This method describes how to determine the capacity for water imbibition (moisture uptake) in barley.
Barley intended for the production of malt is evaluated on the basis of its capacity for water imbibition.
Barley is steeped according to a defined scheme, and the absorption of the steeping liquor by the kernels at defined times is determined by calculating the moisture content. The moisture content after 72 h steeping time is used to assess the absorption of steeping liquor or the capacity for water imbibition in barley.
Hops and hop products intended for use in beer brewing or elsewhere in the food industry
The polyphenols are extracted from the hops using hot water. In an alkaline environment, they form a red pigment with iron (III) ions, which is measured spectrophotometrically at 600 nm.
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
Using a buffer solution, malt extract is produced, and then under defined conditions the extract is incubated on an azo-barley glucan substrate. The substrate is coupled with an azo dye, which is degraded by the β-glucanase activity to form low-molecular weight fragments. After addition of the precipitating agent, these fragments stay in solution and can be spectrophotometrically determined in the supernatant after centrifugation. The absorbance in the supernatant depends directly upon the activity of the β-glucanase in the analyzed malt.
This method describes how to determine the true color of water by means of spectrophotometry.
Water intended for use as an ingredient in the production of beer (brewing liquor) or other foods
The color of water is determined by measuring the absorbance at a minimum of three wavelengths at various points across the visual spectrum:
λ1 = 436 nm (obligatory), λ2 = 525 nm, λ3 = 620 nm (for λ2, λ3 minor deviations are permitted). If necessary, measurements at additional wavelengths must be carried out.
Water intended for use as an ingredient in the production of beer (brewing liquor) or other foods
The nickel content is determined by employing a flameless method which utilizes graphite furnace atomic absorption spectrophotometry. This technique is suitable for determining the nickel content of water with very little nickel contamination. Any matrix effects can be eliminated by using the standard additions calibration technique.
An aliquot of the sample is dosed into a graphite tube and is subsequently subjected to a program comprising a three-step temperature regime through electrothermic resistance heating. As the temperature increases in each step, the consecutive steps include drying, matrix pyrolysis (incineration) and thermal dissociation into free atoms (atomization). These can be carried out separately. During the analysis, the graphite tube is under an inert gas atmosphere (argon).
Also important for graphite furnace AAS is background correction, which can be achieved using a continuum radiation source (deuterium) or through the Zeemann effect. Background correction with the Zeemann effect is used for particularly difficult sample matrices.
A hollow-cathode lamp usually serves as the light source.