Determination of the soluble dry matter by means of a refractometer
non-alcoholic beverages, juices
The quantity of soluble dry matter is determined refractometrically. This is related to the percent by weight of sucrose in an aqueous sucrose solution, which under defined conditions possesses the same refraction index as that of the product being analyzed. The amount of soluble dry matter is expressed in g per 100 g of solution. The refraction index is not determined directly for non-alcoholic soft drinks, but rather by means of a scale based on the percentage of sucrose by weight (°Brix). Since the °Brix scale uses sucrose, correction factors for other sugars must be taken from tables for each individual type of sugar. The presence of other substances, such as organic acids, minerals and amino acids, has an effect on the refraction index of a product. Due to the high acidity of citrus juices and citrus juice concentrates, correction factors are also necessary for measuring their °Brix values.
beer, beer-based beverages, beverages
The refraction of a light beam as it passes from an optically less dense (sample liquid) to an optically denser medium (prism) is a function of concentration (alcohol/extract), temperature and wavelength. The density of the test liquid is a function of the concentrations of alcohol and extract content. Therefore, from the refractive index (or alternatively the refractive index nD20 and the density or the SGA20/20, the real extract), the alcohol and original gravity can be determined from nomograms or using regression equations.