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What Is The Maximum Alcohol Content Achievable By Fermentation? Fermentation is the process of converting sugar into alcohol. Sugar is a carbohydrate, which means it contains carbon, hydrogen, and oxygen in varying proportions. Alcohol production occurs when yeast consumes sugar and produces ethanol and carbon dioxide through aerobic respiration.
Yeast cells are sensitive to high concentrations of alcohol, typically between 12% and 18%. The tolerance limit for yeast cells makes it difficult to produce anything higher than 18% alcohol solely by fermentation alone. It is possible, however, to use other methods such as distillation or adding sugar post-fermentation to increase the concentration of the resulting liquor above this threshold.
What Yeast Makes The Highest Alcohol Content?
While the general answer to the maximum amount of alcohol is that most yeasts will be able to produce alcohol concentrations between 12 and 18% there is one type of yeast available that will produce alcohol concentrations up to 20% called turbo yeast.
This type of yeast has been around since the 1980s, however, it has only been recently that it has become popular with homebrewers due to its high alcohol content and speedy fermentation time. Turbo yeast ferments sugar within 2 days in some cases and they are particularly suitable for making spirits rather than beer.
There are 24-Hour & 48-Hour Turbo Yeasts that will produce around 14% alcohol within a 1 day or two days which can rise to 20% after 5 days. There are also yeasts that are designed specifically for specific classes of spirits including vodka, rum, and Whiskey, and other ones designed for brewing in warm conditions where the temperature exceeds 80°F (27°C).
How Do You Measure % Alcohol?
As there are some variables associated with the fermentation process that provide a degree of uncertainty it is common for brewers to measure the alcohol content using a hydrometer which measures the specific gravity or density of the brew. The monitoring of the specific gravity of the brew is also a useful way to determine that the fermentation is complete.
The hydrometer is a simple device that looks like a long glass tube with scales on the side and its main function is measuring density based on how high it floats in water. By observing how far it sinks below the surface of your test sample, you can determine its density.
As the alcoholic beverages you are brewing have different densities due to their different compositions it is necessary to measure the density of the brew before and after the fermentation process as the differential can only be due to the conversion of the sugar into alcohol.
To measure the specific gravity place the sample in the hydrometer tube and place the hydrometer into the tube and spin it gently to remove any bubbles that are clinging to its surface. Before taking the reading ensure that the hydrometer is floating freely, and is not touching the sides of the hydrometer tube.
For the most accurate reading adjust your position to ensure that your eye is level with the height of the liquid in the tube. When taking the measurement take it from the bottom of the curved surface which is known as the meniscus. Doing these two things will ensure that the readings taken are consistent. Take note of your reading before the fermentation has started and also after it is complete.
Your figures can be placed into an online calculator at Brewer’s Friend or you can manually complete the calculation using the formula below.
ABV(%) = (Initial Gravity – Final Gravity) * 131.25.
How Do I Estimate The Alcohol % From The Amount Of Sugar Added To The Brew?
When making alcohol it is important that you some idea about the amount of sugar you need to add to achieve your desired alcohol level. But in short the more sugar you add the more alcoholic it will become.
Based on using refined white sugar which is 100% fermentable sucrose you can typically expect to get a conversion rate of around 55%, which means that for every 1 kg of sugar that is added you will generate approximately 550 grams of alcohol or for every 35oz of sugar you will generate 19.4 oz of alcohol. This may vary a little using different strains of yeast or different types of sugar, for example, brewing sugar that is 95% fermentable will give slightly lower alcohol levels than white sugar.
The % alcohol can then be generated by dividing it by the volume of water used. For your convenience, a quick reference table has been included in imperial and metric units.
Ounces of Sugar Required To Create Different % Of Alcohol
| % Alcohol | 1 Quart | 1 Gallon | 2 Gallons | 4 Gallons | 5 Gallons |
| 3 | 1.8 | 7.4 | 14.8 | 29.6 | 36.9 |
| 5 | 3.1 | 12.3 | 24.6 | 49.3 | 61.6 |
| 7 | 4.3 | 17.2 | 34.5 | 69.0 | 86.2 |
| 9 | 5.5 | 22.2 | 44.3 | 88.7 | 110.8 |
| 11 | 6.8 | 27.1 | 54.2 | 108.4 | 135.4 |
| 13 | 8.0 | 32.0 | 64.0 | 128.1 | 160.1 |
| 15 | 9.2 | 36.9 | 73.9 | 147.8 | 184.7 |
| 17 | 10.5 | 41.9 | 83.7 | 167.5 | 209.3 |
Grams of Sugar Required To Create Different % Of Alcohol
| % Alcohol | 1 Litre | 4 Litre | 10 Litre | 15 litre | 20 litres |
| 3 | 55 | 218 | 545 | 818 | 1091 |
| 5 | 91 | 364 | 909 | 1364 | 1818 |
| 7 | 127 | 509 | 1273 | 1909 | 2545 |
| 9 | 164 | 655 | 1636 | 2455 | 3273 |
| 11 | 200 | 800 | 2000 | 3000 | 4000 |
| 13 | 236 | 945 | 2364 | 3545 | 4727 |
| 15 | 273 | 1091 | 2727 | 4091 | 5455 |
| 17 | 309 | 1236 | 3091 | 4636 | 6182 |
Alternatively, if you are planning to ferment liquids from commercial sources you can use the Sugar values provided to calculate the alcohol content using a chart on delishably.com which is shown below. It is a really quick way to work out the approximate alcohol content that will be created.
How To Use The Sugar To Alcohol Calculator?
In most countries around the world food labeling laws require the manufacturer to disclose the nutritional information on the packaging this is commonly displayed on the basis of per serving or per 100ml. In the example provided below, it is on a per-serving basis.
To calculate the potential alcohol content the data needs to be converted into grams per litres. This can be done by taking 42g from the Total Carbohydrate line and dividing it by 355 which has been converted into litres (0.355). The grams per litre of the Apple Juice is 118g/L, by comparing the grams per litre line of the chart above with the alcohol line will allow the alcohol content to be estimated at 6.6%.