/ WORT, BEER AND BEER-BASED BEVERAGES / Beverages in General / pH

B-590.00.040 [2020-10] pH Measurement

The value of pH is defined as the negative decadal logarithm of the concentration of hydrogen, or more precisely, hydronium ions:

pH = −log c (H₃O⁺)

The pH scale, ranging from 0–14, is based on the dissociation equilibrium.

The pH value of a liquid is commonly determined with a pH measuring device consisting of the measurement electrode (glass) and the reference electrode (calomel), combined into a single unit, which is connected to a signal amplifier and a display instrument. The device is calibrated using standard buffer solutions.

The pH is measured in the millivolt range. In order to eliminate changes in voltage between the glass and the reference electrodes, an electrolytically conductive connection is required. This bridge is created over the diaphragm in the electrode shaft. A potassium chloride solution normally serves as a reference electrolyte.

With “problem” solutions, for instance, fiber-rich mixtures with a low ion content, etc., ground-joint diaphragms offer a number of advantages over the more common ceramic diaphragms.

Generally, pH measurement devices are employed, in which the measurement and reference electrodes are combined to form a single unit. With modern pH measuring devices, testing a pH electrode consistent with objective criteria according to GLP/ISO 900X can be carried out automatically. In order to ensure that the measurement meets the specifications in the handbook of quality assurance according to ISO 900X, a code number is entered. The device then only measures and records data according to a preset configuration.

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Application/Purpose

Determination of acidity or H⁺ ion concentration of beverages

Scope of Application

Suitable for wort, beer, beer-based beverages, non-alcoholic beverages, juices, beverages

Principle

The pH value influences the enzymatic degradation processes during mashing and determines the solubility of the proteins, the hop bitters and the coloration during wort boiling. Furthermore, there is a dependence between the pH of the wort and that of the beer prepared from it. Beers with high pH values are more susceptible to chemical-physical turbidity due to inadequate protein coagulation in the brewhouse. Measuring the pH of wort and beer is therefore part of routine quality control.

The pH value is determined electrometrically [1-4].

Determination of pH is always done in the same way for wort, beer, beer-based beverages, NAB, juices and beverages.

Carbonated beverages must be decarbonated before measurement.