This invention provides improvements in tobacco expansion processes which are capable of dramatically improving tobacco throughput in high pressure tobacco impregnation systems. In accordance with various aspects of the invention, tobacco can be impregnated in a high pressure impregnation zone and removed from the zone for expansion in complete cycle times of less than one minute, typically less than about 15-30 seconds. In addition, tobacco throughputs are further improved in accordance with other aspects of the invention by achieving dramatically improved use of the available treatment space in a high pressure impregnation zone. In addition, the invention provides processes for minimizing the amount of expansion agent used to treat tobacco.