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.
Malt intended for use in beer brewing or elsewhere in the food industry
While α-amylase is active in a gelatinized solution of amylopectin, the viscosity of the solution is constantly dropping due to the degradation of the starch molecules, which can be tracked using a rotational viscometer. The change in the reciprocal of the specific viscosity serves as a measure for the activity of α-amylase.
Suitable for any wort or mash
The time required for a volumetrically defined amount of fluid (the volume between two marks on the tube of the viscometer) to flow through a capillary of a defined length is measured.
Definition:
1 square meter per second is the kinematic viscosity of a homogenous fluid with a dynamic viscosity of 1 Pa × s and a density 1 kg/m3.
The unit for expressing kinematic viscosity (the relationship of viscosity to density = viscoplasticity) is 1 m2/s = 106 mm2/s
Malt intended for use in beer brewing or elsewhere in the food industry
Through the action of endo-β-glucanase on a β-glucan solution, the viscosity of the solution continuously decreases, due to the degradation of the substrate molecules, which is measured using a rotary viscometer. The change in the reciprocal of the specific viscosity is a measure for the activity of endo-β-glucanase.
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.
The method describes how to determine the viscosity of the laboratory wort using various kinds of falling ball viscometers.
Suitable for all worts and mashes
The amount of time required for a special ball to fall while sinking through a glass tube filled with a test fluid between two marks is measured. The precision of this method is increased if the time is measured using a photoelectric beam to an accuracy of 0.01 s, rather than manually with a stop watch.