Beer fermentation control using ion mobility spectrometry - Results of a pilot study

Beer fermentation - a time consuming part of the production process - is typically terminated based on the degradation of diacetyl and 2,3-pentanedione below the odour threshold. Presently no on-line control of both analytes is available. As a consequence, fermentation is often carried out longer than necessary, thus decreasing productivity. In this pilot study, an ion mobility spectrometer using a UV-lamp as an ionisation source and a GC column (30 degrees C constant) for pre-separation were used for the rapid determination of both analytes from the headspace of beer wort, during and after fermentation. Samples were heated to 60 degrees C. Results from such analyses were available after a few minutes without further sample treatment or pre-concentration. Detection limits were below the odour threshold (ng/L range in the gas phase corresponding to the pg/L range in the liquid phase). Results were validated by comparison with the brewery's standard GC-MS method. When applied on-line and in-situ, as a routine test in a brewery, it will help to ensure low levels of diacetyl and 2,3-pentanedione in the product on the one hand and will increase productivity by saving time during fermentation on the other (up to one day in large breweries and even more than one day in smaller ones) by obtaining on-line data of the relevant analytes. After optimisation of the method, further odour or taste relevant analytes could be determined simultaneously.