Hi AllyMelmac, Coincidentally, I am making a gallon of strawberry wine (picked the fruit in the summer , froze it and thawed it just last week to produce the juice. Going to be racking this tonight into a secondary)
When you ferment the yeast converts all the sugar to CO2 and alcohol so all the sweetness is removed. What you are left with is the tartness of the acidity of the fruit unbalanced by any sweetness. If it is very tart I would measure the pH and see where it falls. You want it to be around 3.4. Much below that and the acidity is too strong to enjoy. You can neutralize some of the acidity by adding K-carbonate but .. I would allow the wine to age as aging often mellows out sharp acids, so in a few months the sharpness may give way to softer edges.
Before you get ready to bottle you might consider stabilizing the wine (adding K-meta AND K-sorbate) and then adding sugar to sweeten the wine. You might find the wine will taste sweet enough at a gravity of 1.000 or 1.005 or 1.010 so it is good to bench test to see how much sugar you want to add.
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