Conditions for back titration of Cu2+
The conditions for the complexometric titra-
tion of Cu2+ that are equivalent to the oxidized reducing
sugars in the starch hydrolysate were determined ex-
perimentally by varying the different parameters: the
necessity of stopping the hydrolysis immediately after
obtaining the analysis sample; the manner and the du-
ration of the heating of the sample for carrying out re-
action (2); the proper acidity of the media for reaction
(3), the volume of the solutions of Fehling I and II for
increasing the preciseness of the analysis. Due to the
high rate of the enzyme hydrolysis it is necessary to
stop the hydrolysis reaction immediately after sampling.
0.5 ml 2mol l1 HCl with 1 ml sample volume are suf-
ficient to stop the hydrolysis.
Under acidic hydrolysis this requirement is not
applicable since the hydrolysis stops simultaneously with
the cessation of heating.
Another factor which had to be taken into con-
sideration was the manner and the duration of heating