Potential Alcohol
Related Documents
About Brix, Glucose+Fructose, and Potential Alcohol
Harvest Fee Schedule - 2014

About º Brix, Glucose + Fructose, and Potential Alcohol

The amount of fermentable sugar (glucose + fructose) in juice and the average conversion rate of sugar into alcohol can be used to predict the potential alcohol level in wines.

Choosing Glucose + Fructose instead of º Brix for Alcohol Predictions:
While ºBrix can provide a quick estimate of sugar content, it is not an accurate representation of the fermentable sugars, but rather a measure of all dissolved matter in the must. Using ºBrix can give you an inaccurate measure of fermentable sugar and may add an additional layer of uncertainty to alcohol predictions. Differences between ºBrix and actual fermentable sugar content are even more pronounced in high ºBrix fruit and in fruit affected by fungal growth.

Glucose + Fructose analysis, on the other hand, provides accurate information on the levels of fermentable sugar. Glucose + Fructose numbers often appear higher than the corresponding ºBrix results in ripe fruit. The reason for this is that ºBrix is measured as a percentage by weight measurements, meaning ºBrix values are greatly influenced by the density of the juice. Glucose + fructose is measured as weight by volume and is independent of juice density.

Estimating Potential Alcohol:
ESTIMATED CONVERSION RANGES
SUGAR (g/L) ETHANOL (% Vol)
180 10.0 - 10.9
190 10.6 - 11.5
200 11.1 - 12.1
210 11.7 - 12.7
220 12.2 - 13.3
230 12.8 - 13.9
240 13.3 - 14.5
250 13.9 - 15.2
260 14.4 - 15.8
The conversion rate used is:
Potential Alcohol (% vol) = glucose + fructose (g/L) / 16.83

It is important to remember that the actual conversion rates vary with yeast properties and fermentation conditions and the potential alcohol is only an approximation. Alcohol conversion ratios are always subject to variability during fermentation, so it’s possible your actual alcohol may be lower or higher than the estimate. Regardless, this calculation provides a good starting point for estimating potential alcohol.

Many clients have found that the conversion rates observed for their own yeasts and fermentation conditions generally remain relatively constant and use their internally observed rates to calculate potential alcohol content based on their glucose + fructose values.




This document is a compilation of information and views from various sources provided for the convenience of our clients. Information in this document is provided "as is" without warranty of any kind, either expressed or implied, including but not limited to the warranties of merchantability, fitness for a particular purpose and freedom from infringement. User assumes the entire risk as to the accuracy and the use of this document. This document may be copied and distributed subject to the following conditions: 1) All text must be copied without modification and all pages must be included; 2) All copies must contain ETS's copyright notice and any other notices provided therein; and 3) This document may not be distributed for profit. All trademarks are acknowledged. Copyright ETS Laboratories 2001-2012.