What is underlet mashing?

Another little video prompted by a viewer request. I explain underlet mashing, a favourite technique of English brewers for more than a century. 

 

Underlet mashing

Yet more stuff from the Brewers' Journal. This time about a topic dear to my heart: underlet mashing.

It's weird that this very common method of mashing gets very little attention nowadays. Despite being a pretty standard process for over a hundred years. 

In principle, it's a simple form of a step mash. It started with a simple infusion, which was allowed to stand for 20 or 30 minutes. Then a smaller quantity of hotter water was introduced to the mash from below via the underlet. The internal rakes were then given a couple of spins to mix the hotter water through the mash. And left to stand for two hours or so.

It seems that some brewers also used steam in addition to hot water to raise the temperature of the mash.

The time for application of the underlet must depend upon the malt itself, but in practical working I believe that 20 minutes is a sufficiently long stand after the malt has all been mashed in, unless the malt should happen to be low in diastase, when the time may well be extended to half an hour. There is, in my experience, no harm at all in bringing the second heat up to quite a high temperature— that is, 155 deg. to 158 deg.; indeed, in several breweries the second temperature is brought up to 159 deg., or even 160 deg., though in that case it is usual to extend the preliminary stand from 20 to 30 minutes. It is in such a case necessary either to use a very large quantity of underlet liquor at a very high temperature, or to supplement the underlet with free steam blown in under the plates. This second process answers perfectly well if the steam inlets are sufficiently numerous to allow of a fairly uniform heating of the mash; but in cases where one steam jet only is provided, there is a danger that one portion of the mash may be almost boiling whilst the other is only slightly heated. I strongly advocate the use of hot underlets, and the raising of a mash heat some 8 deg. or 10 deg. after 20 to 30 minutes’ stand, for by this means a wort low in albuminoids, a strong yeast, and a beer carrying a tough viscous head, brightening very rapidly and not prone to fret, are secured.
The Brewers' Journal vol. 38 1902, November 15th 1902, page 668.

Here's an example of an underlet mash from my favourite, Barclay Perkins. Who were very keen users of this technique.

Barclay Perkins X Ale mashing scheme 27th October 1909
operation	barrels water	strike heat	tap heat	time stood (minutes)	OG wort
mash 1	140	160º F		30
underlet	26	175º F	150º F	90	1082
sparge 1	36	168º F
underlet	63	168º F	156º F	30	1029
sparge 2	190	165º F	150º F		1010
Source:
Barclay Perkins brewing record held at the London Metropolitan Archives, document number ACC/2305/1/601.

Note that they used the longer pre-underlet rest of 30 minutes and a shorter post-underlet rest of just 90 minutes. 

Eldridge Pope mashing scheme 1896

The fermenting room at Eldridge Pope in the 1890s.

I thought some of you might be interested in a typical Eldridge Pope mashing scheme to go along with all the recipes of theirs I've been publishing.

For the 19th century, it's not that complicated a procedure. It's a typical example of what I would call an underlet mash. A mashing system that was incredibly popular in England. Not so much in Scotland, where most brewers seem to have gone for a single infusion, followed by a couple of sparges.

In an underlet mash, there's an initial infusion, followed 15 to 20 minutes later by the addition of a relatively small amount of hotter water from the bottom of the tun. Using an entrance called an underlet. The internal rakes would then be spun a couple of times to mix the hotter water evenly through the mash. Raising the temperature of the mash by a few degrees. The mash was then left to stand for a couple of hours.

In essence it was a simple type of step mash. The only slight downside was that you needed to have internal rakes in your mash tun. Which most breweries, where Steel's mashers were installed, didn't really need otherwise.

Admittedly, the table below would be more useful for anyone trying to recreate it if the initial heats were given. Let me know if you give it a try.

Eldridge Pope XX and PA mashing scheme 15th April 1896
operation	barrels water	strike heat	tap heat	time stood (minutes)
mash	72	161º F		17
underlet	5	190º F	152º F	147
sparge 1	62	170º F	156º F
sparge 2	61	160º F
Source:
Eldridge Pope brewing record held at the Dorset History Centre.

 

 

Underlet mashing

I'm so excited to have found some stuff on underlet mashing. Another one of my multiple obsessions.

