Potential Alcohol

December 18, 2009

The fermentation equation:
C6H12O6 -> 2 C2H5OH + 2 CO2
Fermentation converts sugar into alcohol and carbon dioxide. In my last post, I talked CO2, so I’m going to focus a little more on the creation of alcohol in this post.

The yeast will eat sugar, fructose, corn sugar, or honey to create alcohol. These types of sugars, when added to water, make water become thicker. There is a device called a hydrometer that can be placed in the solution. The thicker the solution, the more the hydrometer rises, and it sinks the thinner the solution is. Water will measure in at 1.000, and a finished dry wine will be a little less than that. This measurement is called Specific Gravity, often noted as SG.

So at the beginning, before yeast is added to the batch, a sample is taken in which the sugar content is found with an SG measurement. There are tables that then say for a given SG at a particular temperature, the yeast’s potential to convert sugar to alcohol will be x amount. This is important because it allows the brewer to know how strong of a drink it will become.

Further tests can be taken to know when the drink is done fermenting, as there will be no more sugar remaining. Also, sometimes the yeast quit working for a little bit, at which point it is “stuck”. Doing the test allows the brewer to recognize this problem and modify it.

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12 Responses to “Potential Alcohol”


  1. […] Test the sugar amount in the juice using a hydrometer to determine the alcohol potential. […]


  2. […] sugar differences were evident, too, as a blend of the two kinds of apples’ juices resulted in 1.040 SG, where as the store bought apples’ juice alone was 1.050 SG. While it was more expensive, the […]


  3. […] it fresh that it was inferior juice to the Gravenstein apples I picked the week before. While the sugar content was decent, I had to add acid to it, and it just didn’t taste as good raw. I would have to call these apples […]


  4. […] needs just a little tiny bit of juice to accomplish what a hydrometer can do, which is to test the amount of sugar in the juice to figure out how much potential alcohol the juice could ferment. With a little bit of juice in the […]


  5. […] removed the table tracking the specific gravity. I believe if I was a large wine maker doing up 50 gallons or more a batch, I would be monitoring […]


  6. […] are a few odd things here and there that don’t jive. For instance, he has a sugar to potential alcohol chart in the back of the book. When I compare it to any other chart I have found, it turns out low. […]


  7. […] who bottles, the method used is bottle conditioning. When the beer, wine, cider, etc is dry and has little to no remaining sugar left in it, leaving a specific gravity of about 1.005 or lower. From there, the product is dosed with a small […]


  8. […] peaches had decent sugar content at about 1.055 SG, which would be about 7% ABV as is. I will raise that to a more stable 12% by […]


  9. […] start fermenting. I doubt it since it is being refrigerated, but his concerns are justified as the sugar reading I took on it measured 1.035 SG. A dry cider is less than 1.005 SG, and a sweet tasting cider will […]

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