U.S. patent application number 11/023582 was filed with the patent office on 2005-05-26 for burley tobacco products having reduced nitrosamine content.
This patent application is currently assigned to Regent Court Technologies LLC. Invention is credited to Williams, Jonnie R..
Application Number | 20050109357 11/023582 |
Document ID | / |
Family ID | 27536975 |
Filed Date | 2005-05-26 |
United States Patent
Application |
20050109357 |
Kind Code |
A1 |
Williams, Jonnie R. |
May 26, 2005 |
Burley tobacco products having reduced nitrosamine content
Abstract
A method of treating tobacco to reduce the content of, or
prevent formation of, harmful nitrosamines which are normally found
in tobacco is disclosed. The method includes the step of subjecting
at least a portion of the plant, while the portion is uncured and
in a state susceptible to having the amount of nitrosamines reduced
or formation of nitrosamines arrested, to a controlled environment
capable of providing a reduction in the amount of nitrosamines or
prevention of the formation of nitrosamines, for a time sufficient
to reduce the amount of or substantially prevent the formation of
at least one nitrosamine, wherein the controlled environment is
provided by controlling at least one of humidity, rate of
temperature change, temperature, airflow, CO level, CO.sub.2 level,
O.sub.2 level, and arrangement of the tobacco plant. Tobacco
products and an apparatus for producing such tobacco products are
also disclosed.
Inventors: |
Williams, Jonnie R.;
(Manakin-Sabot, VA) |
Correspondence
Address: |
BANNER & WITCOFF
1001 G STREET N W
SUITE 1100
WASHINGTON
DC
20001
US
|
Assignee: |
Regent Court Technologies
LLC
Town and Country
MO
|
Family ID: |
27536975 |
Appl. No.: |
11/023582 |
Filed: |
December 29, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11023582 |
Dec 29, 2004 |
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10141117 |
May 9, 2002 |
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10141117 |
May 9, 2002 |
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09668144 |
Sep 25, 2000 |
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6425401 |
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09668144 |
Sep 25, 2000 |
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09397018 |
Sep 15, 1999 |
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6202649 |
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09668144 |
Sep 25, 2000 |
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08998043 |
Dec 23, 1997 |
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08998043 |
Dec 23, 1997 |
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08879905 |
Jun 20, 1997 |
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6135121 |
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08879905 |
Jun 20, 1997 |
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08757104 |
Dec 2, 1996 |
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5803081 |
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60100372 |
Sep 15, 1998 |
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Current U.S.
Class: |
131/347 ;
131/364 |
Current CPC
Class: |
A24B 3/18 20130101; A24B
15/22 20130101; A24B 15/18 20130101; A24B 15/245 20130101 |
Class at
Publication: |
131/347 ;
131/364 |
International
Class: |
A24B 015/22 |
Claims
I claim:
1. A tobacco product comprising cured non-green or yellow Burley
tobacco suitable for human consumption, substantially free of
organic liquids used to extract expanded organic materials and
having a collective content of N'-nitrosonornicotine,
4-(N-nitrosomethylamino)-1-(3-pyridyl)-- 1-butanone,
N'-nitrosoanatabine and N'-nitrosoanabasine which is 0.05 .mu.g/g
or less.
2. The tobacco product of claim 1, wherein said tobacco suitable
for human consumption is cured yellow tobacco.
3. The tobacco product of claim 1, which is a product selected from
the group consisting of cigarettes, cigars, chewing tobacco, snuff
and tobacco-containing gum and bits.
4. A tobacco product comprising cured non-green or yellow Burley
tobacco suitable for human consumption, in leaf form and having a
collective content of N'-nitrosonornicotine,
4-(N-nitrosomethylamino)-1-(3-pyridyl)-- 1-butanone,
N'-nitrosoanatabine and N'-nitrosoanabasine which is 0.05 .mu.g/g
or less.
5. The tobacco product of claim 4, wherein said tobacco suitable
for human consumption is cured yellow tobacco.
6. The tobacco product of claim 4, which is a product selected from
the group consisting of cigarettes, cigars, chewing tobacco, snuff
and tobacco-containing gum and bits.
7. A tobacco product comprising cured non-green or yellow Burley
tobacco suitable for human consumption, substantially free of
organic liquids used to extract expanded organic materials and
having a content of
4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone which is 0.002
.mu.g/g or less.
8. The tobacco product of claim 7, wherein said content of
4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone is 0.001 .mu.g/g
or less.
9. The tobacco product of claim 7, wherein said tobacco suitable
for human consumption is cured yellow tobacco.
10. A tobacco product comprising cured non-green or yellow Burley
tobacco suitable for human consumption, in leaf form and having a
content of 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone which
is 0.002 .mu.g/g or less.
11. The tobacco product of claim 10, wherein said content of
4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone is 0.001 .mu.g/g
or less.
12. The tobacco product of claim 10, wherein said tobacco suitable
for human consumption is cured yellow tobacco.
13. A tobacco product comprising cured non-green or yellow United
States Burley tobacco suitable for human consumption, substantially
free of organic liquids used to extract expanded organic materials
and having a collective content of N'-nitrosonornicotine,
4-(N-nitrosomethylamino)-1-(- 3-pyridyl)-1-butanone,
N'-nitrosoanatabine and N'-nitrosoanabasine which is less than 0.2
.mu.g/g.
14. The tobacco product of claim 13, wherein said collective
content is 0.15 .mu.g/g or less.
15. The tobacco product of claim 14, wherein said collective
content is 0.1 .mu.g/g or less.
16. The tobacco product of claim 15, wherein said collective
content is 0.05 .mu.g/g or less.
17. The tobacco product of claim 13, wherein said tobacco suitable
for human consumption is cured yellow tobacco.
18. The tobacco product of claim 13, which is a product selected
from the group consisting of cigarettes, cigars, chewing tobacco,
snuff and tobacco-containing gum and bits.
19. A tobacco product comprising cured non-green or yellow United
States Burley tobacco suitable for human consumption, in leaf form
and having a collective content of N'-nitrosonornicotine,
4-(N-nitrosomethylamino)-1-(- 3-pyridyl)-1-butanone,
N'-nitrosoanatabine and N'-nitrosoanabasine which is less than 0.2
.mu.g/g.
20. The tobacco product of claim 19, wherein said collective
content is 0.15 .mu.g/g or less.
21. The tobacco product of claim 20, wherein said collective
content is 0.1 .mu.g/g or less.
22. The tobacco product of claim 21, wherein said collective
content is 0.05 .mu.g/g or less.
23. The tobacco product of claim 19, wherein said tobacco suitable
for human consumption is cured yellow tobacco.
24. The tobacco product of claim 19, which is a product selected
from the group consisting of cigarettes, cigars, chewing tobacco,
snuff and tobacco-containing gum and bits.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No.
10/141,117, filed May 9, 2002, which is a continuation of
application Ser. No. 09/668,144, filed Sep. 25, 2000, now U.S. Pat.
No. 6,425,401, which is a continuation of application Ser. No.
09/397,018, filed Sep. 15, 1999, now U.S. Pat. No. 6,202,649, which
is based on provisional application Ser. No. 60/100,372, filed Sep.
15, 1998, and which is a continuation-in-part of application Ser.
No. 08/998,043, filed Dec. 23, 1997, now abandoned, which in turn
is a continuation-in-part of application Ser. No. 08/879,905, filed
Jun. 20, 1997, now U.S. Pat. No. 6,135,121, which in turn is a
continuation-in-part of Ser. No. 08/757,104, filed Dec. 2, 1996,
now U.S. Pat. No. 5,803,081. U.S. provisional application Ser. No.
60/100,372, U.S. application Ser. Nos. 08/998,043 and 08/879,905,
and U.S. Pat. No. 5,803,081 are all incorporated herein by
reference in their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to an improved method of
treating tobacco to reduce the content of, or to prevent the
formation of, harmful nitrosamines, which are normally found in
tobacco. The present invention also relates to tobacco products
having low nitrosamine content.
