What is the primary use of a refractometer in brewing?

The refractometer is primarily used in brewing to determine the sugar concentration before fermentation. This instrument measures the degree to which light is bent, or refracted, when it passes through a liquid. In brewing, this property allows brewers to assess the concentration of sugars in the wort, which is crucial for predicting the potential alcohol content of the finished beer.

By measuring the specific gravity of the wort prior to fermentation, brewers can make informed decisions about how much additional sugar or adjuncts to add, as well as monitor fermentation progress. Since yeast consumes sugars during fermentation, initial sugar concentration plays a critical role in the overall brewing process and influences the final flavor, body, and alcohol content of the beer.

Other options, while relevant to the brewing process, do not represent the primary use of a refractometer. For example, fermentation temperature is typically monitored with a thermometer rather than a refractometer, hop bitterness is usually quantified using different methods like the International Bitterness Units (IBU) scale, and carbonation levels are assessed through pressure gauges or carbonation tests, not a refractometer. Thus, the most accurate answer regarding the refraction's primary role in brewing is determining sugar concentration before fermentation.