A widespread method was underlet mashing. A technique that was developed in the last half of the 19th century and remained popular way past WW II. It wasn’t as common in Scotland as in England, but it was still practised north of the border, for example at Maclay. 

After an initial mash at quite a low temperature, 30 minutes later, more hot water was added via the underlet, i.e. from the bottom of the mash tun. The internal rakes were given a couple of spins to mix the new water through the mash. The underlet water was at a hotter temperature than the striking heat and raise the temperature of the goods. In effect it’s a step mash.

After standing for 120 minutes or so, the wort was run off and there were one or two sparges. The exact details varied from brewery to brewery. Because of the need to stir the mash after the underlet, brewers had to have rakes fitted to their tuns. 

There was an explanation for using the method other than improving extract.

“Underletting was not brought into favour merely as assisting in obtaining full extract, but by mashing at a lower initial temperature and then bringing the goods heat up to a high temperature by underlet, it was thought to obtain a wort of more desirable carbohydrate composition for certain classes of beer. There is some reason to think that a sweeter beer was thus obtained. But apart from carbohydrate composition due to controlled diastatic action, there is the question of proteolytic action being more effective at the lower initial temperature and so affecting the nitrogenous composition of the wort favourably. Many experiments have shown that 148°-150° is the temperature at which proteolytic action in the mash tun is inhibited, but at 144 -145º it is positive so that 20 minutes to half an hour at this lower figure might have a very desirable effect in reducing the amount of those bodies which are potentially troublesome in bottled beers. Moreover when an underlet is to be used the mash is generally thicker and in a thick mash proteolytic action is said to be a little stronger.”
The Brewing Trade Review, October 1943, page 309.

I won’t pretend to understand the science there. It does seem underletting influenced the character of the finished beer. If you believe the scienticians.

Here’s a typical underlet mash schedule from my favourite London brewery. It was for a total grain weight of 9,408 lbs.:

1941 Barclay Perkins A and X Ale underlet mash
action	water (barrels)	water heat	goods heat
mash	56	154º F	147º F
underket after 30 mins	14	180º F	151º F
sparge	102	165º F	154º F
Source:
Barclay Perkins brewing record held at the London Metropolitan Archives, document number ACC/2305/01/624.

 

 

Leftovers

My new Scottish book is full of information. Too full. But even then, there's the odd bit I can't shoehorn in.

I spent the weekend looking at mashing details. I know that sounds a bit dull, but it was both English and Scottish mashing schemes. Which adds an extra piquancy.  It meant putting together loads of fascinating tables.

But there wasn't room for all of them in full. I couple I just used extracts from. That's how stuffed full the book is. 70,000 words, at the moment. Though probably half of those "words" are numbers. That's how many tables there are.

The tables below I assembled for a larger table on mashing schemes in the 1930's. A fascinating topic. No, I'm not taking the piss. It is dead interesting. And through looking at mashing details more closely I've learned stuff. In particular, stuff about underlet mashing.

I've always though of underlet mashing - adding more hot water to the mash through the bottom of the tun a while after the initial infusion - as a particularly London practice. After looking in more detail, it seems that the practice was widespread in England. Though the process wasn't exactly the same everywhere.

Courage 1930 KKK, MC and X mashing scheme
	strike heat	mash heat	stood hours
mash 1	158.5º F	146º F
underlet	173º F	149º F	2
sparge 1	160º F
sparge 2	160º F
Source:
Courage brewing record held at the London Metropolitan Archives, document number ACC/2305/08/258.

Courage's underlet was relatively cool compared to Camden's:

Camden 1922 PA mashing scheme
	strike heat	mash heat	tap heat
mash 1	157.5º F	149º F
underlet	185º F	155º F	154.5º F
sparge 1	165º F		157.8º F
sparge 2	161º F
Source:
Camden Brewery brewing record held at the London Metropolitan Archives, document number ACC/2305/9/5.

While Tetley's was hotter still:

Tetley 1934 X1 mashing scheme
	strike heat	mash heat	tap heat	stood hours
mash	154º F	147º F	155º F	0.75
underlet	200º F	152º F	153º F	1
sparge	168º F		147º F
Source:
Tetley brewing record held at the West Yorkshire Archives, document number WYL756/ACC3349/552.

Maybe I should start looking more at mashing. There's so much fun to be had.