BACKGROUND OF THE INVENTION
[0003] Prior attempts to reduce tar and harmful carcinogenic
nitrosamines primarily have included the use of filters in smoking
tobacco. In addition, attempts have been made to use additives to
block the effects of harmful carcinogens in tobacco. These efforts
have failed to reduce the oncologic morbidity associated with
tobacco use. It is known that fresh-cut, green tobacco has
virtually no nitrosamine carcinogens. See, e.g., Wiernik et al,
"Effect of Air-Curing on the Chemical Composition of Tobacco,"
Recent Advances in Tobacco Science, Vol. 21, pp. 39 et seq.,
Symposium Proceedings 49th Meeting Tobacco Chemists' Research
Conference, Sep. 24-27, 1995, Lexington, Ky. (hereinafter "Wiernik
et al."). On the other hand, cured tobacco products obtained
according to conventional methods are known to contain a number of
nitrosamines, including the harmful carcinogens
N'-nitrosonornicotine (NNN) and
4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK). It is
widely accepted that such nitrosamines are formed post-harvest,
during the conventional curing process, as described further
herein. Unfortunately, fresh-cut green tobacco is unsuitable for
smoking or other consumption.
[0004] It is believed that tobacco-specific nitrosamines (TSNAs)
are formed primarily during the curing process. While not wishing
to be bound by theory, it is believed that the amount of
tobacco-specific nitrosamine (TSNA) in cured tobacco leaf is
dependent on the accumulation of nitrites, which accumulate during
the death of the plant cell and are formed during curing by the
reduction of nitrates under conditions approaching an anaerobic
(oxygen deficient) environment. It is believed that the reduction
of nitrates to nitrites occur by the action of the micro flora on
the surface of the leaf under anaerobic conditions, and it is also
believed that this reduction is particularly pronounced under
certain conditions (e.g., humid conditions). Furthermore, during
the curing process, the tobacco leaf emits carbon dioxide, which
can further dilute oxygen levels in the environment.
[0005] Once the nitrites are formed, these compounds are believed
to combine with various tobacco alkaloids, including
pyridine-containing compounds, to form carcinogenic
nitrosamines.
[0006] In 1993 and 1994, Burton et al. at the University of
Kentucky carried out certain experiments regarding TSNA, as
reported in the Abstract, "Reduction of Nitrite-Nitrogen and
Tobacco N'-Specific Nitrosamines In Air-Cured Tobacco By Elevating
Drying Temperatures," Agronomy & Phytopathology Joint Meeting,
CORESTA, Oxford 1995. Burton et al reported that drying harvested
tobacco leaves for 24 hours at 71.degree. C., at various stages of
air curing, including end of yellowing (EOY), EOY+3, EOY+5, etc.
resulted in some reduction of nitrosamine levels. Reference is also
made to freeze drying and microwaving of certain samples, without
detail or results. It has been confirmed that in the actual work
underlying this Abstract, carried out by Burton et al. at the
University of Kentucky, the microwave work was considered
unsuccessful. Certain aspects of Burton et al.'s 1993-94 study are
reported in Wiernik et al, supra, at pages 54-57, under the heading
"Modified Air-Curing." The Wiernik et al article postulates that
subjecting tobacco leaf samples, taken at various stages of
air-curing, to quick-drying at 70.degree. C. for 24 hours, would
remove excess water and reduce the growth of microorganisms; hence,
nitrite and tobacco-specific nitrosamine (TSNA) accumulation would
be avoided. In Table II at page 56, Wiernik et al. includes some of
Burton et al's summary data on lamina and midrib nitrite and TSNA
contents in the KY160 and KY171 samples. Data from the
freeze-drying and the quick-drying tests are included. The article
contains the following conclusion:
[0007] It can be concluded from this study that it may be possible
to reduce nitrite levels and accumulation of TSNA in lamina and
midrib by applying heat (70.degree. C.) to dark tobacco after loss
of cell integrity in the leaf. Drying the tobacco leaf quickly at
this stage of curing reduces the microbial activity that occurs
during slow curing at ambient temperature. It must be added,
however, that such a treatment lowers the quality of the tobacco
leaf.
[0008] Id. at page 56. The Wiernik et al. article also discusses
traditional curing of Skroniowski tobacco in Poland as an example
of a 2-step curing procedure. The article states that the tobacco
is first air-cured and, when the lamina is yellow or brownish, the
tobacco is heated to 65.degree. C. for two days in order to cure
the stem. An analysis of tobacco produced in this manner showed
that both the tobacco-specific nitrosamine (TSNA) and the nitrite
contents were low, i.e., in the range of 0.6-2.1 micrograms per
gram and less than 10 micrograms per gram, respectively. Wiernik et
al. theorized that these results were explainable due to the rapid
heating which does not allow further bacterial growth. Wiernik et
al. also noted that tobacco-specific nitrosamine (TSNA) and nitrite
contents of 0.2 microgram per gram and less than 15 micrograms per
gram, respectively, were obtained for tobacco subjected to
air-curing in Poland.
[0009] In practice, tobacco leaves are generally cured according to
one of three methods. First, in some countries, such as China, a
variation of the flue curing process (described below) is still
being used on a commercial scale to cure tobacco leaves.
Specifically, this variation of the flue curing process features
the use of a heat exchanger and involves the burning of fuel and
the passing of heated air through flue pipes in a curing barn.
Accordingly, in this older version of the curing process, primarily
radiant heat emanating from the flue pipes is used to cure the
tobacco leaves. While a relatively low flow of air does pass
through the curing barn, this process utilizes primarily radiant
heat emanating from the flue pipes to cure the tobacco leaves
within the barn. In addition, this process does not appreciate, and
does not provide for, controlling the conditions within the barn to
achieve prevention or reduction of TSNAs. This technique has been
largely replaced in the United States by a different flue-curing
process.
[0010] For more than twenty years, the heat exchanger method
described above has been supplanted in the U.S. with a more
economical version which features the use of a propane burner. This
second method is the so-called "flue curing" method. This process
involves placing the tobacco leaves in a barn and subjecting the
leaves to curing with the application of convective heat using a
hot gaseous stream that includes combustion exhaust gases. When
convective heat is used to dry the tobacco leaves, the combustion
exhaust gases (including carbon monoxide, carbon dioxide, and
water) are passed directly through the tobacco. In processes where
convective heat is used for curing, no attempt is made to separate
the heat from the combustion exhaust gases (i.e., to prevent an
anaerobic condition) or to control the ambient conditions to reduce
or suppress the formation of TSNAs.
[0011] The third method is known as "air curing." This process
involves placing the tobacco leaves in a barn and subjecting the
leaves to air curing without controlling the ambient conditions
(e.g., air flow through the barn, temperature, humidity, and the
like) and without the application of any heat.
[0012] U.S. Pat. No. 2,758,603 to Heljo discloses a process for
treating tobacco with relatively low moisture levels (i.e., already
cured tobacco) with radio frequency energy to accelerate the aging
process. Although the patent states that the tobacco being treated
is "green" tobacco, it is clear that the patent is using the term
"green" in a non-conventional sense because the tobacco being
treated therein is already cured (i.e., the tobacco is already
dried). This is clearly evident from the disclosed moisture levels
for the tobacco being treated in the Heljo patent. In fact, Heljo
rehydrates the fully cured tobacco prior to the radio frequency
treatment. By contrast, in the present invention, the term "green
tobacco" refers to freshly harvested tobacco, which contains
relatively high levels of moisture.
[0013] Additionally, the use of microwave energy to dry
agricultural products has been proposed. For example, use of
microwave energy to cure tobacco is disclosed in U.S. Pat. No.
