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La Boehme - The Decoction Mash

Having just taken delivery of some European and speciality malts, I decided to give Pilsner making a crack.  I was not sure I’d be able to achieve very low temperature fermentation and lagering for weeks at 4°, but the decoction mash is something I could experiment with. The decoction mash was developed in Europe in the nineteenth century, to enable pale, clear beers to be made from what was then low quality, poorly modified malt. I am assured that this is no longer necessary with modern malts and few commercial breweries still practice it.

So why do it? Well flavour for one thing, apparently it makes a difference, but mainly to get into the spirit of making a different kind of beer. Was it worth it? Well that remains to be seen, but I can tell you it was hard work!  The beauty of the single infusion mash to the home brewer is that once you’ve got it to the right temperature you can leave it in your insulated mash tun happily getting along by itself, while you go and make a cup of tea, put your feet up or put the finishing touches to the symphony you happen to be writing, whatever. Not so with the decoction mash, it takes at least twice as long and is much more labour intensive. It’s not for a devotee of the Australian brew in the bag method that’s for sure.

Decoction means to prepare by boiling. Essentially the process involves taking out a proportion of the mash, and slowly heating it to boiling point, while the main mash rests at the various points of a temperature stepped mash. The boiling proportion is added back to the main mash after each rest to raise the temperature to the next level. Boiling the grain breaks down their cell walls, making the starches more accessible to the enzymes and extracts more flavour from the malt. Enzymes in the boiled proportion will be destroyed by the process, which would be a reason to bring it to boil slowly with a rest for twenty minutes or so at a temperature suitable for converting the starches. Not sure I was entirely successful doing this but the mash proved a good one none the less.

So for the recipe; I had no plan to try and recreate Pilsner Urquel especially as if I am honest, I think I tend to prefer the German versions, also I thought I would go a little stronger, but still all malt. So this is my recipe for ‘La Boehme’

For 25 Litres   5,200 grams Pilsner malt

290 grams Carapils

96 grams Saaz – 26 grams Halletauer Mittelfrüh – added half at beginning of 90 minute boil half at 45 minutes

Last 15 minutes – 22grams Halletauer Mittelfrüh

Wyeast liquid culture Pilsner Yeast

Try this recipe with a single infusion mash for 90 minutes and I’m sure it will make an excellent beer; this is what I did however:

Pilsner mashes apparently can have a quite high liquid to grain ratio, so I poured a little more than I would usually into the mash tun 20 litres in fact. With the grain in, and the temperature stabilised around 40°, for the first rest, I ladled out what I estimated as something between one quarter to one third of the mash into the biggest pan I could find. The plan was to slowly raise the temperature in the pan on the stove, while the main mash rested for 30 minutes for the first step. Lack of attention to the job in hand however meant that the mash in the pan was soon far too hot, so I just turned the burner off and let it stand for a bit, hoping for the best. I had it boiling again in time to add back to the main mash at the end of the first rest.  Adding less than the whole contents of the pan brought the temperature to 50°. Getting the temperature right is not all that easy, as measurements vary wildly as the decoction is stirred in and it needs a little time to settle down. 50° is an important step, as this is the protein rest where enzymes break down large insoluble proteins into smaller soluble ones. This rest was held for 45 minutes. In the meantime I drew off the next decoction into the pan, and that proceeded in much the same hit and miss fashion as the previous. I intended a final rest for an hour, for saccharification at 67° but adding the entire second decoction only achieved 65°, so I decided to go with that. After the final hour I did boil a portion of the mash and added it back to raise the temperature further for Mash out, but I dare say that step could be dispensed with the whole mash was then sparged and boiled for 90 minutes.

I pitched the yeast when the wort had been cooled to around 16°. at this temperature the OG was 1.0054. I put it out in a cold garrage, by the morning it was down to 12° and has not been any higher at the time of writing. Well within the target range then.

Hurglitz La Boehme, brewed 12th March 2012 – tasting in a couple of months maybe -

By Paul.

Any queries phone Paul on 020 8644 0934

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