Abstract: A method of and an apparatus for crushing raw materials such as fruit and vegetables while heating the raw materials by using a heating medium such as steam or an inactive heating gas in an enclosed device from which the outside air is excluded.

Abstract: Expanded porous tobacco stems with a low apparent density and an excellent quality of smoking taste are obtained by heating under a pressurized atmosphere tobacco stems separated from tobacco leaves, as such or after moisturization, at a temperature of 150.degree. to 300.degree. C. and a pressure of 3 kg/cm.sup.2 (gage) or more in the presence of superheated steam for a period of 30 seconds or less and suddenly releasing the pressure to effect expansion of the stems. The resulting expanded stems are shredded into cut tobacco stems or made into reconstituted tobacco sheet to provide a tobacco material of excellent filling capacity.