Trials of a near infrared spectroscopic instrument (LT Industries "Quantum 1200") for on-line beer analysis to improve the control of the dilution of high gravity brewed beer are described. Calibration standards were developed by comparing the NIR spectra of beer samples with their alcohol content, original gravity and calorie count as determined by the approved methods of the American Society of Brewing Chemists, using a SCABA automatic analyser. This was followed by practical trials in a commercial brewery, monitoring the blending of ten different high gravity brewed beers for over 18 months. On this basis, the "Quantum 2000" NIR beer analyser was developed, incorporating additional features particularly useful in the conditions of the beer blending application (such as a purge mechanism, a PID temperature controller and a retractable probe housing which allows the probe to be withdrawn from the beer pipe, without disturbing the process, for manual cleaning if any fouling builds up which is not adequately dealt with by CIP). Automatic transmission of analytical data to the process control unit once every minute allows dilution to be carried out with far greater accuracy and consistency than by calculating the blending liquor dose from laboratory analysis of the undiluted beer, as is the practice in many high gravity breweries. Possible applications of on-line NIR analysis in other brewery processes were under investigation at the time of writing.
Keywords : alcohol analysis automatic beer dilution high gravity brewing NIR spectroscopy on-line original gravity process control