Apparatus and process for producing surface-worked granular product

A process of producing a surface-worked granular product, comprising:

• supplying raw granular material to a cylindrical retainer declining, with respect to the horizontal, toward a product takeout site from a raw material supply site, and having apertures and retaining sites for temporarily retaining each granule of the raw granular material circling and traveling along an inner surface of the cylindrical retainer, the cylindrical retainer having a passage for the raw granular material between the inner surface of the cylindrical retainer and a rotary working device connected to a rotary shaft extending along a central longitudinal axis of the cylindrical retainer, wherein the passage comprises a ring-shaped space extending along the central longitudinal axis, and wherein the apertures in an upper part of the cylindrical retainer are covered with an occurring dust collector of saddle shape which is installed further to cover the apertures in the upper part of an upward rotation side where rotation of the rotary working device is upward,
• floating the raw granular material in the passage of the upward rotation side by suctioning air from the occurring dust collector through the apertures, thereby creating a floated granular material in the passage of the upward rotation side,
• rotating the rotary working device to fluidize the floated granular material in the passage of the upward rotation side and to cause the floated granular material to circle and travel in a floated and fluidized state throughout a whole circumference of the passage wherein the floated granular material in the passage moves to go back and forth between the cylindrical retainer and the rotary working device in a spiral shape of total movement along the inner surface of the cylindrical retainer, thereby creating a floated and fluidized granular material,
• providing a working protrusion which extends from an outer surface of the rotary working device, and
• contacting the floated and fluidized granular material in the passage with the working protrusion to remove foreign substances and to form a number of irregular and minute scrapes on a skin layer of the floated and fluidized granular material without degeneration, denaturation or substantial removal of useful ingredients so as to impart surface characteristics on the skin layer different from the raw granular material, wherein a polishing yield of the raw granular material is 99.8 to 99.9%.