Corn Mash Recipe for Home Distillers

Which Type of Corn to Use

The form of corn you use changes how you process the mash. The three most common options for home distillers are cracked corn, flaked corn, and cornmeal.

For most home distillers starting out, flaked corn is the most forgiving option because it skips the cook step entirely. Cracked corn gives a slightly more traditional character and is cheaper per kilogram. Cornmeal works well but requires more attention during the cook to avoid a lumpy mash.

The Role of Enzymes

Corn starch cannot ferment directly. Yeast can only consume sugars, not raw starch. To turn corn starch into fermentable sugar, you need enzymes called amylases to break the starch chains apart.

There are two amylase enzymes that do this work. Alpha-amylase breaks long starch chains into shorter chains called dextrins. Beta-amylase then breaks those dextrins into maltose, the main fermentable sugar yeast consumes. Both are needed for a full conversion.

There are two ways to provide these enzymes in a corn mash:

• Malted barley. Adding at least 10 to 15% malted barley by total grain weight introduces both alpha-amylase and beta-amylase naturally. This is the traditional approach used in bourbon production. The malted barley also contributes a small amount of flavor.
• Commercial enzymes. Alpha-amylase and glucoamylase (also called amyloglucosidase) are sold for home brewing and distilling. They allow a mash built entirely from corn with no barley contribution at all. Follow the manufacturer's dosing and temperature guidance, as these vary by product.

Cooking the Corn

Corn starch gelatinizes between approximately 62 and 74°C (144 to 165°F). Below this range, the starch granules remain tightly packed and enzymes cannot reach them. Above this range, the granules absorb water, swell, and become accessible. The mash thickens noticeably at this point, which is a sign the cook is working.

For cracked corn and cornmeal, the cook step works as follows:

1. 1
   Heat your water to around 74°C (165°F). Use enough water to cover the grain and allow room for stirring. A ratio of roughly 3 to 4 litres of water per kilogram of corn is a common starting point.
2. 2
   Add the corn slowly while stirring. Adding it all at once can cause clumping, especially with cornmeal. Stir continuously as you add the grain to keep it dispersed.
3. 3
   Hold the temperature for 30 to 60 minutes. Keep the mash between 74 and 80°C (165 to 176°F) for at least 30 minutes. Stir regularly to prevent scorching on the bottom of the pot. The mash will thicken as the starch gelatinizes.
4. 4
   Cool to conversion temperature before adding enzymes. Do not add malted barley or commercial enzymes while the mash is still above 68°C (154°F).

If you are using flaked corn, skip steps 1 to 3. Add the flaked corn directly to water at the conversion temperature (around 65 to 68°C) and proceed to the enzyme step.

Enzyme Conversion

Once the corn has gelatinized and the mash has cooled to the conversion range, add your enzyme source. The target temperature window for saccharification using malted barley is around 63 to 68°C (145 to 154°F). In this range, both alpha-amylase and beta-amylase are active and will convert the gelatinized starch into fermentable sugars over 60 to 90 minutes.

You will know conversion is progressing because the mash thins out noticeably as the starch breaks down into dissolved sugars. The iodine test can confirm conversion: a drop of iodine solution on a sample of the liquid will remain amber if conversion is complete, and will turn dark blue or black if starch is still present.

Cooling and Pitching Yeast

After conversion, cool the mash to the pitching temperature for your yeast. Most distilling yeasts pitch well between 25 and 30°C (77 to 86°F). Pitching into a mash that is still too hot will kill the yeast before fermentation starts.

You can cool the mash by placing the vessel in an ice bath, running cold water around the outside of the pot, or using an immersion chiller. Stir the mash while cooling to help heat transfer and ensure the temperature is even throughout the vessel rather than just at the surface.

Transfer the cooled mash to your fermentation vessel. For grain mashes, you have two options:

• Ferment on the grain. Leave the corn solids in the fermenter. The yeast will continue to work with any remaining unconverted starch, and the solids are strained out before the still run. This is the traditional approach and gives a fuller character.
• Strain before fermenting. Press the grain through a bag or strainer to collect the liquid wort and ferment only the liquid. This is cleaner and easier to manage in the still.

Pitch the yeast according to the manufacturer's guidance and seal the fermenter with an airlock.

The Sour Mash Technique

Sour mash is the practice of replacing a portion of fresh water in a new mash with backset. Backset is the spent liquid that remains in the still pot after a distillation run. It is acidic, rich in minerals from the previous fermentation, and contains no alcohol because the distillation has removed it.

Adding backset lowers the pH of the new mash to around 5.2 to 5.4, which is close to the optimal range for amylase enzyme activity and also inhibits the growth of unwanted bacteria. It creates a degree of flavor continuity from one batch to the next because each new mash is seasoned with the character of the previous run.

Bourbon distilleries in the United States commonly use backset at rates of approximately 25 to 33% of total mash water volume. For home distillers, starting at 25% and adjusting based on the pH of the resulting mash is a reasonable approach. A pH meter or pH strips will tell you where you land. If the pH drops below 4.8, use less backset on the next batch.

Fermentation

Corn mashes generally ferment well with distilling yeasts such as DADY (Distillers Active Dry Yeast), EC-1118, or a dedicated whiskey yeast. Bread yeast will also work and is widely available, though the flavor contribution differs from dedicated distilling strains.

Fermentation typically takes 5 to 10 days at temperatures between 25 and 30°C (77 to 86°F). Grain mashes with moderate original gravity will usually finish within this window. Do not rely on the airlock to tell you fermentation is complete. Use a hydrometer and confirm the gravity has been stable for two consecutive readings taken 24 to 48 hours apart before moving to the still.

Expected final gravity for a corn mash with a healthy fermentation is typically between 1.000 and 1.010 SG, depending on the original gravity and yeast strain. A mash that stalls well above this range is likely experiencing a stuck fermentation caused by low temperature, nutrient deficiency, or a yeast health issue.

Bourbon Mash Bill Requirements

Under US federal regulations (Title 27 CFR Part 5), bourbon must meet specific production requirements. The mash bill must contain at least 51% corn by grain weight. The spirit must be distilled to no more than 160 proof (80% ABV). It must be stored at no more than 125 proof (62.5% ABV) in new charred oak containers. No coloring, flavoring, or blending materials may be added. Bourbon must be produced in the United States.

There is no minimum age requirement for bourbon, but "straight bourbon" must be aged for at least two years. "Straight bourbon" aged for less than four years must carry an age statement on the label.

If you are making corn-based spirit for home use, these regulations do not apply to you directly. They are useful context for understanding what a bourbon mash bill represents and why corn content matters.

Frequently Asked Questions