Spectrophotometric determination of the iodine value of brewery spent grain
Brewery spent grain, wet spent grain, dry spent grain
High molecular weight dextrins and starch present in the wort extracted from brewery spent grain are precipitated through the addition of ethanol, centrifuged and dissolved in phosphate buffer, followed by the addition of an iodine solution. Depending on the molecular weight and degree of branching, a red to blue color forms, the intensity of which is measured spectrophotometrically at 578 nm.
Applicable for all (laboratory) worts
Medium and high molecular weight proteins are precipitated by phosphomolybdic acid. The nitrogen is determined in the filtrate. Therefore, the results express the amount of low molecular weight proteins.
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
Determination of the high-molecular weight proteins in wort and beer by precipitating them with magnesium sulfate
This method is suitable for wort and beer.
The high molecular weight proteins are precipitated by magnesium sulfate, and the nitrogen content in the sediment is determined, e.g., according to Kjeldahl.
In order to measure the portion of the high molecular weight protein fractions in wort and beer, precipitation with magnesium sulfate is recommended. Through gel chromatography it has been established that magnesium sulfate precipitates nitrogenous compounds possessing molecular weights of approximately 2600 Da and higher [2]. A strong correlation between the nitrogenous substances precipitated by magnesium sulfate and beer foam has also been observed [3, 4].
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.
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).