430,806 to Hopkins. Further, U.S. Pat. No. 4,898,189 to Wochnowski
teaches the use of microwaves to treat green tobacco in order to
control moisture content in preparation for storage or shipping. In
U.S. Pat. No. 3,699,976, microwave energy is described to kill
insect infestation of tobacco. Still further, techniques using
impregnation of tobacco with inert organic liquids (U.S. Pat. No.
4,821,747) for the purposes of extracting expanded organic
materials by a sluicing means have been disclosed wherein the
mixture was exposed to microwave energy. In another embodiment,
microwave energy is disclosed as the drying mechanism of extruded
tobacco-containing material (U.S. Pat. No. 4,874,000). In U.S. Pat.
No. 3,773,055, Sturgis discloses the use of microwave to dry and
expand cigarettes made with wet tobacco.
[0014] Using a novel breakthrough curing technology, U.S. Pat. No.
5,803,081 to Williams discloses a method of reducing the
nitrosamine levels or preventing the formation of nitrosamines in a
harvested tobacco plant using microwave energy.
[0015] In U.S. Pat. No. 6,338,348 to Williams, a process for
reducing the amount of or preventing the formation of nitrosamines
in harvested tobacco plant is disclosed, wherein the process
comprises subjecting at least a portion of the plant to microwave
radiation, while the portion is uncured and in a state susceptible
to having the amount of nitrosamines reduced or formation of
nitrosamines arrested, for a time sufficient to reduce the amount
of, or substantially prevent formation of, at least one
nitrosamine.
[0016] Further, U.S. Pat. No. 6,311,695 to Williams discloses that
microwave and other types of radiation are useful for treating
tobacco to reduce the amount of, or prevent the formation of,
nitrosamines in tobacco.
BRIEF SUMMARY OF THE INVENTION
[0017] It has now been discovered that by controlling the
conditions to which tobacco leaves are subjected to within the
curing barn during the curing process, the formation of TSNAs in
the tobacco product can be prevented or reduced. The parameters
that can be varied to control the conditions within the curing barn
(or curing apparatus) during the curing process include humidity,
rate of temperature change, temperature, the time of treatment of
the tobacco, the airflow (through the curing apparatus or barn), CO
level, CO.sub.2 level, O.sub.2 level, and the arrangement of the
tobacco leaves.
[0018] By controlling the conditions during the curing process
within certain parameters, it is believed that it is now possible
to prevent or reduce the formation of microbes capable of causing
the formation of TSNAs in the tobacco. Thus, under the conditions
contemplated for the present invention, it is believed that there
would be little or no nitrites available for the formation of TSNAs
by reaction of the nitrites with various tobacco alkaloids. For
example, it is postulated that if the conditions are made aerobic,
the microbes will consume the oxygen in the atmosphere for their
energy source, and therefore no nitrites will form. Further, it is
believed that the microbes are "obligate" anaerobes, and thus when
they are subjected to certain conditions, they will be suppressed
and cannot participate in the formation of nitrites.
[0019] Accordingly, one object of the present invention is to
substantially eliminate or reduce the content of nitrosamines in
tobacco intended for smoking or consumption by other means.
[0020] Another object of the present invention is to reduce the
carcinogenic potential of tobacco products, including cigarettes,
cigars, chewing tobacco, snuff and tobacco-containing gum and
lozenges.
[0021] Still another object of the present invention is to
substantially eliminate or significantly reduce the amount of
tobacco-specific nitrosamines, including N'-nitrosonornicotine
(NNN), 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK),
N'-nitrosoanatabine (NAT) and N'-nitrosoanabasine (NAB), in such
tobacco products.
[0022] Another object of the present invention is to treat uncured
tobacco at an appropriate time post-harvest so as to arrest the
curing process without adversely affecting the tobacco's
suitability for human consumption.
[0023] Another object of the present invention is to reduce the
content of tobacco-specific nitrosamines by treating uncured
tobacco in a controlled environment.
[0024] Yet another object of the present invention is to reduce the
content of tobacco-specific nitrosamines, particularly NNN and NNK,
and metabolites thereof in humans who smoke, consume or otherwise
ingest tobacco in some form, by providing a tobacco product
suitable for human consumption, which product contains a
substantially reduced quantity of tobacco-specific nitrosamines,
thereby lowering the carcinogenic potential of such product. The
tobacco product may be a cigarette, cigar, chewing tobacco or a
tobacco-containing gum or lozenge.
[0025] Yet another object is to provide a novel curing barn (or
curing apparatus) which is capable of providing tobacco suitable
for human consumption, wherein the tobacco contains relatively low
levels to zero tobacco-specific nitrosamines.
[0026] In one embodiment, the above and other objects and
advantages in accordance with the present invention can be obtained
by a process for reducing the amount of or preventing the formation
of nitrosamines in a harvested tobacco plant, comprising subjecting
at least a portion of the plant, while said portion is uncured and
in a state susceptible to having the amount of nitrosamines reduced
or formation of nitrosamines arrested, to a controlled environment
capable of providing a reduction in the amount of nitrosamines or
prevention of the formation of nitrosamines, for a time sufficient
to reduce the amount of or substantially prevent the formation of
at least one nitrosamine, wherein said controlled environment is
provided by controlling at least one of humidity, rate of
temperature change, temperature, airflow, CO level, CO.sub.2 level,
O.sub.2 level, and the arrangement of the tobacco leaves.
[0027] In a preferred embodiment of the invention, the step of
subjecting tobacco leaf to the controlled environment is carried
out on a tobacco leaf or portion thereof after onset of yellowing
in the leaf and prior to substantial accumulation of
tobacco-specific nitrosamines in the leaf. It is also preferred
that in the process of the invention, the step of subjecting the
tobacco leaf to the controlled environment is carried out prior to
substantial loss of the leafs cellular integrity.
[0028] It is also preferred in accordance with the present
invention that the tobacco leaf or a portion thereof is subjected
to the controlled environment for a time sufficient to effectively
dry the leaf, without any charring when heat is applied, so that it
is suitable for human consumption.
[0029] The present invention also seeks to subject tobacco leaves
to the controlled environment to prevent normal accumulation of at
least one tobacco-specific nitrosamine, such as
N'-nitrosonornicotine,
4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone,
N'-nitrosoanatabine and N'-nitrosoanabasine.
[0030] In another embodiment, the process of the invention further
comprises treating the tobacco leaves, while in a state susceptible
to having the content of at least one TSNA prevented or reduced, to
microwave energy or other forms of high energy treatment.
[0031] The present invention in its broadest forms also encompasses
a tobacco product comprising non-green tobacco suitable for human
consumption and having a lower content of at least one
tobacco-specific nitrosamine than conventionally cured tobacco.
[0032] In another embodiment, the present invention relates to a
novel curing barn which is capable of providing a controlled
environment in which the formation of tobacco-specific nitrosamines
can be prevented or reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 illustrates a tobacco-curing apparatus according to
the present invention.
[0034] FIG. 2 illustrates the air-handling device/heat exchanger
system of the tobacco-curing apparatus according to the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0035] For purposes of the invention, the phrase "controlling the
conditions" means determining and selecting an appropriate
humidity, rate of temperature change, temperature, time of
treatment of the tobacco, airflow, CO level, CO.sub.2 level,
O.sub.2 level, and arrangement of the tobacco leaves to prevent or
reduce the formation of at least one TSNA. For a given set of
ambient conditions, it may be necessary to adjust, within the
curing apparatus or barn, one or more of these parameters. For
example, it is possible to prevent or reduce the formation of TSNAs
by simply setting a high airflow through the curing apparatus or
barn. In other situations, it is possible to produce the tobacco
products of the present invention with low airflow, provided that
other parameters such as humidity, temperature, etc. are
appropriately selected.
