O-3
Analysis of hop alpha- & beta-acids & beer iso-alpha-acids by micellar electrokinetic chromatography and diode-array detection during beer production
Presenter: Ekaterina Lebedeva, "Baltika" Brewery

Compounds derived from hops determine the bitter taste of beer. Hops and hop extracts used in the wort boiling process contain three main alpha-acids (humulone, cohumulone, adhumulone) and three beta-acids (lupulone, colupulone, adlupulone). During wort boil, six iso-alpha-acids are formed from the three hop alpha-acids. Control of the contents and ratio of alpha- and beta-acids in hops and the concentration of iso-alpha-acids in wort and beer is very important for the brewery, because bitterness is one of the main flavor and taste characteristics of beer. A number of analytical techniques have been developed for determining concentrations of alpha-acids in hops and iso-alpha-acids in worts and beers. The methods employed by the hop and brewing industries for alpha-acid and iso-alpha-acid quantification are based on lead conductance, ultraviolet spectrophotometry, and high-performance liquid chromatography (HPLC). Recent papers presented by Belgian and German chemists have demonstrated a new sample preparation technique named stir bar sorptive extraction (SBSE) followed by HPLC. We have connected a sample preparation technique SBSE with micellar electrokinetic chromatography. For determination of both acid types (hop alpha-and beta-acids and beer iso-alpha-acids), the same buffer and electrophoretic conditions are proposed. For analysis of iso-alpha-acids, the sample preparation by SBSE is used. Application of this method allows control of hop and hop-product quality, the transformation of these compounds during technological processes, beer bitterness, and degree of oxidative deterioration of beer.

Ekaterina Lebedeva received the first-class Diploma of engineer-technologist of beer and non-alcoholic beverages production from the University of Low Temperature and Food Technologies in St. Petersburg, Russia. She began employment with Baltika Brewery in 2000 as a chemist in the analytical laboratory. Since 2002, she has functioned as 1st category specialist of the Baltika Brewery Research Center. From 2000 to 2004 she wrote her dissertation about flavor compounds of beer. She received a D.S. in beer biotechnology in December 2004.