If a water sample is run through a strongly acidic cation exchanger, all of the cations are replaced with hydrogen ions, thus producing the corresponding free acids in equivalent quantities (total mineral acid value). Since the carbonates and bicarbonates are transformed into carbon dioxide and therefore escape determination, their content must be determined through titration with acid to a pH of 4.3 (m value).
This method describes how to calculate the concentration of sodium and potassium ions in water.
Since analyses for determining the concentrations of sodium and potassium ions in water require considerable effort, and these ions are not very relevant for evaluating the suitability of water for the processes of brewing and malting, a simple calculation will suffice. The difference in the concentrations of anions and cations in the water is determined, allowing the calculation to be performed under the assumption that only sodium ions are present in the water.
Determination of hydrogen peroxide (H2O2) in disinfectants.
Suitable for all solutions that contain hydrogen peroxide (H2O2) but no other peroxides.
Hydrogen peroxide oxidizes iodide to iodine, which is reduced by sodium thiosulfate (Na2S2O3) and recalculated as hydrogen peroxide.
|
H2O2 + 2 NaI +H2SO4 |
→ |
I2 + Na2SO4 + 2 H2O |
|
I2 + Na2S2O3 |
→ |
2 NaI + Na2S2O3 |
If the sample contains other peroxide-containing disinfectants in addition to hydrogen peroxide (H2O2), the method T-757-01-032 Peracetic-acid-based-disinfectants must be used.
Determination of the amount of cold break material in the pitching wort
Cast-out wort, wort from the midpoint of chilling/pitching wort (without yeast)
The hot break material (trub) and any hop particles which may be present in the wort, must first be removed. After the wort has been cooled to 2 °C, it is filtered through a glass fiber filter. The residue remaining on the filter is dried and then weighed.
Cold break material or cold trub refers to all material that settles out in the process of chilling wort after separation of the hot trub or hot break material. Cold trub can be filtered out of the wort and primarily consists of proteins (48–57 %), tannins (11–26 %) and carbohydrates (20–36 %). The amount of cold break material in wort depends on the quality and composition of the raw materials, brewhouse equipment and wort handling. In academic and professional circles, opinions regarding the significance of cold break material for downstream processes and for the quality of the finished beer are strongly divided [1, 2, 5]. Under certain circumstances, the quantity of cold break material in wort may exceed 250 mg/l, especially where accelerated fermentation is practiced. Ultimately, this can detract from the flavor of the finished beer [3]. Breweries, where removal of the cold break material has been practiced successfully, determine the quantity of cold break in their pitching wort at regular intervals, in order to evaluate the efficacy of their separation equipment.
Suitable for analysis of all (laboratory) wort samples
Zinc in wort is measured using the AAS technique by directly aspirating the diluted sample into an acetylene oxygen flame or through electrothermal atomization; the measurement is made at 213.9 nm.
The cations in beer and wort are determined with this analysis.
This method is suitable for both wort and beer.
Inductively coupled plasma optical emission spectroscopy (ICP-OES) is a fast and reliable method for the laboratory analysis of metals. Inductively coupled plasma (ICP), a high frequency field of ionized gas, serves as a medium for atomizing and exciting the substances found in samples. Liquid, dissolved or aerosol samples are injected into the ionized gas stream. In emission spectroscopy, ICP can be used in conjunction with a number of optical and electronic systems either simultaneously or sequentially in multi-element spectrometers. In the plasma, the atoms and ions are excited to a higher energy state bringing about the emission of electromagnetic radiation (light), primarily in the ultraviolet and visible region of the spectrum. Metals ordinarily occur as ions in the temperature range typical for ICP of 6000 to 10000 K; however, non-metals and metalloids are only partially ionized.
ICP-OES operates within a very wide range. This usually encompasses six orders of magnitude in concentrations smaller than μg/l up to g/l, depending upon the element and the concentrations used for the set of analysis data. With ICP-OES, beer and wort can also be analyzed without prior processing of the samples, in contrast to AAS. Methods for determining the following in beer and wort will be described below: Al, B, Ba, Ca, Co, Cu, Fe, K, Mg, Mn, Mo, Na, P, Si, Sr, Sn and Zn.