A near Infrared Spectroscopic Sensor for the Monitoring of Brewing Processes

Abstract

The use of near infrared (NIR) analysis in the on-line process control of beer production (brewing) is exemplary reviewed. The real-time monitoring of both the mashing and fermentation processes appears to be an interesting but still unsolved problem, mainly due to the high and varying content of solid particles in the respective fluids. Intrinsic sensors, based on the effect of Attenuated Total Reflection, offer a possibility for even in-line measurements in such cases. U-shaped intrinsic sensors were fabricated of fused silica rods with a diameter of 3 mm and coupled to a NIR spectrometer via two fibre bundles. The sensor spectra turned out to be similar to transmission spectra of an optical pathlength of about twenty micrometers, confirming theoretical values obtained by an extended raytracing calculation. Spectra of brewing fluids were taken during the mashing and fermentation process, respectively, and evaluated by PLS. The sensor performance allows to monitor the progress of both processes in terms of the sugar and the ethanol production, respectively. However, further work is necessary to realise a proper industrial sensor.