Effect of Steam Flash Explosion Pretreatment on Phytate Degradation of Wheat Bran

Whole wheat flour contains many nutrients which is mainly located in wheat bran, but it has a poor bioavailability because of the massive presence of antinutritional factor phytate. To improve the bioavailability, steam flash explosion (SFE) was first employed to phytate degradation in wheat bran. Five levels of steam pressure (0.5, 1.0, 1.5, 2.0, and 2.5 MPa) and six levels of residence time (30, 60, 90, 120, 150, and 180 s) were used to investigate the phytate and color changes of wheat bran treated by SFE. The optimum process was determined at steam pressure of 2.5 MPa and residence time of 60 s. Under this process, the satisfactory phytate degradation (around 87 %) could be obtained, whereas the degree of color deepening of treated wheat bran is proportional to the phytate degradation. Observation of scanning electron microscopy (SEM) revealed that the structure of wheat bran was completely destroyed by SFE. This destruction causes the phytate to be exposed to high temperature and high pressure and consequently degraded. High-performance liquid chromatography (HPLC) results indicated that SFE could effectively change phytate into low inositol phosphate salts. As shown in the Fourier transform infrared (FT-IR) spectroscopy analysis, this change was attributed to the decomposition of phytate by interrupting the P-O-C group. Overall, phytate degradation in wheat bran during SFE attributed to the interaction of high pressure, high temperature, and acid hydrolysis.