The use of adjuncts is allowed for the production of beer which is not brewed according to the beer purity law – as long as they comply with national guidelines for beer production [1].
The gelatinization temperature (GT) is the temperature at which starch grains experience tangential water uptake, while simultaneously losing their crystalline structure. Below this critical temperature, only a very slow enzymatic hydrolysis of the starch granules occurs [1, 2].
As gelatinization first begins in many unmalted cereals at temperatures between 60–90 °C [3, 4], and amylolytic enzymes are already inactivated at temperatures between 70 and 80 °C [5], the addition of malt for conversion of adjunct starch can be ineffectual. Therefore, information about the GT of the adjunct being utilized can be of great interest to the brewer. Otherwise, losses in yield, filtration problems and turbidity in the finished beer can result from incomplete starch gelatinization and saccharification [6, 7].
Unmalted grains, such as rice, corn (maize), sorghum, barley or starch products, subjected to various degrees of processing (e.g., grits, flakes), which are to be added at certain points in the processes of beer or other beverage production
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.