, the temperature might start as low as 42 C, rising in stages to perhaps 79 C. I will refer to the lauter tun later, but not the mash filter or centrifuges.
• Decoction mashing, using a mash mixing vessel, a mash cooker, followed by lauter tun, or possibly mash filter. I don’t expect anyone is using decoction mashing with centrifuges as they are a recent innovation, and decoction mashing is generally dying out, though some German brewers in particular swear by it for flavours – though recent careful research and trials could find no difference.

Mash tuns
Isothermal mashing traditionally uses an insulated vessel with a false floor. Traditional BREWERY mash tuns do not have rakes (some whisky distilleries for example are different, they have mixers, but no lautering rakes). You mash in and convert, and then run off the wort and sparge all in the same vessel. The grist is ground coarsely, and when mixed with water, the partial grain husks in particular, trap air and cause the mash to float. As a result, the mash floats above the false floor and doesn't blind the slots in the false floor. This coarse grind, plus probably the effect of the entrained air, means the grain bed is highly porous compared to the grist used for a lauter tun, let alone a mash filter. As a result of the coarse grind and floating mash, no rakes are required to maintain the porosity of the bed. Think of a coarse shingle beach and compare to a fine sand beach. The water drains rapidly through the shingle but most runs back over the surface of a fine sand beach.

So traditional mash tuns mix the grain and water once only. There is no need to stir because we do not add heat to the mash and need to ensure consistent temperature throughout the mash. If we do stir excessively, we can knock the air out of the mash, and it will compress and sink to the false floor, creating an impermeable layer of mash.

Lauter tuns
Proper, large brewery lauter tuns use a finer milled grist. The grist is mashed into a separate mash mixing vessel, fitted with stirring paddles and heating facilities, normally steam jackets. As a result of the finer milled grist not being able to trap much air (a specific requirement of some brewers, to prevent oxidation and production of undesirable flavours), and the stirrers in the MMV beating the air out, when the mash is transferred to the lauter tun, the mash sits on the false floor and the excess liquid sits on top - the opposite of a mash tun. The combination of the finer grind, and lack of air makes the bed much denser means it is less porous, so the LT is fitted with rakes to break up the bed, but NOT to mix it. The idea is to make the bed consistently permeable. Without the rakes, the bed will form channels, leaving large amounts of extract in some parts of the grain bed, and probably extract undesirable matter from the grains close to the channels.

Large brewery LTs such as those from Steinecker, Huppman, Ziemann, Briggs have a heck of a lot of rakes. So many, they have to be spread across a number of arms rather than simply one or two balanced arms. The tracks of the rakes created are say 2 to 3 cm apart. Two designs are typically used to enhance the porosity of the bed but not allow the sparge water to run straight through at high speed, the slow percolation allows time for the sugars to migrate from the grain particles into the liquid and get carried away. The two principal styles of rakes are zig zag, to slow the trickling sparge down and increase the contact area and time and straight rakes with wings, which help break up the bed very slightly. To enhance the effectiveness of the rakes, i.e. cut different portions of the bed, they are programmed to raise and lower – with numerous different control programs, according to the individual supplier and mash materials used.

This system developed because of the need to use poorly modified malts, to produce very pale beers so loved by the middle European drinking public, with light taste and colour than the heavier, more flavoursome darker coloured ales that used to exist, and still dominated the British market. This all comes down to climate conditions. Hotter summers than in the UK meant that lighter beers were more enjoyable. The need to brew in autumn and spring only was a result of not being able to brew good beer in winter - too cold, or in summer, too hot, so beers were stored cold. And guess what? Cold beer was considered preferable to warm beer. Put those two conditions together, and possibly also things like the Reinheitsgebot, made conditions such that different temperature mashes were required to complete the malting process in the brewery. Hence the development of decoction mashes. As a result of decoction mashing, there was no air in the mash in the runoff vessel, so rakes were developed to take the place of a man and a paddle, to maintain decent runoff. However, modern temperature controls and improvements in malting have allowed the use of rising temperature mashes instead of decoction mashes.


Rakes are very poor at mixing, as they are not designed for mixing, but for cutting the bed, specifically without turning or spinning the bed - so are a waste of time from that perspective. When you are mixing in a mash mixing vessel, it is necessary to get heat even distributed across the whole of the mash, from outside (the heating panels) to the centre. Rakes simply are not designed for this.
Having said that, I know a fair number of smaller brewers will dispute this, but my experience and those of sometime colleagues get within 3 degrees C at best of target temperature at all points in the mash with rakes (not a mixer), which is not accurate enough for enzyme activity control

Because most of the micro brewers use well modified malt (I accept that some countries home produced malt will be poorer quality than for example, Europe, the US or Australasia), and grind it coarsely, and then use a single temperature mash, there is no need for temperature rises throughout the mashing process and thus no need for any post mash in mixing to ensure consistent temperatures - so the rakes are a waste of time in this situation as well!

