Monday, 9 February 2015

German brewing in the 1970’s – wort production

We’ve finally stumbled out of the forest and onto the fertile plains of brewing. Or at least producing wort.

As so often is the case, changing in brewing techniques were being driven by the desire to save dosh:

Technology of Wort Production
Developments in recent years have resulted in a shortening of the time necessary for mashing one brew so that the number of brews can be raised to 8 or, in some cases, even to 10 brews per day. At the same time, automation of some operations or of the total brewing process has been possible, resulting in reduced brewery staffing levels and improved safety at work.”
Journal of the Institute of Brewing, Volume 83, Issue 1, March-April 1977, page 74.

Obviously, the more mashes you can perform in a day, the more beer you can squeeze out of your kit. And to do that, you either need to install more equipment or mash more quickly:

“It is possible to reduce the mashing time, even with all-malt grists, by using only malts with a laboratory fine-coarse difference of less than 1.8% DM and with a Congress wort viscosity of < 1.55 cP. The Kolbach index should be more than 40% and the a-amino nitrogen content should be higher than 140 mg/100 g malt if a flocculent yeast is used. Such malts can be extracted, for example, by an infusion method in 150 min with an extract loss of less than 1.2% in the wet spent grains. Malt is ground either in wet milling systems or by dry milling in mills which contain usually three pairs of rolls. For wet milling, the maximum time that can be allowed is 35 min giving a high peak electricity demand. For the larger size mashes 2 or 3 wet mills are necessary and this also means that the brewery power plant has to have a greater capacity. With dry milling, time is not so important and the electricity demand can be spread over a longer period.”
Journal of the Institute of Brewing, Volume 83, Issue 1, March-April 1977, pages 74 - 75.

Funnily enough, the topic of wet milling came up when I was at Adnams last month. When I asked head brewer Fergus if they had a Steel’s masher. They don’t because, as they mill wet, they don’t need one. The grains are already moistened before they hit the mash tun. Of course, they do have a German-built brewhouse with a lauter tun.

Now mash filter versus lauter tun:

“At present mash filters are preferred for lautering, probably as a result of the introduction of polypropylene filter cloths. The former cotton filter cloths had to be removed and washed after every brew; this required more staff and the higher labour costs could not be compensated by the better extract yield. Polypropylene filter cloths only need to be cleaned once a week with caustic soda and only once every 4 weeks (i.e. after about 200 brews) with a high pressure jet. This ease of cleaning and the fact that, compared to the lauter tun, more brews can be processed per day with better yield has influenced the trend to the use of mash-filters. It must be mentioned, however, that worts from both lauter tuns and mash-filters run off with more turbidity nowadays than they did when either cotton filter cloths were used or when only 6 brews in 24 hours had to be produced with lauter tuns. Table X shows the relative turbidities of worts from different types of lauter tuns and from different filter cloths. A reduced load on the lauter filter plate leads to less turbid worts and a mash-filter equipped with a cotton filter cloth yields clearer worts than a mash filter equipped with polypropylene cloths. This difference in wort quality has not been considered as a hinderance by many bigger breweries since the technical advantages of using mash-filters with polypropylene cloths has by far compensated for the disadvantages. Table XI provides a further illustration of these advantages and it can be seen that with a lauter tun only 7-8 brews can be made in 24 hours, whilst with the aid of a mash filter 9-10 brews can be carried out.”
Journal of the Institute of Brewing, Volume 83, Issue 1, March-April 1977, page 75.

Here are the accompanying tables:

TABLE X. Relative Turbidity of Worts from Lauter Tuns and Mash Filters.
First worts Washing stages
Begin End 1 2 3 Average turbidity
Lauter tun 190 kg malt/M3 13 4 1 5 0 4.6
Lauter tun 340 kg malt/M3 37 10 25 4 13 12.4*
Mash filter, cotton cloth 7 0 0 0 2.6
Mash filter, polypropylene cloth 28 8 2 0 11.6*
* Sometimes more.

TABLE XI. Utilization of Lauter Tun and Mash Filter.
Lauter tun Mash filter
Brews per 24 hours 7-8 9-10
Extract as % of laboratory fine grind mash 98.0-98.5 99.0-99.3
Personnel per shift 1 1.5

So polypropylene cloths were the worst in terms of wort clarity, but because they were cheaper and easier, lots of breweries used them anyway. With mash filters, you can see it’s a bit swings and roundabouts. Extract was good, you could get more brews in a day, but you needed more manpower.

How does this compare to a traditional mash tun? Briggs has the answer:

An example comparison between a mash tun, a lauter tun and a modern mash filter
Mash tun  Lauter tun (modern, 1996)  2001 Mash filter
Mashing rate (hl/100 kg)  2.8 3 2.9
Sparging rate (hl/100 kg)  4.2 3.8 2.4
Total liquor/grist (hl/100 kg)  7 6.8 5.3
Filtration area* (m2)  50 90 708
Bed depth* (m) 0.9-1.2 (2 max.)  0.3-0.5  0.03-0.06
Bed loading* (kg/m2)  400 160-220  28
Capacity range (% normal)  -60 to +10  -50 to +20  -20 to +10
Initial wort haze (ºEBC)  10 >20  >20
Average wort haze(ºEBC)  4 5-8 <2
First wort gravity (ºSacch)  80 94 100
Copper gravity (ºSacch)  61 67 70
Lipid content (ppm)  2 18 17
Solids (Imhoff cone, ml/l)  <8  <12  <5
Polyphenols (ppm)  165 180 195
Extract recovery (% lab. extract)  96-97  98-99  102
Moisture draff (%)  81 76 64
* For 20 t mashes.

Mash tun cycle: mash in, 20 min.; stand, 75 min.; run off, 185-330 min.; drain and unload draff, 20 min. Total time, 300-440 min.
Lauter tun cycle: underlet, 3 min.; fill, 11 min.; re-circulate first wort, 4 min.; collect first wort, 41 min.; second wort, 74 min.; last wort, 10 min.; weak worts, 16 min.; drain, 8 min.; grains out, 25 min. Total, 192 min.
2001 Mash filter cycle time: filling, 4 min.; filtration, 20 min.; pre-compression, 3 min.; sparging, 46 min.; compression, 8 min.; drain and grains out, 34 min. Total, 115 min.
"Brewing Science and Practice" by Dennis E. Briggs, Chris A. Boulton, Peter A. Brookes and Roger Stevens, 2000, page 210.

Isn’t that interesting? It makes you wonder why anyone still uses an old-fashioned mash tun when you look at the difference in time. Double that of a lauter tun and triple that of a mash filter. Though it looks to me that a mash tun provides better quality wort.

Now something about boiling:

“For wort boiling some German breweries now use the Calandria system, whilst some other breweries use the so-called Kochtassen (i.e. tubular heaters similar to the Calandria heater) which are installed in the conical zone of the copper. Only one brewery in Germany uses a continuous wort production system where the separation of the wort, produced from a powdered grist, is effected by a vacuum drum filter. At present German breweries show a marked preference for batch wort production systems.”
Journal of the Institute of Brewing, Volume 83, Issue 1, March-April 1977, page 75.

What’s a Calandria heater? It’s an external pre-heater, used to heat the wort before it enters the copper. This is what one looks like:

I’m amazed even one brewery in Germany used a continuous wort production system.

Cooling next time.

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