Most fruit wines need a little help. there is not one fruit wine I make without making a F-PAC (flavor pac).
You can do this a few different ways. The most popular is take 20-30% of the weight used in the primary and simmer in a large pot/frying pan. constantly stirring and mashing the fruit. then run it thru a kitchen strainer and add to the wine.
Make sure you have added k-meta and sorbate 1st. After adding the f-pac you will need to clear again and rack at least 2 more times.
Also consider making and adding "simple syrup" for sweetness. (2 parts sugar added to 1 part boiling water and stir till clear. Cool down and add to YOUR taste)
Best is to take the tartness out before you start making the wine.
Do you have an acid titration kit ??
If not that is the first step in adjusting the must before making the wine.
Make sure the acidity is not higher as .6 and the alcohol around 11-12%. That way the wine will be balanced.
There are several ways to reduce acidity at preparing the must like:
- adding chalk
- diluting with water
- diluting with a low acid juice like banana juice
A finished wine can be blended with another low acid wine to reduce acidity.
You can even use chalk in a finished wine to lower acidity.
It is more difficult to adjust a wine when it is finished as when you are preparing the must in the beginning.
Tom, adding an F-pack to a finished wine adds sugar and flavor but will not lower the acidity. It will however lower the alcohol by volume as you are adding juice without alcohol to the wine.
In fact by boiling (simmering) juice you will concentrate juice. That means also concentrating flavor, sugar and acid. Therefore acidity will rise even more.
Again, in my opinion it is best to adjust the must before making the wine.
Blackberry wine is a good wine to do a malolactic fermentation on after yor wine has gone through normal fermentation. If yo are going to do this do not add any sulfites after fermentation is done and introdue the malolactic bactria to it. This will rid your wine of that harsf tart acid and turn it into a smooth lactic acid.