The popularity of barley in fermented beverages is due to the high levels of the enzyme α‐amylase which is the chemical that converts the starches in the grain into fermentable sugars. Beyond that, barley is not a great grain for making bread or other food items, so it is mostly used in beer production and distillation and a significant amount is utilized as animal feed.
Distillers barley can be either 2-row or 6-row variety. Historically, 6-row malt had a higher enzymatic power but 2-row malt was and still is preferred for its flavour. Historically 6-row malt was considered feed grade whereas two-row malt was preferred for brewing. For distilling, you could go either way but modern 2-row malt has been bred for high diastatic power and better brewing characteristics.
The Canada Malting Company has rebranded its 2-row distiller’s malt to Bourbon Malt, which clearly demonstrates the disconnect between the marketing department and distilling floor. There are new varieties of malt that are being bred specifically for distilling, to reduce the amount of ethyl carbamate produced. Canada Malting makes a distillers grain, from a Scottish program called Pot Still Malt that is low the ethyl carbamate precursor glycosidic nitrile.
The unit of measurement for the diastatic power of malt is degrees Lintner (°L) and should not be confused with a Lovibond number which represents the colour/darkness of a grain. To find the °L of a malted grain, you can look at the specification sheet from your grain supplier. You can then use this number to create a mash bill that ensures complete conversion of the starches to simple sugars so yeast can ferment them.
In your final mash bill you typically want your Lintner degree to be around 30 to 45°L.
Distillers Malt 200°L
50 kg Unmalted Barley 0°L
To reach 40°L you would need to be 20% of the mash bill
Enzymes have an optimal range to work, and typically brewers and distillers operate at the higher end of the scale because the enzyme reaction is faster, but that doesn’t mean a lower temperature won’t work, it does just slower.
Alpha-Amylase: 66° to 70°C
Beta-Amylase: 60° to 65°C
In modern times barely is still used in mash bills because it is cheap, known and effective, however, it isn’t necessary anymore if you have access to powdered enzymes, and they are readily available everywhere. The enzymes alpha and beta-amylase are found in germinated barley but there is nothing special about those enzymes. Humans have alpha-amylase in our saliva to help digest starch (bread), so using commercially available enzymes shouldn’t present a barrier unless you feel you need to do a historical approach or have a conflicted feeling that makes you feel like you are cheating…which you are not.
Using commercial enzyme powders can improve your starch conversions and speed up the mashing process which can help you improve your distillery efficiency (i.e. increase profits). At the worst, they offer an insurance policy that if your mash bill didn’t fully convert you can dash in some enzymes and complete the mashing process without having to eat the lost productivity. And have no doubt, many commercial distilleries have enzymes on hand to ensure that the grains they mash are fully converted and the distillery remains profitable.
There is an environmental and cost savings benefit to using commercial enzymes as well, since the malting process requires heat and water for a few days to germinate and then the malted grain needs to go through a drying process, which increases the carbon footprint further as well as the price. If a distillery used unmalted barley and enzymes (or a portion of malted barley), the malting step can be mostly removed. Un-malted grain has about 1/5th more fermentable sugars than malted grain because the germination of the grain uses roughly 20% of the stored starches to do its thing. For distilling purposes, there may be cost savings in using a portion of malt and then the rest of the mash bill being unmalted barley.
The one caveat is that there may be flavour variations between the two methods, so experiment and see what happens.
Benefits of using unmalted and pearl barley: onlinelibrary.wiley.com/doi/full/10.1002/jib.319
Flavors in Malt Whisky: A Review (Akira Wanikawa, 2020)
The Manufacture of Scotch Grain Whiskey