Determination of the fermentability and extract content of industrial worts by NIR

The aim of this work was to investigate the use of transmission near-infrared spectroscopy (NIR) to determine the fermentability of brewery worts. Samples were collected from two breweries (A and B). The fermentabilities 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 yeast strain was used for the determination of fermentability, a standard error of prediction (SEP) of 0.35% was obtained. This corresponded to 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 types and three yeast strains were used, the SEP was 1.08%. This indicates that it is necessary to divide the product range into subgroups for which separate calibrations have to be developed. Calibrations were also developed for the extract content of wort. An SEP of 0.03% (w/w), corresponding to an accuracy of ±0.05% (w/w), was obtained for both breweries. The results demonstrate the possibility of using NIR spectroscopy for immediate process control in the brewhouse. The standard method to determine the fermentability of wort is time-consuming. Using the NIR method the results are available within a few minutes of sampling and could, therefore, be used for making adjustments to the mashing program. A summary of previous work using NIR spectroscopy for wort analysis is also presented.