Journal of
Brewing and Distilling

  • Abbreviation: J. Brew. Distilling
  • Language: English
  • ISSN: 2141-2197
  • DOI: 10.5897/JBD
  • Start Year: 2010
  • Published Articles: 30

Full Length Research Paper

Malt roasting quality control by mid-infrared spectroscopy

Deborah Herdt
  • Deborah Herdt
  • Center for Mass Spectrometry and Optical Spectroscopy, Mannheim University of Applied Sciences, Mannheim, Germany.
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Tobias Teumer
  • Tobias Teumer
  • Center for Mass Spectrometry and Optical Spectroscopy, Mannheim University of Applied Sciences, Mannheim, Germany.
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Sindhu Nair Balan
  • Sindhu Nair Balan
  • Center for Mass Spectrometry and Optical Spectroscopy, Mannheim University of Applied Sciences, Mannheim, Germany.
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Nur Adibah Kamarulzman
  • Nur Adibah Kamarulzman
  • Center for Mass Spectrometry and Optical Spectroscopy, Mannheim University of Applied Sciences, Mannheim, Germany.
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Thomas Kunz
  • Thomas Kunz
  • Institute of Food Technology and Food Chemistry, Technische Universität Berlin, Berlin, Germany.
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Sarah Kühnemuth
  • Sarah Kühnemuth
  • Institute of Food Technology and Food Chemistry, Technische Universität Berlin, Berlin, Germany.
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Frank-Jürgen Methner
  • Frank-Jürgen Methner
  • Institute of Food Technology and Food Chemistry, Technische Universität Berlin, Berlin, Germany.
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Matthias Rädle
  • Matthias Rädle
  • Center for Mass Spectrometry and Optical Spectroscopy, Mannheim University of Applied Sciences, Mannheim, Germany.
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  •  Received: 20 January 2021
  •  Accepted: 22 April 2021
  •  Published: 31 May 2021

Abstract

In the presented investigation, the chemical composition of malt during roasting is estimated using diffuse reflectance mid-infrared fourier transform (DRIFT-MIR) spectroscopy and multiple linear regressions. Accordingly, the corresponding test setup is presented and evaluated. A total number of sixty-five stop roasting, having temperature range from 140 to 220ºC, and one unroasted sample of 1500 g Avalon malt are performed in an eddy current roaster. Roasted and unroasted malt samples are milled and then analysed. Additionally, analytical standard reference methods are performed for colour, spectral tristimulus L*a*b* - values, colour difference (DE), iron-content, quantitative radical generation and the formation of specific intermediates, such as 5-(hydroxymethyl) furfural (HMF) as well as 3?deoxy?hexosulose (3-DH) and end products of Maillard reaction on all sixty-six samples. Multiple linear regression models were used to predict analysed references based on mid-infrared data, modified with spectral pre-processing for better prediction performance. The obtained results indicate that DRIFT-MIR spectrometry, combined with pre-processing and selection of evaluated wave number areas, is a useful analytical tool for the measurement of quality attributes of malt and therefore, shows potential for application in quality and process control.

 

Key words: Malt roasting, mid-infrared, optical spectroscopy, process control, EBC, L*a*b*, DE, quality control.