Determination of copper content in beer
This method is also suitable for dark and turbid beers. The turbidity particles must be evenly distributed before sampling.
This method is based on the formation of a yellowish-brown, (insoluble in aqueous medium) copper (II) chelate with zinc benzyl dithiocarbamate (ZDBT), a compound that may be extracted with trichloroethane.
Determination of copper content in beer
This method is suitable for beer
Copper in beer is measured using the AAS technique by directly aspirating the diluted sample into an acetylene oxygen flame; the measurement is carried out at 324.7 nm.
Barley intended for the production of malt is evaluated with regard to pre-germination.
Visible pre-germination is evident at the rootlet and is therefore grounds for rejecting a barley lot. However, after the barley is cleaned and the rootlets are removed, the so-called “hidden pre-germination” can be made visible using the staining methods described below.
Kernels suspected of having pre-germinated are boiled for ½−1 min in a 20 % solution of copper sulfate, allowed to remain for 30 min in the hot solution and are subsequently rinsed with water. The acrospire is stained green, making it clearly visible.
The method describes how to determine the copper content of water using atomic emission spectrometry.
Water intended for use as an ingredient in the production of beer (brewing liquor) or other foods
Determination of the original gravity, alcohol and extract content in beer or beer-based beverages using a thermoanalytical method
wort, beer, beer-based beverages
Rather than utilizing the classic method for analyzing beer by means of density measurement and/or alcohol determination, this device employs thermoanalytical analysis techniques. With two thermoanalytical measuring cells, the beer sample is heated to 40 °C and 65 °C, and the specific heat capacity is determined. Algorithms are used to assign the results to the concentration of the various ingredients. In this way, alcohol content, apparent and real extract, and original gravity are calculated.
Determination of glucose and fructose by enzymatic means.
Suitable for beer, malt drinks, low-alcohol beer, beer-based mixed drinks, non-alcoholic soft drinks, NAB, fruit juices, soft drinks and other beverages.
Glucose and fructose are phosphorylated by the enzyme hexokinase (HK) and adenosine 5'-triphosphate (ATP) to glucose 6-phosphate (G-6-P) and fructose 6-phosphate (F-6-P):
\(\text{Glucose + ATP} \space ^{\underrightarrow{\text{HK}}} \space \text{G-6-P + ADP}\)
\(\text{Fructose + ATP} \space ^{\underrightarrow{\text{HK}}} \space \text{F-6-P + ADP}\)
In the presence of the enzyme glucose-6-phosphate dehydrogenase (G6P-DH), G-6-P is oxidized from nicotinamide adenine dinucleotide phosphate (NADP+) to gluconate-6-phosphate. Reduced nicotinamide adenine dinucleotide phosphate (NADP + H+) is formed:
\(\text{G-6-P + NADP}^+ \space ^{\underrightarrow{\text{G6P-DH}}} \space \text{Gluconate-6-phosphate + NADPH + H}^+\)
The amount of NADP + H+ formed during the reaction is equivalent to the amount of glucose. NADPH + H+ is a measurand and is determined based on its absorbance at 340 nm.
After the reaction is complete, F-6-P is converted to G-6-P by phosphoglucose isomerase (PGI):
\(\text{F-6-P} \space ^{\underrightarrow{\text{PGI}}} \space \text{G-6-P}\)
The amount of NADPH + H+ formed during the reaction is equivalent to the amount of fructose. NADPH + H+ is the parameter being measured and is determined on the basis of its absorption at 340 nm.
G-6-P reacts in turn with NADP+ to form gluconate-6-phosphate and NADP + H+. The additional amount of NADP + H+ formed is equivalent to the amount of fructose and is determined photometrically based on its absorption at 340 nm.
Note:
Alternatively, NAD+/NAD + H+ can be used instead of NADP+/NADPH + H+:
\(\text{G-6-P + NAD}^+ \space ^{\underrightarrow{\text{G6P-DH}}} \space \text{Gluconate-6-Phosphate + NAD + H}^+\)