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).
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.
This method describes how to determine the α-acids and β-acids in hop extract using high-pressure liquid chromatography.
Hop extract intended for use in beer brewing or elsewhere in the food industry
Applicable for all (laboratory) worts
The quantitative determination described here is based upon a separation of analytes using reverse phase chromatography after pre-column derivatization and detection with fluorescence detection.
Aside from the quantitative determination of the individual amino acids (methods using an ion exchanger, HPLC, GC), cumulative methods of determination are customary. However, these methods also measure NH4+ ions and amines to some degree.
With methods involving color reactions, the amino acids display color at different levels of intensity. Therefore, the reaction is based upon a “standard amino acid”; glycine usually serves as the standard amino acid for comparison.
With the ninhydrin method, the color yield varies with the individual amino acids between 70 and 105 %, based on glycine. Up to approx. 30 % of ammonium salts are quantified using this method and up to approx. 7 % of proline.
This method describes how to determine the epichlorohydrin content of drinking water using solid-phase extraction.
Drinking water intended for use as an ingredient in the production of beer (brewing liquor) or other foods
Epichlorohydrin is separated from a water sample by means of solid-phase extraction and is determined using gas chromatography with mass spectrometric detection (MS). Alternatively, an electron capture detector (ECD) can be employed.
Hops and hop products intended for use in beer brewing or elsewhere in the food industry
After milling, hops and hop powder products are extracted using a diethyl ether/methanol mixture and a hydrochloric acid solution. The α-acids and β-acids dissolved in the ether phase are separated using reversed phase high-pressure liquid chromatography (RP-HPLC) and measured spectrophotometrically at a wavelength of 314 nm.
Hop extracts are dissolved in methanol. The α-acids and β-acids dissolved in the methanol are separated using reversed phase high pressure liquid chromatography (RP-HPLC) and measured spectrophotometrically at a wavelength of 314 nm.