Adding Sugar During Fermentation

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Jul 7, 2010
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I am trying to caclulate my sugar requirements before I start my 1st batch, (just ballpark stuff so I can get an idea of what I need to look for).

I am using the Hydrometer Table method listed in The Home Winemaking Book (M. Pesgens)

I need clarification on the last part

We want to get 10 litres of wine with 12.5 %vol alcohol content.
The must has an SG of 1035.
Amount of sugar present in must:
SG 1035 gives us 95 g / litre
10 * 95= 950 g
Amount of sugar needed at fermentation start:
(a good starting SG for a must is SG 1080, which equals 208 grammes sugar/l)
SG 1080 gives us 208 g / litre
10 * 208 = 2080 g
Amount of sugar needed totally:
12.5 %vol doesn't exist, so we look at 12.7 %vol and take a bit less. This gives us 250 g / litre
10 * 250 = 2500 g
Amount of sugar to be added totally:
2500 - 950 = 1550 g
Amount of sugar to be added before fermentation start:
2080 - 950 = 1130 g
Amount of sugar to be added during fermentation:
2500 - 2080 = 420 g

Exactly when is this additional sugar added?

I have scanned other posts on adding sugar during fermentation and a lot of replies say "NO".

Please advise.
You want to add the sugar up front. Add sugar until you get to the desired SG.

Then you pitch your yeast and yeast nutrient.

You want to add all you other additives, tannin, acid blend (make sure you take readings first), k-meta, pectic, etc 24 hours prior to adding the sugar and yeast.

Adding during fermentation or once fermentation has started will just fuel the fire - and you will not have an accurate ABV reading.
Well in all honesty - pectic should be added 12 hours after the k-meta.

The k-meta will fight off any unwanted bacteria - this will also keep the yeast from working.

Pectic will pull out the juices from the skins.

All this will enable the yeast to perform better.
Sugar and K-Meta can be added together to the Must , but you should wait 12 hours and then

Pectic Enzyme can be added because its action is retarded by an excess of Sulfur Dioxide .

Pectic enzyme works best at cooler temperatures. Do not add it to musts above 75 degrees F.

I have the same book and I do not understand that. You should have all your sugar up front. Don't add sugar during fermentation unless it needs it and you really know what you are doing or you'll end up with something that will give you 30 miles to the gallon.
The only reason to add sugar later in the game is if you are trying to push the yeast hard to get a higgh abv wine or a Port because adding all that sugar up front would stress the yeast and it may not get going. Other then that add it all up front and get true readings with your hydrometer and take the possible mistake out of the equation.

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