How does the specific gravity of wort change during fermentation, and what does this change indicate about the progress of the fermentation process?

During fermentation, the specific gravity of wort decreases as yeast consumes sugars and converts them into ethanol and carbon dioxide. Specific gravity is the ratio of the density of a liquid to the density of water. Wort, which is rich in sugars extracted from malt, has a higher specific gravity than water. The initial specific gravity of wort, known as the original gravity (OG), is a measure of the total amount of dissolved solids, primarily sugars, in the wort before fermentation begins. As fermentation progresses, yeast consumes these sugars (primarily glucose, fructose, and maltose) through glycolysis, breaking them down into ethanol and carbon dioxide. Ethanol is less dense than water, and carbon dioxide is released as a gas. As the sugars are converted into less dense substances, the overall density of the liquid decreases, resulting in a lower specific gravity. The specific gravity is typically measured using a hydrometer or a refractometer. By monitoring the specific gravity over time, brewers can track the progress of fermentation. A steady decrease in specific gravity indicates that the yeast is actively fermenting the sugars. The rate of decrease provides information about the fermentation rate and yeast activity. As the fermentation nears completion, the rate of decrease in specific gravity slows down, eventually reaching a stable value. The final specific gravity, known as the final gravity (FG), is a measure of the remaining dissolved solids after fermentation is complete. The difference between the OG and FG provides an indication of the amount of sugar that has been fermented and can be used to calculate the alcohol content of the beverage. A stuck fermentation, where the specific gravity stops decreasing prematurely, indicates that the fermentation has stalled due to factors such as insufficient yeast, nutrient deficiencies, or unfavorable fermentation conditions. Therefore, monitoring specific gravity is a crucial tool for brewers to track fermentation progress, assess yeast health, and ensure complete and consistent fermentation.