Since 1870 we’ve lived and breathed malting. With this passion and expertise, and by combining traditional and modern techniques, we create an impressive range of malted and non-malted products, including several unique and exclusive barley malts.
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Mike is the sales manager for Wales and the West of England and is located in Wigan.
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There are plenty of online grist ratio calculators to help you work out how much grain to add to each brew, but it’s not as satisfying as doing it yourself. It’s also very easy to do. Although it could lead to an unhealthy obsession with creating spreadsheets.
As with all calculators we need to know a few things:
The expected volume in FV is dead simple, it’s how much wort you want to collect from the kettle. It’s important as we use it to work out the total extract we need.
The OG is calculated from the ABV of the final beer and the final gravity (FG) of the beer:
OG= (%ABV/F)+FG
F is a factor agreed with the UK custom’s and excise so it may be different around the world. The factors can be found in section 30.3 of notice 226 but they are also below.
Screen clipping taken: 28/07/2021 19:09
The OG is often written as 10 something. It’s actually the specific gravity of the wort in grams per litre. Water has a specific gravity of 1.000. Brewers would drop the decimal point and call it 1000. When we use it for calculations we drop the 1st two numbers. A wort with a specific gravity of 1.040, would be 1040 to brewers and 40 for the calculation.
To work out the total extract we simply multiply the volume in litres by the OG.
Example:
40*1000 = 40000 ltr degrees
It’s a sad fact that during the brewing process we experience losses. We lose volume in the spent grain, last worts, evaporation and trub. When we calculate the grist we need to take these losses into consideration and add extra extract to make up for these losses.
As a rule of thumb:
The efficiency will decrease as the OG increases, you need to consider this with high ABV beers.
We can calculate the efficiency and will look at it later.
Our 1000 ltrs of 1040 OG wort will be produced on a commercial mash tun, so we can expect 90% efficiency.
100/90=1.11
To make sure we add enough extract we need to multiply the total extract by 1.11
40000*1.11=44400
It’s up to you, the world is your oyster! Well within reason. Whatever it is you add, we add them as a % of total extract.
A simple Bitter recipe may be made up of:
By thinking of them in %, it’s easy to scale to any brew size and also makes sure you can correct for the actual extract of the ingredients you use.
When you get the malt certificate of analysis you will often find 2 extract results, ‘dry’ and ‘as is’. Dry is good for comparing different malts but you cant use it for this calculation. Malt has moisture in it. Lighter coloured malts have higher moisture levels and higher coloured malts have lower moisture levels. We need to take that moisture into consideration so we use the ‘as is’ result.
If your malt certificate does not have ‘as is’ extract, you can work it out. Multiply the dry extract by the percentage and then subtract the result from the dry extract. The extract changes from batch to batch so always check it and make the adjustments.
We now have everything we need to calculate the amount of each grist addition to add.
Remembering the total extract needed was 44400 ltr degrees, we work out how much extract each grist addition will add.
So there you have it. Yes it’s easy to use a calculator but there is something very satisfying about doing it yourself and it’s so much easier than working out the BU!
In a commercial brewery every brew would be checked for loss.
Using the example above just imagine we actually brewed a beer and got the expected 1000 ltrs but the OG was only 1038.
The extract we have in the FV is:
1000*38=38000 ltr degrees of extract.
But we added 44000 ltr degrees of extract
The efficiency of this brew was (38000/44000)*100=86.3%
If we get this on a few brews we can adjust the extract efficiency in the grist calculation.
100/86.3= 1.158
It’s a great opportunity to have a look at the process and see what you can do to improve the extract efficiency.
We will be back with another blog post on how to calculate grist for EBC so be sure to sign up to our newsletter to make sure you don’t miss out. If you need any help or advice feel free to contact our technical sales managers, Mike Benson or Stuart Swann.
I hope you found this information useful and you can apply it in your brewery. If you have any questions or would like some advice, please email hello@crispmalt.com or phone 01328 829391
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