Analytical procedure
A sample of 1.00 ml hydrolysate is taken after
various intervals of time and is placed in a 100ml mea-
surement flask. Immediately after sampling, 0.5 ml 2
mol l-1 HCl is added in order to stop further hydroly-
sis in the enzymatic case. Under acidic hydrolysis the
addition of HCl is not necessary. 25 ml distilled wa-
ter, 25.00 ml Fehling I and 25.00 ml Fehling II solu-
tions are added to the sample. The resulting solution
is homogenized. The flask is placed in a boiling water
bath for 5 minutes. Then the solution in the flask is
cooled to room temperature and filled up to the mark
with distilled water. The resulting sediment of Cu2O is
filtered through a paper filter suitable for the filtering
of fine crystalline residues.
A sample of filtrate with a volume of 25.00 ml is
transferred to a 300 ml Erlenmeyer flask. 8 ml acetate
buffer and 0.10 0.15g PAR are added. The surplus Cu2+
is titrated with a standard solution of EDTA until the color
of the solution changes from red to yellow-green.
The quantity of Cu, g, (contained in Cu2O)
equivalent to the oxidized sugar is calculated by the
formula