WO2015101558A1

WO2015101558A1 - Method of treating whole tobacco leaf

Info

Publication number: WO2015101558A1
Application number: PCT/EP2014/079175
Authority: WO
Inventors: Lukas HOTTINGER
Original assignee: Philip Morris Products S.A.
Priority date: 2013-12-31
Filing date: 2014-12-23
Publication date: 2015-07-09

Abstract

A method of processing whole tobacco leaf for use in tobacco cut filler comprises the steps of: conditioning whole tobacco leaf to increase the moisture content; rolling the whole tobacco leaf to a thickness of between 0.1 millimetres and 0.5 millimetres; and cutting the whole tobacco leaf. Preferably, the whole tobacco leaf is rolled between two counter-rotating rollers rotating at different speeds to each other.

Description

METHOD OF TREATING WHOLE TOBACCO LEAF

The present invention relates to a method of treating whole tobacco leaf for use in tobacco cut filler. It also relates to the production of cut filler comprising tobacco leaf that has been treated using such a method.

It is known that tobacco cut filler for smoking articles may be manufactured predominantly from the lamina portion of the tobacco leaf, which is separated from the stem portion of the leaf before processing. In order to increase the amount of the tobacco material that can be used, it has also been previously proposed to add some tobacco stems back into the cut filler together with the lamina. In order to improve the taste and burning characteristics of the tobacco stem for use in the cut filler, the stems are often first subjected to one or more treatment procedures, such as rolling or expansion. The treated stems are then re-combined with the lamina to form the cut filler.

The tobacco leaf is typically separated into the lamina portion and the stem portion in a threshing process. Threshing is a complex process requiring several steps, which include the conditioning of the leaf with moisture and heat, the mechanical removal of the lamina from the stems using knives or blades and the sorting of the resultant lamina and stem portions. The threshing process may result in the undesirable physical degradation of the tobacco, the production of tobacco dust, and tobacco waste.

It would be desirable to provide a method for processing tobacco leaf for cut filler which can be carried out more effectively. It would further be desirable to provide such a method that minimises degradation of the tobacco leaf, the production of tobacco dust, and tobacco waste during the processing steps. It would be particularly desirable if such a method could be carried out using conventional apparatus, therefore making it cost efficient to implement such a method.

According to the invention there is provided a method of processing tobacco leaf comprising the steps of:

conditioning whole tobacco leaf to increase the moisture content;

rolling the whole tobacco leaf to a rolled thickness of between 0.05 millimetres and 0.5 millimetres; and

cutting the whole tobacco leaf.

The method of the present invention produces "flaked" tobacco leaf which is suitable for use in tobacco cut filler.

In the present specification, the term "whole tobacco leaf" is used to refer to a tobacco leaf which has a substantially intact structure and has not been separated into lamina and stem portions, for example in a threshing process. The "whole tobacco leaf" may be an entire leaf or a portion of a leaf, provided the lamina portion and the stem portion are present and remain substantially intact. The term "stem" is used herein to refer to the structural portion of the tobacco connecting the lamina to the stalk, and connecting the lamina to the veins or ribs that extend through the leaves between the lamina portions.

The "rolled thickness" of the rolled tobacco leaf produced by methods according to the invention refers to the distance between a first surface of the tobacco leaf that has been contacted with a rolling apparatus and a second surface of the tobacco leaf opposite the first surface that has been contacted with a rolling apparatus. For example, the "rolled thickness" of the rolled tobacco leaf may refer to the distance between an upper surface of the tobacco leaf and a lower surface of the tobacco leaf. The rolled thickness therefore corresponds to the dimension of the tobacco leaf that is reduced in size during the rolling process. The rolled thickness of an individual tobacco leaf can be measured using a conventional measuring device under a microscope. The rolled thickness of an individual tobacco leaf is taken at the point along the direction of cutting that yields the largest cross-sectional area.

In the method of the present invention, the whole tobacco leaf is processed such that it is not necessary to separate the lamina from the stem prior to the processing steps. Instead, the lamina and stem remain substantially intact and are subsequently subjected to the rolling and cutting. This advantageously eliminates the need for any threshing of the tobacco leaf before processing.

The processing of the whole leaf with the lamina and stems substantially intact has been found to minimise degradation of the leaf compared to conventional processes incorporating a threshing step. The production of tobacco dust is therefore advantageously minimised. Furthermore, the lamina and stem can be processed together in a single processing line, rather than having to provide separate processing lines for the lamina and stems as in conventional processes. The tobacco leaf can therefore be processed in a more efficient manner, both in terms of time and cost.

