Malt intended for use in beer brewing or elsewhere in the food industry
Using a buffer solution, malt extract is produced, and then under defined conditions the extract is incubated on a specific substrate of BPNPG7 oligosaccharide (a p-nitropheny-maltoheptaoside blocked at the non-reducing end) in the presence of thermostable α-glucosidase. The α-glucosidase is initially unable to degrade the "blocked" oligosaccharide. Only when the oligosaccharide is hydrolyzed by the activity of the α-amylase (an endoenzyme) from the malt are the resulting fragments vulnerable to the enzyme. Then, they are quantitatively degraded to glucose and free p-nitrophenol by the α-glucosidase, which is present in excess.
Adding a weakly alkaline solution halts the enzymatic activity and simultaneously induces a color reaction. The absorbance measured at 400 nm is proportional to the activity of α-amylase in the sample.
Malt intended for use in beer brewing or elsewhere in the food industry
While α-amylase is active in a gelatinized solution of amylopectin, the viscosity of the solution is constantly dropping due to the degradation of the starch molecules, which can be tracked using a rotational viscometer. The change in the reciprocal of the specific viscosity serves as a measure for the activity of α-amylase.
This method describes the fluorimetric determination of high-molecular weight β-glucans in malt.
Malt intended for use in beer brewing or elsewhere in the food industry
Barley malt (pilsner malt) and smoked malt intended for use in beer brewing or elsewhere in the food industry
The phenol fraction collected through steam distillation is mixed with 4-amino- 2,3-dimethyl-1-phenyl-3-pyrazolin-5-one (4-aminophenazone) under alkaline conditions and oxidized by potassium hexacyanoferrate(III) to form a pigment (fig. 1), which after extraction with chloroform, can be measured spectrophotometrically.
This method describes how to determine malted barley varieties and how to detect mixtures of different barley varieties in one lot of malt.
Malt intended for use in beer brewing or elsewhere in the food industry
The method is suitable for the determination of water vapor volatile aroma compounds in beer.
Volatile aroma compounds are driven out of the sample through steam distillation. The ethanolic distillate is saturated with NaCl. Potassium hydrogen sulfite is added to separate carbonyl groups that might interfere with the analysis. The extraction of the aroma compounds is performed by shaking out with dichloromethane and the phases separated by centrifuging.