Abstract:
Rice flour based food processing industries pay more attention on the
parameters which affect the final quality of the product. In this context
gelatinization and viscosity are the two main quality parameters needed to
be concerned more to increase the final product palatability and
consumerbility. Gelatinization causes physical and chemical changes in the
starch granule where water will be absorbed by the granules as a result of
breaking hydrogen bonds in amylose and amylopectin. Far-infrared (FIR) is
a heating technique, getting more popularized in food processing sector in
worldwide because of its bounteous advantages. Research on gelatinization
of rice flour by FIR is not reported elsewhere and is a new attempt.
The polished rice (Oriza sativa indica) was grinded and sieved through
150µm sieve and gelatinized by using three ceramic coated FIR elements
each having 650W by changing the combination of FIR intensity (17125.1,
14123.5 and 11254.3 W/m2
) and FIR exposure time (1, 2, 3, 4, 6, 8, 9 and
10 seconds). FIR intensity was measured with a pyranometer. The degree of
gelatinization percentage of rice flour was measured with the Iodomatric
method as guidelines given by Wootton and Kensington (1989). Viscosity
measurements were taken for 55% gelatinized starch solution using No 2
spindle, while shear rate was set up at 60 rpm throughout the experiment.
The viscosity of gelatinized rice flour increases with gelatinization
percentage linearly with a correlation coefficient (R2
) of 0.9548. The
increase of FIR intensity and exposure time with the gelatinization
percentage, cause water absorption which results in viscosity incremental
effect. There is a strong relationship between gelatinization percentage and
viscosity; thus viscosity can be used as an alternative measurement for
gelatinization.