[0036] In this disclosure, tobacco that has been "conventionally
cured" is tobacco that has been air-cured or flue-cured, without
the controlled conditions described herein, according to
conventional methods commonly and commercially used in the U.S.
[0037] Further, the term "green tobacco" means tobacco that is
substantially uncured and is particularly inclusive of freshly
harvested tobacco.
[0038] In flue curing processes that utilize a heat exchanger
capable of providing relatively low airflow through the curing
barn, I have discovered that it is possible to somewhat reduce the
TSNA levels by not venting combustive exhaust gases into the curing
apparatus or barn. The preferred aspects of the present invention
are premised on the discovery that other parameters, as identified
above (e.g., airflow), can be adjusted to ensure the prevention or
reduction of at least one TSNA regardless of the ambient
conditions. Thus, even under the most extreme conditions (i.e.,
conditions that enhance the formation of TSNAs), it is possible to
achieve the prevention or reduction of at least one TSNA.
[0039] It has been said that the practice of tobacco curing is more
of an art than a science, because curing conditions during any
given cure must be adjusted to take into account such factors as
varietal differences, differences in leaves harvested from various
stalk positions, differences among curing barns in terms of where
they are used, and environmental variations during a single season
or over multiple seasons, especially in terms of weather
fluctuations during air-curing. For example, the practice of flue
curing is empirical to a certain degree, and is optimally carried
out by individuals who have accumulated experience in this art over
a significant period of time. See, e.g., Peele et al, "Chemical and
Biochemical Changes During The Flue Curing Of Tobacco," Recent
Advances In Tobacco Science, Vol. 21, pp. 81 et seq., Symposium
Proceedings 49th Meeting Chemists' Research Conference, Sep. 24-27,
1995, Lexington, Ky. (hereinafter "Peele et al"). Thus, one of
ordinary skill in the art of tobacco curing would understand that
the outer parameters of the present invention, in its broadest
forms, are variable to a certain extent depending on the precise
confluence of the above factors for any given harvest.
[0040] In one embodiment, the present invention is founded on the
discovery that a window exists during the tobacco curing cycle, in
which the tobacco can be treated in a manner that will essentially
prevent the formation of TSNA. Of course, the precise window during
which TSNA formation can be effectively eliminated or substantially
reduced depends on the type of tobacco and a number of other
variables, including those mentioned above. In accordance with this
embodiment of the present invention, the window corresponds to the
time frame post-harvest when the leaf is beyond the fresh-cut or
"green" stage, and prior to the time at which TSNAs and/or nitrites
substantially accumulate in the leaf. This time frame typically
corresponds to the period in which the leaf is undergoing the
yellowing process or is in the yellow phase, before the leaf turns
brown, and prior to the substantial loss of cellular integrity.
(Unless otherwise clear from the context, the terms "substantial"
and "significant" as used herein generally refer to predominant or
majority on a relative scale, give or take.) During this time
frame, the leaves are susceptible to having the formation of TSNAs
substantially prevented, or the content of any already formed TSNA
reduced, by subjecting the tobacco to a controlled environment
capable of providing a reduction in the amount of nitrosamines or
prevention of the formation of nitrosamines, for a time sufficient
to reduce the amount of or substantially prevent the formation of
at least one nitrosamine, wherein said controlled environment is
provided by controlling at least one of humidity, rate of
temperature change, temperature, airflow, CO level, CO.sub.2 level,
O.sub.2 level, and arrangement of the tobacco leaves. This
treatment of the tobacco essentially arrests the natural formation
of TSNAs, and provides a dried, golden yellow leaf suitable for
human consumption. If TSNAs have already begun to substantially
accumulate, typically toward the end of the yellowing phase, the
treatment according to the present invention effectively arrests
the natural TSNA formation cycle, thus preventing any further
substantial formation of TSNA. When yellow or yellowing tobacco is
treated in this fashion at the most optimal time in the curing
cycle, the resulting tobacco product has TSNA levels essentially
approximating those of freshly harvested green tobacco, while
maintaining its flavor and taste. In addition, the nicotine content
of the tobacco product according to the present invention remains
unchanged, or is substantially unchanged, by the treatment
according to the present invention. Accordingly, the tobacco
product of the present invention has relatively low contents of
TSNAs, and yet the user of the tobacco product can experience the
same sensations that are obtainable from using conventional tobacco
products.
[0041] As discussed above, it is believed that tobacco-specific
TSNAs are formed primarily during the curing process. Specifically,
it is believed that the amount of TSNAs in cured tobacco leaf is
dependent on the accumulation of nitrites, which are formed during
the curing process by reduction of nitrates to nitrites under
conditions approaching an anaerobic (i.e., oxygen deficient)
environment. The nitrites accumulate during the death of the plant
cell. Experimental evidence suggests that the nitrites are formed
by the micro flora on the surface of the leaf under conditions
approaching an anaerobic environment. If, for example, conditions
are made aerobic, the microbes will consume the oxygen in the
atmosphere for their energy source, and thus, no nitrites will
form. Once nitrites are formed, however, they can then combine with
various tobacco alkaloids, including pyridine-containing compounds,
to form carcinogenic substances such as nitrosamines.
[0042] In one conventional curing technique, the combustion exhaust
gases pass through the tobacco, thereby creating a condition
approaching an anaerobic environment. This conventional curing
technique utilizes air that is normally recirculated within the
curing barn and is often air having high humidity. Conventional
curing has been developed over time without any appreciation for
subjecting tobacco to a controlled environment for the purpose of
eliminating or reducing TSNAs. Accordingly, such conventional
curing techniques do not provide suitable conditions (e.g.,
adequate oxygen flow) and fail to prevent an anaerobic condition in
the vicinity of the tobacco leaves. Additionally, during such
conventional curing processes, the tobacco leaves will emit carbon
dioxide, which will further dilute the oxygen present in the curing
environment. Under such anaerobic conditions, it is believed that
the micro flora reduce nitrates to nitrites. Consequently, TSNA are
formed and become part of the tobacco product that is ultimately
consumed by the tobacco user.
[0043] The present invention is applicable to the treatment of
harvested tobacco, which is intended for human consumption. Much
research has been performed on tobacco, with particular reference
to tobacco-specific nitrosamines (i.e., TSNAs). Freshly harvested
tobacco leaves are called "green tobacco" and contain no known
carcinogens, but green tobacco is not suitable for human
consumption. The process of curing green tobacco depends on the
type of tobacco harvested. For example, Virginia flue (bright)
tobacco is typically flue-cured, whereas Burley and certain dark
strains are usually air-cured. The flue-curing of tobacco typically
takes place over a period of five to seven days compared to about
one to two or more months for air-curing. According to Peele et al,
flue-curing has generally been divided into three stages: yellowing
(35-40.degree. C.) for about 36-72 hours (although others report
that yellowing begins sooner than 36 hours, e.g., at about 24 hours
for certain Virginia flue strains), leaf drying (40-57.degree. C.)
for 48 hours, and midrib (stem) drying (57-75.degree. C.) for 48
hours. Many major chemical and biochemical changes begin during the
yellowing stage and continue through the early phases of leaf
drying.
[0044] In a typical flue-curing process, the yellowing stage is
carried out in a barn. During this phase the green leaves gradually
lose color due to chlorophyll degradation, with the corresponding
appearance of the yellow carotenoid pigments. According to the
review by Peele et al, the yellowing stage of flue-curing tobacco
is accomplished by closing external air vents in the barn, and
holding the temperature at approximately 35.degree.-37.degree. C.
The yellowing stage typically lasts about 3 to 5 days. After the
yellowing stage, the air vents are opened, and the heat is
gradually and incrementally raised. Over a period of about 5 to 7
days from the end of yellowing, the tobacco product is dried. Thus,
this process utilizes a somewhat controlled environment, but the
controlled environment is insufficient to ensure the prevention or
reduction of nitrosamines as in the present invention.
