Abstract:
Phytic acid (myo- inositol hexaphosphate or phytate when in salt form) is the principal
storage form of phosphorous in cereal grains. Many of the phytate-mineral complexes
are insoluble and therefore reduce the bioavailability of mineral nutrients such as Fe,
Zn, Ca, Mg. Recently, micronutrient malnutrition problem has been raised by scientists
and they have shown a great concern to find out solutions to alleviate micronutrient
deficiencies found in rice consumers. Although brown rice (unpolished rice) is richer
in phytic acid, it has a nutritional advantage over milled rice. Therefore, it is important
to promote brown rice consumption rather than polished rice.
Studies were undertaken to determine the total phosphorous and phytate contents in
unpolished, rice, to analyze the correlation between total phosphorous and phytate in
unpolished rice and to find out the effect of soaking on phytate content of ten rice
varieties. For this study Beath Heenati, Kalu Heenati, Rathu Heenati, Sudu Heenati,
Pachchaperumal, Batapolal, Kattamanjal, Rathal, Suwanda Samba, and Bw 267-3
varieties of 2006/2007 Maha- Bombuwala were used. Phosphorous content was
determined by using colorimetric method while phytate content was determined by
using anion exchange method. Three varieties with highest, medium and lowest phytate
contents were used to find out the effect of soaking.
There was a significant (p<0.05) difference between some unpolished rice varieties in
their phosphorous content. Beath heenati had the highest phosphorous content and Bw
267-3 had the lowest phosphorous content. Also Suwanda Samba had the highest
phytate content while Bw 267-3 had the lowest phytate content. There was a positive
correlation between total phosphorous and phytate levels based on correlation analysis.
Correlation coefficient for unpolished rice was 0.76. Furthermore, it can be concluded
that 60-80% of total phosphorous is present as phytate in unpolished rice. There was a
significant difference between phytate levels before and after soaking in high phytate
containing varieties such as Suwanda Samba and Pachchaperumal. When the soaking
time increased phytate reduction also became significant. But in the case of low phytate
containing varieties there was no significant difference in phytate reduction. Phytate
level can be reduced by soaking which is a simple pre-treatement practiced at domestic
level before preparing complementary foods. Phytate reduction by soaking occurs due
to activation of phytase enzyme. Therefore, if optimum conditions for phytase enzyme
activation can be maintained, more phytate reduction may be observed.
