Determination of Total Carbohydrate Content in Beer Using Its Pre-column Enzymatic Cleavage and HPLC-RI
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Determination of Total Carbohydrate Content in Beer Using Its Pre-column Enzymatic Cleavage and HPLC-RI Marie Jurková & Pavel Čejka & Karel Štěrba & Jana Olšovská
Received: 21 November 2013 / Accepted: 20 January 2014 # Springer Science+Business Media New York 2014
Abstract Beside ethanol, carbohydrates are the main source of total energy in beer. While analyses of fermentable carbohydrates are important from the technological point of view, the total content of carbohydrates is relevant in terms of nutrition. A high-performance liquid chromatography (HPLC) method with refractometric (RI) detection was developed for determination of total carbohydrate content in beer. Using enzymatic reaction with amyloglucosidase, the carbohydrates were cleaved to yield glucose and short glucose oligomers of less than 10 units, and separated on HPLC ion exchanger Rezex RSO-Oligosaccharide column in Ag+ mode. Optimum parameters were established for the enzymatic sample treatment and for the HPLC separation of reaction products. Calibration curves of glucose, fructose, maltose and simultaneously analyzed glycerol ranged from 0.001 to 0.5 g/100 ml, correlation coefficients of all calibration curves were 0.9999. The instrumental limits of quantification were 0.001 g/100 ml and they were verified using repetitive injections, with coefficient of variation (CV) less than 10 % in five replicates. The method limit of quantification was 0.01 g/ 100 ml since it was necessary to dilute the beer samples before chromatographic analysis. Recovery of the method in nonalcoholic and alcoholic beer was 98.5 %, and 92.3 %, respectively. Finally, ten non-alcoholic and 15 alcoholic beers from Czech market were analyzed using the method, the average content of total carbohydrates in non-alcoholic and alcoholic beers being 4.21 and 3.70 g/100 ml, respectively. These results are in a good correlation with the real extract of beer, which is on average 4.58 and 4.27 g/100 ml.
M. Jurková : P. Čejka : K. Štěrba : J. Olšovská (*) Research Institute for Brewing and Malting, PLC, Lípová 15, 120 44 Prague 2, Czech Republic e-mail: [email protected]
Keywords Total carbohydrate content . Glucose . Beer . Enzymatic cleavage . High-pressure liquid chromatography with refractive index detection . Real extract of beer
Introduction Beer is an important source of chief nutritional compounds such as carbohydrates and proteins, carbohydrates being the main source of total energy of beer. In this context, beer has become a basic part of the diet in many cultures (Bamforth 2004). The total content of carbohydrates in fermented beverages including beer is a very important parameter from nutritional viewpoint. EU regulation No. 1169/2011 of the European parliament and the Council defines inter alia Union rules on food labelling applicable to all foods. The development of a reproducible method for determining total carbohydrates and also glycerol content in beverages is therefore necessary. Although the development of modern chromatographic separation and detection
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