Rheological, texture and in vitro digestibility properties on steamed rice bread modified by ultrafine grinding and high pressure homogenization on rice-okara slurry

Summary In this study, the ultrafine grinding (UG) and high pressure homogenization (HPH) treated slurry on the particle size and rheological property of slurry, texture, in vitro starch digestibility, and multiscale structure of steamed rice bread (SRB) were investigated. Then, it was found that the average particle size of slurry treated by UG and HPH reduced from 84.6 to 38.6 μm and 22.6 μm, respectively. The rheological properties results demonstrated that G′ resulted in higher values than G″, and that the values of G′, G″ and tan δ of slurry decreased obviously after UG and HPH treatment. Obviously, the hardness and viscidity of SRB made by UG and HPH were lower, while the elasticity and specific volume were higher. The determination of in vitro starch digestibility revealed that UG treated on slurry accelerated the starch hydrolysis rate of SRB, resulting in an increase in the pGI from 76.17 to 79.36, while HPH treatment reduced the pGI from 76.17 to 73.49. Furthermore, XRD and FTIR demonstrated that both UG and HPH increased the intermolecular hydrogen bonds, and both treatments also assisted in starch arrangement for increasing the ordered crystallization of starch, which may contribute to the increasing amylose content.