METHOD OF TREATING TOBACCO TO REDUCE NITROSAMINE CONTENT, AND PRODUCTS PRODUCED THEREBY

PROCEDES DE TRAITEMENT DU TABAC VISANT A REDUIRE LA TENEUR EN NITROSAMINES, ET PRODUITS RESULTANTS

English Abstract

Methods of reducing the content of and preventing formation of carcinogenic
nitrosamines in harvested leafy plants such as tobacco and
marijuana are disclosed. The methods are directed to subjecting the plant to
microwave and/or higher frequency radiation, at appropriate times
in the cure cycle. With tobacco, products suitable for human consumption, such
as cigarettes, cigars, etc., can be made in accordance with
the present invention, having contents of tobacco-specific nitrosamines on a
par with fresh-cut, green tocacco. In preferred embodiments,
the resultant tobacco products are dried, golden-yellow leaves having almost
negligible amounts of the known carcinogens NNN and NNK,
in comparison to conventionally cured tobacco.

French Abstract

L'invention concerne des procédés visant à réduire la teneur en nitrosamines cancérigènes dans certains végétaux à feuilles cultivés (par exemple, tabac et marijuana) et à empêcher la formation de ces substances, lesdits procédés consistant à soumettre les feuilles récoltées à des rayonnements en hyperfréquences et/ou aux fréquences plus élevées, à des stades appropriés du cycle de traitement. S'agissant du tabac, on peut fabriquer des produits convenant à la consommation humaine (cigarettes, cigares, etc.) grâce aux procédés décrits, ce qui donne dans les produits résultants une teneur en nitrosamines spécifiques du tabac qui équivaut à la teneur propre au tabac vert fraîchement coupé. Dans les modes de réalisation préférés, les produits résultants sont séchés, et les feuilles de tabac jaune doré ont alors une teneur presque négligeable en substances cancérigènes connues, NNN et NNK, par rapport au tabac traité de manière classique.

Claims

CLAIMS:
1. A process of substantially preventing formation of
nitrosamines in harvested tobacco plant, the process
comprising
subjecting at least a portion of the plant to a
concentrated form of radiation having a frequency higher
than the microwave region of the electromagnetic spectrum,
while said portion is uncured, yellow, and in a state
susceptible to having the formation of nitrosamines
arrested, for a sufficient time to substantially prevent
formation of at least one nitrosamine.
2. The process according to claim 1, wherein said
subjecting to radiation is carried out on a tobacco leaf or
portion thereof prior to substantial accumulation of
tobacco-specific nitrosamines in the leaf or portion
thereof.
3. The process according to claim 2, wherein said
subjecting to radiation is carried out on tobacco leaves
arranged in single layer thickness, without stacking or
piling of the leaves.
4. The process according to claim 3, further
comprising, prior to said subjecting to radiation, a step
selected from (a) removing stems from the tobacco leaves,
(b) pressing the tobacco leaves to remove excess moisture,
and (c) subjecting the tobacco leaves to a stem treatment.
5. The process according to claim 1, wherein said
subjecting to radiation is carried out prior to substantial
loss of cellular integrity of the plant.
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6. The process according to claim 1, wherein the
tobacco is flue tobacco and said subjecting to radiation is
carried out within about 24 to about 72 hours post-harvest.
7. The process according to claim 1, wherein said
radiation is applied to the plant for a period of at least
about one second at a predetermined power level.
8. The process according to claim l, wherein said
subjecting to radiation prevents normal accumulation of at
least one tobacco-specific nitrosamine in the leaf of said
plant.
9. The process according to claim 6, wherein said at
least one tobacco-specific nitrosamine is selected from the
group consisting of N'-nitrosonornicotine,
4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone,
N'-nitrosoanatabine and N'-nitrosoanabasine.
10. The process according to any one of claims 1 to 9,
further comprising drying the portion after carrying out the
radiation step.
11. The process according to any one of claims 1
to 10, wherein said radiation is generated by a laser beam.
12. The process according to any one of claims 1
to 10, wherein said radiation is an electron beam generated
by an electron accelerator.
13. The process according to any one of claims 1
to 10, wherein said radiation is gamma radiation.
14. A method of manufacturing a tobacco product,
comprising subjecting tobacco leaves to a concentrated form
of radiation having a frequency higher than the microwave
region of the electromagnetic spectrum, while said leaves
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are uncured and in a state susceptible to having the amount
of tobacco-specific nitrosamines reduced or formation of
tobacco-specific nitrosamines arrested, for a sufficient
time to reduce the amount of or substantially prevent
formation of at least one tobacco-specific nitrosamine in
the leaves, and forming said tobacco product comprising the
irradiated leaves, the tobacco product being selected from
the group consisting of cigarettes, cigars, chewing tobacco,
snuff and tobacco-containing gum and lozenges.
15. The method according to claim 14, wherein the
leaves are subjected to said radiation after onset of
yellowing in the leaves and prior to substantial
accumulation of tobacco-specific nitrosamines in the leaves.
16. 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 µg/g or less.
17. The tobacco product of claim 16, wherein said
tobacco suitable for human consumption is cured yellow
tobacco.
18. The tobacco product of claim 16 or 17, 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 Burley tobacco suitable for human consumption, in
leaf form and having a collective content of
N'-nitrosonornicotine, 4-(N-nitrosomethylamino)-1-
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(3-pyridyl)-1-butanone, N'-nitrosoanatabine and
N'-nitrosoanabasine which is 0.05 µg/g or less.
20. The tobacco product of claim 19, wherein said
tobacco suitable for human consumption is cured yellow
tobacco.
21. The tobacco product of claim 19 or 20, which is a
product selected from the group consisting of cigarettes,
cigars, chewing tobacco, snuff and tobacco-containing gum
and bits.
