Homebrewers typically make beer in either 5 or 1-gallon batch sizes but they might wonder how long it takes for both sizes to ferment and if there are any differences.
Under normal circumstances, it will take about 2-4 weeks for both a 5-gallon and 1-gallon batch of homebrew ale to finish primary fermentation despite the difference in total volume. Using a yeast start can help the fermentation start quicker for both batch sizes but the total amount of time will be similar.
Although there are methods by which to accelerate fermentation, note that some can result in unwanted “side effects.” Implementing proper yeast management, with or without a starter, and controlling fermentation temperature are the best ways to avoid delays in fermentation.
How Long Does It Take Homebrew Beer to Ferment (Both 5 and 1 Gallon)
Impatient to taste your homebrew? I can relate. There it is, brown and foamy in your fermenter. Would it go faster if you had brewed less wort?
The process of preparing and boiling your wort seems short compared to the fermentation time. It may seem that a larger batch takes more time to process, but the volume of your homebrew does not impact the fermentation time – both 5-gallon and 1-gallon batches of beer will ferment in about the same amount of time. This is because the quantity of yeast pitched should be relative to the size of your batch. Whether you are preparing five gallons or one, you will have to wait the same length of time for fermentation to complete.
Depending on the style of beer, primary fermentation can take from one week to several months. (Then, second fermentation and bottle conditioning.) Ales generally require less time to ferment than lagers, like dark and beers with higher alcohol content. I included a chart in the section on one gallon, for your reference.
There are however, several factors that can noticeably expedite (or slow!) fermentation. I will discuss some of these – such as temperature, yeast strain, and ratio – later on.
The style of beer is the first factor in determining the fermentation time, regardless of the volume. Take a look at this chart by Midwest Supplies:
|Light Beer||1 week primary plus 1-2 weeks secondary||1-2 months primary plus 2 months secondary|
|Amber Beer||1 week primary plus 2-3 weeks secondary||2 months primary plus 3-4 months secondary|
|Dark Beer||1 week primary plus 3-4 weeks secondary||2-3 months primary plus 9 months secondary|
|High-Alcohol Beer||2 weeks primary plus 9-12+ months secondary||2-3 months primary plus 9-12+ months secondary|
How long does it take to ferment 5 gallons of beer?
For those just starting out, most beer kits require one to three weeks of primary fermentation. However, dark lagers with a high alcohol content can push two months in primary fermentation. For those eager to brew their first beer, a light ale is a great option, as they take about one week in primary, then two weeks in secondary fermentation.
For a technical approach:
Use a (sanitized!) hydrometer to get a gravity reading of your batch. If you get the same reading for three consecutive days, you’re good to go. If you choose this method, I recommend taking a sample from your batch, then discarding it after each reading. That way, if your sample becomes contaminated, it will not affect the rest of your batch.
For a more casual approach:
If your airlock is still bubbling, your brew probably needs more time.
How long does it take to ferment 1 gallon of beer?
For the most part, the quantity of your brew does not affect the fermentation time.
If you are brewing an ale, the fermentation can take from one to five weeks total to ferment, excluding beer with a high alcohol content. As I mentioned at the start, you should pitch an amount of yeast relative to the size of your batch. (Less beer means less yeast.) It may be tempting to pitch more, but too much yeast can cause unwanted results in your beer.
Do smaller batches of homebrew beer ferment faster?
No, smaller batches do not ferment notably faster.
Smaller batches can decrease the overall brewing time, especially using the BIAB (“brew in a bag”) method. For instance, boiling one gallon of water on your kitchen stove will take less time than five gallons. Likewise, one gallon will cool faster at room temperature.
However, the fermentation time will remain the same, as the amount of yeast is relative to the quantity of your brew. Your homebrew, regardless of the gallon count, should experience a phase of active, then a few days of “passive” fermentation.
Make sure to pitch the right amount of yeast. Pitching rates vary based on the gravity of your wort, which is based on the style of beer.
What speeds up or slows down beer fermentation
There’s even a term for this in our handy Oxford Companion to Beer:
“Accelerated batch fermentation is an attempt to gain economic advantage through the production of more beer with the same equipment in less time.”
Here are a few methods to accelerate the primary fermentation:
Yeast starters – a faster start means a faster finish
Once your wort is brewed, make sure to cool it off before pounding into your sanitized fermenter. Then, add the yeast. During the main fermentation, yeast converts the sugar in your wort into alcohol and carbon dioxide. The process can take more than a day to begin. This is called the lag phase. Agitate the fermenter, so that your wort receives more oxygen, which helps to start the fermentation process.
This concept regarding oxygen applies to yeast starters as well. Oxidation, or aerobic respiration, of the starter keeps it fresh for your wort. Yeast starters increase the efficiency of the yeast during the fermentation process. This pre-step allows the yeast to propagate, so that it enters your main batch healthy and ready.
Boil a small amount, like a cup, of wort and wait for it to cool. Pour it into a small container with an airlock and add the yeast. You can use either dry or liquid yeast. Voila! Your starter is ready to pitch 24 to 48 hours later.
