Milling Flashcards
Conditioning grain
Either spray hot water onto the grains or allow water vapour to flow through them to protect the husk during milling by moistening them.
Dressers
Remove material based on size using screens
Destoners
Remove material heavier than grain based on weight (using upward air flow)
The five sieves of the EBC analysis
Sieve 1 - 1.25mm husk
Sieve 2- 1.01mm coarse grits
Sieve 3 - 0.547mm fine grits 1
Sieve 4 - 0.253mm fine grits 2
Sieve 5 - 0.152mm flour
Base - fine flour
Grist calculations
°P is a weight/weight measure, e.g. the grams (g) of extract (sugar) in 100 g of wort. However, our liquid (wort) is measured in litres (L) rather than kg. We thus need to convert our °P reading to a weight/volume figure. We can use conversion tables for this or we can apply a complex formula. We don’t have space to show the tables here and the calculation is too complex for this level of study so we will just use the figure we would have obtained from them. You will be given this figure in any exam questions on grist calculations.
In this example our 10°P wort gravity converts to 0.1038 kg/L. In other words, for every litre of wort we need 0.1038 kg of extract.
2.
We can now calculate the total amount of extract we need:
We need 50,000 litres of wort at 0.1038 kg per litre so we multiply the volume required by the density we need to get the weight as shown below.
Volume (L) x density (kg / L) = mass (kg)
50,000 L x 0.1038 kg/L = 5,190 kg of extract (often abbreviated as KgE)
3.
As we now know how much extract we need for our brew (5,190 kg), and we know that extract comes from malt, we now need to calculate how much malt we need.
When the maltsters sell their malt, they will measure the amount of extract in the malt and communicate this to the brewer in the certificate of analysis which arrives with the malt. As brewers we can also set a specification for extract for the maltster to achieve.
Typical extract values will be between 74% and 78%. For this example, we will use 77.9%.
Make sure the extract figure used is not on a dry basis. Maltsters often quote malt extract on a dry basis. We need to know the actual value of extract in the malt in the form we use it for our calculations. If a dry basis extract is quoted then this needs to be reduced by the % w/w moisture in the malt. So a malt dry extract of 82% w/w and a moisture content of 5% w/w has extract of 82 x 95 / 100 = 77.9% w/w.
If all the malt was extract (100%) we would need 5,190 kg. As it is not 100% extract, we need to divide this weight by the extract percentage and multiply by 100. This is shown below:
Quantity of malt x % extract = kgE
Quantity of malt = kgE / % extract
Quantity of malt = (5,190 / 77.9) x 100
Quantity of malt = 6,662 kg
In this example we will need 6,662 kg of malt with 77.9% extract to produce 500 hL of wort at 10°P.
Two roll mill
Two rollers rolling inwards crack grain
- only suitable for use with mash tubs and well modified malt.
As the grain modifies, the cell walls are broken down and the grain becomes increasingly more friable. The endosperm of a well modified grain is therefore easier to crush than less well modified grains. This makes the mill’s job much easier, so we can use a simple two-roll mill.
Four roll mill
First set of rollers remove husk
- husk and flour remove according to size
- bigger and Javier grits sent to second set of rollers
Should only be used with well modified malt
Six roll mill
-first roller set cracks grain, flour separated out, grits sent to second rollers.
- husk and flour to be crushed into fine grits
-can milk less modified malt
-most suited to a lauter tun.
Five roll mill
Same as a 6 roll mill but the first and second rolls are created by 3 rollers
Hammer mills
- metal hammers fixed to a rotating shaft
-only suitable for a mash filter
-only milk strong enough to crack unmalted cereals (rice,maize)
Wet mills
Steeps the grains in water before milking
- as we mill mashing water is also added
-usually only 2 rollers
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Advantages of pre milled malt
-saves the cost of buying and operating a mill
- shortens the total brew time by eliminating milling
-no milk means less risk of dust explosion
Disadvantages of pre mill malt (overweight the advantages)
-deteriorates more quickly because the husk is broken open
- more likely to go mouldy
-less control over grist quality as there are limited amounts and types of grind’s available
- handling of grist can damage grist quality, as the particles are broken down.
- pre milled grain are dustier and this more hazardous to handle
- handling multiple sacks poses a manual handling hazard