22. 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 µg/g or less.
23. The tobacco product of claim 22, wherein said
content of 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone
is 0.001 µg/g or less.
24. The tobacco product of claim 22 or 23, wherein
said tobacco suitable for human consumption is cured yellow
tobacco.
25. 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 µg/g or less.
26. The tobacco product of claim 25, wherein said
content of 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone
is 0.001 µg/g or less.
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27. The tobacco product of claim 25 or 26, wherein
said tobacco suitable for human consumption is cured yellow
tobacco.
28. 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 µg/g.
29. The tobacco product of claim 28, wherein said
collective content is 0.15 µ,g/g or less.
30. The tobacco product of claim 28, wherein said
collective content is 0.1 µ,g/g or less.
31. The tobacco product of claim 28, wherein said
collective content is 0.05 µ,g/g or less.
32. The tobacco product of any one of claims 28 to 31,
wherein said tobacco suitable for human consumption is cured
yellow tobacco.
33. The tobacco product of any one of claims 28 to 32,
which is a product selected from the group consisting of
cigarettes, cigars, chewing tobacco, snuff and
tobacco-containing gum and bits.
34. 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 µg/g.
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35. The tobacco product of claim 34, wherein said
collective content' is 0.15 µg/g or less.
36. The tobacco product of claim 34, wherein said
collective content is 0.1 µg/g or less.
37. The tobacco product of claim 34, wherein said
collective content is 0.05 µg/g or less.
38. The tobacco product of any one of claims 34 to 37,
wherein said tobacco suitable for human consumption is cured
yellow tobacco.
39. The tobacco product of any one of claims 34 to 38,
which is a product selected from the group consisting of
cigarettes, cigars, chewing tobacco, snuff and
tobacco-containing gum and bits.
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Description

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METHOD OF TREATING
TOBACCO TO REDUCE NITROSAMINE CONTENT,
AND PRODUCTS PRODUCED THERBY
Field Of The Invention
The present invention relates to a method of
treating tobacco to reduce the content of, or prevent
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
Others have described the use of microwave energy
to dry agricultural products. Use of microwave energy to
cure tobacco is disclosed in U.S. Patent No. 4,430,806 to
Hopkins. In U.S.
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Patent No. 4,898,189, 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. Patent No.
3,699,976, microwave energy is described to kill insect
infestation of tobacco. Moreover, techniques using impregnation
of tobacco with inert organic liquids (U. S. Patent 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. Patent No. 4,874,000). In U.S. Patent
No. 3,773,055, Stungis discloses the use of microwave to dry and
expand cigarettes made with wet tobacco.
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. ~t 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, Sept. 24-27, 1995, Lexington, Kentucky
(hereinafter "Wiernik et al"). However, cured tobacco is 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
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accepted that such nitrosamines are formed post-harvest, during
the curing process, as described further herein. Unfortunately,
fresh-cut green tobacco is unsuitable fcr smoking or other
consumption.
In 1993 and 1994, Burton et al at the University of Kentucky
carried out certain experiments regarding tobacco-specific
nitrosamines (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°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.
Applicant has 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°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. T_n 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-
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drying and the quick-drying tests are included, but there is no
mention of the microwaved samples. The article contains the
following conclusion:
It can be concluded from this study that it
may be possible to reduce nitrite levels and
accumulation of TSNA in lamina ar~d midrib by
applying heat (70°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.
Id. at page 56. The Weirnik 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°C for two clays in order to
cure the stem. An analysis of tobacco produced in this manner
showed that both the nitrite and the TSNA values were low, i.e.,
less than 10 micrograms per gram and 0.6-2.1 micrograms per
grams, respectively. Weirnik et al theorized that these results
were explainable due to the rapid heating which does not allow
further bacterial growth. Weirnik et al also noted, however,
that low nitrite and TSNA values, less than 15 micrograms per
gram of nitrite and 0.2 microgram per gram of TSNA, were obtained
for tobacco subjected to air-curing in Poland.
Summary of the Invention
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.
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Another object cf the present invention is to reduce the
carcinogenic potential of tobacco products, including cigarettes,
_ cigars, chewing tobacco, snuff and tobacco-containing gum and
lozenges.
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.
Another object of the present invention is tc 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.
Another object of the present invention is to reduce the
content of tobacco-specific nitrosamines in fully cured tobacco.
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 contains a
substantially reduced quantity of tobacco-specific nitrosamines,
thereby lowering the carcinogenic potential of such product.
Preferably, the tobacco product is a cigarette, cigar, chewing
- tobacco or a tobacco-containing gum or lozenge.
The above and other objects and advantages in accordance
with the present invention can be obtained by a process for
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reducing the amount of or preventing formaticn of nitrosamines
in a harvested tobacco plant, comprising
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.
It is preferred that in 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 the
process of the invention, the step of subjecting to microwave
radiation is carried out prior to substantial loss of the leaf's
cellular integrity.
In additional preferred embodiments of the process, the
tobacco is flue tobacco and the step of subjecting to microwave
radiation is carried out within about 24 to about 72 hours post-
harvest, even more preferably within about 24 tc about 36 hours
post-harvest.
In still other embodiments of the process, the harvested
tobacco is maintained under above-ambient temperature conditions
in a controlled environment prior to the step cf subjecting to
microwave radiation.
Preferred aspects of the process include a step, prior to
subjecting a tobacco leaf which preferably includes the stem to
microwave radiation, of physically pressing the leaf to squeeze
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excess moisture therefrom, to ensure more uniform drying by the
microwave unit. This step can be conveniently carried out by
passing the leaf through a pair of appropriately spaced rotating
cylindrical rollers prior to entering the microwave cavity.