Specifically, the process during the yellowing maintains the
relative humidity in the barn at approximately 85%, limits moisture
loss from the leaves, and allows the leaf to continue the metabolic
processes that has begun in the field. The goal of the flue-curing
process is merely to obtain a dry product that has a lemon or
golden orange color. In the flue-curing process, there is no
appreciation for subjecting the tobacco leaves to a set of
controlled conditions in order to ensure the prevention or
reduction of TSNAs.
[0045] With one particular variety of Virginia flue tobacco on
which testing has been carried out as described herein, freshly
harvested green tobacco is placed in a barn for about 24-48 hours
at about 100-110.degree. F. until the leaves turn more or less
completely yellow. The yellow tobacco has a reduced moisture
content, i.e., from about 90 weight % when green, versus about
70-40 weight % when yellow. At this stage, the yellow tobacco
contains essentially no known carcinogens, and the TSNA content is
essentially the same as in the fresh-cut green tobacco. This
Virginia flue tobacco typically remains in the yellow stage for
about 6-7 days. At the end of curing, Virginia flue tobacco
typically has a moisture content of about 11 to about 15 weight
percent. The conversion of the tobacco during the curing process
results in formation and substantial accumulation of nitrosamines,
and an increased microbial content. The exact mechanism by which
tobacco-specific nitrosamines are formed is not clear, but is
believed to be enhanced by microbial activity, involving microbial
nitrate reductases in the generation of nitrite during the curing
process.
[0046] As previously mentioned, tobacco-specific nitrosamines are
believed to be formed upon reaction of amines with nitrite-derived
nitrosating species, such as NO.sub.2, N.sub.2O.sub.3 and
N.sub.2O.sub.4 under acidic or anaerobic conditions. Wiernik et al
discuss the postulated formation of TSNAs at pp. 43-45, the
discussion being incorporated herein by reference; a brief synopsis
is set forth below.
[0047] Tobacco leaves contain an abundance of amines in the form of
amino acids, proteins, and alkaloids. The tertiary amine nicotine
(referenced as (1) in the diagram below) is the major alkaloid in
tobacco, while other nicotine-type alkaloids are the secondary
amines nornicotine (2), anatabine (3) and anabasine (4). Tobacco
also generally contains up to 5% of nitrate and traces of
nitrite.
[0048] Nitrosation of nornicotine (2), anatabine (3), and anabasine
(4) gives the corresponding nitrosamines: N'-nitrosonornicotine
(NNN, 5), N'-nitrosoanatabine (NAT, 6), and N'-nitrosoanabasine
(NAB, 7). Nitrosation of nicotine (1) in aqueous solution affords a
mixture of 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK,
8) (NNN, 5) and 4-(N-nitrosomethylamino)-4-(3-pyridyl)-1-butanal
(NNA, 9). Less commonly encountered TSNAs include NNAL
(4-N-nitrosomethylamino)-1-(3-pyridyl)-1-b- utanol, 10), iso-NNAL
(4-N-nitrosomethylamino)-4-(3-pyridyl)-1-butanol, 11) and iso-NNAC
(4-(N-nitrosomethylamino)-4-(3-pyridyl)-butanoic acid, 12). The
formation of these TSNAs from the corresponding tobacco alkaloids
is shown schematically below, using the designations 1-12 above
(reproduced from Wiernik et al, supra, p. 44, and incorporated
herein by reference): 1
[0049] It is now generally agreed that green, freshly harvested
tobacco contains virtually no nitrite or TSNA, and that these
compounds are generated during curing and storage of tobacco.
Studies have been made during the past decade to try to determine
the events related to the formation of TSNA during curing of
tobacco, and several factors of importance have been identified.
These include plant genotype, plant maturity at harvest, curing
conditions and microbial activity.
[0050] Studies have shown that nitrite and TSNA accumulate on
air-curing at the time intervals starting after the end of
yellowing and ending when the leaf turns completely brown, e.g.,
2-3 weeks after harvest for certain air-cured strains, and
approximately a week or so after harvest in flue-cured varieties.
This is the time during which loss of cellular integrity occurs,
due to moisture loss and leakage of the content of cells into the
intercellular spaces. Therefore, there is a short window in time
during air-curing when the cells have disintegrated, making the
nutrition available for microorganisms. Wiernik et al have
suggested that nitrite may then substantially accumulate as a
result of dissimilatory nitrate reduction, thus rendering formation
of TSNA possible.
[0051] There are a few published reports on the effects of
microbial flora on the tobacco leaf during growth and curing and on
cured tobacco, as cited in Wiernik et al. However, the involvement
of microbial nitrite reductases in the generation of nitrate during
curing is presumed. When cell structure is broken down after the
yellow phase, and nutrients are made accessible to invading
microorganisms, these may produce nitrite under favorable
conditions, i.e., high humidity, optimal temperature and anoxia.
There is normally a rather short "window" in time when the water
activity is still sufficiently high, and the cell structure has
disintegrated.
[0052] In accordance with one embodiment of the present invention,
the formation of nitrosamines in a harvested tobacco plant is
substantially prevented or arrested by a process, comprising
subjecting at least a portion of the plant, while said portion is
uncured and in a state susceptible to having the amount of
nitrosamines reduced or formation of nitrosamines arrested, to a
controlled environment capable of providing a reduction in the
amount of nitrosamines or prevention of the formation of
nitrosamines, for a time sufficient to reduce the amount of or
substantially prevent the formation of at least one nitrosamine,
wherein said controlled environment is provided by controlling at
least one of humidity, rate of temperature change, temperature,
airflow, CO level, CO.sub.2 level, O.sub.2 level, and arrangement
of the tobacco leaves.
[0053] In accordance with preferred embodiments of the present
invention, non-green and/or yellow tobacco products can be obtained
which are suitable for human consumption, and which have a lower
content of at least one tobacco-specific nitrosamine than
conventionally cured tobacco. Green or fresh-cut tobacco is
generally unsuitable for human consumption as noted above;
"non-green" as used herein means the tobacco has at least lost the
majority of chlorophyll, and includes without limitation partially
yellow leaves, full yellow leaves, and leaves which have begun to
turn brown in places.
[0054] The present invention is applicable to all strains of
tobacco, including flue or bright varieties, Burley varieties, dark
varieties, oriental/Turkish varieties, etc. Within the guidelines
set forth herein, one of ordinary skill in the art could determine
the most efficient time in the cure cycle for carrying out the
treatment step to achieve the objects and advantages of the present
invention.
[0055] Although the airflow through the barn may vary on a
case-by-case basis and may be dependent on the arrangement of the
tobacco leaves to be treated (i.e., the degree of tobacco leaf
surface exposure) and the size of the curing apparatus or barn, the
minimum flow of air is preferably about ten percent higher than the
flow of flue gas commonly used in the prior art. As discussed
above, however, it is within the scope of the present invention to
provide relatively low airflow, provided that other parameters
(e.g., humidity, temperature, etc.) are selected so that the
prevention or reduction of at least one TSNA is achieved.
[0056] The specific minimum flow of air needed for a given set of
conditions may be determined on a routine basis given the
disclosure of the present invention.
[0057] To maximize the effects of the present invention, the
humidity of the heated or unheated air is desirably controlled
using a commercially-available dehumidifier or humidifier.
Preferably, the heated or unheated air flow comprises dehumidified
air with a humidity level of less than about 85%, more preferably
less than about 60%, most preferably less than about 50%.
[0058] In one aspect, the air is fresh outside air, while the
heated air is substantially free from combustion exhaust gases
including water vapor, carbon monoxide, and carbon dioxide.
[0059] In addition, the air may be recirculated as long as an
anaerobic condition is avoided.
[0060] The temperature within the curing barn of the present
invention may range from ambient (i.e., outside) temperature to as
high as about 250.degree. F. or more, without charring the tobacco
product. If heated air (i.e., convective heat) is used to
accelerate the drying of the tobacco product, suitable temperatures
may range anywhere from about 100.degree. F. to about 250.degree.
