SEVERAL NEW FACTORS INFLUENCING THE MEASUREMENT OF β-GLUCAN CONTENT USING CALCOFLUOR FLOW-INJECTION ANALYSIS METHOD

Factors such as temperature, calcofluor concentration, sample injection volume, void volume of the mixing tube and other factors have been reported to influence the calcofiuor flow-injection analysis (FIA) of β-glucan. In addition to these factors, we revealed the following factors and elucidated their effects on the FIA of β-glucans: the inside diameter and arrangement of the mixing tube, calibration method using peak area or peak height of the edition patterns, and the quality of the calcofluor reagent. An apparently lower value was obtained when (1) the mixing tube had a smaller inside diameter, (2) the mixing tube was looped in a ring of smaller diameter, or (3) the mixing tube was wound as double coils in a figure eight instead of a loop. Furthermore, it was indicated that the peak area calibration produced higher measures values than the peak height calibration. The reagent also affected the results; a calcofluor reagent from Sigma Chemical Co. gave a higher value than one from Polyscience Inc. It was concluded that these troublesome phenomena were derived from the difference between the test sample and the standard solution of β-glucan, that is, the molecular weight distribution of β-glucans and/or the sugar and ethanol in the sample solutions. Based on these findings, it is suggested that international standardization of the FIA method for β-glucan be made.     

Analysis of Aldehyde-bisulfites in Beer by HPLC-Fluorescence Detection with Post-column Derivatization

An analytical method was based on the aldehyde-bisulfite (separated by HPLC) reaction with o-phthalaldehyde in the presence of ammonium acetate, producing a fluorescent compound. Detection limits of alkanalbisulfite (from formaldehyde- to octylaldehyde-bisulfite) and 2-alkenalbisulfite (from trans-2-hexenal- to trans-2-nonenal-bisulfite) ranged from 5 nM to 25 nM. The method was less sensitive for free sulfite (detection limit 100 μM) than for aldehyde-bisulfite. Increasing acetaldehyde-bisulfite with addition of 25 mM acetaldehyde to a beer sample showed free sulfite in the beer. Free sulfite and acetaldehyde-bisulfite were detected in commercial beers but other aldehyde-bisulfites were not.