In yet additional preferred embodiments of the invention,
the microwave radiation has a frequency of about 900 to about
2500 MHz, and is applied to the plant for a period of at least
about 1 second, and preferably from about 10 seconds to about S
minutes at a predetermined power level. The power level used
generally determines the length of time to which the tobacco is
subjected to the microwave radiation, and can range from about
600 to about 1000 watts when using conventional kitchen-type
microwave ovens, up to several hundred or more kilowatts for
commercial, multimode applicators. Preferred power levels using
applicators designed to handle single leaves range from about 2
to about 75 kilowatts, more preferably from about 5 to about SO
kilowatts, which permit relatively rapid treatment to be carried
out.
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.
The present invention also seeks to subject tobacco leaves
- to microwave radiation 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.
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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 ccnventionally cured tobacco.
In preferred embodiments, the non-green tobacco product has
a TSNA (NNN, NNK, NAB and NAT) content of less than .2 ~.g/g, more
preferably less than about .15 ~cg/g, and even more preferably
less than about .1 ~.g/g, an NNN content of less than about .15
~.g/g, more preferably less than about .10 ~cg/g, and even more
preferably less than about .05 ug/g, and an NNK content of less
than about .002 ~g/g, more preferably less than about .001 ~g/g,
and even more preferably less than about .0005 ~g/g.
The present invention is also directed to a tobacco product
comprising dried yellow tobacco suitable for human consumption
and having a lower content of at least one tobacco-specific
nitrosamine than conventionally cured tobacco. In preferred
embodiments, the yellow tobacco product has a TSNA (NNN, NNK, NAB
and NAT) content, an NNN content, and an NNK content within the
above preferred ranges.
In other embodiments, the non-green or yellow tobacco
product comprises non-green or yellow tobacco suitable for human
consumption, and having a TSNA (NNN, NNK, NAB and NAT) content
within about 25% by weight of the content of such TSNA in the
freshly harvested green tobacco crop from which the product was
made. It is more preferred that the non-green or yellow tobacco
product have a TSNA content within about 10% by weight, more
preferably within about 5% by weight and most preferably
essentially approximating (e. g. within an amount up to several
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percent by weight) the conter_t of such TSNA in the freshly
harvested tobacco crop from which the product was made. It is
- also preferred that the non-green or yellow tobacco product
comprises non-green or yellow tobacco suitable for human
consumption, and having content of at least one TSNA selected
from NNN, NNK, NAB and NAT, which is within about 25% by weight,
preferably within about 10% by weight, more preferably within
about 5% by weight and most preferably essentially approximating
(e.g. within an amount up to several percent by weight) of the
content of the corresponding TSNA or TSNAs in the freshly
harvested green tobacco crop from which the product was made.
In yet additional embodiments of the invention, the non-
green or yellow tobacco product comprises non-green or yellow
tobacco suitable for human consumption, and having a TSNA (NNN,
NNK, NAB and NAT) content which is at least about 75% by weight,
preferably at least about 90% by weight, more preferably at least
about 95% by weight, and most preferably at least about 99% by
weight lower than the content of such TSNA in a tobacco product
of the same type made from the same tobacco crop as the product
of the invention, but which was cured in the absence of microwave
radiation or other techniques designed to reduce TSNA content.
It is also preferred that the non-green or yellow tobacco product
comprises non-green or yellow tobacco suitable for human
consumption, and having a content of at least one TSNA selected
from NNN, NNK, NAB and NAT which is at least about 75 % by weight,
preferably at least about 90% by weight, more preferably at least
about 95% by weight, and most preferably at least about 99% by
weight lower than the content of the corresponding TSNA or TSNAs
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in a tobacco product of the same type made from the same tobacco
crop as the product of the invention, but which was cured in the
absence of microwave radiation or other techniques designed to
reduce TSNA content.
A preferred form of the present invention relates to a
tobacco product comprising tobacco having a reduced content of
at least one tobacco-specific nitrosamine, produced by a process
comprising subjecting the tobacco, while the tobacco is uncured
and susceptible to having formation of at least one tobacco-
specific nitrosamine arrested, to microwave radiation.
In another embodiment, the present invention is directed to
a method for reducing the content of at least one tobacco-
specific nitrosamine in cured brown tobacco, comprising
rehydrating the cured brown tobacco, and
subjecting the rehydrated tobacco to microwave radiation at
a predetermined energy level for a predetermined length of time.
Similarly, the present invention includes within its scope
a tobacco product comprising cured brown tobacco having a reduced
content cf at least one tobacco-specific nitrosamine, produced
by a process comprising
rehydrating the cured brown tobacco, and
subjecting the rehydrated tobacco to microwave radiation at
a predetermined energy level for a predetermined length of time.
In yet another embodiment, the present invention relates to
a method of manufacturing a tobacco product, comprising
subjecting harvested tobacco leaves to microwave radiation,
while said leaves are uncured and in a state susceptible to
having the amount of tobacco-specific nitrosamines reduced or
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formation of tobacco-specific nitrosamines arrested, for a
sufficient time to reduce the amount of or substantially prevent
formation of at least one tobacco-specific nitrosamine in the
leaves, and
forming the tobacco product comprising the microwaved
leaves, the tobacco product being selected from cigarettes,
cigars, chewing tobacco, snuff and tobacco-containing gum and
lozenges.
It has also been discovered that 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 also
relates to 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.
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
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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 leaf's 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 beam such as electron beams,
x-rays and gamma radiation.
According to one aspect of the present invention,
there is provided a process of substantially preventing
formation of nitrosamines in harvested tobacco plant, the
process comprising subjecting at least a portion of the
plant to a concentrated form of radiation having a frequency
higher than the microwave region of the electromagnetic
spectrum, while said portion is uncured, yellow, and in a
state susceptible to having the formation of nitrosamines
arrested, for a sufficient time to substantially prevent
formation of at least one nitrosamine.
