Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Treated tobacco
Description
The present invention relates to treated tobacco material. In particular, the
present
3 invention relates to tobacco that carries diluent and barrier material,
products
comprising the same and a method of producing the same.
It is known to include diluents in smoking articles such as cigarettes.
Diluents are
compounds that are vapourised during smoking and transfer to the mainstream
smoke in aerosol form. They are generally selected such that they transfer to
the
smoke substantially intact. Other components of the smoke (tobacco-derived
components in the case of tobacco-containing smoking articles) are therefore
"diluted" by this means.
A cigarette can comprise a filter at the mouth end, a tobacco rod comprising
smokable filler material, and cigarette paper wrapped around the rod. When
diluent
is present in the smokable filler material, this may be as a simple mixture
with the
other ingredients (particularly for diluents in solid form), or the diluent
may be
carried on one or more of the other ingredients (particularly if the diluent
is in
liquid form). If incorporated into the fillet material as a simple mixture,
this may
present disadvantages during manufacturing, and the diluent may be easily
dislodged
from the finished product, especially if it is in fine powder form.
Accordingly, it is
preferred for the diluent to be held in intimate contact with another
ingredient of
the filler material.
It is known for the diluent to be provided in intimate contact with the
tobacco
itself. For instance, WO 2007/012980 and US 2006/283469 describe a tobacco-
containing composition comprising added diluents, which may be administered by
spraying, admixing or soaking of the tobacco.
It has been discovered that, although the diluent is vapourised during smoking
in
the course of performing its function, vapourisation of the diluent at lower
temperatures can cause problems during storage of the cigarettes.
Specifically, the
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diluent can migrate during storage and subsequently be lost to the atmosphere
or
interact with other parts of the product such as the cigarette paper. This may
also
lead to staining or marking of the cigarette paper, either by the diluent
itself or by
compounds released from the diluent interaction.
There is therefore a need in the art to avoid migration of the diluent during
storage
of a cigarette or other smoking article.
Accordingly, the present inventors have devised the invention defined in the
claims.
Figure 1 is a schematic illustration of a treated tobacco particle found in
treated
tobacco in accordance with one embodiment of the invention.
Figure 2 is a schematic illustration of a treated tobacco particle found in
treated
tobacco in accordance with another embodiment of the invention.
Figure 3 is a schematic illustration of another treated tobacco particle.
The tobacco used in the invention may be, for example, stem, lamina, dust,
reconstituted tobacco or a mixture thereof. Suitable tobacco materials include
the
following tobacco types: Virginia or flue-cured tobacco, Burley tobacco,
Oriental
tobacco, or a blend of tobacco materials. The tobacco may be expanded, such as
dry ice expanded tobacco (DIET), or processed by any other means such as
extrusion. The stem tobacco may be pre-processed or unprocessed, and may be,
for
instance, solid stems, shredded dried stems or steam treated stems.
The diluent is at least one aerosol forming agent which may be, for instance,
a
polyol aerosol generator or a non-polyol aerosol generator, preferably a non-
polyol
aerosol generator. It may be a solid or liquid at room temperature, but
preferably is
a liquid at room temperature. Suitable polyols include sorbitol, glycerol, and
glycols
like propylene glycol or triethylene glycol. Suitable non-polyols include
monohydric
alcohols, high boiling point hydrocarbons, acids such as lactic acid, and
esters such
as diacetin, triacetin, triethyl citrate or isopropyl myristate. A combination
of
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diluents may be used, in equal or differing proportions. Triacetin, triethyl
citrate
and isopropyl myristate are particularly preferred.
Application of the diluent to the tobacco is by any suitable method known to
the
skilled person, including washing, soaking, spraying or admixture.
The diluent may reside as a surface covering on the tobacco material, and/or
at least
some may be absorbed into the material. In the present invention, however, it
is
not essential for the diluent to be in any precise location on the tobacco.
There may be several factors influencing the stability and migration of
diluents
under ambient conditions. These factors may include hydrophobicity or
hydrophilicity, viscosity, saturated vapour pressure at room temperature,
boiling
point, molecular structure (such as hydrogen bonding or Van der Waals forces)
and
the absorptive/adsorptive interaction between diluent and the tobacco. Some
diluents will suffer from migration problems to a greater extent than others;
for
instance, it has been found that triacetin, isopropyl myristate and triethyl
citrate
particularly benefit from immobilisation as in the present invention.
Another relevant factor is the loading level of the diluent. For instance, if
a diluent
such as glycerol is included in a large amount, migration problems can still
be
significant.
The diluent loading level in the present invention may depend upon the
specific
diluent. Preferably, however, the treated tobacco of the invention carries at
least
0.05 g diluent per g tobacco, more preferably at least 0.1 g diluent per g
tobacco,
more preferably at least 0.2 g diluent per g tobacco. In terms of the total
weight of
the treated tobacco, it preferably contains at least 5 % by weight diluent,
preferably
at least 10 %, 15 %, 20 % or 50%.
