Determination of the steam-volatile acids by means of titration
This method serves as a means for determining the titratable steam-volatile acids in beverages and concentrates
Volatile acids are distilled using steam, and the distillate is analyzed through titration. Sulfurous acid present in the distillate is determined iodometrically and subtracted from the total.
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).
Hops and hop products intended for use in beer brewing or elsewhere in the food industry
After extraction with toluene, the α-acids and β-acids in the hops and hop pellets are determined using spectrophotometry.
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 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.
Hop products with isomerized or reduced iso α-acids intended for use in beer brewing or elsewhere in the food industry
Hop products with isomerized or reduced iso α-acids are dissolved with methanol. The bitter acids are separated through reverse phase high-pressure liquid chromatography (RP-HPLC) and isocratic elution. They are then measured at a wavelength of 270 nm.