According to another aspect of the present
invention, there is provided a method of manufacturing a
tobacco product, comprising subjecting tobacco leaves to a
concentrated form of radiation having a frequency higher
than the microwave region of the electromagnetic spectrum,
while said leaves are uncured and in a state susceptible to
having the amount of tobacco-specific nitrosamines reduced
or formation of tobacco-specific nitrosamines arrested, for
a sufficient time to reduce the amount of or substantially
prevent formation of at least one tobacco-specific
nitrosamine in the leaves, and forming said tobacco product
comprising the irradiated leaves, the tobacco product being
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selected from the group consisting of cigarettes, cigars,
chewing tobacco, snuff and tobacco-containing gum and
lozenges.
According to still another aspect of the present
invention, there is provided 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 ~g/g or less.
According to yet another aspect of the present
invention, there is provided 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 ~g/g or less.
According to a further aspect of the present
invention, there is provided 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 ~g/g or less.
According to yet a further aspect of the present
invention, there is provided 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 ~g/g or less.
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CA 02294130 2004-08-26
69275-129
According to still a further aspect of the present
invention, there is provided 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 ~.g/g.
According to another aspect of the present
invention, there is provided 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 ~.g/g .
Brief Description Of The Drawings
FIG. 1 is a photograph illustrating "yellow"
Virginia flue tobacco aged 24 to 72 hours post-harvest.
FIG. 2 is a photograph illustrating
low-nitrosamine microwaved "yellow" Virginia flue tobacco in
accordance with the present invention.
Figure 3 is a partial, side-perspective
illustration of a mobile, commercial-scale microwave
applicator which can be employed to carry out the microwave
treatment in accordance with the present invention.
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CA 02294130 2004-08-26
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Detailed Description Of The Invention
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 where
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used, and environmental variations during a single season or over
different seasons, especially weather fluctuations when 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, September
24-27, 1995, Lexington, Kentucky (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.
In one preferred 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, method of curing, and a number of other variables,
including those mentioned above. In accordance with this
preferred 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
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leaf is undergoing the yellowing process or is in the yellow
phase, before the leaf begins to turn brown, and prior to the
substantial loss cf 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 TSNAs reduced,
by exposing the tobacco to microwave radiation at a predetermined
energy level for a predetermined length of time, as discussed
further below. This microwave treatment 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
yellow phase, the application of microwave energy to the leaf in
accordance with the 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 another embodiment, the present invention relates to
treatment of cured (brown) tobacco to effectively reduce the TSNA
content of that cured tobacco, by rehydrating cured tobacco and
subjecting the rehydrated cured tobacco to microwave radiation,
as described further below.
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The present invention ,~s applicable to treatment of the
harvested tobacco which is intended for human. consumption. Much
- research has been performed on tobacco, with particular reference
to tobacco-specific nitrosamines. 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 one to two+ months for air-curing. According to
Peele et al, flue-curing has generally been divided into three
stages: yellowing (35-40°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°C) for 48 hours, and midrib (stem) drying (57-75°C) for
48 hours. Many major chemical and biochemical changes begin
during the yellowing stage and continue through the early phases
of leaf drying.
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°-
37°C. This process utilizes a controlled environment, maintains
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the relative humidity in the barn at approximately 85%, limits
moisture loss from the leaves, and allows the leaf to continue
the metabolic processes begun in the field. The operator
constantly monitors the progress of the cure, primarily by
observing the loss of chlorophyll and green color from the
leaves, and the development of the desired lemon to golden orange
leaf color.
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°F until the leaves turn more or less completely
yellow (see Figure 1). The yellow tobacco has a reduced moisture
content, i.e., from about 90 weight s when green, versus about
70-40 weight o 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, after which time the leaves turn from yellow to
brown. The brown Virginia flue tobacco typically has a moisture
content of about 11 to about 15 weight percent. The conversion
of the tobacco from yellow to brown 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.
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Tobacco-specific nitrosamines are believed to be formed upon
reaction of amines with nitrite-derived nitrosating species, such
. as NO-" N~O, and N204 under acidic conditions . Weirrik et al
discuss the postulated formation of TSNAs at pp. 43-45; a brief
synopsis is set forth below.
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.
Nitrosation of nornicotine (2 ) , anatabine ( 3 ) , and anabasine
(4) gives the corresponding nitrosamines: N'-nitrosonornicotine
(NNN, 5), N'-nitrosoanatabine (NAT, 6), and N'-nitrosonabasine
(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-butanol,
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 Weirnik et al, supra,
p. 44)
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O N. . , J
i Dcmethrlatfon ~ N ~ N
CHI N H N H N ~ .
N
( = Nicotine 1 = Norntcotine 3 = Anatabine < = Anabastne
............... N;(rosation-.-_......
......... Ni(rosatlon .........
N
NO
a Nh'N '~ NJ
N NO
OZIdation N-NO NO
CHO H-CH) 6 a NAT
O 9=NNA O 8= NNK N NO
N-NO N ~......... N _ 7 = NAB
~COOH -~ Reducttan~~-~~-~
~7
12 = tso-NNAC N~NO H NO
~ ~ ~ n-~H(
~~CH=OH H
~NJ N
I ! = lso~NNA L 10 = NNAL
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 eTrents 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.
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
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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. Weirnik et al have
suggested that nitrite may then substantially accumulate as a
result of dissimilatory nitrate reduction, thus rendering
formation of TSNA possible.
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 Weirnik 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.
