Phytate Degradation in a Mixture of Ground Wheat and Ground Defatted Soybeans during Feed Processing:  Effects of Temperature, Moisture Level, and Retention Time in Small- and Medium-Scale Incubation Systems

The optimal conditions for degradation of phytate (IP6, myo-inositol hexaphosphate) in a mixture of ground wheat and ground defatted soybeans (1:2, w/w) with added exogenous E. coli phytase were investigated at different temperatures (45, 60, 75, and 95 °C), moisture levels (25%, 35%, and 45%), and retention times (2−45 min). All treatment combinations were investigated in a small-scale mixer conditioner (experiment 1). The combined 45 °C and 45% moisture treatment was most efficient and reduced the content of IP6 by 86% during 45 min of incubation. This treatment combination was applied in a medium-scale mixer conditioner (experiment 2), and 76% reduction of IP6 at 45 min was obtained. During incubation, the content of lower groups of inositol phosphates, such as IP4 (myo-inositol tetraphosphate) and IP3 (myo-inositol triphosphate), increased significantly as the content of IP6 decreased. The major isomer formed was Ins(1,2,5,6)P4. Keywords: Phytate; phytase; soybean; wheat; temperature; moisture; retention time; incubation