Tetley Ale malt specifications (part four)

Still more types of nitrogen to plough through. I never realised there were so many different types of the stuff in malt. I bet you'll be glad when I get to Tetley's beers.

Righto, then. Here we go with FAN (free amino nitrogen).

FAN compounds are formed naturally during malting and mashing by the action of protein degradation enzymes on hordein, a protein found in the grain. The level of amino acids available in the wort relies on several variables including grain variety, as well as malting and mashing conditions, but the overall types of amino acids available will be similar among all whole malt worts.

Together with ammonia, FAN/PAN makes up what is known as Yeast Assimilable Nitrogen or YAN.
Brewers Journal, Free Amino Nitrogen, January 24, 2017.
https://www.brewersjournal.info/free-amino-nitrogen/

OK, that's how the FAN thingies are formed. Let's take a look at what it does.

Free amino nitrogen (FAN)
FAN is the weight per unit weight of amino nitrogen available from the malt. FAN is principally amino acids which as stated above are vital for yeast nutrition. While it might seem that having high FAN can only be a good thing if there is too much breakdown of the nitrogenous materials in the grain it is detrimental to the foam stability of the beer because the longer chained polypeptides and proteins which stabilize the bubbles in the head of beer are broken down into smaller molecules as FAN is produced. It is also thought that more extensively modified proteins in the grain detract from the body of the beer as some of the mouthfeel is conferred by polypeptides and proteins. The amount and degree of modification of protein in the malt is one of the many compromises in the process that you need to manage as a brewer.
The Craft Brewing Handbook by Stewart Howe, 2020, chapter 1.

FAN helps yeast nutrition. So, obviously useful for promoting a healthy fermentation. A characterictic which is pretty handy in malt. But too much buggers up head formation. How much is the right amount? How much is too little? The next source spells that out:

There has been much debate regarding the minimal FAN required to achieve satisfactory yeast growth and fermentation performance in normal gravity (10–12 °P) wort, and it is generally agreed to be around 130 mg FAN/L, with the minimum varying between 100 mg FAN/L and 140 mg FAN/L. This is consistent across both brewing and wine fermentations. Below 100 mg FAN/L, yeast growth is nitrogen-dependent, and sub-optimal concentrations of available nitrogen are associated with lagging, incomplete fermentation and sulfide evolution. In the stationary phase of yeast development, only low levels are required as a fermentation stimulant of the yeast, while higher levels are required during the growth phase.

Optimum FAN levels differ from fermentation to fermentation and also with yeast strain, wort sugar levels and type. For wine fermentation, the optimal nitrogen concentration in the must is 190 mg FAN/L, with similar levels (200–250 mg FAN/L) regarded as optimal for standard gravity brewery fermentations. There are differences between lager and ale yeast strains with respect to wort-assimilable nitrogen uptake characteristics. However, with all brewing strains, the amount of wort FAN content required by yeast under normal brewery fermentation is directly proportional to yeast growth.
Hill, Annie E., and Graham G. Stewart. 2019. "Free Amino Nitrogen in Brewing" Fermentation 5, no. 1: 22. https://doi.org/10.3390/fermentation5010022
https://www.mdpi.com/2311-5637/5/1/22

That's pretty clear: 200-250 mg/l is optimal for standard-strength beer; minimum amount for a healthy fermentation 130 mg/l. Which means that the standard for the Leeds brewery was about the minimum, given that the tolerance of +-20 would permit malt with just 130 mg/l.

Why is the figure for Castlemaine 4X higher? Probably because it was fermented with Lager yeast and a dry finished beer was required.

Almost done now. We can rattle through the rest of these. Arsenic and lead. I think it's pretty obvious why you wouldn't want either in any great quantity in what was, essentially, a food product.

Dust and offal. The former might be a little irritating, but the latter sounds positively scary. Depending on what they exactly mean by offal. For me, it's the innards of animals. Was 2% of unidentified animal bits really acceptable?

Finally, another type of nitrogen, NDMA (N-Nitroso-dimethylamine), is next. This sounds quite scary.

NDMA (n-nitrosodimethylamine) in Malt/Beer
During the malting process, barley is forced to germinate, after which the grain is dried in kilns. This process freezes the sugar and flavour compounds for the brewing process. During the kiln drying process, nitrosamines may be formed in the grain, which could remain within the extract and still be present in the final brewed product. Many recently used techniques, minimise the formation of nitrosamines. However, low levels of these carcinogenic compounds still remain.
The Analytical Scientist, NDMA in Malt and Beer by Ellutia, published 11/13/2017.
https://theanalyticalscientist.com/app-notes/ndma-in-malt-and-beer

Right, the stuff is carcinogenic. No shock, then, that the permitted amount was tiny.

Barley varieties next time. A topic you may find more amusing. 

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.