Rapid determination of the attenuation limit of beer using middle-infrared (MIR) spectroscopy and a multivariate model.

Stefan Castritius, Mirko Geier, Gerold Jochims, Ulf Stahl, Diedrich Harms

Central Laboratory, Research and Teaching Institute for Brewing in Berlin (VLB Berlin) , Seestrasse 13, 13353 Berlin, Germany.

Journal of agricultural and food chemistry 2012 Jun 27

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A new approach for the determination of the attenuation limit of beer samples using the specific fingerprint region of middle-infrared (MIR) spectroscopy in combination with multiple regression by partial least-squares (PLS) was developed using an attenuated total reflectance (ATR) module. A specific spectral region between 1200 and 800 cm(-1) was identified as highly informative for the quantification of the limit of attenuation. The absorptions in this region are induced by vibrational bands of ethanol (1080, 1040, and 880 cm(-1)) and dissolved extract, in majority maltotriose (1160-1140 and 1040-980 cm(-1)). The multivariate calibration results in a root mean squared error of calibration (RMSEC) of 0.40% and a validation procedure with independent samples results in a root mean squared error of validation (RMSEV) of 0.50%. A repeatability test, concerning the precision of the developed MIR method as well as the reference method, was analyzed using Student's t test. The test has shown no significant difference between the two random samples.

Citation

Stefan Castritius, Mirko Geier, Gerold Jochims, Ulf Stahl, Diedrich Harms. Rapid determination of the attenuation limit of beer using middle-infrared (MIR) spectroscopy and a multivariate model. Journal of agricultural and food chemistry. 2012 Jun 27;60(25):6341-8