Tobacco – Tobacco treatment – Puffing
Patent
1996-05-08
1997-06-17
Bahr, Jennifer
Tobacco
Tobacco treatment
Puffing
131296, 131300, 131303, A24B 318
Patent
active
056388349
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to the treatment of a hygroscopic material such as tea or tobacco. Such treatments are carried out, for example, with the intention of increasing the materials pliability by the introduction of moisture and heat into the material or with the intention of introducing cellular expansion. The introduction of pliability is advantageous since it reduces the material's fragility and the material becomes better able to resist mechanical damage in subsequent handling. The introduction of cellular expansion is advantageous for products made from the material where a principle judgement criteria is minimisation of the mass of material required to occupy a given volume. The relevancy of the invention can be illustrated by reference to tobacco processing.
It is well known that moisture penetration into the structure of a hygroscopic material requires a heat energy input known as the energy of moisture adsorption. This energy may be derived from the surrounding environment gradually with time, or more quickly by passing steam through the material to provide both heat and moisture.
It is well known that hygroscopic organic materials such as tobacco are thermally sensitive and that their exposure to heat will introduce chemical change and related changes in their physical properties. In particular heating of the material, while inducing temporary pliability to the product while it is at elevated temperature, will also induce chemical change so that when the material cools and loses it's temporary pliability, it's pliability at normal temperature and moisture is actually less that it was prior to the heating operation. Further the higher the temperature the material is subjected to, the less pliable and more fragile it becomes when it reverts to normal temperatures.
This is illustrated below, which shows the effect of average tobacco temperatures as it exits from an expansion process and the quantity of small particles in the tobacco after it has been reduced to normal temperature and moisture by a subsequent drying process.
______________________________________ Tobacco Concentration of
Tobacco Average temperature
Small Particles after
at Exit from Expansion
Subsequent Drying Process %
Process .degree.C.
below 1 mm
______________________________________
94 8.0
102 8.5
104 11.4
______________________________________
The results indicate that as the expansion process average temperature increases so does the quantity of small particles in the resultant tobacco product. This increase in small particles will lower the efficiency of the subsequent manufacturing process and increase the wastage of tobacco by increasing the quantity of dust removed.
It is the current expert view that tobacco cellular expansion results from an increase of water vapour pressure within the cell. One form of process equipment to achieve cellular expansion in this way is given in Patent GB2138666 in which a substantially horizontal vibrating tunnel is used to convey tobacco and steam is emitted from the base to the interior of the tunnel and passes through the transporting tobacco. That patent indicates average tobacco temperatures of 100.5.degree. C. to 120.degree. C. resulting from the use of steam at 2.5 to 25 bar and at steam temperature of 126.degree. C. to 400.degree. C.
In this apparatus steam is emitted into the tunnel in comparatively widely spaced streamlets and in practise the apparatus is operated typically with 3 to 7 bar pressure. For a tunnel 2.0 meter long by 0.4 meter wide GB2138666 utilises 7 rows of 15 holes per row and 0.8 mm diameter.
In operation an average product temperature of about 105.degree. C. results from the use of steam at 5 bar having a temperature of 152.degree. C. In practice, however, some particles of tobacco attain close to the steam temperature ie, 152.degree. C. while other particles experience fewer contacts with the steam streamlets and will only reach lower temperatures.
In consequence the resultant average tobacco temperature of
REFERENCES:
patent: 4235249 (1980-11-01), Psaras et al.
patent: 4523598 (1985-06-01), Weiss et al.
patent: 4697604 (1987-10-01), Brown et al.
patent: 4844101 (1989-07-01), Hirsch et al.
Potts Stephen Edward
White Victor Albert Montgomery
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