You can now brew lagers, including German, Czech, Belgian, French, Australian etc. using an isothermal mash tun now that maltings can produce well modified very pale malts, and pre-gelatinised adjuncts, which don't require enzymes, cooking etc. At one brewery I worked at, we used to brew two similar lagers, using the same malts, one with isothermal mashing, one with rising temperature mashing. If we had changed the hops and yeast, we really would not have found any difference, but had to brew the two beers like this because they were both brewed under licence.

Some German brewers in particular claim they can tell the difference between a beer that has been brewed using decoction mashing and rising temperature infusion mashing or isothermal mashing - but I am definitely not one of them.

So for truly effective temperature control throughout the mash to get within less than 0.5 deg C (and I accept again that this is going to be far more difficult with a 10 tonne grist mash than a 200 Kg mash), you need a proper stirrer.

The next problem is that because you have knocked the air out of the mash and the mash sits on the plates, you need rakes to maintain porosity, and fitting both a mash mixer and rakes in the same vessel, whilst I am sure it wouldn’t be impossible, would be difficult.

Another problem is that the mash would block the slots in the plate with being stirred for let us say an hour during the conversion stand, leading to poorer runoff, and almost certainly lower extract and possibly wort quality.

Modern large breweries at least, with several brews a day obtain more brews by separating the mashing process from the lautering process, it being possible for example, to have a single mash vessel feeding two lauter tuns, each with a 4 hour turn around time, instead of what would be a 5 hour plus turnround time for combined mash / lautering vessels. So it becomes cost effective purely on that basis (I accept this is not likely to be applicable to a very small brewery).

Finally, the mash temperature is not normally raised in the lauter tun, but in the mash mixing vessel. It is not raised in a simple isothermal floating mash, mash tun (no mixer or rakes) either.

[blonberg]

The above is a great answer, but I'll give you an example from a small brewpub I worked at with a German brewing setup:
It made decoction mashing possible. And decoction mashing is incredible.

[Fausto Yu-Shan]

My query is why cannot manufacturers fabricate a SINGLE equipment for both for large scale breweries - something covered and insulated that can conduct the mash in, allow for heating in the case of multistep infusions to ready the mash and proceed with the mashout, recirculation, the drain off through the slotted or perforated false bottom assisted by rakes within the tun? What is the idea of having separate mash tuns and lauter tuns and have the mash pumped out to the lauter tuns only for extraction of wort? Is the pump out so clean, efficient and cost efficient that it is worth. this trouble for the additional amount of wort? Simple why cannot the whole f the two processes be done in a single equipment ?

It is better to have separated vessels because you can continuously brew several batches to fill a big fermenter. As an example suppose your brew house is 30 barrels and your fermenters are 240 barrels capacity, this means you will have to brew 8 batches to fill it in a period of 24 hours, in other words, every 3 hours you start a new batch depending on the beer style.
Likewise, if the brewing system has separated vessels, then while you are lautering, the wort is transferred to a pre run tank and hold it there for some time, meanwhile the Kettle is still boiling the wort of a previous batch until finishing the process to later transfer it to the Whirlpool.
Bigger breweries may even have several brewhouses brewing at the same time, also it is done this way, in case one brewhouse for any reason breaks down, they can continue brewing.

[perfection]

i understand, but if mash tuns can also lauter just having more mash tuns would solve the problem (instead of having to release the mash tun for another batch). So can lauter tun run off the wort more efficiently than if a mash tun had to do it (then its probably worth it)?

[Fausto Yu-Shan]

Mash tun or vessel is designed to mix plus heat the grains and water with an agitator, in some cases it can boil the wort for which they have enough head space to avoid an overspill, likewise the agitator is designed to stir the mash from the bottom to the top, the speed should not damage the grain particles (Shear forces), likewise is practical to transfer the mash from the bottom from one vessel to another in case of decoction.

The lauter tun is designed to filter the mash when is ready and to handle specific original gravity, reason why the diameter is much wider to spread the mash to certain height for easier run off. The lauters at the bottom have a false bottom and the opening is for spent grain discharge.

Also, suppose the brewery decides to use a Mash Filter instead of a lauter tun for efficiency purposes because they mill completely the malt to obtain a higher yield.

A combi Mash tun / lauter is generally used in small scale for economical reasons.

[gitchegumee]

Separating wort from grain residue is best done with screens under the mash. A quiet place for grain to settle. The reason that most breweries use separate vessels is because heating the mash requires circulation of the mash against the bottom & sides of the mash tun. Can't do that with screens there. Lauter tuns are usually wider than mash tuns because filtering and heating require different geometries for peak efficiency.