Determination of carbohydrates in brewer's wort by capillary electrophoresis with indirect UV detection

Beer is produced by fermenting a wort which is, basically, an aqueous solution of different sugars obtained from the enzymatic conversion of starchy materials present in malted grains. Even if the type and quantities of raw materials and yeast remain the same, different operational conditions lead to different types of beers, since the mashing temperature directly influences the activity of the amylolytic enzymes found in malt. This work aimed at developing a method by CE-UV for the indirect and simultaneous determination of five carbohydrates (sucrose, fructose, glucose, maltose, and maltotriose) in brewer's wort. Since glucose, maltose and maltotriose exhibit different fermentation kinetics (in this order - glucose being the fastest and maltotriose, the slowest), their relative concentration can determine whether a beer will end up dry or will exhibit a full mouthfeel and residual sweetness after fermentation. In this work, samples were prepared according to typical brewing conditions and treated by protein precipitation followed by centrifugation. Electrophoretic separation was performed using BGE at pH 12.5, which was composed by 5 mmol L-1 phthalic acid (chromophore), 0.4 mmol L-1 cetyltrimethylammonium bromide and 100 mmol L-1 NaCl. The optimized instrumental parameters were temperature of 20. C, potential of 15 kV, hydrodynamic injection at 80 mbar for 15 s, and indirect detection at 220 nm. Linearity from 125 to 1000 mg L-1, characterized by R-2> 0.99, was obtained for all carbohydrates, as well as detection limits were achieved between 15.02 and 22.52 mg L-1, showing that the developed method is suitable for the determination of carbohydrates in wort. Recoveries between 83.4% and 91.5% indicate that the accuracies of the proposed method for the determination of the studied carbohydrates are acceptable. The present work is convenient for monitoring the beer production process, being an attractive alternative for its quality control, mainly for local brewhouses.