F., more preferably from about 160.degree. F. to about 170.degree.
F. However, the optimum temperature within the curing barn can be
determined for each case, depending on the overall conditions of
the environment and the tobacco product being treated.
[0061] The determination of the time for treating the tobacco
according to the process of the present invention can be determined
by trial and error. Typically, the treatment time may be from about
48 hours up to about 2 weeks.
[0062] The arrangement of the tobacco leaves is not critical, but
it is advantageous to provide the highest exposed surface area for
the tobacco leaves.
[0063] While it is not essential, it may be desirable to expose the
tobacco product to UV light, either simultaneously with, or
separately from, the treatment described above. It is believed that
this UV light exposure can further reduce the amount of TSNA
accumulation. For example, the UV light can be supplied using
"Germicidal Sterilamp" tubes obtained from Philips Lighting,
wherein the light has wavelengths of between 100 and 280 nm.
[0064] Although the curing process as described above is preferable
over microwave curing techniques because microwaving requires moist
tobacco whereas the inventive curing process does not, it is within
the scope of the present invention to further treat the tobacco
product with microwave or other high energy treatment, as described
in U.S. Pat. Nos. 6,338,348 and 6,311,695, respectively, both of
which are incorporated herein by reference. This additional
microwave or other high energy treatment is conveniently performed
within the window of time in which it is possible to further
prevent or reduce the formation of at least one TSNA. While U.S.
Pat. Nos. 6,338,348 and 6,311,695 are incorporated herein by
reference, the preferred aspects of the microwaving or other high
energy treatment are described below.
[0065] The process of this invention may further comprise a
microwaving process for reducing the amount of or preventing
formation of nitrosamines in a harvested tobacco plant, which
microwaving process comprises subjecting at least a portion of the
plant to microwave radiation, while said portion is uncured and in
a state susceptible to having the amount of nitrosamines reduced or
formation of nitrosamines arrested, for a sufficient time to reduce
the amount of or substantially prevent formation of at least one
nitrosamine.
[0066] It is preferred that in this aspect of the process of the
invention, the step of subjecting to microwave radiation is carried
out on a tobacco leaf or portion thereof after onset of yellowing
in the leaf and prior to substantial accumulation of
tobacco-specific nitrosamines in the leaf. It is also preferred
that in this aspect of the process of the invention, the step of
subjecting to microwave radiation is carried out prior to
substantial loss of the leafs cellular integrity. Using microwave
energy eliminates the potential for activation of the microbes that
cause TSNAs in tobacco, particularly in tobacco that has been
rehydrated.
[0067] The term "microwave radiation" as used herein refers to
electromagnetic energy in the form of microwaves having a frequency
and wavelength typically characterized as falling within the
microwave domain. The term "microwave" generally refers to that
portion of the electromagnetic spectrum which lies between the
far-infrared region and the conventional radio frequency spectrum.
The range of microwaves extends from a wavelength of approximately
1 millimeter and frequency of about 300,000 MHz to wavelength of 30
centimeters and frequency of slightly less than about 1,000 MHz.
The present invention preferably utilizes high power applications
of microwaves, typically at the lower end of this frequency range.
Within this preferred frequency range, there is a fundamental
difference between a heating process by microwaves and by a
classical way, such as by infrared (for example, in cooking): due
to a greater penetration, microwaves generally heat quickly to a
depth several centimeters while heating by infrared is much more
superficial. In the United States, commercial microwave
apparatuses, such as kitchen microwave ovens, are available at
standard frequencies of approximately 915 MHz and 2450 MHz,
respectively. These frequencies are standard industrial bands. In
Europe, microwave frequencies of 2450 and 896 MHz are commonly
employed. Under properly balanced conditions, however, microwaves
of other frequencies and wavelengths would be useful to achieve the
objects and advantages of the present invention.
[0068] Microwave energy can be generated at a variety of power
levels, depending on the desired application. Microwaves are
typically produced by magnetrons, at power levels of 600-1000 watts
for conventional kitchen-level microwave apparatuses (commonly at
about 800 watts), but commercial units are capable of generating
power up to several hundred kilowatts, generally by addition of
modular sources of about 1 kilowatt. A magnetron can generate
either pulsed or continuous waves of suitably high frequency.
[0069] The applicator (or oven) is a necessary link between the
microwave power generator and the material to be heated. For
purposes of the present invention, any desired applicator can be
used, so long as it is adapted to permit the tobacco plant parts to
be effectively subjected to the radiation. The applicator should be
matched to the microwave generator to optimize power transmission,
and should avoid leakage of energy towards the outside. Multimode
cavities (microwave ovens), the dimensions of which can be larger
than several wavelengths if necessary for large samples, are
useful. To ensure uniform heating in the leaves, the applicator can
be equipped with a mode stirrer (a metallic moving device which
modifies the field distribution continuously), and with a moving
table surface, such as a conveyor belt. The best results are
attained by single leaf thickness exposure to microwave radiation,
as opposed to stacks or piles of leaves.
[0070] In preferred embodiments of the invention, the microwave
conditions comprise microwave frequencies of about 900 MHz to about
2500 MHz, more preferably about 915 MHz and about 2450 MHz, power
levels of from about 600 watts up to 300 kilowatts, more preferably
from about 600 to about 1000 watts for kitchen-type applicators and
from about 2 to about 75 kilowatts, more preferably from about 5 to
about 50 kilowatts, for commercial multimode applicators. The
heating time generally ranges from at least about 1 second, and
more generally from about 10 seconds up to about 5 minutes. At
power levels of about 800-1000 watts the heating time is preferably
from about 1 minute to about 21/2 minutes when treating single
leaves as opposed to piles or stacks. For commercial-scale
applicators using higher power levels in the range of, e.g., 2-75
kilowatts, heating times would be lower, ranging from about 5
seconds up to about 60 seconds, and generally in the 10-30 second
range at, say, 50 kilowatts, again for single leaves as opposed to
piles or stacks. Of course, one of ordinary skill in the art would
understand that an optimal microwave field density could be
determined for any given applicator based on the volume of the
cavity, the power level employed, and the amount of moisture in the
leaves. Generally speaking, use of higher power levels will require
less time during which the leaf is subjected to the microwave
radiation.
[0071] However, the above-described conditions are not absolute,
and given the teachings of the present invention, one of ordinary
skill in the art would be able to determine appropriate microwave
parameters. The microwave radiation is preferably applied to the
leaf or portion thereof for a time sufficient to effectively dry
the leaf, without charring, so that it is suitable for human
consumption. It is also preferred to apply the microwave radiation
to the leaf or portion thereof for a time and at a power level
sufficient to reduce the moisture content to below about 20% by
weight, more preferably about 10% by weight.
[0072] It is also preferred in accordance with the present
invention that the microwave radiation is applied to the leaf or
portion thereof for a time sufficient to effectively dry the leaf,
without charring, so that it is suitable for human consumption.
[0073] It is also possible to use forms of electromagnetic
radiation having higher frequencies and shorter wavelengths than
the microwave domain discussed above and in more detail below, can
be used to achieve the basic objects of the present
invention--reduction or substantial elimination of TSNAs in tobacco
products, by treating the tobacco with such energy forms in the
same time frame post-harvest as discussed above with regard to the
microwave embodiment. Thus, the present invention further comprises
a method for reducing the amount of or preventing formation of
nitrosamines in a harvested tobacco plant, comprising subjecting at
least a portion of the plant to radiation having a frequency higher
than the microwave domain, while said portion is uncured and in a
state susceptible to having the amount of nitrosamines reduced or
formation of nitrosamines arrested, for a sufficient time to reduce
the amount of or substantially prevent formation of at least one
nitrosamine.