In accordance with the present invention, the formation of
TSNAs in tobacco is substantially prevented or arrested by
subjecting the harvested leaves to microwave radiation under the
conditions described herein. In one preferred embodiment, the
tobacco leaves are exposed to the microwave energy at a time
between the onset of yellowing and the substantial loss of
cellular integrity. For optimal results, it is preferred to pass
the harvested leaves through the microwave field as single
leaves, as opposed to stacks or piles of leaves. Treating the
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leaves in this manner has been determined to completely or
substantially prevent the formation of tobacco-specific
nitrosamines, including the known carcinogens NNN and NNK.
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 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. In preferred embodiments,
the non-green tobacco product has a TSNA (NNN, NNK, NAB and NAT)
content of less than .2 ~.g/g, more preferably less than about .15
~g/g, and even more preferably less than about .1 ~cg/g, an NNN
content of less than about .15 ~.g/g, more preferably less than
about .10 ~cg/g, and even more preferably less than about .05
~g/g, and an NNK content of less than about .002 ug/g, more
preferably less than about .001 ug/g, and even more preferably
less than about .0005 ~.g/g. As noted above, given the number of
factors which can influence TSNA formation in tobacco, one of
ordinary skill in the art would understand that these numbers are
not absolute, but rather preferred ranges.
The present invention is also directed to a tobacco product
comprising dried yellow tobacco suitable for human consumption
and having a lower content or at least one tobacco-specific
nitrosamine than ccnventionally cured tobacco. In preferred
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embodiments, the yellow tobacco product has a TSNA (NNN, NNK, NAB
and NAT) content, an NNN content, and an NNK content within the
above preferred ranges.
In other embodiments, the non-green or yellow tobacco
product comprises non-green or yellow tobacco suitable for human
consumption, and having a TSNA (NNN, NNK, NAB and NAT) content
within about 25% by weight of the content of such TSNA in the
freshly harvested green tobacco crop from which the product was
made. It is more preferred that the non-green or yellow tobacco
product have a TSNA content within about 10% by weight, more
preferably within about 5% by weight and most preferably
essentially approximating (e. g. within an amount up to several
percent by weight) the content of such TSNA in the freshly
harvested tobacco crop from which the product was made. For
example, the present invention permits tobacco products to be
made which have a TSNA content within the above-described ranges
as to amounts, whereas normally cured tobacco from the same crop
would typically generate many times the amount of TSNA in the
fresh-cut tobacco. The present invention can effectively lock
in the low amounts of nitrosamines found in fresh-cut green
tobacco. It is also preferred that the non-green or yellow
tobacco product comprises non-green or yellow tobacco suitable
for human consumption, and having content of at least one TSNA
selected from NNN, NNK, NAB and NAT, which is within about 25%
by weight of, preferably within about 10% by weight of, more
preferably within about S% by weight of, and most preferably
essentially approximating (e. g., within an amount up to several
percent by weight ) the content of the corresponding TSNA or TSNAs
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in the freshly harvested green tobacco crop from which the
product was made. In other words, the content of, e.g., NNN in
the tobacco of the invention falls within the above ranges vis-a-
vis the amount of NNN in the fresh-cut green tobacco, or the
amount of NNN + NNK in the tobacco of the invention falls within
the above ranges vis-a-vis the amount of NNN + NNK in the fresh-
cut green tobacco, etc. In making these comparisons, the fresh-
cut green tobacco is preferably analyzed for TSNA content within
about 24 hours after harvest.
In yet additional embodiments of the invention, the non-
green or yellow tobacco product comprises non-green or yellow
tobacco suitable for human consumption, and having a TSNA (NNN,
NNK, NAB and NAT) content which is at least about 75% by weight,
preferably at least about 90% by weight, more preferably at least
about 95% by weight, and most preferably at least about 99% by
weight lower than the content of such TSNA in a tobacco product
of the same type made from the same tobacco crop as the product
of the invention, but which was cured in the absence of microwave
radiation or other steps specifically designed to reduce the TSNA
content. It is also preferred that the non-green or yellow
tobacco product comprises non-green or yellow tobacco suitable
for human consumption, and having a content of at least one TSNA
selected from NNN, NNK, NAB and NAT which is at least about 75%
by weight, preferably at least about 90% by weight, more
preferably at least about 95% by weight, and most preferably at
least about 99% by weight lower than the content of the
corresponding TSNA or TSNAs in a tobacco product of the same type
(e.g., comparing a cigarette to another cigarette) made from the
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same tobacco crop as the product of the invention, but which was
cured in the absence of microwave radiation or other techniques
for reducing TSNA content. In these embodiments, the TSNA weight
o comparisons can be made by taking, for example, a cigarette
made using dried yellow tobacco in accordance with the present
invention, and taking a cigarette made from tobacco from the same
crop as the dried yellow tobacco was made from, but curing it by
conventional means without subjecting it to microwave radiation.
The yellow stage, in which the step of subjecting the
tobacco leaf to microwave radiation is preferably carried out,
can be broadly defined in any one of the following ways: (a) by
examining the color of the leaf, when the green color has
substantially given way to a yellowish color; (b) by measuring
the percent of chlorophyll conversion to sugars; (c) by observing
the onset of either nitrite formation or nitrosamine generation,
which typically coincide with the end of the yellow phase, or (d)
by measuring the moisture content of the leaves, e.g., when they
have a moisture content from about 40 to about 70 percent by
weight. If the microwave radiation is applied to green tobacco,
the arrestation or prevention of nitrosamine formation is not
observed. However, when microwave energy is applied after the
onset of yellowing and prior to the loss of cellular integrity
or substantial accumulation of TSNAs in the leaf, the observed
reduction in the amount of, or prevention of formation of
nitrosamines is dramatic and unexpected, as shown by the data
discussed below.
