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Capillary viscometers measure the kinematic viscosity of Newtonian fluids, unlike falling ball and the rotational viscometers, which directly measure the dynamic viscosity. However, with values for the kinematic viscosity and the density of the test liquid, the dynamic viscosity can be calculated.

The time required for a volumetrically defined amount of fluid (the volume between two marks on the tube of the viscometer) to flow through a capillary of a defined length is measured.

1 square meter per second of a homogenous fluid with a dynamic viscosity of 1 Pa × s and a density 1 kg/m³

The unit for expressing kinematic viscosity (the relationship of viscosity to density = viscoplasticity) is 1 m²/s = 10⁶ mm²/s

The kinematic viscosity is expressed as 1 square meter per second of a homogenous fluid with a dynamic viscosity of 1 Pa × s and a density 1 kg/m³.

5-Hydroxymethylfurfural (HMF) is separated using HPLC and reversed phases. This substance is measured with a UV detector.
HPLC analysis specifically detects 5-hydroxymethylfurfural.

A photometric method, B-590.59.111 Hydroxymethylfurfural - photometrisch, using barbituric acid and o-toluidine detects all aldehydes present in the sample. This method serves as an alternative for laboratories without HPLC.

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.

Titratable acidity represents the sum of the free acids present in a beverage, with the exception of the dissolved carbon dioxide (carbonic acid). In fruit juices and the beverages prepared from them, they usually consist of malic acid, citric acid and tartaric acid.

The titration of the degassed beverage sample (freed from carbonic acid) is carried out potentiometrically using 0.25 mol/l sodium hydroxide solution either to a pH of 7.0 calculated as tartaric acid or to a pH of 8.1 calculated as citric acid.

Volatile acids are distilled using steam, and the distillate is analyzed through titration. Sulfurous acid present in the distillate is determined iodometrically and subtracted from the total.

The fruit juice content of beverages and soft drinks is a very important quality characteristic. In Germany, there are guidelines that define the amount of juice contained in fruit-based beverages and soft drinks.

The guidelines specify that beverages made with fruit juice from seeded fruits or grapes must contain a minimum of 30 % juice, while those made from citrus fruits must contain at least 6 %, and beverages made from all other fruits or fruit combinations must contain at least 10 % juice. At least half of the juice content specified for fruit-based beverages must be present in fruit-flavored soft drinks. 

Under special conditions, a high fruit juice content can also be determined. In order to evaluate these conditions, equations for calculating the juice content have been developed by the working group for fruit juices and fruit-flavored beverages within the Society of German Chemists.

The RSK values serve as the basis for the calculation and are used to aid in the evaluation for evaluating the authenticity of fruit juices and products made from them (the values are not legal standards).

The different levels of importance attributed to individual analytes and, in part, the large range of fluctuation typical of certain values, were taken into account by assigning a weight to the value for each analyte in the equation.