An improved, dual-shaft preconditioner, which is used upstream of extruders, has an independent drive mechanism coupled with a corresponding preconditioner shaft, permitting selective rotation of the shafts at speeds and directions independent of one another. Preferably, the speed differential between the shafts is at least 5:1. A digital device allows rotational speed and direction control. Ideally, the preconditioner is supported on load cells also coupled with a control device to permit on-the-go changes in material retention time within the preconditioner, which is particularly useful for the preconditioning and partial gelatinization of starch-bearing food materials, to an extent to achieve at least about 50% cook in the preconditioned materials.