The optimal time fcr subjecting the harvested tobacco tc the
microwave radiation during the yellow phase varies depending on
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a number of factors, including varietal differences,
environmental variations, etc. Thus, within the time frame
beginning with onset of yellowing (defined, e.g., by a loss of
the majority of green color in the leaf) through the time a-t
which the leaf substantially loses cellular integrity (as it
turns brown), one of ordinary skill in the art could determine
the optimal time for carrying out the microwave treatment for any
given variety of tobacco. For example, for a given genotype,
sample leaves could be tested by the procedures described herein
to measure either nitrite or TSNA content, to identify the
relative time in a given cure cycle at which significant TSNA
accumulation begins, or identify the transition phase in which
loss of cellular integrity occurs. While subjecting the leaves
to the microwave radiation prior to significant TSNA accumulation
is the most preferred form of the method of the present
invention, the principles of the invention can also be applied
to tobacco leaves which are in the process of forming, and have
already accumulated significant amounts of TSNAs. When the
microwaving is carried out at this latter stage, further
formation of TSNAs can be effectively arrested. However, once
the leaves are fully cured, TSNA levels have essentially
stabilized, and application of microwave radiation is ineffective
to reduce the TSNA context, except under rehydration conditions
described below.
Upon being subjected to microwave radiation in accordance
with the present invention, the tobacco leaf generally has a
reduced moisture content , i . a . less than about 10 % by weight , and
often approximately 5%. If desired, the leaf can be rehydrated
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back to the typical moisture range for brown, cured tobacco
(e. g., about 11-15~ for Virginia flue) before manufacturing into
- tobacco products such as cigarettes.
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 microwave step to achieve the objects and
advantages of the present invention.
Preferred aspects of the process include a step, prior to
subjecting a tobacco leaf which preferably includes the stem to
microwave radiation, of physically pressing the leaf to squeeze
excess moisture therefrom, to ensure more uniform drying by the
microwave unit . This step can be conveniently carried out by
passing the leaf through a pair of appropriately spaced rotating
cylindrical rollers prior to entering the microwave cavity. Such
a pressing step will aid in wringing moisture from the stem and,
to a lesser extent, the midrib and larger veins, and lead to a
better and more evenly dried product. The rollers can be made
of hard rubber, plastic or steel and be of any desired length,
and are preferably spaced about one-eighth to about one-quarter
inch apart, but the distance is preferably selected so as to
accomodate the thickness of a single leaf, which can vary. The
rollers can be belt or chain driven by an appropriately selected
motor. Besides rotating rollers, other types of squeezing or
pressing means could be used to accomplish the same result, if
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desired, as would be apparent to one of ordinary skill in the
art.
The above-described preferred embodiment of pressing the
leaves permits more high-speed production to be carried out;
since the stems do not have to be cut out, and the microwave time
can be reduced. This embodiment is particularly advantageous for
tobacco leaves destined to be used in cigarettes, which typically
contain some tobacco stems as part of a blend. Alternatively,
the pressing step can be omitted if desired, in applications
where the stem is trimmed from the leaves and discarded.
In another preferred embodiment, instead cf pressing the
leaves or cutting out the stems, the leaves can be subjected to
a steam treatment prior to microwaving. As with the pressing
step, steaming the whole leaves, including the stems, has been
demonstrated to more evenly distribute the moisture in the stems
and larger veins, thus leading to more uniform drying of the
entire leaves upon microwaving. As a result, the entire leaves
including the stems can be used in tobacco products when this
particular technique is employed. Although the details would be
apparent to one of ordinary skill in the art, successful results
have been obtained when the leaves have been placed in a suitable
steam vessel for a time sufficient to allow the leaves to become
somewhat soft and pliable, generally from about 30 seconds up to
about five minutes.
The principles of the present invention can also be applied
to brown or already cured tobacco, which has been rehydrated.
In such cases, while important and unexpected reductions in the
amount of the TSNAs, particularly NNN and NNK, are observed when
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rehydrated brown tobacco is subjected to microwave radiation, the
results are not as dramatic as when the invention is applied to
uncured yellow tobacco, prior to the time when substantial
quantities of TSNAs or nitrites have accumulated in the leaves:
Nonetheless, the addition of moisture to the cured leaves, such
as by spraying with enough water to effectively soak the leaves,
followed by microwaving the rehydrated leaves, reduces the
content of TSNAs as demonstrated in the following Examples.
As noted above, when treating cured or brown tobacco,
microwaving alone has little effect on the nitrosamine content.
However, it has been determined that rehydration of the cured
tobacco prior to subjecting it to microwave radiation facilitates
the action of the microwave energy in reducing nitrosamines. In
one preferred embodiment, the cured tobacco product is rehydrated
by adding an appropriate amount of water, generally at least
about 10% by weight, up to the maximum absorption capacity,
directly to the leaves . Exposure of the rehydrated leaves to
microwave radiation, in the same manner as described herein with
regard to the uncured tobacco, reduces the nitrosamine content,
as shown below. The leaves can be wetted in any suitable
fashion. If the cured tobacco is in a form other than leaves,
such as reconstituted "sheet" tobacco, it can similarly be
rehydrated with, e.g., 10-70% by weight water, and then
microwaved. Suitable microwave condition can be selected
depending on the degree to which the leaves are re-wetted, but
typically fall within the parameters discussed above for
microwaving yellow tobacco.
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In accordance with the present invention, microwaving of the
rehydrated brown tobacco can preferably reduce the TSNA (NNN,
NNK, NAB and NAT) content, measured individually or collectively,
by at least about 25% by weight, more preferably by at least
about 35-°s by weight, and even more preferably by at least about
50% by weight from the TSNA levels contained the cured brown
tobacco prior to rehydration.
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
radiofrequency 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
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frequencies of 2450 and 895 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.
Microwave energy can be generated at a variety of power
levels, depending on the desired application. Microwaves are
typically produced by magnatrons, 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 magnatron
can generate either pulsed or continuous waves of suitably high
frequency.
