Glucan instability

Dubourdieu et al. (1981) proposed two tests for glucans in wine at levels ranging from 3 to 15 mg/L. Concentrations 3 mg/L may create clarification and filtration problems. 

Acidulated ethanol Into approximately 90 mL of 95% (vol/vol) ethanol, add 1 mL stock HCL. Bring to 100 mL volume with ethanol. 

Transfer 10 mL of suspect wine to a convenient-sized test tube. Add 5 mL of acidulated ethanol. 

Interpretation Formation of filamentous strands suggests the presence of glucans ( 15 mg/L). 

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Figure 2. Electrophoretic profiles of glucan synthase fractions purified from celery. Proteins were transferred to nitrocellulose and stained by colloidal gold. Symbols PM, plasma membranes SOL, CHAPS-solubilized RC, reconstituted glucan synthase preparations. Plasma membranes were isolated by two-phase partitioning. Specific activities of the three membrane preparations were 398, 1355, and 626 nmol/min/mg, respectively. The low specific activity of RC relative to SOL may be a reflection of enzyme instability following the gel filtration step.

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