Advantageously, the whole tobacco leaf can be processed using conventional apparatus and techniques, for example those used in existing primary processing lines for lamina or stems. The costs of implementing the method of the present invention and incorporating the resultant tobacco leaf into cut filler are therefore minimised. Further, a tobacco product can be obtained that includes more stem material and wherein stem material blends more effectively with the lamina. The method of the present invention may be carried out on tobacco leaf from any type of tobacco plant, including but not limited to Burley tobacco, Virginia tobacco or Oriental tobacco. The method may be carried out on a single type of tobacco leaf or on a blend of two or more different types.

In the first step of the method according to the invention, the whole tobacco leaf is conditioned to increase the moisture content prior to rolling the tobacco leaf so that the leaves are sufficiently pliable to be rolled with minimal breakage, cracking or other physical damage occurring. The conditioning step additionally reduces the risk of cellular damage to the leaf as a result of the rolling. Preferably, during the conditioning step the moisture content of the whole tobacco leaf is increased to about 20 to 40 percent oven volatiles, more preferably to about 25 to 35 percent oven volatiles.

The moisture content of the tobacco material is expressed herein as "percent oven volatiles", which is determined by measuring the percentage weight loss from the tobacco leaf due to evaporation upon drying the material in an oven at 103 degrees Celsius for 100 minutes. The moisture content of the tobacco leaf can readily be determined at any stage of the treatment method using this process.

The conditioning of the whole tobacco leaf is preferably carried out by contacting the whole tobacco leaf with water, steam, or a mixture of water and steam. For example, the whole tobacco leaf may be contacted with a counter flow of steam and water while being tumbled in a rotating cylindrical drum. The whole tobacco leaf may alternatively be conditioned in a humidity chamber. In a further alternative, the whole tobacco leaf may be left to soak for a period of time in order to allow the moisture to penetrate into the internal structure of the leaves.

After the conditioning step, the whole tobacco leaf is rolled to reduce the thickness of the leaf to between about 0.05 millimetres and about 0.5 millimetres. More preferably, the whole tobacco leaf is rolled to a thickness of the leaf to between about 0.1 millimetres and about 0.4 millimetres. The rolling of the whole tobacco leaf reduces the thickness of the stem portions of the leaf such that the stem portions have a similar thickness to the lamina portions. The overall thickness of the leaf is therefore more uniform, such that the material produced after cutting has a uniform appearance. It shall be understood that, in general, the thickness of any tobacco leaf, be it a rolled leaf produced by methods according to the invention or a non- rolled leaf, varies across the leaf. In particular, there may be portions of the lamina which, by nature, are even thinner than the rolled stems. Throughout this specification, expressions such as "reduced thickness" or "reduce the thickness of the leaf" refer to a portion of the leaf the thickness of which is materially reduced by the rolling operation.

As a result of the rolling, the cellular structure of the stem portion of the leaf will typically change and this change will be visible when the leaf is viewed under a microscope. The stem portion of the leaf will additionally spread as a result of the rolling of the leaf and this will be visible to the naked eye. For cut filler tobacco produced using the disclosed method, it is typical that both the rolled stem and rolled leaf will be present. A cut filler tobacco produced using the disclosed method shall generally be more uniform and, therefore, easier to blend.

Preferably, during the rolling step of the method of the present invention, in the stem rolling machine the rollers are adjusted by the machine such that they apply a compressive force of at least about 50 tonnes to the whole tobacco leaf, more preferably at least about 70 tonnes. The rolling is preferably carried out in a single step rolling process, although in some cases a two step rolling process may be suitable. The gap between the rollers may be varied to achieve the desired rolled thickness of the tobacco leaf.

Preferably, during the rolling step the whole tobacco leaf is rolled between a pair of counter-rotating rollers. In particularly preferred embodiments, the whole tobacco leaf is rolled between a pair of counter-rotating rollers that are rotating at different speeds to each other, that is, differential speed rollers. It has advantageously been found that the use of differential speed rollers facilitates the rolling of the whole tobacco leaf to the required thickness and in particular facilitates the reduction in thickness of the stem portions of the leaf. It is believed that this is due to the stretching of the tobacco leaf as a result of the shear force to which the leaves are subjected as they pass through rollers that are travelling at different speeds to each other. In fact, if rolls rotate at approximately the same speed, the leaves are substantially subjected to a compressive force. On the other hand, with rolls rotating at different speed, the leaves are subjected to both compressive and shear loads. This stretching of the whole tobacco leaf occurring at the same time as the compression of the leaf optimises the rolling process and enables a greater overall reduction in the stem thickness. Further, the use of differential speed rollers allows for a finer particle size output.

