What are the four methods to produce sweet wines?

The production of sweet wines can be achieved through several distinct methods that focus on manipulating the fermentation process and sugar levels. Using concentrated sugars, removing yeast, killing yeast, and adding sweetness encompasses the essential approaches to create sweetness in wine.

Concentrated sugars can be derived from various methods, including drying grapes to concentrate the sugars or using methods like cryo-extraction. Removing yeast or killing yeast interrupts the fermentation process at an appropriate time, allowing some of the natural sugars in the grape juice to remain unfermented, which leads to a sweeter final product. Additionally, adding sweetness generally involves either adding grape juice or other sweetened components to adjust the final sugar levels after fermentation has taken place.

This approach directly addresses the core techniques utilized in sweet wine production, providing winemakers with the flexibility to achieve desired sweetness levels in their wines. The other options each present combinations of practices that do not align as closely with the established methods used in sweet wine production. For example, fermentation alone does not lead to sweetness unless other factors are controlled, and practices like boiling and clarifying do not directly influence the sweetness level in the same way as the methods outlined in the correct answer.