[0074] As with the microwave embodiments, it is preferred that in
the process of the invention, the step of subjecting to radiation
having a frequency higher than the microwave domain is carried out
on a tobacco leaf or portion thereof after onset of yellowing in
the leaf and prior to substantial accumulation of tobacco-specific
nitrosamines in the leaf. It is also preferred that in the process
of the invention, the step of subjecting to such radiation is
carried out prior to substantial loss of the leafs cellular
integrity. Preferred energy sources capable of producing such
radiation are described further below, and include far-infrared and
infrared radiation, UV (ultraviolet radiation), soft x-rays or
lasers, accelerated particle beams such as electron beams, x-rays
and gamma radiation.
[0075] On a scale within the electromagnetic spectrum where
microwaves are generally defined as inclusive of those forms of
electromagnetic radiation having a frequency of 10.sup.11 Hz and a
wavelength of 3.times.10.sup.-3 meters, such energy sources
include, without limitation, far-infrared and infrared radiation
having frequencies of about 1012 to 1014 Hz and wavelengths of
3.times.10.sup.-4 to 3.times.10.sup.-6 meters, ultraviolet
radiation having frequencies of about 10.sup.16 to 10.sup.18 Hz and
wavelengths of 3.times.10.sup.-8 to 3.times.10.sup.-10 meters, soft
x-rays or lasers, cathode rays (a stream of negatively charged
electrons issuing from the cathode of a vacuum tube perpendicular
to the surface), x-rays and gamma radiation typically characterized
as having frequencies of 10.sup.21 Hz and higher at corresponding
wavelengths.
[0076] As would be apparent to one of ordinary skill in the art,
the greater the dose of radiation delivered by the energy source,
the less time the leaves need to be subjected thereto to achieve
the desired results. Typically, radiation application times of less
than one minute, preferably less than 30 seconds and even more
preferably less than about ten seconds are needed when using such
higher frequency radiation sources. Defined another way, radiation
application times of at least about one second are preferred.
However, the exposure rate can be controlled to deliver the
radiation dosage over time, if desired. For example, 1 megarad of
radiation can be delivered instantaneously, or at a predetermined
exposure rate. When using high frequency radiation sources, it is
preferred to use an amount of radiation which achieves at least a
50% reduction in TSNAs, in comparison to untreated samples. While
the particular radiation dosages and exposure rate will depend on
the particular equipment and type of radiation source being
applied, as would be apparent to one of ordinary skill in the art,
it is generally preferred to subject the tobacco samples to
radiation of from about 0.1 to about 10 megarads, more preferably
from about 0.5 to about 5 megarads, and more preferably from about
0.75 to about 1.5 megarads.
[0077] It is preferred that the microwaving or other high energy
treatment, as described above, is conducted after subjecting the
tobacco to the controlled environment of the present invention.
However, it is also possible to conduct the optional microwaving or
high energy treatment prior to subjecting the tobacco to the
controlled environment of the present invention.
[0078] The treatment according to the present invention, with or
without microwaving or other high energy treatment, may be
performed in conventional barns as well as large-scale processing
centers capable of treating tens of acres of tobacco. It is also
possible to perform the process of the present invention in any
size, including miniature curing apparatuses or barns.
[0079] On a bench scale, the treatment of the tobacco product
according to the present invention, using airflow and temperature
control, would be similar to treating tobacco product using a
convective heating air oven or treating the tobacco product using a
clothes dryer. Thus, it is within the present invention to operate
the process of the present invention in a convective heating air
oven or a clothes dryer, although these apparatuses are not within
the scope of the curing apparatus or barns as defined in the
appended claims.
[0080] In another embodiment, the present invention relates to a
tobacco product comprising cured non-green or yellow tobacco
suitable for human consumption and having a content of at least one
tobacco-specific nitrosamine selected from N'-nitrosonornicotine
(NNN), 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK),
N'-nitrosoanatabine (NAT) and N'-nitrosoanabasine (NAB) which is
less than about 50% by weight of the content of said at least one
tobacco-specific nitrosamine in conventionally cured tobacco, more
preferably less than about 75% by weight, most preferably less than
about 95% by weight, without the use of organic solvent
extraction.
[0081] Thus, it is possible to reduce the TSNA content by about 97%
or more by practicing the present invention, even down to "food
safe" TSNA levels.
[0082] For example, the NNN level of the tobacco product according
to the present invention is typically less than about 0.05 .mu.g/g,
the combined NAT and NAB level is typically less than about 0.10
.mu.g/g, and the NNK level is typically less than about 0.05
.mu.g/g. Further, the combined TSNA level is typically less than
about 0.16 .mu.g/g, even as low as less than about 0.009
.mu.g/g.
[0083] Thus, in yet another aspect of the present invention, the
tobacco product according to the present invention comprises cured
non-green or yellow tobacco having a NNN content less than about
0.05 .mu.g/g.
[0084] In a further aspect, the tobacco product of the present
invention comprises cured non-green or yellow tobacco having a
combined NAT and NAB content of less than about 0.10 .mu.g/g.
[0085] Still further, the tobacco product of the present invention
comprises cured non-green or yellow tobacco having a NNK content of
less than about 0.05 .mu.g/g.
[0086] Additionally, the present invention also contemplates
tobacco product comprising cured non-green or yellow tobacco having
a total TSNA content of less than about 0.16 .mu.g/g.
[0087] In a preferred embodiment, the tobacco product of the
present invention has a NNN level of less than about 0.05 .mu.g/g,
a combined NAT and NAB level of less than about 0.10 .mu.g/g, and a
NNK level less than about 0.05 .mu.g/g.
[0088] The tobacco product according to the present invention can
be converted to various final tobacco products, including, but not
limited to, cigarettes, cigars, chewing tobacco, snuff and
tobacco-containing gum and lozenges.
[0089] In yet another embodiment, the present invention is directed
to an apparatus for curing tobacco products comprising: an enclosed
or substantially enclosed container comprising a base frame,
optionally at least one wall, optionally a roof, and optionally a
door; an air handling device capable of providing an air flow of at
least about 25,0000 CFM, wherein said air flow is at least
partially and at least temporarily in communication with the
interior of said container; and a heat exchanger capable of
providing at least about 1,000,000 BTU/hr.
[0090] If desired, the container may be in the form of a mobile
unit with transport means. The container may be constructed to any
suitable size typical of tobacco curing barns. For example, tile
container may have a width of about 120 inches, a depth of 60
inches, and a height of 82 inches. It is possible to provide a
container that is significantly smaller or larger than this
exemplified container size. In addition, the container may be
insulated.
[0091] The container may comprise means that are capable of
receiving the tobacco products to be cured. Preferably, these means
are arranged so that the tobacco product is exposed for optimal
curing.
[0092] Preferably, the air circulation within the container may be
of a vertical or horizontal draft design, with the flow of air
being in any suitable direction, with manually or automatically
controlled fresh air dampers and weighted exhaust dampers.
[0093] The heat exchanger is preferably constructed of stainless
steel. The heat exchanger system is preferably supplied with a
flame detector, igniter wire, sensor cable, dual valve gas train
and/or air proving switch. The burner setting can be variable. As
mentioned previously, however, it is possible to carry out the
process of the present invention without the use of any heat. That
is, the process can be conducted using simply a sufficient flow of
air.
[0094] In the present invention, the apparatus for curing the
tobacco products uses air that is free from combustion exhaust
gases, such as carbon monoxide and carbon dioxide. However, it
should be noted that with sufficient airflow, the effects of the
present invention can be realized even with air containing
combustion exhaust gases.
[0095] Reference is now made to the drawings. FIG. 1 shows a
container (1) and an air handling device/heat exchanger system (2).
