Note: Descriptions are shown in the official language in which they were submitted.
~ ~35 2~
Background of the Invention
The present invention relates to a process for increas-
ing the filling power of tobacco. More particularly, the
present invention relates to a process for expanding tobacco
which includes overwetting the tobacco with water and rapidly
overdrying the overwetted tobacco in a turbulent steam atmos-
phere.
The heretofore known expansion processes may be broadly
characterized as involving penetration or impregnation of the
tobacco with a blowing or puffing agent, sometimes referred
to hereinafter as an "impregnant", which when removed during
a subsequent expansion step generates elevated pressure in
the tobacco and thereby causes expansion of the cell volume.
The impregnant may be a solid, a liquid, or a gas.
Among the impregnants which have been employed are
pressurized steam, air, water, organic solvents, ammonia,
carbon dioxide, combinations of ammonia and carbon dioxide,
and compounds capable of liberating a gas when subjected to
chemical decomposition, as by heating. Where gases or other
chemicals are utilized to cause or aid in expansion, physio-
chemical changes may occur in the tobacco.
'
~ Among the means disclosed for removing the impregnant
- to expand the cell volume are a sudden reduction in pressure,
freeze-dryingt convection heating, radiant transfer, and the
application of a microwave field.
33~20
However, some of the aforementioned processes provide only
a low level of expansion.
Processes employing water as an impregnant ha~e
tended to produce a more satisfactory result with tobacco
stems than with tobacco lamina filler. It may be that the
greater permeability of the leaf structure permits the
water impregnant to escape before substantial expansion
can take place. Removal of the water impregnant has
typically been effected by such techni~ues as freeze-drying
or exposure to a micxowave field. ~reeze-drying is a
comparatively slow and expensive approach and may result,
in some instances, in a product which has an objectionable
amount of tackiness because of the hygroscopicity of a
film-like layer of water-extracted solids which forms on
the surface of the tobacco. The use of a microwave field
requires elaborate and expensive e~uipment and may tend to
be more effective with tobacco stems than with tobacco
lamina filler.
Many of the prior art processes possess various
disadvantages, most of which can be generally categorized
as requiring prolonged treatment, batch processing and
high energy usage. The process o~ the present invention
offers advantages over many of these prior art processes
and does not require foreign agents or chemical additives
to achieve the objective of significantly increas~d filling
power by expansion of the tobacco, which may be cut filler
or the like.
Definitions
.
Oven Volatiles (OV)
As used herein, oven volatiles is the percent
weight loss of tobacco in a circulating air oven in three
(
3 5 2 ~
hours at 100C. OV is used herein to mean the-"moisture
content" of -the tobacco.
Filling Power
As used herein, filling power is the ability of
5- the material to provide a firm rod. The filling power is
the minimum weight of tobacco which will produce a tobacco
rod of specified dimensions and firmness and may be measured
as the volume occupied by a specified ~eight of filler in
an upright cylinder when a specified piston weight is
applied to its top surface, as set forth in "Filling
Volume of Cut Tobacco and Cigarette Hardness", H. Wakeham,
et al., Tohacco Science xx: 164 167, 1976. Standard
equilibrium conditions for measurement of filling power
are usually 60% relative humidity (RH) at 75F (23.9C).
Cylinder Volume (CV)
As used herein, cylinder volume is a measurement
of filling power and is determined by placing 10.0 grams
of filler in a standard metal cylinder, 3.358 cm. in
diameter~ and then vibrating the assembly for one-half
minute to settle the tobacco column. The tobacco is then
compressed under a piston ~eighing 1875 grams and having a
diameter of 3.335 cm for five minutes and the volume reading
is then taken. The standard deviation of the cylinder
volume measurement is about 1.5%.
Summary of the Invention
The present invention provides a process for
~ expanding tobacco by means of overwetting the tobacco to a
; moisture content of at least 20% and then overdrying the
tobacco in a period of a few seconds in a turbulent steam
E~ .
- - ~
3 ~ ~ 0
atmosphere to a moisture content below the moisture co~tent
normally encountered in processing. It has been determined
that such overdrying must occur to a moisture content of
less than 7% to achieve increased filling power.
Description of Preferred Embodiments
According to the process of the present invention,
tobacco lamina or cut tobacco filler is moisturized to a
moisture content of at least 20% which is above the moisture
level of unprocessed tobacco and appreciably above the
normal 12% processing moisture level of tobacco. It has
been found that when tobacco having a moisture content
above 20% is treated according to the process of the present
invention, significant increases in filling power are
; achieved. At a moisture content of 20%, expansion may
also be attained by rapidly overdrying the tobacco according
to the process of the present invention, but the chemical
and physical properties of the tobacco will have a greater
influence on the effectiveness of the process.