Preferably, the counter-rotating rollers are operated such that the differential in surface speed of the rollers is at least about 5 percent, more preferably at least about 8 percent. This means that the surface speed of the faster of the two rollers is preferably at least about 5 percent greater than the surface speed of the slower roller. Preferably, the differential in surface speed of the rollers is less than about 15 percent, more preferably less than about 10 percent.

Preferably, the rollers operate at an average surface speed of between about 3 metres per second and about 8 metres per second, more preferably between about 4 metres per second and about 6 metres per second and most preferably about 5 metres per second.

In alternative embodiments, the whole leaf may be rolled between a single roller and a substantially flat surface.

Methods according to the invention further comprise the step of cutting the whole tobacco leaf to produce strips of the rolled leaves of a suitable cut width for use in cut filler. The cutting step may be carried out before or after the rolling step described above, but should always be carried out after the conditioning step. The cut width can be adjusted according to the desired use of the tobacco leaf. For example, a smaller, finer cut width may be preferred for cut filler intended for use in smoking articles, in particular slim cigarettes, than for a roll-your- own or pipe tobacco product. Preferably, the tobacco leaf is cut with a cut width between the blades of about 0.1 millimetres and about 1 .5 millimetres, more preferably between about 0.6 millimetres and about 1.2 millimetres.

After cutting, the tobacco leaf may optionally be dried to reduce the moisture content. Preferably, the moisture content is reduced to between about 10 percent and about 15 percent oven volatiles, more preferably between about 12 percent and about 14 percent oven volatiles. The drying step may be carried out at room temperature, but preferably the tobacco leaf is heated in a stream of hot air at a temperature of between about 70 degrees Celsius and about 200 degrees Celsius. Suitable apparatus for drying of the tobacco leaf include but are not limited to a rotary dryer and a flash tower dryer.

In certain embodiments, the method according to the invention may further comprise the steps of applying a casing solution to the tobacco leaf and heating the tobacco leaf with the casing solution applied. The casing solution is preferably applied after the rolling and cutting steps described above.

The casing solution may be applied to the tobacco leaf using any suitable means, including for example, spraying. The casing solution is preferably an aqueous solution comprising sugar. Typically, sugar will be the main component of the solution although a suitable humectant, such as glycerine, may be added. Optional flavour components may also be incorporated into the casing solution, if desired.

During the heating step, the tobacco leaf to which the casing solution has been applied is heated in order to bring about a reaction between the casing solution and certain components of the tobacco. This step is responsible for the main development of the flavours of the tobacco which arises as a result of the reaction of the tobacco compounds with the sugar in the casing solution.

During the heating step, the tobacco leaf is preferably heated to a temperature of at least about 50 degrees Celsius. The heating of the tobacco leaf may be carried out using any suitable means. In preferred embodiments, the tobacco leaf is heated by a stream of hot air within a dryer. The stream of hot air is preferably at a temperature of between about 70 degrees Celsius and about 140 degrees Celsius, more preferably around about 200 degrees Celsius, to bring the temperature of the tobacco leaf up to the preferred temperature of at least 50 degrees Celsius.

After the heating step, the tobacco leaf may be re-conditioned to increase the moisture content. This may be advantageous, for example, where a further cutting step is required, to ensure that the tobacco leaves are sufficiently pliable to be cut without damage or breakage. During the re-conditioning step the moisture content of the tobacco leaf is preferably increased to at least about 20 percent oven volatiles.

Methods according to the invention may be carried out on green tobacco leaf that has not been cured. This may advantageously reduce the time required for the curing of the tobacco leaf. Optionally, methods according to the invention may further comprise the step of curing the tobacco leaf after the steps of rolling and cutting. Suitable curing methods would be known to the skilled person. Alternatively, methods according to the invention may be carried out on whole tobacco leaf that has already been cured. The flaked tobacco leaf produced by the method of the present invention may advantageously be incorporated into cut filler products for use in smoking articles, either alone or in combination with other tobacco materials.

The present invention further provides a tobacco cut filler for a smoking article comprising tobacco leaf processed according to the method described above. The flaked tobacco leaf may optionally be blended with at least one type of tobacco lamina, tobacco stems, expanded tobacco, reconstituted tobacco or combinations thereof to provide the cut filler. The flaked tobacco leaf and any additional tobacco lamina or stems may include any type of tobacco leaf, including for example Burley tobacco leaf, Oriental tobacco leaf, flue-cured tobacco leaf, or a combination thereof. The expanded and reconstituted tobacco, where present, may be formed of any suitable tobacco type using known apparatus and methods.

