Search: Dimethylphenol

The NDMA is extracted from the wort (plant wort) and beer on Extrelut®, Tox Elut® or comparable material using dichloromethane and the eluate is then concentrated. The determination is carried out by gas chromatography with the specific TEA detector ("Thermal Energy Analyzer"). Nitrosodipropylamine (NDPA) or nitrosodiisopropylamine (NDiPA) is used as the internal standard (ISTD). This detector detects nitrosamines according to the following scheme: After exiting the GC column, the separated substances first enter a pyrolysis oven, where they are heated to around 500 °C. The detector is used as an internal standard (ISTD). At this temperature, the (N-NO) bond of the nitrosamines breaks down, forming an NO radical (NO^-):
 

The gas mixture then passes through a special filter (CTR Gas Stream Filter), which only allows the carrier gas and NO radicals to pass through. The NO radicals and ozone produced by a special generator then flow into a reaction chamber, where the following reaction takes place:

These NO radicals react with ozone to form nitrogen dioxide in an excited state (NO₂^-) and oxygen. The NO2- decomposes spontaneously into ordinary nitrogen dioxide (NO₂) by emitting radiant energy (h-ν) at a wavelength of around 600 nm.

The compound 3-hydroxy-2-butanone (acetoin) is derived from diacetyl and is created through the reductive activity of yeast. One further reaction mechanism for the formation of 3-hydroxy-2-butanone is condensation of both free and activated (bound to thiamine pyrophosphate [TPP]) acetaldehyde.

3-Hydroxybutanone is oxidized to 2,3-butanedione (diacetyl) by iron chloride in the presence of iron sulfate and determined using gas chromatography and the headspace analysis method.

Caffeine and theobromine are separated using HPLC and reversed phases and determined by means of UV detection.

One of the basic prerequisites for properly conducting sensory analysis is selecting suitable candidates as members of the tasting panel.

In an acidic sulfurous solution containing phosphorus, nitrate ions react with 2,6-dimethylphenol to produce 4-nitro-2,6-dimethylphenol.

The method is suitable for determining approx. 0.5–25 mg/l NO₃^-. If the ratio of chloride to nitrate ions is larger than 10, this may interfere with the reaction (if this is the case, according to DEV D 9-3, follow DIN 38405); likewise, nitrite ions exceeding approx. 0.2 mg/l may also interfere with the reaction. For their removal, refer to Remarks below.

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.