Application of Compact High-Performance Electron Spin Resonance for Malt Quality Estimation

摘要

The application of a compact high-performance electron spin resonance (ESR) instrument for quality control during malting was studied. The ESR can analyze not only liquids but also solid samples without complicated sample preparation procedures. The ESR spectrum of the green malt or malt was measured by using Mn~(2+) as an internal standard with a compact high-performance ESR spectrometer (ES-10; Nikkiso Co., Ltd., Tokyo). Routine malt quality tests were also carried out according to the methods of the European Brewery Convention. Barley, green malt, and malt showed one peak signal derived from a stable organic radical (g = 2.005). The signal intensity of the green malt or malt increased with the increasing steep-out moisture or germination time periods or both. The signal intensity of the malt showed a correlation with several parameters indicating malt modification, such as the Kolbach index, Hartong index at 45℃, diastatic power, viscosity, friability, and beta-glucan content. Therefore, the ESR analysis can be used as a simple quality control technique for malting.