2.5 Phytic acid content determination
Phytic acid of the polished rice samples was
determined according to Wei et al. (2012). The rice
flour (0.5 g) was placed into a 50-ml centrifuge tube
and extracted with 10 ml 0.2 mol/L HCl, and vibrated
in a rotary shaker for 2 h, then centrifuged at 10 000×g
for 10 min. The resulting supernatants (2.5 ml) were
transferred into an anther centrifuge tube, and 2 ml of
2 g/L FeCl3 was added, then mixed thoroughly. The
mixtures were boiled in a bath for 30 min, cooled at
room temperature, and then centrifuged at 10 000×g
for 15 min. The resulting supernatants were discarded,
while the precipitates were washed three times with
5 ml ultrapure water. After adding 3 ml of 1.5 mol/L
NaOH to the precipitates, the tubes were then centrifuged
at 10 000×g for 10 min. Supernatants was
discarded, and 3 ml of 0.5 mol/L HCl was added to
dissolve the precipitates. Finally, ultrapure water was
added to the solution up to a volume of 20 ml. The Fe
concentration in the solution was determined by ICPMS
(Agilent 7500a, USA). Phytic acid content was
measured by multiplying Fe content by the factor 4.2.
2.5 Phytic acid content determinationPhytic acid of the polished rice samples wasdetermined according to Wei et al. (2012). The riceflour (0.5 g) was placed into a 50-ml centrifuge tubeand extracted with 10 ml 0.2 mol/L HCl, and vibratedin a rotary shaker for 2 h, then centrifuged at 10 000×gfor 10 min. The resulting supernatants (2.5 ml) weretransferred into an anther centrifuge tube, and 2 ml of2 g/L FeCl3 was added, then mixed thoroughly. Themixtures were boiled in a bath for 30 min, cooled atroom temperature, and then centrifuged at 10 000×gfor 15 min. The resulting supernatants were discarded,while the precipitates were washed three times with5 ml ultrapure water. After adding 3 ml of 1.5 mol/LNaOH to the precipitates, the tubes were then centrifugedat 10 000×g for 10 min. Supernatants wasdiscarded, and 3 ml of 0.5 mol/L HCl was added todissolve the precipitates. Finally, ultrapure water wasadded to the solution up to a volume of 20 ml. The Feconcentration in the solution was determined by ICPMS(Agilent 7500a, USA). Phytic acid content wasmeasured by multiplying Fe content by the factor 4.2.
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