Why does spiced blackberry liqueur taste too medicinal or bitter?

Expanded Explanation

A medicinal or bitter taste usually comes from over-extracting strong spices rather than from the blackberries themselves. Clove, star anise, cinnamon and black pepper can become aggressive when left too long, particularly in high-proof alcohol. Too much crushed spice also speeds extraction and can produce a harsh, woody or mouth-drying character.

If the liqueur is still infusing, remove the dominant spices immediately and allow the blackberries and vanilla to continue on their own. After straining, a small increase in honey or sugar can soften bitterness, while a little lemon can brighten a flat, heavy profile. Avoid adding more spice to correct imbalance.

Time can also help. A harsh young infusion often becomes smoother after several weeks in the bottle as alcohol heat and spice edges integrate. If the bitterness remains strong after resting, blending the batch with a small amount of unsweetened blackberry-vodka infusion is often safer than trying to hide the problem with excessive sugar.