Whiskey Mash Recipe

Unlike a sugar wash, a whiskey mash requires you to extract fermentable sugars from grain — a process that depends on precise temperature control, the right grain ratios, and active enzymes. The worked example in this guide uses a bourbon-style grain bill (70% corn), which is the most widely made style and the most forgiving starting point. The same temperatures and process apply to rye whiskey, wheat whiskey, and any other grain combination.

The Grain Bill

The grain bill is the recipe — the mix of grains and their proportions by weight. Each grain contributes differently to the flavour, fermentability, and character of the finished whiskey.

Common mash bills by whiskey style

The table below covers the three main American whiskey styles. Malted barley is present in all of them because it supplies the enzymes needed for starch conversion — reduce it below 10% and you risk incomplete conversion unless you supplement with commercial enzymes.

The worked recipe below uses the standard bourbon mash bill (70/15/15) as it produces reliable results and is the easiest to troubleshoot. To make a different style, swap the grain percentages in the table above — the temperatures, process steps, and fermentation approach are identical.

Enzymes and Conversion

Grain starch cannot be fermented directly by yeast — it must first be broken down into fermentable sugars by enzymes. Two enzymes do the work in a whiskey mash.

Alpha-amylase breaks long starch chains into shorter fragments. It is most active at 68–72°C (154–162°F) and is more heat-stable than beta-amylase. It produces a mix of fermentable and non-fermentable sugars, resulting in a fuller body.

Beta-amylase breaks down those shorter fragments into maltose, a highly fermentable sugar. It is most active at 60–65°C (140–149°F) but is destroyed above 70°C (158°F). Mashing at lower temperatures produces a more fermentable, drier wash.

Malted barley contains both enzymes in sufficient quantities to convert the starch in all the other grains in a typical mash bill. You need at least 10–15% malted barley by total grain weight for reliable conversion. If you want to use commercial enzymes instead (alpha-amylase and glucoamylase), follow the manufacturer's dosing — this allows a pure corn or pure rye mash without any barley.

Mash Temperatures

Temperature control is the most critical variable in an all-grain mash. The two key temperatures are the strike water temperature (the temperature of your water before adding grain) and the saccharification rest temperature (the temperature you hold during conversion).

For corn and raw rye, you need a gelatinisation step first — heat the grain to 74°C or higher to break open the starch granules before cooling down to saccharification temperature to add your malted barley. Flaked corn and flaked rye skip this step as they are pre-gelatinised.

Step-by-Step Process (Bourbon-Style Mash)

This recipe is written for a 20-litre batch using the 70/15/15 bourbon grain bill. For rye or wheat whiskey, substitute the corn percentage with your chosen grain — the process steps and temperatures are the same. Scale to any batch size using the Grain Bill Calculator.

Ingredients for 20L batch (target OG ~1.065):

• 3.5 kg cracked corn (or flaked corn)
• 0.75 kg malted barley (crushed)
• 0.75 kg rye malt or flaked rye
• 20 litres water
• Distiller's yeast (as per packet instructions)

1. 1
   Heat strike water. Bring 15 litres of water to 76°C (169°F). Reserve the remaining 5 litres for later. If using flaked corn, target 68°C instead — no gelatinisation step needed.
2. 2
   Add corn and hold for gelatinisation. Slowly stir in the cracked corn. Maintain 74–78°C for 30–45 minutes, stirring every 5–10 minutes to prevent scorching. The mash will thicken noticeably. If using flaked corn, skip to step 4.
3. 3
   Cool to saccharification temperature. Add the reserved cold water to bring the temperature down to 65°C (149°F). Stir well. Confirm temperature with a thermometer before the next step.
4. 4
   Add malted barley and rye. Stir in the crushed malted barley and rye. The mash will thin slightly as enzymes begin breaking down starches. Maintain 63–65°C for 60–90 minutes. Insulate the vessel with towels or a blanket to hold temperature.
5. 5
   Test for conversion. Take a small sample, cool it, and test with iodine tincture. No colour change to dark blue means conversion is complete. If still blue, extend the rest by 20 minutes and retest.
6. 6
   Cool the mash. Cool as quickly as possible to below 30°C (86°F). Use an ice bath, wort chiller, or cold water addition. Fast cooling reduces the risk of bacterial contamination.
7. 7
   Take an OG reading. Strain a sample through a fine-mesh strainer and measure with a hydrometer. A typical OG for this recipe is 1.060–1.070. Record this number — you'll need it to calculate ABV at the end of fermentation.
8. 8
   Transfer to fermenter and pitch yeast. Transfer the cooled mash to a clean, sanitised fermenter. You can ferment on the grain (on the solids) or strain first — both approaches work. Pitch your yeast according to the packet instructions, seal with an airlock, and move to a stable temperature environment.

Yeast Selection

Yeast choice affects the congener profile of your wash and ultimately the flavour of your whiskey. For an all-grain mash, use a strain designed for distilling — not bread yeast, and not wine yeast.

Pitch at the rate specified on the packet. Underpitching stresses the yeast and increases off-flavour production. Maintain fermentation temperature at 25–30°C for most distiller's yeasts — check the packet for the specific strain's optimal range.

Fermentation

A whiskey mash typically ferments in 5–7 days at 25–30°C. Fermentation is complete when the final gravity has been stable for two consecutive readings taken 24–48 hours apart — not when the airlock stops bubbling. An airlock can stop due to a temperature drop or CO₂ escaping through a small leak while fermentation is still active.

Expected final gravity for a 70/15/15 mash bill at OG 1.065 is approximately 1.010–1.015, giving a wash ABV of around 6–7%. This is normal for a grain mash — lower than a sugar wash — and produces the congener load that gives whiskey its character through distillation.

Bourbon Requirements

If you want to make a spirit that qualifies as bourbon under US regulations (Title 27 CFR Part 5), the grain bill and process must meet specific requirements. Home distilling is not legal in the US without a permit, but understanding the requirements is useful for anyone producing bourbon-style spirits in a jurisdiction where distilling is legal.

• Grain mixture must be at least 51% corn
• Distilled to no more than 160 proof (80% ABV)
• Entered into the barrel at no more than 125 proof (62.5% ABV)
• Aged in new, charred oak containers
• Produced in the United States
• No added colouring, flavouring, or blending materials other than water

Straight bourbon requires a minimum of two years aging. Bourbon with no age statement (NAS) must be aged for at least two years if the statement "straight" appears on the label.

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