The method describes the photometric determination of the ß-amylase content in malt. In addition to α-amylase, β-amylase is also responsible for the enzymatic degradation of the starch in malt. The activity of these enzymes is therefore important for assessing malt quality. This analysis quantifies the diastatic power, in which, above all, the β-amylase activity is measured.
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 PNPβ-G3 (p-nitrophenyl-β-D-maltotrioside) in the presence of highly pure β-glucosidase. The PNPβ-G3 molecule is hydrolyzed through the activity of the β-amylase in the malt to maltose and p-nitrophenyl-β-D-glucose. This is cleaved directly to form D-glucose and p-nitrophenol by the β-glucosidase in the substrate mixture. The formation of p-nitrophenol is proportional to the release of maltose by the activity of β-amylase.
Adding an alkaline solution halts the enzymatic activity and simultaneously induces a color reaction. The absorbance measured at 400 nm is directly dependent upon the activity of β-amylase in the sample.