This method describes how to determine the capacity for water imbibition (moisture uptake) in barley.
Barley intended for the production of malt is evaluated on the basis of its capacity for water imbibition.
Barley is steeped according to a defined scheme, and the absorption of the steeping liquor by the kernels at defined times is determined by calculating the moisture content. The moisture content after 72 h steeping time is used to assess the absorption of steeping liquor or the capacity for water imbibition in barley.
Boiler water for use in the production of beer and other foods
Analogous to the p and m values obtained in the determination of acid capacity (pH 8.2 and 4.3), this analysis is performed according to W-000.13.031 Acid Consumption (Alkalinity, p-Value and m-Value)/Acid Capacity to pH of 8.2 and/or 4.3 for Water. The alkaline capacity of the boiler water is determined through titration of the sample with 0.1 N sodium hydroxide (instead of hydrochloric acid) to a pH of 4.3 and/or 8.2.
Hop extract intended for use in beer brewing or elsewhere in the food industry
SO2 in the Karl Fischer solution creates an ester with methanol, which is neutralized through a reaction with a base. The anions of methylated sulfuric acid are the reactive component in the chemical reaction. In the water titration, the methyl sulfite anions are oxidized by iodine to form methyl sulfate. The endpoint can be determined either by a color change (addition of a starch solution) or electrochemically.
Determination of dissolved oxygen concentration by electrochemical oxygen sensors with exposed electrodes
The measurement process using a Digox Analyzer works according to the principle of the potentiostatic three-electrode measurement system developed by TÖDT and TESKE and does not require a membrane.
The measuring electrode consists of solid silver, while the counter electrode is made of stainless steel. The reference electrode is composed of silver/silver chloride.
After generating a defined “polarization voltage”, an electrochemical reaction occurs at the measuring electrode, inducing a reduction of the oxygen molecules in the sample.
Measuring electrode (silver):
O2 + 2 H2O + 4 e− → 4 OH− (cathodic process)
Counter electrode (stainless steel):
4 OH− → O2 + 2 H2O + 4 e− (anodic process)
The flow of current as a result of this reaction is directly proportional to the amount of dissolved oxygen in the sample, if the polarization voltage is fixed as close to the level of the diffusion threshold current as possible.
In this case, the relationship can be represented as follows:
I = K × CO2, whereupon K = n × F × A × 1/d
I = sensor current
CO2 = oxygen concentration
F = Faraday constant
n = number of electrons per molecule
A = cathode surface
d = thickness of the “undisturbed layer” along the wall
The thickness of the undisturbed layer along the wall is determined by the hydrodynamic relationships at the measurement electrode and the transportation of oxygen molecules across the boundary layer brought about by temperature-dependent diffusion processes. Both of these clearly defined factors are precisely measured and compensated.
In order to adjust the polarization voltage between the two electrodes, a third electrode, the reference electrode, is employed in Digox measurement devices. This reference electrode remains in contact with the surface of the measuring electrode over a diaphragm in order to prevent mass transfer [1, 2, 3].
Active calibration:
In-line calibration is integrated into the device and is initiated by pressing a button. Taking advantage of Faraday’s Law, an exactly defined amount of oxygen is produced through the electrolysis of water.
I × t = m × F
I = current required for electrolysis
t = time
m = mass, g/mol
F = Faraday constant
The oxygen dissolves in the medium as it flows through and is detected at the measuring cell. The hydrogen liberated during the electrolysis reaction is not relevant for the measurement. The microprocessor monitors the calibration values and carries out any necessary corrective measures. The electrolysis enables the calibration of the device to be carried out under the same conditions and in the same medium as the analysis. Measurement operations are not disrupted during the calibration process [3].
The following applies to Digox 6.1 and all later models: In order to precisely determine the necessary potential for the measurement system, the Digox Analyzer possesses a scanner, which records the product-specific behavior of the medium subject to analysis. This can establish, whether the medium – due to the additives or supplements – must be measured at another potential. In this way, all types of beer-based beverages, non-alcoholic beverages and wine can be analyzed. Moreover, oxygen-reducing substances which can cause the calibration to be inaccurate may also be detected using the calibration scanning process. The device automatically implements the necessary compensative measures with the factors it has determined.
This method describes how to determine the true color of water by means of spectrophotometry.
Water intended for use as an ingredient in the production of beer (brewing liquor) or other foods
The color of water is determined by measuring the absorbance at a minimum of three wavelengths at various points across the visual spectrum:
λ1 = 436 nm (obligatory), λ2 = 525 nm, λ3 = 620 nm (for λ2, λ3 minor deviations are permitted). If necessary, measurements at additional wavelengths must be carried out.
This method describes how to determine the color of water by visual means.
Water intended for use as an ingredient in the production of beer (brewing liquor) or other foods