Bottling a Sweet Wine  
Fall Bright, The Winemakers Shoppe

 

Potassium Sorbate inhibits (doesn't really kill) yeast and is used as a preservative for sweet wine.  The use of sorbate on an amateur basis yields varied results.  There is more than meets the eye than just adding the recommended amount given on the package instructions.  

The instructions for most sorbate give a range of amounts to use.  That amount to be used in a given wine is determined by:  

1. the alcohol level % by volume.  The higher the alcohol the less sorbate is required to achieve the desired results.  
2. the yeast cell concentration or population.  Have this as low as possible by racking or filtering. 
3. SO2 level.  This level should be proper 40 ppm.  If you do not use meta, do NOT use sorbate.  
4. We don't know about pH, but it is probably a factor.   We do know that if your pH is over 3.4 you may want to use 80 ppm of meta.
5. The density/concentration of the sorbate is also a factor.  The density of sorbate is different from one supplier to the next.  The instructions will vary accordingly.   

If you need to add sugar to sweeten to taste, use cane sugar (sucrose) instead of corn sugar.  Calorie for calorie there is twice the taste of sweetness with cane sugar.  We are often asked whether to add sweetness before sorbate or after.  I like the logics of inhibiting the yeast first and then adding the sugar to taste while they are in poor condition.

So, do you need to use Sorbate?  Is the wine dry or does it have residual sugar present?  Test the sugar level, using a -5 to +5 hydrometer.  If the reading is below a -1.5 degrees or -2 degrees brix, then the wine is dry and safe to bottle without sorbate.  If the hydrometer reading is higher than a minus 1.5, such as a 0 reading or a plus 1 degrees, then there is residual sugar.  

Determine the alcohol level of this wine.  If it is dry you may use a vinometer to test it or go with the potential alcohol based on the initial brix at the start of fermentation.  If you did a residual sugar test (Clinitest) you may deduct the alcohol that you did not obtain from the residual sugar from the initial potential alcohol.  The general conversion of sugar to alcohol is approximately 58% (0.575%~).  That will put you in the ball park for the alcohol %.

Test the SO₂ level of the stuck wine with a Titret SO₂ test kit.  It should be about 40 ppm.  
Dose the metabisulfite to 40 ppm at the same time you do the sorbate.  If you do not have proper K Metabisulfite levels at this time and any malolactic bacteria are present, it will consume the Sorbate.  The result is an off taste and an odor of geraniums for which there is no fix. 

ADD SORBATE:  Different rates we have seen range from 5-6 grams per 5 gallons or 1 1/2 to 4 grams per 5 gallons.   Some instructions just give 1/4 or 1/2 teaspoon per gallon.  SO....What to do?  Read your label and shoot high.  It may help to cross your fingers, too.

Now, you can cold stabilize.  Put glycerin or sufficient alcohol (vodka) in the airlock to prevent freezing.  Place the carboy at 25-30^o F for 2 weeks or more.

Excess tartrates will precipitate from the wine. This mellows the wine by reducing the acid. It will help stabilize the wine by preventing these tartrates from settling out after bottling. Rack into a clean carboy while cold.  Add proper metabisulfite. 

If you add SORBATE without cold stabilizing, allow 24 hours before bottling.  However, the addition of any potassium ion will make the wine unstable.  You may end up with floaters in a bottled wine.  This is why cold stabilization is recommended after adding sorbate.  Cold treatment stabilizes the wine. 

If you do not want to use sorbate and have a sweet wine to bottle, use pressure safe bottles such as champagne or beer bottles.   The residual sugar should be 2% or a 1 degree reading on a –5 to +5 hydrometer.  If you have a dry wine (by hydrometer reading) and add sugar to taste, add 2%.  See sugar calculations.