Whole tobacco leaves treated by methods according to the invention may be incorporated into a variety of smoking articles. In particular, whole tobacco leaves treated by the methods according to the invention may be incorporated into smoking articles as such or after having undergone one or more other operations, such as a treatment with a casing solution. In some embodiments, whole tobacco leaves treated by methods according to the invention find application for the production of a cut filler that may be used in the tobacco rod of a combustible smoking article, such as a filter cigarette, cigarillo or cigar. Alternatively, the cut filler may be used to provide the tobacco aerosol generating substrate in a distillation based smoking article, or an electrically heated smoking system. Alternatively, the cut filler may be used as a roll-your-own or make-your-own product, or loose tobacco product for use in a pipe.

Tobacco products obtained by methods according to the invention may comprise at least 5 % by weight of rolled tobacco stem material, preferably at least 10 % by weight, and more preferably at least 20 % by weight. Tobacco cut fillers according to the invention may comprise up to 100 % by weight of rolled tobacco stem material, preferably up to 40 % by weight, more preferably up to 35 % by weight. For example, certain cut fillers according to the invention may contain between 5 % and 95% by weight of rolled tobacco stem material, preferably between 5% and 40% by weight, or more preferably between 10 % and 35 %.

Smoking articles comprising cut filler including flaked tobacco leaf produced using methods according to the invention may be packaged in containers, for example, containers formed of one or more folded laminar blanks. Suitable containers include but are not limited to hinge lid containers and slide and shell containers.

The invention will be further described, by way of example only:

Example A method according to the present invention is carried out on whole tobacco leaves which have been harvested from the tobacco plant but have not been subjected to any process to separate the lamina and stems, such as threshing.

The whole tobacco leaves are first conditioned in order to increase the moisture content. In the conditioning step, the tobacco leaves are placed into a cylindrical drum which is rotated to continuously move the leaves. A counter flow of steam and water is passed through the cylinder to contact the tobacco leaves until the moisture content of the tobacco leaves reaches approximately 30 percent oven volatiles.

The conditioned tobacco leaves are then rolled between counter-rotating rollers to a substantially uniform rolled thickness of 0.3 millimetres. The rollers are operated with a differential speed of 8 percent and apply a compressive force of 95 tonnes.

The conditioned rolled leaves are then mixed with other tobacco material and cut with the blades set at a standard cut width of 0.9 millimetres to form the tobacco cut filler. The tobacco cut filler is then processed into a cigarette.

It will be appreciated that the moisture levels, rolled leaf thickness, cut width and other parameters of the treatment process may be varied, as described above, depending upon the desired characteristics and intended use of the final cut filler.

Claims

1 . A method of processing tobacco leaf, the method comprising the steps of:

conditioning whole tobacco leaf to increase the moisture content;

rolling the whole tobacco leaf to a thickness of between 0.05 millimetres and 0.5 millimetres; and

cutting the whole tobacco leaf.

2. A method according to claim 1 wherein during the rolling step the whole tobacco leaf is rolled between two counter-rotating rollers rotating at different speeds to each other.

3. A method according to claim 2 wherein the differential in surface speed of the pair of counter-rotating rollers is at least 5 percent.

4. A method according to any preceding claim wherein the cutting step comprises cutting the whole tobacco leaf with blades set at a cut width of between 0.1 millimetres and 1 .5 millimetres.

5. A method according to any preceding claim wherein during the conditioning step the moisture content of the whole tobacco leaf is increased to at least 20 percent oven volatiles.

6. A method according to any preceding claim wherein the conditioning step comprises contacting the whole tobacco leaf with steam, water or a mixture of steam and water.

7. A method according to any preceding claim wherein during the rolling step a compressive force of at least 50 tonnes is applied to the whole tobacco leaf.

8. A method according to any preceding claim further comprising the steps of:

applying a casing solution to the cut rolled leaf; and

heating the cut rolled leaf with the casing solution applied.

9. A method according to claim 8 wherein the cut rolled leaf is re-conditioned after heating.

10. A tobacco cut filler obtained by the method comprising:

conditioning whole tobacco leaf to increase the moisture content;

rolling the whole tobacco leaf to a thickness of between 0.05 millimetres and 0.5 millimetres; and cutting the whole tobacco leaf.

1 1 . A tobacco cut filler according to claim 10 wherein during the rolling step the whole tobacco leaf is rolled between two counter-rotating rollers rotating at different speeds to each other.

12. A tobacco cut filler according to claim 1 1 wherein the differential in surface speed of the pair of counter-rotating rollers is at least 5 percent.

13. A tobacco cut filler according to any preceding claim wherein the cutting step comprises cutting the whole tobacco leaf to a cut width of between 0.2 millimetres and 1.5 millimetres.

14. A tobacco cut filler according to claims 10 through 13 wherein during the conditioning step the moisture content of the whole tobacco leaf is increased to at least 20 percent oven volatiles.

15. A smoking article comprising the tobacco cut filler according to claim 10.