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
29
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thickness exposure to microwave radiation, as opposed to stacks
or piles of leaves.
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 S 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 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.
However, the above-described conditions are not absolute,
and given the teachings of the present invention, one of ordinary
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skill iri 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.
Referring now to Figure 3, an embodiment of a commercial
scale microwave applicator is depicted in partial, perspective
TM
view. In particular, a Microdry 300 kW microwave tobacco drying
system 1 is shown, comprising a mobile truck frame 2 (front end
at right side of drawing not shown), a conveyorized microwave
oven 3 which interiorly includes four modular oven cavities of
single wall construction (which can be suitably constructed from
3003H14 aluminum), each cavity measuring approximately 16' in
length x 84" in width x 48" in height. Each cavity is equipped
with 'four access doors located two per side. The doors are
double interlocked to prevent accidental exposure to microwave
energy.
In Figure 3, an automatic cutting mechanism S is shown,
including multiple (e. g., twelve) rotating blades for removing
the stem from the leaves 4. The cutter can be a straight strip
approximately 3.4" in width down the center of the leaves,
manually fed. An appropriate guard can be provided, if desired,
to prevent insertion of= operators' hands. Although Figure 3
depicts'a stem cutting mechanism, as noted above the whole leaves
can be used in accordance with other embodiments o~ -the
31

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invention. Thus, in place of the cutting mechanism, the
apparatus could employ a steam vessel or a pair of rollers for
pressing moisture from the leaves.
Returning to Figure 3, after the stem cutting operation the
cut tobacco leaves 6 are conveyed by a belt conveyor 7 to the
main microwave oven 3 housing the four cavities. In one
embodiment, the system has an oven length of approximately 78
feet. Leading into and within the oven, the conveyor system can
alternatively comprise multiple, e.g., six, variable speed
polypropylene belts arranged in such a way so as to allow the cut
stems to fall from between the pairs of belts and into a hopper
located below the belts (not shown). The belts will then carry
the cut tobacco leaves through one of two traps located one at
each of the cavities, designed to contain the microwave energy,
and then into a selected cavity where each leaf is subjected to
microwaving in accordance with the principles of the invention
described above. After being microwaved, the conveyor carries
the leaves through the cavity exit, through an oven discharge
trap and out of the oven where they are then conveyed into
appropriate vessels to be taken for further processing.
To remove the moisture laden air from the cavities and oven,
an exhaust system including suitable blowers providing
recirculating air can be included in the system (see moisture
exhaust vents, item 8 being one labeled as representative, in
Fig. 3}. Also, if desired, the interior of the oven can be
temperature controlled by appropriately spaced circulating air
convection heating sources so that the interior of the oven
outside the microwave cavities is maintained at a preferred
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constant temperature, e.g., 160-180° F, during conveyorized
transport of the leaves. In a mobile system such as depicted in
Figure 3 for field usage, the electrical requirements can be
supplied by a pair of conventional diesel-powered generators 9-,
10. Of course, the microwave drying system can also be operated
in a fixed location, if desired, powered by conventional
electrical sources.
Each of the four cavities within oven 3 in Fig. 3 receives
microwave energy from a corresponding Microdry Model IV-75
microwave power source. The microwave energy enters each
respective cavity via a splitter through two ports located in the
top of each cavity. A mode stirrer is located below the ports
in each cavity to assist in the distribution of the microwave
energy. Each microwave power unit is acompletely self-contained
cabinet that houses the required components to operate a 75 kW
magnetron. Controls for the microwave power are located on the
cabinet. The units are designed for unattended continuous
operation in an industrial environment. Each microwave power
generator may be located at each cavity, or at a distance from
the cavity. However, at a distance of 50', the transmission line
losses will be about 20. Each power generator provides
adjustable microwave energy for industrial operation. The output
power is adjustable from 0 to about 75 kW at the FCC assigned
frequency of 915 MHz, and is controlled by a solid state control
circuit manually adjusted by a control knob on the panel or by
remote control with a 4-20 milliamp control signal from a process
controller. While the circuitry will control the power output
from zero, the frequency spectrum becomes broad at levels below
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about 5 kW. The power generator for each cavity is basically a
direct current power supply operating an industrial magnetron
which is operated and protected by circuit functions designed for
automatic and manual operation. The electrical functions of the
generator are monitored by meters on the control panel, located
on cabinet door. The metering includes anode current, anode
voltage, output power, filament current, electromagnet current
and reflected power. Operation of the electromechanical
interlock functions are monitored by designated lamps located on
the control panel. Each microwave power generator cabinet has
full width doors for maximum accessibility to the components.
A built-in electromagnetic interference shielding enclosure
houses the magnetron and associated microwave components. A door
allows for installation of the magnetron and electromagnet. The
system includes a circulator and water load, mounted inside the
cabinet, which functions as an isolator to protect the magnetron
in the event of a high reflected power condition. The microwave
power generator uses both forced air and water for cooling the
heat producing components. The magnetron and electromagnet are
water cooled by a closed loop demineralized water system. A
separate water source and a heat exchanger can be used to cool
the water in this loop. The separate water source also flows
through a water to air heat exchanger inside the cabinet to cool
the cabinet air. A high pressure centrifugal blower provides
cooling to the magnetron output window and the cachode structure.
Water and cabinet temperatures are interlocked in the control
power chain. Typical reference data for each microwave generator
in a system of this are as follows:
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Power input 95 KVA, 440-480 VAC, 3 phase, 60 Hz
Power output 75 kW at 915 +/- 10 MHz
Magnetron tube CTL, CWM 75 I
Typical magnetron operation reference data are as follows:
AC f=lament voltage 11.4 V
Filament current 85 A
DC anode voltage 17 KV
Anode current 5.0 A
DC electromagnet current 4.3 A
Efficiency 80%
Further, a typical microwave generator can employ a carbon steel
enclosure and have an output connection (WR 975 waveguide) in the
top of the cabinet at an appropriate location.
