Tobacco – Tobacco treatment – Puffing
Patent
1998-10-20
2000-10-03
Derrington, James
Tobacco
Tobacco treatment
Puffing
131291, 131301, 131300, 131900, A24B 318, A24B 102
Patent
active
061258555
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for treating tobacco. More particularly, it relates to a process for expanding tobacco to increase its filling capacity.
Tobacco leaves, after harvesting, are subjected to curing processes. As a result of water loss suffered during the curing process, the leaves undergo variable shrinkage. It is conventional practice in the tobacco industry to treat cured tobacco intended for cigar or cigarette manufacture to recover the shrinkage by increasing its filling capacity. It is generally considered that by treating the tobacco in this way the cellular structure of the cured tobacco leaf is expanded to a state similar to that found in the leaf prior to curing.
A number of processes exist for increasing the filling capacity of tobacco. These are widely used within the industry to achieve product recovery after curing. The present invention is based on the discovery that filler expansion levels similar to and sometimes better than those achieved by conventionally used expansion processes and hence recovery can be achieved by the use of isopentane as the expansion medium in the vapour phase in a carefully controlled process.
Accordingly, the invention provides a process for treating tobacco comprising the series of steps: greater than 70 mbar (7 kPa); range of 70.degree. C. to 100.degree. C. and maintaining the tobacco in contact with isopentane vapour at a pressure of at least 4 bar (400 kPa) to cause impregnation of the tobacco structure; without causing damage to the structure in the tobacco; mbar/minute (10 kPa/minute); and
The tobacco which is treated according to the process of the invention will typically be in the form of pieces of cured tobacco leaf obtained by threshing, failing or slicing whole cured leaves. The tobacco may alternatively be in the form of strips cut from whole leaf or may be shredded leaf. The tobacco to be treated will typically be arranged in baskets in the processing chamber.
The cured tobacco is, according to the present invention, subjected to a reduced pressure of not greater than 70 mbar (7 kPa) i.e., to a pressure, in the chamber, of 70 mbar or lower. By this treatment, air in the processing chamber and air retained in pockets between tobacco leaf pieces or within the cell structure which would otherwise interfere with the subsequent impregnation of the cellular structure by the isopentane vapour is removed. The application of a pressure above 70 mbar does not sufficiently remove occluded air in the tobacco and, as a result, the subsequent impregnation of the tobacco cellular structure by isopentane vapour is impaired. Preferably, the pressure in the chamber is reduced to below 25 mbar (2.5 kPa), more preferably to about 10 mbar (1 kPa), to remove air from within the tobacco structure to enable optimum replacement by isopentane vapour in the subsequent stage of the process. Isopentane vapour is then pumped into the processing chamber. It is important in the invention that no liquid isopentane is allowed to enter the process chamber. Therefore, liquid isopentane stored outside the process chamber is injected in the chamber through a vaporiser which forms isopentane vapour at between 70.degree. C. and 100.degree. C. before it is able to come into contact with the tobacco. Since isopentane is a highly volatile and flammable solvent, engineering design of the process and recovery system must be carefully undertaken. The temperature of the isopentane vapour entering the chamber will be in the range of from 70.degree. C. to 100.degree. C. although on contacting the tobacco in the chamber the temperature may be reduced to from 60.degree. to 80.degree. C. Isopentane vapour having a temperature greater than 100.degree. C. should not be introduced into the chamber since it impairs the subsequent steam expansion treatment and does not enable sufficient expansion of the tobacco to be achieved. Furthermore, if the vaporiser is set to produce isopentane vapour at a temperature less than 70.degree. C. there is a risk that liquid isopentane might pass th
REFERENCES:
patent: 3575178 (1971-04-01), Stewart
patent: 3683937 (1972-08-01), Fredrickson et al.
patent: 3753440 (1973-08-01), Ashburn
Chard Brian Chester
Henneveld Clifford Hendrik
Matthews Keith Alan
Nevett Robert
Derrington James
Imperial Tobacco Limited
Walls Dionne A.
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