Fig 1.
Dissolved concentration of metal phytate P in two different buffer systems at three different times (1h, 30d, and 90d).
The initial concentration of metal phytate complex in the solution was 300 mg/L (about 0.227–0.397 mM of phytate or equivalent of 1.38–2.38 mM phytate-P) in each experiment. The concentration of metal phytate was quantified as the difference between total soluble P and inorganic P (Pi). The numerals in X-axis represent: 1) 20 mM NaAc (pH 5.0), 2) 20 mM NaAc + 3 mM EDTA, 3) 20 mM NaAc + 3 mM citric acid, 4) 20 mM Tris-HCl (pH 7.5), 5) 20 mM Tris-HCl + 3 mM EDTA, and 6) 20 mM Tris-HCl + 3 mM citric acid.
Fig 2.
Dissolved inorganic P (Pi) from metal phytate complexes.
The initial concentration of metal phytate complex was 300 mg/L in each experiment (about 0.227–0.397 mM of phytate or equivalent of 1.38–2.38 mM phytate-P). The numerals in X-axis correspond to: 1) 20 mM NaAc (pH 5.0), 2) 20 mM NaAc + 3 mM EDTA, 3) 20 mM NaAc + 3 mM citric acid, 4) 20 mM Tris-HCl (pH 7.5), 5) 20 mM Tris-HCl + 3 mM EDTA, and 6) 20 mM Tris-HCl + 3 mM citric acid.
Fig 3.
Comparison of dissolved phytate-P concentration at 30 d (in mM) from colorimetric and ion chromatography methods.
For the colorimetric method, phytate-P was calculated as the difference between total soluble and inorganic P.
Fig 4.
Thermal stability of anhydrous metal phytate complexes in autoclave treatment (at 121° C and 15 psi).
The initial concentration of metal phytate complex was 300 mg/L (about 0.227–0.397 mM of phytate or equivalent of 1.38–2.38 mM phytate-P) in each experiment. Different P measurements and calculations are the same as in Fig 3.
Fig 5.
Stability of metal phytate complexes in acid (1 M HCl).
Pi and Ptotal before acid hydrolysis refer to that already present in the solution before treatment. The initial concentration of metal phytate complex in the solution was 300 mg/L in each experiment. The difference of soluble phytate P before and after hydrolysis is insignificant.
Fig 6.
Released inorganic P in phytate metal complexes (2 mM P) after 20 h incubation with Aspergillus enzyme at pH 2.5 and 5.0.
Control refers to treatment without the enzyme. For enzymatic treatments, 0.1 U/mL Aspergillus phytase was used.
Fig 7.
Effect of EDTA and dithionite on the dissociation of metal-phytate complexes (starting concentration of 2 mM P) at pH 5.0.
(a) Incubation for 20 h in the presence of EDTA (5 mM); (b) Incubation for an additional 20 h after spiking with sodium dithionite (10 mM). Aspergillus phytase enzyme (0.1 U/mL) was used for the hydrolysis.