Malt intended for use in beer brewing or elsewhere in the food industry
Viscometric Determination of Gelatinization Temperature (GT)
The gelatinization temperature (GT) can be determined using a rotary viscometer (e.g., amylograph or viscograph, Brabender GmbH & Co. KG, Germany [7] or Rapid-Visco-Analyser (RVA), Perten Instruments, a PerkinElmer Company, USA [8]).
Unlike the analysis method for adjuncts which do not contain a large amount of enzymes, for the analysis of barley malt, a mash with a mash to sparge ratio of 1 : 4 (similar to that commonly found in the brewing process) is used [9]. The sample is heated according to a programmable temperature/time program (refer to table 1) and the viscosity is measured using measuring stirrer throughout the process.
A gelatinization begins to occur, an increase in viscosity is registered; temperature of the sample is measured and identified as the corresponding gelatinization temperature. An increase in viscosity of a minimum of 24 cP (mPa × s) within six seconds is the evaluation criterion for the pasting temperature.
Determination of maltose and maltotriose by enzymatic means
Suitable for malt, beer, NAB, sports drinks, energy drinks.
Starch, the main carbohydrate in malt, is hydrolyzed during the mashing process partly to fermentable sugars and partly to (iodine-normal) dextrins. The determination of starch is therefore of interest for brewing technology.
In the beverage industry, maltodextrins are used in sports and energy drinks
Starch is cleaved to glucose by the enzyme amyloglucosidase at pH 4.6:
Starch + (n–1) H2O \(\xrightarrow{amyloglucosidase}\) n D-glucose
The D-glucose formed is phosphorylated by the enzyme hexokinase (HK) and adenosine 5'-triphosphate (ATP) to glucose 6-phosphate (G-6-P):
Glucose + ATP \(\xrightarrow{HK}\) D-G-6-P + 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:
G-6-P + NADP+ \(\xrightarrow{G6P-DH}\) D-gluconate-6-phosphate + NADPH + H+
The amount of NADPH formed during the reaction is equivalent to the amount of glucose. NADPH is a measurand and is determined on the basis of its absorption at 334, 340 or 365 nm.
It is not possible to distinguish enzymatically between high-polymer and low-molecular starch.