Of course, I was aware of the significance of the nitrogen content of malt. It's only when I started looking at what all these terms in the analysis meant that I got an inkling of just how complex it is. I still don't really understand it all. Or even much. Those of you lucky enough to have studied brewing properly will have to bear with me.
I'm going to repeat the table so you don't have to keep flicking backwards and forwards from one post to another.
It's wonderful getting hold of documents like this. If any of you have something similar from another brewery, I would love to see it. They go a couple of levels deeper than brewing records.
Enough of my waffle. Here's that lovely table again.
| Tetley Ale malt specifications | |
| 1.1 Extract | 282 brl°/336 lb (on dry) |
| 301 l°/kg (on dry) | |
| 1.2 Fine coarse difference | 2-7 brl°/226 lb. |
| 1.3 Moisture | not more than 3.5% |
| 1.4 Colour | 5.5 ± 1.5° EBC |
| 6.5 ± 1.5° EBC (Leeds) | |
| 4.5 ± 1.5° EBC (Castlemaine 4X) | |
| 1.5 Total N | 1.60 ± 0.1% average |
| not more than 1.90% on individual samples | |
| 1.6 TSN (total soluble nitrogen) | 0.60 ± 0.04% (Burton, Warrington) |
| 0.58 ± 0.04% (Leeds, Romford) - | |
| not more than 0.70% on individual samples. | |
| 0.65 ± 0.5% (Castlemaine 4X) | |
| 1.7 SNR (specific nitrification rate) | 38 ± 2 (Burton, Warrington) |
| 36 ± 2 (Leeds, Romford) | |
| 41 ± 2 (Castlemaine 4X) | |
| 1.8 FAN (free amino nitrogen) | 180 ± 20mg/1 at 1048 0G |
| 200 ± 20mg/1 at 1048 0G (Castlemaine 4X) | |
| 150 ± 20mg/1 at 1048 OG (Leeds) | |
| 1.9 Arsenic | not more than 0.5 mg/kg. |
| 1.10 Lead | not more than 1.0 mg/kg. |
| 1.11 Dust and Offal | not more than 2.0% (2.2 mm screen) |
| 1.12 NDMA (N-Nitroso-dimethylamine) | not more than 5 μg/k |
| Source: | |
| Tetley Beer and Malt Specifications, 1985, malt page 1. | |
Let's start at the beginning, with extract. Note that it's given per 336 lbs, that is, per quarter. I couldn't help but covert that into lbs per barrel. Which is 101.4 lbs per quarter. I'm pretty sure that this is the theoretical extract under lab conditions, not what could be achieved in the mash tun. Around 90 lbs or a little more per quarter was the highest actually achievable.
I'll skip over 1.2 and 1.3. The first, because I'm not quite sure what it means. And moisture, well, that's pretty obvious.
It's interesting that the colour specifications vary. It's fairly obvious why the malt for Castlemaine 4X, a Lager, would need to be paler. Less clear is why the Tetley brewery in Leeds allowed slightly darker malt that all Allied's other sites. Including the Tetley brewery in Warrington.
Now we get all the different types of nitrogen. Starting with TSN.
"Soluble nitrogen (% TSN): The amount of nitrogen in soluble form, expressed as a percentage of malt weight. The TSN parameters are used to calculate the soluble nitrogen ratio."
https://www.geterbrewed.com/blog/2017/08/23/how-to-read-malt-analysis/
That's quite simple. Though it's not clear to me why a higher value was permitted in Castlemaine 4X.
I think that's enough for today. There's lots of technical stuff coming in the next post. Won't that be fun?
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4 comments:
The fine/coarse difference is the difference between the extract of a finely milled sample and a coarse milled sample. Now it seems to be expressed in %. And good values seem to be between 0.5% and 1.5%.
https://www.greatwesternmalting.com/make-sense-of-your-certificate-of-analysis/
Higher allowance for the soluble nitrogen for Castlemaine 4x might be due to it have a very large portion of adjuncts like corn or sugar used? This could compensate for the lack of FAN the brew would otherwise have due to the adjuncts contributing next to none.
A brewery that used something like Torrefies Wheat for foam stabiliy would probably want less nitrogen in the base malt, to avoid cloudiness. So I guess the differing specifications come from differing grain bills in the breweries beers.
If there was something about the kit in Leeds that left the wort paler than at other breweries (coppers came up to temperature more quickly?) then they could tolerate a darker colour of malt as an input?
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