Suitable for analysis of all (laboratory) wort samples.
Calcium in wort is measured using AAS by directly aspirating the diluted sample into a nitrous oxide-acetylene flame; the measurement is made at 423 nm.
Lanthanum chloride reduces interference.
This method describes how to calculate the magnesium ion content of water.
Magnesium ions are calculated by subtracting concentration of calcium ions (W-000.17.031 - Calcium in Wasser, Komplexometrische Bestimmung mit EDTA) from the total hardness (W-000.11.031 - Gesamthärte in Wasser).
Determination of organic acids using ion chromatography
This method is suitable for beer, wort, green beer, NAB, water and wastewater
Separation by ion chromatography followed by conductivity detection.
Determination of acetic acid by enzymatic means
This analysis is suitable for malt, wort, beer, beer-based beverages and soft drinks
Acetic acid (acetate) is converted to acetyl-CoA in the presence of the enzyme acetyl-CoA synthetase (ACS) by adenosine-5'-triphosphate (ATP) and coenzyme A (CoA).
Acetate + ATP + CoA \(^{\underrightarrow{ACS}}\) Acetyl-CoA + AMP + pyrophosphate
Acetyl-CoA reacts with oxaloacetate in the presence of citrate synthase (CS) to form citrate.
Acetyl-CoA + oxaloacetate + H2O \(^{\underrightarrow{CS}}\) citrate + CoA
The oxaloacetic acid required for reaction (2) is produced from malic acid and nicotinamide adenine dinucleotide (NAD) in the presence of malate dehydrogenase (MDH). In doing so, NAD is reduced to NADH:
Malate + NAD+ \(^{\underleftrightarrow{L-MDH}}\) oxaloacetate + NADH + H+
The formation of NADH forms the basis of this analysis, which is measured as an increase in the absorbance at 340, 334 or 365 nm. Since this concerns a previous indicator reaction, the quantity of NADH is not linearly proportional to the acetic acid concentration.
Determination of citric acid by enzymatic means
This analysis is suitable for malt, wort, beer, beer-based beverages and soft drinks
Fruit juices:
The acid spectrum typical of certain types of fruit are used, along with other criteria, as a basis for recognizing unadulterated fruit juices. Tartaric acid, citric acid and L-malic acid are recorded here, which, with a few exceptions, determine the total acidity of the fruit.
Citric acid occurs as the primary acid in citrus juices and other juices. Orange juice usually contains 3–17 g/l citric acid (AIJN).
In citrus juices, an addition of citric acid can be detected via the citric acid/D-isocitric acid ratio, as this lies within relatively narrow limits. In orange juice, values below 130 are found.
D-isocitric acid is partly present in fruit products as a lactone. The lactone must first be saponified prior to enzymatic determination in order to detect the total D-isocitric acid content.
Malt, wort and beer:
Citric acid is an organic acid and is present in malt and wort and is also produced during fermentation.
Citric acid (citrate) is converted to oxaloacetic acid and acetic acid catalyzed by the enzyme citrate lyase (CL):
Citrate oxaloacetic \(^{\underrightarrow{CL}}\) acid + acetate
In the presence of the enzymes malate dehydrogenase (MDH) and lactate dehydrogenase (LDH), oxaloacetic acid and its decarboxylation product pyruvic acid are reduced to L-malic acid and L-lactic acid, respectively, by reduced nicotinamide adenine dinucleotide (NADH):
Oxaloacetate + NADH + H+ \(^{\underrightarrow{L-MDH}}\) L-malate + NAD+
Pyruvate + NADH + H+ \(^{\underrightarrow{L-LDH}}\)L-lactate + NAD+
The sum of the quantity of NADH consumed during the reaction is equivalent to the quantity of citric acid. The absorbance is determined photometrically at 334, 340 or 365 nm.
The method describes how to determine the residual alkalinity in the water used as an ingredient in beer production (brewing liquor).
The residual alkalinity is calculated using the following parameters: total hardness, calcium hardness and magnesium hardness.