DETERMINATION OF THE FERMENTABILITY AND EXTRACT CONTENT OF INDUSTRIALWORTS BY NIR

The aim of this work was to investigate the use of transmission near-i nfrared spectroscopy (NIR) to determine the fermentability of brewery worts. Samples were collected from two breweries (A and B). The fermen tabilities of the worts were determined using the breweries' own yeast strains. NIR spectra of the worts were scanned using an LT Industries Quantum 1200 Plus spectrophotometer. For brewery A, where only one ye ast strain was used for the determination of fermentability, a standar d error of prediction (SEP) of 0.35% was obtained. This corresponded t o an accuracy of +/-0.5%, which is on the same level as the precision of the reference method (+/-0.6%). For brewery B, where three wort typ es and three yeast strains were used, the SEP was 1.08%. This indicate s that it is necessary to divide the product range into subgroups for which separate calibrations have to be developed. Calibrations were al so developed for the extract content of wort. An SEP of 0.03% (w/w), c orresponding to an accuracy of +/-0.05% (w/w), was obtained for both b reweries. The results demonstrate the possibility of using NIR spectro scopy for immediate process control in the brewhouse. The standard met hod to determine the fermentability of wort is time-consuming. Using t he NIR method the results are available within a few minutes of sampli ng and could, therefore, be used for making adjustments to the mashing program. A summary of previous work using NIR spectroscopy for wort a nalysis is also presented.