This method describes how to determine the moisture content of specialty malt.
Specialty 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 the extract content of roasted and caramel (crystal) malt by means of a modified Congress mash method.
Roasted and caramel (crystal) malts intended for use in beer brewing or elsewhere in the food industry
Pilsner malt, of which the moisture content, extract and color are known, is mashed together with roasted or caramel (crystal) malt according to the Congress mash method. The extract content of the roasted or caramel (crystal) malt is determined by taking the analysis values for the pilsner malt into account.
Malt intended for use in beer brewing or elsewhere in the food industry
A (modified) Congress wort is produced from malt samples prior to analysis. NDMA present in the Congress wort is extracted using dichloromethane followed by concentration of the eluate. The determination is performed with a gas chromatograph using a packed Carbowax 20M column with a specific TEA detector (thermal energy analyzer); nitrosodipropylamine (NDPA) serves as an internal standard.
This detector analyzes nitrosamine according to the following procedure:
After exiting the GC column, the separated substances are heated to 500 °C in a pyrolyzer. At this temperature, the N-NO bond of the nitrosamine is broken, thus forming an NO radical (NO۰):
The gas mixture then flows through a special filter (CTRTM gas stream filter), which only allows the carrier gas and the NO radicals to pass. After exiting the filter, the NO radicals flow into a reaction chamber along with ozone, which is created by a special generator. The following chemical reactions take place in the chamber:
|
NO• + O3 |
→ |
NO2• |
|
NO2• |
→ |
NO2 + h•ν |
These NO radicals react with ozone, forming nitrogen dioxide in an excited state (NO2•). The NO2• molecules decompose spontaneously to form nitrogen dioxide in its common form (NO2), emitting radiation (h•ν) with a wavelength of approx. 600 nm.
Determination of maltose and maltotriose by enzymatic means
Suitable for wort, beer, malt beverages, nutrient beer, mixed beer beverages, NAB, juices and beverages.
Maltose is the main component of beer wort or wort extract.
Maltose and sucrose are cleaved by the enzyme α-glucosidase (maltase) at pH 6.6 into two molecules of D-glucose and D-fructose, respectively:
\(\text{Maltose}+H_2O \hspace{0.8em} \xrightarrow{α–glucosidase} \hspace{0.8em} {2 \hspace{0.2em} \text{D–glucose}}\)
\(\text{Sucrose}+H_2O \hspace{0.8em} \xrightarrow{α–glucosidase} \hspace{0.8em} {\text{D–glucose}+\text{D–fructose}}\)
The D-glucose formed is phosphorylated by the enzyme hexokinase (HK) and adenosine 5'-triphosphate (ATP) to glucose 6-phosphate (G-6-P):
\(\text{Glucose}+\text{ATP} \hspace{0.8em} \xrightarrow{HK} \hspace{0.8em} \text{G-6-P} \hspace{0.2em} + \hspace{0.2em} \text{ADP}\)
In the presence of the enzyme glucose-6-phosphate dehydrogenase (G6P-DH), G-6-P is oxidized from nicotinamide adenine dinucleotide phosphate (NADP) to gluconate-6-phosphate. Reduced nicotinamide adenine dinucleotide phosphate (NADPH) is formed:
\(\text{G-6-P} \hspace{0.2em} + \hspace{0.2em} \text{NADP}^+ \hspace{0.8em} \xrightarrow{G6P-DH} \hspace{0.8em} \text{gluconate-6-phosphate} \hspace{0.2em} + \hspace{0.2em} \text{NADP}^+ \hspace{0.2em} + \hspace{0.2em} \text{H}^+\)
The amount of NADPH formed during the reaction is equivalent to the amount of glucose. NADPH is measurand and is determined based on its absorbance at 334, 340 or 365 nm.
The enzyme α-glucosidase is group specific, i.e., the specificity is directed to the type of glycosidic bond.
Only α-1,4 bonds, i.e., in addition to maltose, sucrose and maltotriose, but not maltotetraose, are cleaved under the given conditions. Therefore, the sucrose content must be taken into account in the maltose calculation (the maltose approach records the glucose formed from maltose and sucrose and the free glucose, the sucrose approach records the glucose formed from sucrose and the free glucose).
Prediction of the extract content and predetermination of the processability and value of a lot of barley for brewing purposes
The behavior of barley during the malting process, which is intended for large-scale malt production, must be known.
MEBAK approved and adopted a micromalting procedure on 6 April 1971 as a standard method for predicting the extract content and for determining the suitability of barley varieties for malting. In 2003, MEBAK shortened the procedure by one day for a total of six days for vegetative growth (steeping and germination), the same length of time as the EBC procedure.