In winemaking, what is associated with the term 'residual sugar'?

Residual sugar refers to the sugar that remains in the wine after the fermentation process has been completed. During fermentation, yeast converts grape sugars into alcohol, and if fermentation stops before all sugars are converted, the unfermented sugar is left in the final product. This contributes to the wine's sweetness and can significantly affect its flavor profile and mouthfeel.

The other options relate to different contexts within winemaking. Added sugar for sweetening is typically referred to as chaptalization, used primarily in regions where grapes may not achieve sufficient ripeness. The sugar used during malolactic fermentation typically refers to the conversion of malic acid to lactic acid, which alters the wine's acidity but does not directly implicate sugar levels. Lastly, the natural sugar in grape skins concerns the inherent sugars found in the grapes themselves prior to fermentation but does not pertain to what remains post-fermentation. Therefore, the definition of residual sugar specifically highlights the amount left after the fermentation process concludes, making it the correct association.