Time dependent changes in the compression behavior of single wheat kernels upon tempering

Tempering, the controlled addition of water to wheat before milling, is an essential step for maximizing flour yield in the milling industry. However, the limited availability of water significantly impacts moisture migration within the kernels, consequently influencing their breakage behavior. This study investigates the effects of tempering time (3, 6, 9, and 12 h) and moisture content (14%, 16% and 18%) on the moisture diffusivity and compressibility characteristics of single wheat kernels from hard red winter (HRW) and hard red spring (HRS) varieties. Uniaxial compression tests revealed a significant influence of tempering time on the viscoelastic properties of the kernels. Tempering moisture content significantly decreased elasticity of HRW kernels from 155. 8 MPa to 89.2 MPa, whereas for HRS the decrease was from 192.2 MPa to 115.0 MPa. Higher tempering moistures decreased the elastic work from 8.8 to 5.4 N. mm while increased the plastic work to 1. 92 N.mm, suggesting improved flour extraction. Compressibility followed first order kinetics, with rate constants ranging from 0.002 to 0.0057 h^− 1 for HRS and from 0.0026 to 0.0066 h^− 1 for HRW. Kernel diffusivity exhibited variations with tempering moisture for both the kernels, although these differences were not statistically significant. These findings provide insights into the interaction between tempering conditions and kernel properties, for optimizing the tempering processes to enhance flour extraction efficiency.