Extract content measurement
The extract content measurement is an industrial method for determining the original wort in beer production.
Information about the sugar content is important to ensure consistent product quality. About the measured value of the original wort, u. a. the beer type is defined. The simplest measuring methods for determining the extract content are based on measuring the density , compensated by a factor that is determined by the temperature. The density changes depending on the temperature, the extract measurement is therefore always compensated to 20 ° C and is indicated accordingly. The actual extract can be determined from the density of a wort and the apparent extract from the density value of a fermented beer, which still has to be compensated for by the content of fermentation products, mainly alcohol.
Density is measured in several ways. Traditionally, a glass spindle is used, which develops a certain buoyancy depending on the density and temperature of the sample. There is a scale on the neck of the spindle that can be read off, and a thermometer is located in the spindle that records the sample temperature. The value can be read off directly.
A very precise measurement is possible with a pycnometer , a glass container whose weight is known, which is exactly filled with a defined volume, then tempered and weighed. The extract value can be taken from a table.
In the process, the density can be measured with the Coriolis effect. The mass flow meters used for this purpose can record the density of the medium flowing through them with good accuracy by changing the resonance frequency of the oscillating system (= measuring tube (s)). The calculation is then carried out in the transmitter; a sensor for temperature compensation is generally integrated in the device. The calculated density can also be converted to reference conditions using appropriate algorithms.
Vibrating fork systems also record the damping caused by the different densities. The evaluation and compensation with an external temperature signal takes place in a computer.
Another possibility to measure the extract in tanks or containers is the hydrostatic method. The load on the lower one, which is higher than that of water, is measured by two pressure sensors and compensated for with a temperature signal in an evaluation unit. The measurement is sensitive and requires that the basic technical requirements be met exactly. The hydrostatic pressure sensors used have been specially developed for this task.
In addition to the mechanical methods, it is also possible to use ultrasonic sensors for density measurement. The changing sound propagation time in the measuring medium is evaluated here. Since the speed of sound is also temperature-dependent, it is also measured and taken into account when calculating the derived density.