Preferably, the moisture content of the tobacco
is from 20% to about 80%, and more preferably from about
30% to about 80%, although moisture contents within the
range of 20% to about 40% are effectively employed.
Moisture contents of about 60% to about 80% may be effec-
tively employed, but penetration or bulking time will
probably increase and drying the tobacco within the desired
times and to the desired post-treatment moisture levels
will be more expensive and time consuming.
It i9 desired that the moisture be allowed to
substantially uniformly penetrate and be distributed or
dispersed throughout the cellular structure of the tobacco
~ .
3 ~ 2 ~
being processed, although homogeneous dispersion is not
required. The bulking penetration time for satisfactory
penetration will depend upon batch size and upon the means
of addition of the water and the desired economics.
Employing a rotary cylinder and a fine mist spray or other
- conventional mixing system known in the art for incorporating
additives, a penetration time of ~ hours or somewhat less
will be sufficient, as is ~urther illustrated in Example 5.
The primary criterion is that the time of penetration be
sufficient to allow the moisture to be distributed within
and absorbed by the tobacco cellular structure of substantial
por-tions of the tobacco. Typically, the o~erwetted tobacco
is bulked from about 1/4 hour to about 4 hours.
As previously stated, after penetration of the
moisture throughout the tobacco structure, the tobacco is
overdried in a period of a few seconds in a turbulent
steam atmosphere. The term "overdrying" in the context of
the present invention means drying the overwetted tobacco
to a moisture content below the moisture contents typically
encountered and utilized in the processing of tobacco.
The normal or conventional moisture content of tobacco to
be processed, particularly that of commonly used tobacco
filler, is usually approximately about 12% to about 21%.
Rapid drying of the tobacco, preferably within
less than 5 seconds, in a turbulent steam atmosphere to a
moisture content of less than 7% expands the tobacco as
the moisture rapidly escapes the tobacco cellular structure.
The cellular structure of the tobacco fibers thereupon
stiffen to retain the expanded nature of the tobacco during
remoisturization to normal processin~ moisture contents.
(
~lG35~0
Preferably, the tobacco is dried to a moisture content of
less than 5% and more preferably to a moisture content of
less than 3%, with drying to a moisture content of 2% to
3% being particularly preferred. Steam drying versus air
drying produces substantial gains in filling power as will
be noted from Example 2.
To achieve and retain the desired expansion, it
has been found that the more rapid the drying, the more
effective the process. In effect, an almost immediate
evaporation of the moisture is sought. Drying times of
5 seconds or less are desired to achieve a 2% to 5% moisture
content, if not even a lower moisture content. The more
rapid the drying step, the more rapid the evolution of the
moisture and the more effective the expansion. Residence
times longer than 5 seconds do not appear to produce the
- desired expansion levels.
To rapidly overdry -the tobacco, a high turbulence
drying unit such as a Proctor & Schwartz dispersion dryer,
or a Jetstream~ dryer or other equivalent drying tower,
capable of producing a turbulent atmosphere high in steam
content, may be utilized. The proportion of steam in the
turbulent steam drying atmosphere is desirably at least
about 60%, and preferably at least about 80% although
~ steam contents of about 60% to about 70% can be effectively
; 25 employed.
With regard to the treatment temperature, that
is, the temperature of the turbulent steam atmosphere in
the drying unit, at temperatures of at least about 232C
and employing properly designed and reasonably efficient
equipment which allows rapid drying of the moisturized
3 ~
tobacco in a period of seconds, the moisture content of
the overwetted tobacco may be reduced to less than about
5% to produce economically significant increases in filling
power. Rapid drying in a turbulent steam atmosphere at a
treatment temperature of at least about 316C, and preerably
from about 316C to about 330C provides substantial -
increases in filling power. As will be seen in Example 3,
treatment temperatures of about 121C provide little
useful increase in filling power; temperatures from about
lQ 149C to about 204C provide perceptible gains in filling
power; temperatures from about 232C to about 288C provide
moderate increases in filling power, and temperature of
from about 288C to about 316C provide significant increases
in filling power. Further, in accordance with the practice
of the present invention, turbulent steam atmospheres
- having temperatures as high as 500C. may be successfully
utilized.
Subsequent to overdrying, the tobacco is prefer-
ably remoisturized under mild conditions, by means and
processes well known in the industry for reordering tobacco,
such as cylinder reordering, to achieve a processing
moisture content of about 12%. The reordering should be
at a moderate rate to prevent loss of expanded fiber
rigidity.
The following examples present illustrative but
non-limiting embodiments of the present invention. Com-
parative examples are also presented.
