I'm confused about grain bills and diastatic power. For example, one of Four Roses grain bill is: Corn: 75%, Rye: 20%, Malted Barley: 5%.
How can you have a diastatic power minimum of 30 with only 5 % barley?
With my calculations for a total of 20lb of grains is: Corn = 15lbs, Rye = 4lbs, Barley = 1lb.
The diastatic power = 7. I'm using a 140 lintner in my math.
Are my calculations incorrect? What am I missing?
as grain sprouts it produces enzymes. the longer its sprouts the more enzymes it produces up to a point.
then it starts going the other way. the the malt most buy is developed for making beer,this is a compromise
between having enzymes and starch. this is because they want the most yield from just using the malt.
distillers malt is a bit different,most work with the maltster.and can be similar to beer malt but usually not
dryed with heat,to more enzymes and little to almost no starch left. they use this to convert other grains.
so not using heat when drying,letting the grain sprout longer both increase the diastatic power,
Ok, so for us home distillers buying 2 row barley from the brew house, we would have to use close to 5lbs of barley for the above example? If not, the alcohol will be lower and we would have longer conversion waiting time.
With 20 lb grain bill your total distic power needed is 600.
20x30=600.
Your barley has 140 L so divide that into 600.
600/140 = 4.29 lbs
4.29/20 = 21.4%
I have gravitaed to using more than 20% unless I'm using a grain with a real high diastic power ( I have some red wheat that's 195L), but 20% is a real good rule of thumb. Hold your mash at 140-145F for as long as you reasonably can and you'll get good saccrification. You'll still get some enzyme activity below 140F but it slows way down. I insulate well and usually let my mashes rest over night and I generally get 7 - 7.5% abv, sometimes around 8% with my AG's.
Big R
"Necessity is the plea for every infringement of human freedom. It is the argument of tyrants; it is the creed of slaves." William Pitt
As I understand it, the 30 Lintner rule is not handed down on stone tablets but is based on what beer brewers typically do. Distillers do longer cooler mashes like bigR says. This gives the enzymes more time to work before they degrade. (Enzymes don't get "used up" in converting starch, they carry on working until they degrade due to high temperature, adverse pH, or the action of other enzymes.)
I use English pale malt (Marris Otter) because it is easily available from home brew shops. It's only 45 Lintner but can easily convert twice its weight of wheat flour mashing overnight at 140 - 145 oF. You might need to experiment a bit using small quantities to see what proportions work best.
You might want to try out enzymes too. The balance of enzyme activity that is desirable in brewing malt (mostly beta with a bit of alpha) is not necessarily optimal for converting loads of unmalted grain. These days I tend to add a bit of alpha amylase enzyme up front to help liquidise the starch, and a little glucoamylase at the back end of the mash to chop up any remaining unfermentable sugars. Enzymes are cheaper than malt and help keep the cost down. Plus it is easier to correct mistakes by adding enzyme than adding malt.
