DETERMINATION OF FERMENTABLE SUGARS AND NITROGENOUS COMPOUNDS IN WORTBY NEARINFRARED AND MIDINFRARED SPECTROSCOPY

Near-infrared (NIR) and mid-infrared (MIR) spectroscopy techniques wer e evaluated for the analysis of brewery worts. Good calibrations were obtained for maltose (SEP(NIR) 2.6 g/l, SEP(MIR) 2.0 g/l) glucose SEP( NIR) 0.6 g/l, SEP(MIR) 0.4 g/l) and the sum of fermentable sugars (SEP (NIR) 2.8 g/l, SEP(MIR) 2.6 g/l) with both methods. Satisfactory calib ration was obtained for maltotriose (SEP(NIR) 1.4 g/l, SEP(MIR) 1.5 g/ l), nitrogen (SEP(NIR) 122 mg/l, SEP(MIR) 92 mg/l) and free alpha-amin o nitrogen (SEP(NIR) 29 mg/l, SEP(MIR) 23 mg/l). MIR spectroscopy gave slightly better results, but sample handling was more difficult than in the NIR region. The NIR measurement is simple and rapid and could b e used for on-line process control during mashing. No sample preparati on other than filtration is needed.