,
Example 1
Five pounds of bright cut filler were placed in
a small rotary cylinder and sprayed with a fine water mist
until the moisture content was raised to 30% water by
~ . .
~ ~i3~i2~
weight. The filler was allowed to bulk for 4 ,lours and
was then dried in a steam atmosphere in a high turbulence
drying tower at 316C for 4 seconds. The rapidly dried
filler was allowed to equilibrate for 18 hours at 21C and
60% RH after which OV and CV measurements were taken and
compared to an untreated control. The results are summa-
rized below in Table 1.
Table 1
Processed Untreated
: 10 - Tobacco Control
Tower Exit OV, % 1.8 --
Equilibrated OV, % 11.8 12.3
Equilibrated CV, cc/lOg
; (Filling Power) 54.2 36.4
CV, cc/lOg (corrected to
12% OV) 52.7 38.7
% Gain in CV 36.2 --
Example 2
Two 5-pound samples of bright cut filler were
processed as in Example 1 except that Sample 2 was dried
in a tower at 316C. in the absence of steam. The results
are summarized below in Table 2.
Table 2
. . .
Sam~le Untreated
i 2Control
Initial OV, % 30 30 --
Tower Exit OV, % 1.7 1.8 --
Equilibrated OV, % 11.6 11.9 12.4
Equilibrated CV cc/lOg. 56.9 43.3 35.7
0 CV, cc/lOg (corrected to
12% OV) 53.9 42.6 38.6
% Gain in CV 39.3 10.1 --
Tower Atmosphere Steam Air --
- ~ ~G3.~0
It can be seen when comparing a sample dried in
a turbulent steam atmosphere with a sample dried in an air
atmosphere that significant gains in filling power are
achieved employing a turbulent steam atmosphere.
Example 3
. .
50 pounds of bright filler were moisturized and
bulked as in Example 1. Samples of the overwetted filler
were processed in a steam atmosphere in a high turbulence
drying tower at 121C, 149C, 177C, 204C, 232C, 26QC,
288C, 316C and 330C in a time period of 4 seconds or
less. The results are summarized in Table 3 below and
illustrate the significant gains in filling power which
are achieved by overdrying the overwetted tobacco at
elevated tempçratures in a turbulent steam atmosphere.
.
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Example 4
Seven 5-pound samples of bright filler were
overwetted and bulked to moisture contents of 15%, 20%,
25%, 30%, 40~, 60% and 80% respectively. Each sample was
then processed in a tower dryer containing a turbulent
-~ steam atmosphere and at the treatment temperature indicated
in Table 4 below to less than a~out 1.5% OV in the indicated
treatment time or less. The moisture levels of 60% and
: 80~ required two passes through the tower to achieve the
desired overdrying to a moisture level of 1.5% OV. ~he
results of these runs are summariæed below in Table 4 and
indicate that the desired increases in filling power are
achieved with tobacco overwetted to moisture contents in
excess of 20%.
11
r ~35 2~
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.
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Example 5
Fifty pounds of bright filler were moisturized
: and equilibrated as in Example 1. The ~iller was allowed
to bulk, and portions were removed after 1/4, 1/2, 1, 2,
3, 4 and 24 hours of bulking. The 7 sample portions were
rapidly dried in a tower containing a turbulent steam
atmosphere at 316C. The results are summarized in Table 5
below.
Table 5
10Initial
Bulking Moisture Tower CV, cc/lOg
~ime Content Exit (Equilibrated
~ Sam~ Hours ) (V?, /Q OV~ % at 12% OV )
1 1/4 30 2.0 53
15 2 1/2 30 2.1 54
3 1 30 2.0 56
. 4 2 30 2.2 57
S 3 30 1.9 58
~: 6 4 30 1.9 57
20 7 24 30 2.0 57
The results indicate that bulking from 4 to
24 hours has no significant effect upon the filling power
increase as compared with bulking from 1/4 hour to 4 hours
and that bulking is not a critical consideration.
,
13
~ ~(i3~2~
Examj~le 6
Fifty pounds of bright filler were processed as
in Example 1. The processed filler, after reordering, had
a filling power of 56 cc/lOg, corrected to 12% moisture.
Cigarettes were made in which 15% of the conventional
filler was replaced by the processed filler and the subjec-
tive qualities of these cigarettes were compared with
those of standard~production cigarettes. There were no
major subjective differences and the cigarettes containing
the 15% expanded tobacco were found to be equally satisfying
and to have full flavor.
It will be understood that the particular er~odi-
ments of the invention described above in Examples 1
through 6 are only illustrative of the principles of the
invention, and that various modifications ca~ be made by
those skilled in the art without departing from the scope
and spirit of the invention.
:;:
,
~ .
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14
