The method described by Engelen et al. (1994) was adopted to
analyze the phytase activity. Briefly, released inorganic phosphate
from phytic acid in 2.0 mL of the above supernatants was reacted
with 300 mL of the color reagent consisting of a mixture of four
volumes of 1.5% ammonium molybdate in 5.5% sulfuric acid and
one volume of 2.7% ferrous sulfate. The absorbance of the reacted
solution was read at 700 nm. The enzyme activity was expressed as
the percentage (%) of the maximum activity.