1070-4272/03/7606-0997 $25.00 C 2003 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 76, No. 6, 2003, pp. 997!1001. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 6, 2003,
Original Russian Text Copyright + 2003 by Losev, Makarova, Lipatova.
AND POLYMERIC MATERIALS
Rate of Acid Hydrolysis of Starch as Influenced
by Intensive Mechanical Effects
N. V. Losev, L. I. Makarova, and I. M. Lipatova
Institute of Chemistry of Solutions, Russian Academy of Sciences, Ivanovo, Russia
Received July 16, 2002; in final form, March 2003
Abstract-The influence of ultrasonic cavitation on the rate of acid hydrolysis of gelatinized starch under
the action of ultrasonic field or strong mechanical stresses in a rotary-pulsating activator is discussed.
The dependences of the hydrolysis rate on the starch concentration, acid content, temperature, and intensity
of mechanical action on the system are analyzed.
Hydrolytic degradation with rupture of the glyco-
side bond is one of the most practically significant re-
actions involving starch. The intensification of starch
hydrolysis is an urgent problem; it is of theoretical
and practical importance. The possibility of enhancing
the reactivity of gelatinized starch by intensive mech-
anical treatment in a rotary-pulsating activator (RPA)
 has been poorly studied as yet. In such devices,
a material is exposed to combined action of ultrasonic
vibrations and strong shear stresses. Some features of
the effect of such treatment in RPA on the state of
starch hydrogels have been reported previously [2, 3].
The possibility of accelerating reactions of starch hy-
drogel with low-molecular-weight reagents by mech-
anical treatment was studied in  for the example of
permanganate oxidation. Previously, it has been con-
sidered that shear strains are decisive factor in the
enhancement of the starch reactivity. However, our
new experimental data on the effect of both shear-free
ultrasonic field  and RPA treatment on the state of
starch hydrogels suggest that the role of the shear and
ultrasonic action in the course of mechanical intensif-
ication of chemical processes in the gelatinized starch
should be revised.
In this study, we examined the possibility of inten-
sifying acid hydrolysis of starch under the influence of
ultrasonic field and combined ultrasonic and shear
treatment in a rotary-pulsating activator.
In this study, we used corn starch [GOST (State
Standard) 7697382]. Starch hydrogels to be mechan-
ically treated were prepared by cooking a starch sus-
pension on a water bath at 90oC for 15 min.
The acid hydrolysis of gelatinized starch was per-
formed by three methods: in a temperature-controlled
vessel with ordinary stirring, in a temperature-con-
trolled beaker with ultrasonic treatment (UZDN-2T
ultrasonic pulverizer), and in a temperature-controlled
Starch hydrogels were treated in a UZDN-2T ul-
trasonic pulverizer at 22 kHz; the volume density of
the acoustic energy, determined by calorimetry, was
1.34 W cm
Starch hydrogels were also treated in a laboratory
RPA. The working chamber of the activator is formed
by a rotor and a stator, which are equipped with spe-
cial fittings. The gap between the rotating and fixed
elements of the working chamber in a given operation
mode determines the tangential stresses in the liquid-
phase material treated. The rotor rotation rate was var-
ied in the 100035000 rpm range, and the gradients
of the shear rate, within (0.5317.4) 0 10
To confirm the occurrence of ultrasonic cavita-
tion in the RPA working chamber, we used the stan-
dard test reaction Fe
in an acidic medium.
This reaction does not occur in the absence of ultra-
sonic cavitation . The same reaction was used to
determine the amount of ultrasonic energy absorbed
by the material (using chemical dosimetry).
The starch concentration in the gels was 23 8%, and
the process temperature, 20370oC; the sulfuric acid
concentration was varied within 0.033 0.15 M, and
the time of mechanical treatment was 10390 s.