Here’s the plot twist: all wine grapes start with sugar. That sweetness turns into alcohol during fermentation, so the final taste is about residual sugar (RS)—the sugar left behind. White wines often have a higher RS because winemakers stop fermentation early to keep it sweet.
Red wines, on the other hand, are usually fermented bone-dry. Why? Because red grape skins have tannins and bitter compounds that need to be balanced with less sugar. If a red is too sweet, it tastes like syrupy cough medicine—nasty.
