Detection of fermentable yeasts and bacteria using a pour plate after prior liquid enrichment.
All cloudy beer-based beverages and lemonades.
The sample, which has been pre-enriched in SSL broth, is suspended in culture medium (OFS agar), incubated and analysed.
Determination of glucose and fructose by enzymatic means.
Suitable for beers, mixed beer beverages, malt beverages, non-alcoholic soft drinks, NAB, juices and drinks.
Glucose is phosphorylated by the enzyme hexokinase (HK) and adenosine 5'-triphosphate (ATP) to glucose 6-phosphate (G-6-P).
\(\text{Glucose + ATP} \space ^{\underrightarrow{\text{HK}}} \space \text{G-6-P + ADP}\)
In the presence of the enzyme glucose-6-phosphate dehydrogenase (G6P-DH), G-6-P is oxidized by nicotinamide adenine dinucleotide phosphate (NADP+) to gluconate-6-phosphate. Reduced nicotinamide adenine dinucleotide phosphate (NADPH) is formed:
\(\text{G-6-P + NADP}^+ \space ^{\underrightarrow{\text{G6P-DH}}} \space \text{gluconate-6-phosphate + NADP + H}^+\)
The amount of NADPH formed during the reaction is equivalent to the amount of glucose. NADPH is determined based upon its absorbance at 340 nm.
Note:
Alternatively, NAD+/NAD + H+ can be used instead of NADP+/NADP + H+:
\(\text{G-6-P + NAD}^+ \space ^{\underrightarrow{\text{G6P-DH}}} \space \text{Gluconate-6-Phosphate + NAD + H}^+\)
The method describes how to determine acrylamide in drinking water using gas chromatography.
Water intended for use as an ingredient in the production of beer (brewing liquor) or other foods
The method facilitates the determination of trace amounts of acrylamide monomers in aqueous matrices and is based upon the bromination of the acrylamide double bond. The reaction product (2,3-dibromopropionamide) is extracted from the mixture with ethyl acetate after precipitation with sodium sulfate. The extract is purified in a Florisil column and analyzed using gas chromatography (GC/ECD). The detection limit in aqueous matrices is approx. 0.032 µg/l.
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.
Determination of the fermentation cellar yield in order to monitor brewhouse operations
Wort from the midpoint of chilling/pitching wort
The fermentation cellar yield is calculated using the value determined for the amount of extract contained in a batch of wort relative to the amount of extract present in the raw materials used to produce the wort.
The sample is extracted with petroleum ether in a Soxhlet apparatus equipped with a reflux condenser; the solvent is evaporated and the crude fat residue weighed.