Determination of the total acidity through titration
This method is used to determine the total titratable acids in beverages and concentrates.
Titratable acidity represents the sum of the free acids present in a beverage, with the exception of the dissolved carbon dioxide (carbonic acid). In fruit juices and the beverages prepared from them, they usually consist of malic acid, citric acid and tartaric acid.
The titration of the degassed beverage sample (freed from carbonic acid) is carried out potentiometrically using 0.25 mol/l sodium hydroxide solution either to a pH of 7.0 calculated as tartaric acid or to a pH of 8.1 calculated as citric acid.
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.
The method describes how to determine the iso-α-acids, α-acids and β-acids in hop extracts and isomerized extracts by means of high-pressure liquid chromatography.
Hop extract and isomerized hop extract intended for use in beer brewing or elsewhere in the food industry
Hop extracts and isomerized hop extracts are dissolved in methanol. The iso-α-acids, α-acids and β-acids are separated using hig-pressure liquid chromatography (HPLC) with gradient elution and measured spectrophotometrically at a wavelength of 270 nm (iso-α-acids) and 314 nm (α-acids and β-acids).
This method describes how to determine iso-α-acids, α-acids and β-acids in isomerized pellets by means of reverse phase high pressure liquid chromatography (RP-HPLC).
Isomerized pellets intended for use in beer brewing or elsewhere in the food industry
The bitter substances in isomerized hop pellets contain a substantial amount of iso-α-acids; however, in addition to these, non-isomerized α-acids and β-acids are also present. In order to determine their content, a specific method is required.
After milling, the substances in question are extracted from the isomerized pellets using a diethyl ether/methanol mixture and a hydrochloric acid solution. The iso-α-acids, α-acids and β-acids dissolved in the ether phase are separated using reversed-phase high-performance liquid chromatography (RP-HPLC) and an elution gradient. They are then measured spectrophotometrically at wavelengths of 270 nm (iso-α-acids) and 314 nm (α-acids and β-acids).
Determination of iso α-acids and α-acids in beer, beer-based beverages and wort
This method is not suitable for beer, beer-based beverages or wort, which contain saccharin, p-hydroxybenzoic acid ester, salicylic acid or sorbic acid.
These bitter substances are extracted from the acidified sample using iso-octane. Certain disruptive substances are eliminated through washing the extract with acidified methanol. The concentration iso-α-acids as well as α-acids is determined by measuring the absorbance in alkaline methanol at 255 nm and 360 nm.
Determination of iso-α-acids, α-acids and β-acids in beer, beer-based beverages and wort
Suitable for all beer, beer-based beverages and wort
iso-α-Acids (isohumulones), α-acids (humulones) and β-acids (lupulones) are chromatographically separated using this method.
The bitter substances are chromatographically separated by means of RHPLC. The humulones and lupulones are detected at 314 nm, whereas the iso-α-acids are detected at 270 nm.
Equipment
Analytical balance, ± 0.0001 g
Water bath, 20 °C
Ultrasound bath
Centrifuge, 750 g
Vials, crimp caps, crimping tool
Disposable syringes, 20 ml
Syringe filter, 0.45 µm, PTFE
High performance liquid chromatography set up for gradient operations, column oven 35 °C, UV-VIS detector (270 nm and 314 nm)
High pressure liquid chromatograph and UV-VIS detector, equipped for gradient operation
HPLC column, Machery & Nagel CC 125 / 4 Nucleodur 100 5 C18 EC or a comparable column
Graduated cylinder, 1000 ml, 50 ml
Beaker, 50 ml
Volumetric flasks, 100 ml, 50 ml
Volumetric pipettes, 30 ml, 10 ml
Erlenmeyer flask, 100 ml