Northern Brewer recommends using a stir plate for best results. It keeps the yeast in suspension, therefore increasing activity. A note on this method in the next section.
A yeast starter increases the yeast cell count in your wort, which reduces lag time and promotes faster fermentation. It is especially helpful for higher gravity wort because of the higher sugar content. A quality starter facilitates faster fermentation, which results in beer with fewer unwanted byproducts, such as esters and phenols. In general, healthy yeast produces reliably crisp beer, with less chance of the fermentation getting “stuck.”
What is “microfluidics?”
There was that story five years ago, when some college kids found a way to brew beer nine times faster. Did you see it?
Three undergraduate students from the University of Pennsylvania developed an approach called “microfluidics,” by which they could accelerate fermentation by nine times, without compromising quality. They developed the process as part of an entrepreneurial engineering competition, which they won. They received a whopping ten grand and some notable press.
I did a little digging and it seems that the students were able to optimize the conversion rate by increasing the surface area of liquid sugar exposed to the yeast. According to a press release by the William and Phyllis Mack Institute for Innovation Management:
“Using the microfluidics technology, which can produce nanoparticles of liquid with extremely precise specifications, the team devised a way to concentrate sugar liquids around individual yeast cells. This technique greatly increases the surface area of the yeast exposed to the sugar, accelerating fermentation by 70%.”
While reading about it, I found a fellow brewer, Greg Foster, who likened the process to yeast starters on a stir plate. He even conducted an experiment on a full five gallons of Amber Ale. The result was positive! Although his beer did not ferment nine times faster, the process did go faster and did not change the flavor profile.
Higher ambient temperatures accelerate fermentation
Increasing the temperature of your initial fermentation can accelerate the process. On the flip side, a lower temperature will slow fermentation.
A higher temperature increases the metabolic rate of your yeast, thereby increasing production capacity. Note, this method may influence the flavor profile of your finished beer.
Krzysztof Kucharczyk and Tadeusz Tuszyński studied the impact of temperature on beer fermentation and found the following results:
By increasing the fermentation temperature, acetaldehyde and vicinal diketones were reduced.
“Fermentation at a temperature range between 8.5 and 11.5 degrees celsius had a significant effect on the concentration of esters and fusel alcohols. However, higher fermentation temperatures (10 and 11.5 degrees celsius) did not have a significant influence on the final sensory assessment of the beer.”
Be sure to note the temperature range recommended for the yeast that you use. If you overdo it, your yeast can become stressed or inviable. Remember, yeast is a living organism. Although adaptable, it will struggle and delay in an uncomfortable environment.
Certain yeast strains ferment faster
There are some yeast strains that are better able to process sugars, thereby fermenting your brew faster. For instance, fermentation time can be expedited with powdery, “non-flocculent” types of yeast. For general inspiration, check a forum, like this one, where fellow homebrewers share advice on fast-acting strains. Some recommend the Wyeast French Saison, San Diego Super, or the California Yeast Ale. For a more technical approach, White Labs provides a comprehensive catalogue of yeast strains, including necessary information on attenuation, flocculation, alcohol tolerance, and fermentation temperature.
As a reminder, top fermentation, in which the yeast floats on top, occurs at higher temperatures, between 18 and 22 degrees celsius. Typical beers fermented in this style are ale and wheat beers. This process can be done at room temperature and occurs somewhat faster than bottom fermentation.
Bottom fermentation, during which the yeast sinks, occurs at lower temperatures, between 9 and 12 degrees celsius. Lagers and pilsners are usually fermented in this style. However, this way can take longer, in part because lower temperatures slow the process.
Increasing the ratio
To speed up the process, you can try increasing the yeast-sugar ratio. This way, you will introduce more yeast to faster consume the sugars in your wort. Note, although unlikely, this method can decrease the health of your yeast, as there are fewer nutrients left for each.
In the aforementioned study, the scholars found that increasing both temperature and pitch quantity will decrease fermentation time by promoting yeast performance. However, this combined approach can detrimentally affect the flavor of your beer, at least after the primary fermentation. It can also damage yeast viability, resulting in poor secondary fermentation. (No double dipping!)
Agitating your fermenting wort
Towards the end of fermentation, you can encourage your yeast by injecting carbon dioxide or re-circulating your fermenting wort. Although this method does not noticeably decrease fermentation time, it facilitates a steady process. More importantly, it can help prevent or reactivate your “stuck” homebrew.
If the gravity of your brew is too high, but the yeast has fallen, it cannot finish converting the remaining sugar in your wort. This situation prolongs the fermentation process. Don’t worry, you can resuspend your yeast by gently (!) swirling your fermenter. Do not shake or sway, as this can cause waves, which can over oxidize your fermenting wort or damage the yeast cells.
Thoughts on expediting the fermentation
Brew big or brew small, you will still have to wait for the yeast to complete its work. Quantity aside, there are several other ways by which to expedite the fermentation of your beer.
That said, I recommend that you choose the yeast strain based on the style of beer that you want, not the turnaround time. Pay attention to the recommended temperature for your type of yeast. It’s there for a reason! Good beer takes time to ferment properly.