A. Suoniemi-Kähärä (1), D.TATE (2);
(1) Thermo Fisher, Vaanta, Finland; (2) Thermo Fischer, Sunnyvale, CA, U.S.A.
Poster Presentation
Malt diastatic power is determined by measuring a D-glucose end product with a specific enzymatic reaction. Instead of using traditional titration measurements or a flow analyzer for reducing sugars, a discrete analyzer is used. The advantage of such a technique is speed, ease-of-use, and the ability to test a broad range of analytes, like free amino nitrogen (FAN), sulfur dioxide (SO2), bitterness, protein, or color. This method principle is based on photometric determination of diastatic power in homogenous liquid malt samples using an automated Thermo Scientific Gallery Plus Beermaster analyzer. The process extracts enzymes by malt infusion, followed by the reaction of a solution with ASBC Malt-6 special starch substrate under the controlled conditions of time, temperature, pH, and enzyme-substrate relations. The resulting sugars, primarily maltose, further react with α-glucosidase to produce glucose. Glucose is measured using the Thermo Scientific D-glucose kit, a method based on the reaction of glucose with hexokinase and glucose-6-phosphate dehydrogenase. Measurements are taken at 37°C with a 340 nm filter. Preparation of the special starch solution, malt infusion, calibrator, and α-glucosidase solution is required. The D-glucose method is based on ready-to-use traceable system reagents. After formation of the sugars, all reagent and sample additions, measurements, and reporting of results are automated. First results are reported quickly and several samples can be analyzed without the need for additional hands-on time. The sample preparation process described in the ASBC Malt-6 method can be used. Megazyme EMAST malt amylase was used as a calibration standard. The lot concentration is usually about 220 ASBC units and a linear calibration type can be used. If additional speed is required, the analyzer’s software allows the enzyme calibration to be changed to a factor calibrated test and the factor can be verified by an automated request for a quality control sample. This method has been tested with samples varying from 52 to 368 ASBC units. A method correlation study compared gallery results to the reference method. Preliminary results were obtained using Sigma-Aldrich α-glucosidase which was diluted with 0.5 % NaCl. The method has been further developed by improving the solution of α-glucosidase. With a new citrate buffer, the α-glucosidase enzyme reagent can be frozen in aliquots enabling cost-effective enzymatic analysis. The discrete analyzer allows flexible, fast, and accurate diastatic power analysis, as well as simultaneous analysis of other analytes. By using the sample and substrate preparation methods already used by the laboratory along with an enzyme preparation as a calibrator, results can be easily correlated to existing methods.
