Abstract: A food product containing starch such as extruded paste, rice grains or like fragments and particles is subjected to a treatment by a method comprising the successive steps of hydration and cooking, initial quick-freezing of grain peripheries so as to cause surface dehydration, defreezing by natural heat transfer from the center to the surface of the grains or kernels, separation of grains by mechanical milling followed by final quick-freezing right through the grains on a fluidized bed.