This method describes the viscometric determination of the gelatinization temperature (GT) of malt.
This provides the temperature at which starch granules exhibit tangential swelling due to moisture uptake. The granules begin to lose their crystalline nature and become vulnerable to degradation by enzymes. Below this critical temperature, the starch granules can only be enzymatically hydrolyzed very slowly [1, 2].
The GT of grain varies according to the type of grain and the variety and is also influenced by the conditions present in the field where it was cultivated and by the climate [3, 4]. The consequences of incomplete gelatinization of the starch and poor saccharification can result in losses in yield, filtration problems and beer turbidity [5, 6].
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.