FIG. 2 shows the air handling device/heat exchanger system (2) in
greater detail. It can be seen from FIG. 2 that the exhausts (3) of
the heat exchanger system is far removed from the air intakes (4)
to minimize the possibility of combustion exhaust gases being
introduced into the curing apparatus. Further, unlike conventional
curing barns, the curing apparatus of the present invention
features an externalized air handling device/heat exchanger
system.
[0096] The following examples illustrate the advantages of the
present invention.
EXAMPLES
[0097] In each of the examples described below, five grams of
ground tobacco were placed in a 300-ml Erlenmeyer flask and
suspended in 150-ml water to which 5 ml of 20% ammonium sulfamate
in 3.6 N H.sub.2SO.sub.4 was added to prevent the artificial
formation of TSNA during extraction. Prior to shaking on the
wrist-action shaker overnight, the flask was capped using parafilm
and wrapped up in aluminum foil to prevent degradation of TSNA by
light. The TSNA were extracted.
[0098] The final TSNA extract (pH 9 fraction) was transferred
quantitative using a Pasteur pipette into a 1 ml volumetric flask
and adjusted for full volume. Samples were stored in GC vials until
GC-TEA analysis.
[0099] For the TSNA analysis, an aliquot of 0.1 ml was dried in a
GC vial with a gentle stream of nitrogen and the GC standard
(N-nitrosoguvacoline; 3.2 ppm) in acetonitrile was added prior to
analysis. The GC-TEA was calibrated with a standard TSNA mixture on
a daily basis, before and after analyses of tobacco extracts.
[0100] GC Hewlett Packard Model 5890 and TEA.TM. Model 543 Analyzer
were used.
Example 1
[0101] This experiment shows the advantages of the present
invention on a reduced scale.
[0102] Yellow tobacco leaf was finely diced with scissors and
subjected to curing for 45 minutes at 167.degree. F. using
convective heat in the form of a hot air stream substantially free
from combustion exhaust gases. (A hot convection air oven was used
for this purpose.) The sample was rather moist, and therefore, a
wet weight was taken and calculations were made to correct the TSNA
content to dry weight basis. 75% of the leaf was moisture, and thus
the wet weight was multiplied by 0.25 to obtain the dry weight. The
results are tabulated in Table 1 below.
[0103] Although the treatment was made only for 45 minutes, longer
or shorter treatment times are envisioned depending on the
conditions and the results desired.
Comparative Example 1
[0104] Instead of the convective heat treatment described in
Example 1 above, yellow tobacco leaf was microwaved. The results
are set forth in Table 1 below.
Example 2
[0105] Instead of the convective heat treatment described in
Example 1 above, yellow tobacco leaf (Virginia) was subjected to a
modified flue-curing technique that eliminates the flow of
combustion exhaust gases into the curing barn. This was
accomplished by using a heat exchanger. The treated tobacco was
tested, and the results are given in Table 1.
1 TABLE 1 .mu.g/g EXAMPLE .mu.g/g NAT + .mu.g/g .mu.g/g NO. NNN NAB
NNK TSNA Ex. 1 0.0310 0.0843 <0.0004 0.1157 Comp. Ex. 1
<0.0004 <0.0006 <0.0005 <0.00014 Ex. 2 0.0451 0.1253
0.0356 0.2061
[0106] As can be seen from Table 1, the process of the present
invention provides tobacco having substantially reduced amounts of
TSNA.
Example 3
[0107] Yellow tobacco leaf was treated with a flow of air using a
MAYTAG clothes dryer under "fluff dry" at 85.degree. F. in Example
3. The results are shown in Table 2.
Example 4
[0108] This experiment shows the efficacy of the present invention
featuring drying without the use of heat. In this example, yellow
tobacco leaf was treated with a flow of unheated air using a MAYTAG
clothes dryer for six hours. The results are shown in Table 2.
Comparative Example 2
[0109] Tobacco leaf was flue cured according to a predominant
version of the conventional flue curing process in a curing barn.
As is the common practice for such conventional flue-curing, the
combustion exhaust gases were vented through the curing barn in
this process. In this conventional flue curing process, tobacco was
placed in a barn with relatively low flow of air and closed
external air vents. The temperature was incrementally increased
(about 0.5 to 1.5.degree. F. per hour) to about 13.degree. F. over
a period of about 3 days. At this point (i.e., end of yellowing),
the external air vents were opened, and the temperature was
maintained at 130.degree. F. for about 24-36 hours. The external
air vents were then closed and the temperature was raised to about
160.degree. F. to initiate the "killing out phase" (i.e., the phase
in which the stem is dried) with relatively low air flow. It is
important to note that in the conventional flue curing process, the
air flow (any fresh air plus any recirculating air) is
significantly lower than what is typically used in the present
invention. The results are shown in Table 2.
Comparative Example 3
[0110] Yellow tobacco leaf was microwaved for 60 seconds in a
commercial tobacco microwaving plant. The results are shown in
Table 2.
Comparative Example 4
[0111] Yellow tobacco leaf was again microwaved for 60 seconds in a
commercial tobacco microwaving plant. The results are shown in
Table 2.
2 TABLE 2 EXAMPLE .mu.g/g .mu.g/g .mu.g/g .mu.g/g NO. NNN NAT + NAB
NNK TSNA Ex. 3 0.037 0.046 <0.001 0.084 Ex. 4 0.042 0.054
<0.001 0.097 Comp. Ex. 2 0.77 0.89 1.37 3.03 Comp. Ex. 3 0.04
0.054 <0.001 0.095 Comp. Ex. 4 <0.001 0.042 <0.001
0.044
[0112] Examples 3 and 4 provided very low levels of TSNA,
especially NNN and NNK, even when microwaving was not used.
Example 5
[0113] Yellow tobacco leaf in the outer portion of a curing barn
was subjected to a flow of air for 7 days according to the present
invention. The results are tabulated in Table 3.
Example 6
[0114] Yellow tobacco leaf in the inner portion of a curing barn
was subjected to a flow of air for 7 days according to the present
invention. The results are tabulated in Table 3.
Comparative Example 5
[0115] Yellow tobacco leaf cured in a curing barn according to a
conventional curing process was tested for TSNA levels. The results
are shown in Table 3.
3TABLE 3 EXAMPLE .mu.g/g .mu.g/g .mu.g/g .mu.g/g NO. NNN NAT + NAB
NNK TSNA Ex. 5 0.03 .+-. .02 0.06 0.05 0.14 .+-. .02 Ex. 6 0.04
.+-. .01 0.08 .+-. .02 0.04 0.15 .+-. .01 Comp. Ex. 5 0.41 .+-. .04
1.16 .+-. .13 1.56 .+-. .21 3.14 .+-. .36
[0116] As is apparent from Table 3, the curing process according to
the present invention provided unexpectedly lower levels of TSNA as
compared to a conventional curing process.
Example 7
[0117] This example illustrates the advantageous effects obtainable
by practicing the present invention even under the most severe
environmental conditions. Throughout all phases of the curing,
combustion exhaust gases were not allowed to flow into the
barn.
[0118] Green tobacco was left in a curing barn according to the
present invention for about 72 hours with the external air vent
closed, but with recirculating air of about 25,000 CFM, and with
heating of about 300,000 BTUs to provide a temperature of about
1050 F. After this period of about 72 hours (end of yellowing), the
external air vents were opened and the air handling device was
adjusted to provide virtually all fresh air flow of approximately
25,000 CFM (with only a minor amount of recirculating air), and the
heat was increased to about 1,000,000 BTUs to provide a rapid
temperature increase to about 140.degree. F. This treatment was
continued for about 72 hours. At this point, the "killing out"
phase (i.e., drying of the stems) was initiated by closing the
external air vents and increasing the temperature to about
160.degree. F. Treatment continued for about 1-2 days.
[0119] The resulting tobacco product was tested for TSNAs according
to the analytical technique described above. The levels for each
individual nitrosamine were so low that they could not be
detected.
* * * * *