Determination of phytic acid
The phytic acid content in the samples was determined via a
colorimetric method described by Haug and Lantzsch (1983) with
some modifications, and the results were expressed as mg phytic
acid equivalents per 1 g of sample. Phytic acid was extracted with 20 ml of 0.2 N HCl by shaking 150 mg of dry sample at 200 rpm for
4 h at room temperature, and centrifugation at 3000 rpm (2300g)
for 20 min. The supernatant was used for analysis. Supernatant
(500 ll) was precipitated with 1 ml of ferric solution. The mixture
was boiled at 100 C for 30 min in a water bath. After cooling, samples
were transferred into Eppendorf tubes and centrifuged at
10,000 rpm for 5 min. The 1 ml of supernatant was used to determine
the phytic acid content estimated using 2,20-bipyridine solution
(1.25 ml). After incubation for 1 min at room temperature, the
absorbance was measured at 519 nm.