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.
This method describes how the extract content of adjuncts is determined.
After gelatinization of the starch in the adjunct, the starch is liquefied and converted through the addition of malt. Subsequently, the extract content is determined according to the procedure given in the method for malt analysis.
The gelatinization temperature can be determined using a rotary viscometer (e.g., Amylograph or Viscograph, Brabender GmbH & Co. KG, Germany [4] or a Rapid-Visco-Analyser, RVA, Perten Instruments, a PerkinElmer Company, USA [8]).
A suspension consisting of a finely ground sample and water is produced, whose precise mixing ratio should correspond to the analysis protocol for the adjunct in question. However, since for many cereals and pseudocereals no official analysis protocol exists, the initial weight for the adjuncts listed in table 2 has been determined empirically [3].
Once the suspension is prepared it is attempered according to a pre-programmed temperature/time program, and the viscosity is determined on a continuous basis by means of a rotor and a rotary torque measurement (fig. 1). When gelatinization begins, an increase in the viscosity is registered, and the corresponding sample temperature is defined as the gelatinization temperature. The standard evaluation criterion (PT) is a viscosity increase of at least 24 cP (≙ mPas) within six seconds.
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.
Spectrophotometric determination of the iodine value of brewery spent grain
Brewery spent grain, wet spent grain, dry spent grain
High molecular weight dextrins and starch present in the wort extracted from brewery spent grain are precipitated through the addition of ethanol, centrifuged and dissolved in phosphate buffer, followed by the addition of an iodine solution. Depending on the molecular weight and degree of branching, a red to blue color forms, the intensity of which is measured spectrophotometrically at 578 nm.
This method describes how the extract content of adjuncts is determined.
After gelatinization of the starch in the adjunct, the starch is liquefied and converted through the addition of malt. Subsequently, the extract content is determined according to the method used for malt analysis.