The barrier material is capable of inhibiting migration of the diluent during
storage
of the smoking article but allows release of the diluent during smoking of the
smoking article. It may be one that melts, decomposes, reacts, degrades,
swells or
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deforms to release the diluent at a temperature above room temperature but at
or
below the temperature reached inside a smoking article during smoking. For
instance, the physical expansion occurring with vapourisation of sufficient
levels of
diluent may break down the structure of the barrier material. In embodiments
of
the invention, the barrier material releases substantial amounts of the
diluent above
50 C, preferably above 60 C, 70 C, 80 C or 90 C.
The barrier material may be, for example, a polysaccharide or cellulosic
barrier
material, a gelatin, a gum, a gel or a mixture thereof. Suitable
polysaccharides
include an alginate, dextran, maltodextrin, cyclodextrin and pectin. Suitable
cellulosic materials include methyl cellulose, ethyl cellulose, hydroxyethyl
cellulose,
hydroxypropyl cellulose, carboxymethyl cellulose, and cellulose ethers.
Suitable
gums include gum Arabic, gum ghatti, gum tragacanth, Karaya, locust bean,
acacia,
guar, quince seed and xanthan gums. Suitable gels include agar, agarose,
carrageenans, furoidan and furcellaran.
In a preferred embodiment of the invention, the barrier material comprises a
polysaccharide. An alginate is especially preferred, due to its encapsulation
properties. The alginate may be, for instance, a salt of alginic acid, an
esterified
alginate or glyceryl alginate. Salts of alginic acid include ammonium
alginate,
triethanolamine alginate, and group I or II metal ion alginates like sodium,
potassium, calcium and magnesium alginate. Esterified alginates include
propylene
glycol alginate and glyceryl alginate.
In an embodiment, the barrier material is sodium alginate and/or calcium
alginate.
Calcium alginate provides a greater inhibition of migration of the diluent at
ambient
temperature than sodium alginate, but also may release the diluent at a higher
temperature than the latter.
The barrier material is applied to the tobacco prior to or simultaneously with
the
diluent. In an embodiment, the barrier material is applied to the tobacco
after the
diluent has been applied. Preferably, the diluent is in intimate contact with
the
tobacco.
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Application of the barrier material is by any suitable method known to the
skilled
person or described herein, which does not cause complete loss of the diluent
in the
process. Preferably, substantially no diluent is lost due to the step of
applying the
5 barrier material. In an embodiment, the method of the invention involves
spraying
of the barrier material or a precursor thereto.
For instance, the tobacco can be sprayed with an aqueous sodium alginate
solution
and dried to form a water-soluble film on the surface. Calcium ions from the
tobacco itself can at least partially gel the sodium alginate to calcium
alginate.
Calcium ions can be added to the tobacco prior to alginate treatment to
enhance
this effect. Alternatively, the tobacco can be sprayed with sodium alginate
and then
treated with a source of calcium ions to form a water-insoluble film or gel
covering
of calcium alginate.
In the resulting product of the invention, the diluent is surrounded by the
barrier
material and its migration is hindered under ambient conditions. A schematic
illustration of a treated tobacco particle found in one embodiment of the
invention
is given in Figure 1. In this embodiment, the treated tobacco particle (1) is
a
tobacco particle (2) containing diluent (3) in a first coating and optionally
also in its
cellular structure. "Pores" (5) or air gaps between the tobacco fibres are
shown;
whilst diluent (3) is shown coating a pore, it may completely fill the pore.
The
barrier material (4) forms an external coating around the tobacco particle. In
practice, the boundary between the barrier material layer and the diluent
layer may
not necessarily be a sharp one, but the barrier material will be substantially
found
external to the diluent.
Another treated tobacco particle (10) of the invention is shown in Figure 2,
in
which the barrier material and diluent have been applied to the tobacco
together
and reside inside the cellular structure and/or as a coating layer (31) on the
surface
of the particle. In an embodiment, a further coating of barrier material (4)
is then
applied to provide an additional barrier to migration.
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In an embodiment, the invention excludes treated tobacco in which the diluent
has
been pre-encapsulated with the barrier material before application to the
tobacco.
This is illustrated by tobacco particle (100) in Figure 3, in which the
diluent (3) has
been pre-encapsulated with the barrier material (4) before application to the
tobacco
(2), and so is not in intimate contact with the tobacco.
In the invention, the treated tobacco contains as much barrier material as is
required
to perform its function. This will be dependent upon the type of tobacco used.
For
example, when shredded dried stem is used, the treated tobacco may contain 1 -
10
% by weight of the barrier material, optionally 3 - 8 % by weight, optionally
4 - 6
% by weight. As will be appreciated by those skilled in the art, the amount of
barrier material by weight of expanded tobacco will be greater than with, for
instance, shredded dried stem.
The treated tobacco can be incorporated into a smoking article by conventional
means. It may be the sole tobacco used in the smoking article or may be
combined
or blended with other tobacco materials. As used herein, the term "smoking
article" includes smokeable products such as cigarettes, cigars and
cigarillos. The
term also includes so-called "heat-not-burn" products, which produce smoke or
a
smoke-like aerosol. The smoking article may be provided with a filter for the
particulate and gaseous flow drawn by the smoker. Preferably, the smoking
article
is a cigarette.
