What is the role of specific gravity in determining the alcohol content of a fermented beverage?

Specific gravity plays a crucial role in determining the alcohol content of a fermented beverage by indicating the amount of sugar present before and after fermentation. Specific gravity is the ratio of the density of a solution (like wort or must) to the density of pure water at a specific temperature. Before fermentation, the specific gravity, known as the Original Gravity (OG), reflects the concentration of sugars in the solution. These sugars are the raw material that yeast will convert into alcohol. As fermentation progresses, yeast consumes the sugars and produces alcohol (ethanol) and carbon dioxide. Ethanol is less dense than sugar, so the density of the solution decreases as fermentation proceeds. After fermentation is complete, the specific gravity is measured again, resulting in the Final Gravity (FG). The difference between the Original Gravity and the Final Gravity provides an indication of how much sugar was converted into alcohol. By using a specific formula, one can estimate the alcohol by volume (ABV) of the fermented beverage based on the OG and FG readings. A higher difference between the OG and FG indicates a greater amount of sugar was fermented, resulting in a higher alcohol content. While more precise methods exist, such as distillation and hydrometry, specific gravity measurements provide a relatively simple and accurate way to estimate the alcohol content of beer, wine, and other fermented beverages. The formulas used to calculate ABV from OG and FG may vary slightly, but all rely on the fundamental principle that the change in specific gravity reflects the conversion of sugars into alcohol.