Understanding Fermentation in Moonshining

The flavor of moonshine is determined not only by the ingredients in the mash including the type of yeast used and the quantity of sugar but also by factors like temperature. While alcohol can be made from just any grain including barley and rye, corn remains to be the favorite ingredient that has been used in the USA for the last more than 150 years and corn whiskey a traditional drink whose value is deeply rooted in the history of moonshine. However, you can never miss a few bad guys in the flock who are only after profits and have replaced corn with white sugar to produce cheaper alcohol known as rum instead of whiskey. 

The process of making moonshine 

Making moonshine involves two main processes: fermentation and distillation. Fermentation is the first process and this is what this article will focus on. Distillation is the second process that takes place after the wash has been fermented into alcohol (beer or wine). Distillation is all about evaporating the alcohol to produce whiskey. Alcohol (ethanol) boils at a lower temperature than water which means that it will be the first to evaporate. Its steam is then collected and condensed back to liquid form to produce whiskey or moonshine which is typically higher-strength alcohol.

What is fermentation? 

Fermentation is both a biological and chemical process where yeast is used to break down sugars and starches to produce alcohol and carbon dioxide. Yeast here acts as a catalyst in the starch and sugar conversion process.

This process basically involves placing the correct mixture of the ingredients in an open container and then sealing the top of the container tightly with a clean cloth. The cloth should be breathable enough to allow in the air while at the same time preventing other particles like dust, bugs, and dirt from getting into your mash.

It is not advisable to use a completely sealed airtight container. This interferes with the fermentation process and actually inhibits the yeast from converting the sugars into alcohol.

The fermentation process

There are two main stages of fermentation. The first phase involves rapid yeast reproductions that result in an exponential increase of the yeast cells in the mash. It’s at this stage that alcohol is produced in your mash. The second stage in the fermentation is characterized by a slowing down of yeast growth. You will notice this phase by observing reduced bubbles. The yeast having completed its metabolism sinks to the bottom of the bucket or the fermentation vessel.

First, let us look at how fermentation is done to produce moonshine. 


  • Cracked corn or cornmeal
  • Sugar
  • Yeast
  • Water
  • Other ingredients can be added for flavor

The fermentation process

  • Most distillers prefer cracked air-dried yellow corn while others would go for the finer cornmeal which is simply ground from cracked corn. Some commercial moonshine producers today prefer to use hog feed which contains much finer corn.   
  • The cornmeal is then soaked in hot water. Some people will add sugar at this stage or replace corn with sugar altogether. However, traditionally, malt was added to convert the starch in corn into sugar as it contains enzymes that catalyze this process. 
  • Yeast is then added to start the fermentation process. The mixture, known as mash, is stirred to mix properly then heated slightly.
  • The mash should be stored at room temperature for one or two weeks. Ensure that the temperature is correct as low temperatures may even stop the fermentation process as it causes the yeast to be dormant. 
  • After fermentation is complete, the mash is strained to remove sediments which by now will have settled at the bottom of the fermentation container. To remove all the particles, the mash is strained through cheesecloth because sediments in the final alcohol can cause serious headaches to the drinkers.

Stages of fermentation 

Fermentation takes place in two phases, the primary phase, and the secondary phase. 

The primary phase of fermentation 

The primary phase mostly happens within the first three to seven days of fermentation with the first days showing off more activity than the last days. The bulk of fermentation happens during this phase as the yeast activity is at its peak. Yeasts are single-celled microorganisms that break down starch and sugar into alcohol and carbon dioxide. 

At this point, you will notice bubbles at the surface of your mash. These bubbles are actually carbon dioxide that escapes from the mixture into the air leaving alcohol into the fermenter. Secondly, the taste of your alcohol also shifts from the sweetness in the malt to a more bitter beer taste. 

