The molecular weight distribution of β-glucan in wort from malts of different barley varieties at different stages of malting

Abstract

The molecular weight distributions of 13-glucans from congress worts of the barley genotypes Minerva (feed barley) and Triumph (malting barley) at 0-9 days of malting were studied by gel permeation chromatography. The amount ofl3-glucan was estimated using a glucose determination method and a specific fluorometric method based on an increase in the fluorescence intensity of Calcofluor when binding to high molecular weight (> 10,000) ~-glucan. The amount of extracted 13-glucan was slightly higher for Minerva than for Triumph barley at all stages of germination. The elution patterns ofl3-glucan in congress worts made from the two harley genotypes were similar, although the high molecular weight 13-glucan analysed in worts from Triumph was decomposed during malting at a faster rate than in those from Minerva. The extracted high molecular weight 13-glucans were found to have molecular weights in the range of 104-l 06. The differences in the contents of high molecular weight ~-glucans cannot explain all the variation in viscosities of the worts.

Quantification of high molecular weight (1→3)(1→4)-β-d-glucan using Calcofluor complex formation and flow injection analysis. II. determination of total β-glucan content of barley and malt

“…HPSEC data indicate that the MW distribution is altered during acid hydrolysis. It was shown by FOLOAGER and JORGENSEN (8) that an increase K.G JORGENSEN & S. AASTRUP: Quantification of total 13-glucan in Calcofluor fluorescence intensity only takes place with 13-glucan molecules having a size which is larger than 104 dalton. It is therefore essential that the 13-glucan during extraction is not degraded to fragments smaller than 104 dalton, a condition which can be achieved by adjustment of both the extraction time and the concentration of the acid.…”

Molecular weight and ionic strength dependence of fluorescence intensity of the Calcofluor/β-glucan complex in flow-injection analysis

“…For the evaluation of MW distribution in the sample, bglucan fractions isolated by size-exclusion chromatography (SEC), both off-line (Foldager and Jo¨rgensen, 1984;Manzanares et al, 1991) and on-line post-column detection (Wood et al, 1991;Gomez et al, 1997;Knuckles et al, 1997) had been employed. Since refractive index (RI) detector does not discriminate target material from unwanted impurities like starches, fluorescence intensity measurement from the Calcofluor/b-glucan complex is the most commonly used technique; however, this technique assumes that the fluorescence intensity from the Calcofluor/b-glucan complex is not dependent on MW of bglucan.…”