Mashing

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done dear ronald pattinson.


Get away from the keyboard, Lexie. Dad wants to write his post. Yes, now. . . . . No links Lexie, OK? . . . . Dad really needs to write his post. . . . Lexie I don't need to know about homo sapiens . . not now . . I'm trying to write something coherent. . . ."leave some stickbread for dad" . . . yes, dad needs stickbread.


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That makes no sense, Andrew. See where democracy gets you? Nonsense.


On with the fun. Not that you'll be having much. It's terribly dry. Full of numbers and tables again. You'll have to wait until I've been to London for any light relief.

Get ready for dullness.

Just . . . . . . . now

It's very satisfying when theory and practice come together in perfect harmony. That happened today. The mashing section in "Brewing Science & Practice" by H. Lloyd Hind, published in 1940, agrees almost exactly with Whitbread's and Barclay Perkins brewing records.

Underlet mashing. What a fascinating topic. It seems to have been the standard method of mashing for at least the first half of the 20th century. In London. I shouldn't generalise. Still need to look at the records of some provincial breweries.


Mashing
With the exception of a few specialist lager brewhouses which decoction mashed, all British breweries used an infusion mash. This method was well-suited to British malt, which was well-modified and had a low nitrogen content. Worts from an infusion were generally higher in maltose and more attenuative than those from a decoction mash.

The mash tun was first heated to close to the mashing temperature by running in hot water until it just covered the false bottom. The grist and mashing water were run through the external masher and into the mash tun. The temperature of the mashing water - the striking heat - was usually 4º or 5º F higher than the intended initial heat. Once the grist and water were "all in" the tun, the rakes were switched on to make a couple of revolutions.

What happened next, depended on if the tun was fitted with an underlet. If it were not, the mash was left to stand for 2 to 2.5 hours before sparging. If there was an underlet, the following processes occurred:

1. mashing for 15 to 20 minutes
2. mash left to stand for 30 minutes
3. water added through underlet, sometimes with the sparge running
4. mash left to stand for 90 to 120 minutes
5. taps set and spage begun

This whole procedure took 6 to 6.5 hours. Some brewers underlet twice, letting the wort stand and sparging briefly between them.

Whitbread, Fullers and Barclay Perkins employed a method very similar to the one just described, making use of the underlet to heat the mash.

Below is an example from Whitbread, mashing 86 quarters of malt.




Water was added through the underlet twice and there were two sparges. Two worts were produced which were boiled separately.

This is an example from Barclay Perkins, where 108 quarters of malt were mashed:


Just like Whitbread, Barclay Perkins underlet and sparged twice.



Mashing temperatures and mash rates
The most important mashing temperature was the initial heat. Varying it by just a couple of degrees could have a big influence on the composition of the final wort. The ideal temperature depended on the type of beer being brewed and the malts being used. The mash rate, that is the number of barrels of water per quarter of malt being mashed, similarly varied according to the type of beer and the malts used.

Because of its lower diastatic power, mild ale malt was usually mashed at a lower temperature than pale ale malt. Grists containing large quantities of dark malts were mashed an an even lower temperature still. Beers where a high degree of attenuation was required had a lower initial mashing heat. Stock Ales, which reuired a large proportion of dextrin in the wort, were mashed at higher temperatures, even when the grist contained a great deal of dark malts.

When using an underlet, the initial temperature could be lower, which was especially useful with less well-modified malts. The underlet could then be used to raise the temperature higher than would normally be used as an initial heat. The production of maltose could be affected by the timing and temperature of underletting. The longer the mash stood before underletting, the greater the amount of maltose produced.

The table below gives typical mashing temperatures for various types of beers. These were not set in stone, but could vary depending on other factors such as the characteristics of the malt and the equipment in the brewery.


These are the Barclay Perkins mashing temperatures from the mid-1930's.


As Hind stated, Stock Ale (KK) and Pale Ale had the highest temperature, Mild (XX, X, A) a rather lower one and Stout (BS, OMS, TT) the lowest of all. Though the range spanned by the different beers is smaller than Hind suggested, with onlt 4º F between the warmest and coolest.


Sources:
"Brewing Science & Practice" H. Lloyd Hind, 1940,
Whitbread and Barclay Perkins brewing records..