The secondary phase of fermentation

Secondary fermentation is usually longer than the primary phase and can take several days to several weeks. It is a continuation of fermentation before or after alcohol has been separated from the sediments from the primary phase. Here you’ll notice fewer bubbles compared to the first phase as the yeast activity slows down as an indication that most of the sugar in the mash has already been broken down into alcohol. You will also notice that some sediments have settled down at the bottom of the container, usually leftover grain and other particles. 

Simple and scientific monitoring of the fermentation process 

The fermentation process should be monitored as this helps to pick up any faults or abnormalities that may hinder the process from being carried out as is supposed to. It is also important to know when the primary phase of fermentation has ended. These two commonly used methods of monitoring fermentation. 

1. Simple monitoring

It is easy to ferment mash in an airlock bucket. 

simply look out for bubbles within the initial 18-24 hours of the process. In case you do not see any activity do the following. 

  • check and ensure that the lid is in place, properly sealed, and is airtight. 
  • If the lid is not the problem, try swirling your bucket just to mix its contents well and then observe it for another 12 hours. 
  • If this does not work, add some more yeast to your mash and start all over to observe the bubbles within the first 18-24 hours after adding the yeast. 

Note that the ideal temperature for fermentation should be between 165.2 °F (74 °C) and 170.6 °F (77 °C). 

If all is well, give fermentation up to about 14 days or wait until the bubbles are not visible anymore. This non-scientific process of observing fermentation will let you know when your alcohol is ready. Fermentation is a slow and tedious process that can take place anywhere between 7 to 14 days. The process ends when there is no more CO2 escaping from the mash. CO2 is usually created during fermentation and it’s what creates bubbles at the top of the mash. 

2. Scientific monitoring 

The scientific process is the most accurate way of monitoring mash fermentation and is used particularly by commercial distillers. A hydrometer is used to take gravity readings, letting you know when fermentation is complete. The hydrometer also helps determine the amount of alcohol in the mash. 

What you need 

  • Hydrometer for beer or wine
  • Hydrometer test jar
  • Beer sampler

A hydrometer gives accurate results. Once your set-up is done, take gravity readings at the start of fermentation and at the end of fermentation as well as in between the process. The hydrometer is used to take Alcohol by Volume (ABV) readings. A reading of 1.000 or less is an indication that fermentation is complete. Anything above 1.020 means that the mash needs more fermentation time. 

The explanation, water has a gravity of 1.0000 thus the gravity for mash will be higher because of the presence of sugar. As sugar is converted by yeast to alcohol during fermentation, the density record will be lowered and be the lowest at the end of the fermentation. 

Factors that affect the fermentation process

Various factors contribute to you having a good or poor fermentation of your mash. These factors are sugar and nutrients content, temperature, oxygen, and yeast used. 

  1. Yeast plays a crucial role in the fermentation process as well as in the final taste of alcohol your alcohol. The Type of the yeast you use will determine the time it takes for the fermentation to be complete. For instance, turbo yeast results in a faster fermentation process when compared to bread yeast and therefore preferred for making neutral spirits that have no flavor. On the other hand, if you want a whiskey moonshine, brandy, or rum, it is advisable to select a yeast brand that will complement the flavor of the ingredients in your drink.
  2. The room temperature where the mash is being fermented also has an impact on the time it takes for the fermentation to be completed. The ideal temperature to maintain for successful fermentation should be between 167 °F (75 °C) and 176 ° (80 °C). Still, care should be taken as extremely high temperature destroys the yeast. 
  3. The amount of sugar in the ingredient will also contribute to how fast or how slow fermentation takes place. A lot of sugar in mash leads to longer fermentation time. Again, too much sugar produces bad flavored alcohol. You can always add water when you notice the sugar is in the mash too much. Many beginners have a challenge measuring the right amount of sugar in their mash. 


The lid of the fermentation bucket should be sealed throughout until fermentation is complete. Some people may be tempted to peek into the bucket to observe the bubbles. This is not right as it increases the risk of bacteria ending up in the bucket which then competes with your yeast to breakdown the sugars. This is why most people have warmed up to using a hydrometer. Alternatively, just observe the airlock for bubbles.