In a throughput test, a microwave tobacco drying system
generally designed as described above was effective to eliminate
over 80% of the moisture content of the leaves. In particular,
in one measured sample, 15 pounds of leaves with an assumed
initial water content of 85 wt% and solids content of 15 wt% was
conveyed through a microwave cavity in single leaf thickness at
a rate of about 180 lbs per hour. The leaves were weighed after
exiting the cavity. The ending weight was 4.6 lbs., or 31% of
the initial weight. Thus, based on the initial assumed water
content, therer remained 2.35 pounds of water in the leaves,
corresponding to 18.5% of the initial water content.
As disclosed in FIG. 2, the microwave treatment of yellow
tobacco in accordance with the present invention preferably
results in a dried, golden-colored tobacco product. The data
presented herein establish that such dried tobacco, in its
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unsmoked form, has dramatically reduced carcinogenic
nitrosamines, particularly NNN and NNK, as opposed to normally
cured tobacco.
It has also been discovered that concentrated forms of
electromagnetic radiation (i.e., concentrated as distinguished
from general exposure to sunlight or electric light within the
visible spectrum) having higher frequencies and shorter
wavelengths than the microwave domain discussed above, 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
approximately the same time frame post-harvest as discussed above
with regard to the microwave embodiment. In other words, the
same general and preferred techniques and principles discussed
above regarding microwaving can be applied when such an alternate
energy source is used; for example, the tobacco is treated with
such radiation at approximately the same time frames post-
harvest, the leaves can be de-stemmed, pressed between rollers
or steamed prior to irradiation, etc.
However, while such alternate energy sources have been
determined to significantly and desirably reduce or substantially
eliminate or prevent formation of TSNAs, none of the other
embodiments tested to date have been as effective in drying the
leaves as the microwave technique described in detail. Thus,
when using such an alternate energy source, it may be preferable
to subject the irradiated tobacco leaves to further processing
to complete the curing cycle, such as combining the irradiation
step with a subsequent oven-drying or tumble-drying step.
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In particular, it is believed that any electromagnetic
radiation source, and accelerated particle beams such as electron
beams, having frequencies higher than the microwave domain within
the conventional electromagnetic spectrum are operative to
significantly reduce, substantially eliminate and/or prevent
formation of TSNAs when tobacco is uncured and in a state
susceptible to having the amount of TSNAs reduced or formation
thereof arrested. On a scale within the electromagnetic spectrum
where microwaves are generally defined as inclusive of those
forms of electromagnetic radiation having a frequency of 1011 Hz
and a wavelength of 3 x 10-' meters, such energy sources include,
without limitation, far-infrared and infrared radiation having
frequencies of about 1012 to 101" Hz and wavelengths of 3 x 10-' to
3 x 10'6 meters, ultraviolet radiation having frequencies of
about 1016 to 1018 Hz and wavelengths of 3 x 108 to 3 x 10-10
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 1021 Hz and
higher at corresponding wavelengths.
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
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preferred. However, as shown in the Examples below, the exposure
rate can be controlled to deliver the radiation dosage over time,
if desired. rr~or example, 1 megarad of radiation can be delivered
instantaneously (as with the electron beam accelerator discussed
below in Example 17), or at a predetermined exposure rate (as
exemplified by the closed chamber gamma irradiation testing
discussed below in Example 19, wherein 1 megarad (10 kGrey) of
irradiation was delivered at an exposure rate of about .8 megarad
per hour). 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 tc 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 .1 to about 10 megarads, more
preferably from about .5 to about 5 megarads, and more preferably
from about .75 to about 1.5 megarads.
As illustrated in the following Examples, testing has been
carried out on various tobacco samples using an accelerated
electron beam, a COz laser and gamma radiation as exemplary of
these additional radiation sources. In each instance, the
uncured, irradiated tobacco samples were demonstrated to contain
significantly reduced and/or substantially eliminated TSNA
contents.
In yet another embodiment of the invention, treating the
tobacco while in its susceptible state in a recirculating air
convection oven has also been demonstrated to reduce the TSNA
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content, albeit with reduced leaf quality. Unlike a conventional
baking oven which is not as effective in lowering TSNA content
and also lowers the tobacco quality, heating in a recirculating
air convection oven at temperatures of from about 100° to about
S00° F, for periods ranging from one hour at the low end down to
about S minutes at the high end of the temperature scale, can
also effectively reduce the content of or arrest formation of
TSNAs in tobacco while in its susceptible state as defined
herein. Even more preferably, an oven combining recirculating
air convection heat and microwave radiation can shorten the
heating time while providing improved quality to the leaves . For
example, when a convection oven alone is used, the veins and
stems are not completely dried at the time the lamina are dried,
thus leading to overdried and crumbly lamina sections. Combining
the microwave treatment with recirculating convection oven heat
can improve the leaf quality by giving a more uniformly dried
product.
In another aspect, the present invention relates to a method
for reducing or substantially eliminating the content of tobacco-
specific nitrosamines in a human or animal subject who smokes,
chews or otherwise ingests tobacco, by providing for consumption
a tobacco product having significantly reduced or substantially
eliminated TSNAs.
Subjecting the uncured tobacco to microwave or other
radiation energy is demonstrated herein to be effective to
provide tobacco have surprisingly low nitrosamine contents.
These techniques can be facilitated by peeling and disposing of
the stem down one-third to one-half length of the tobacco leaf,
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especially in cases where the stem is to be discarded and the
moisture-wringing or steaming steps described above are not
employed. Where the stem is removed in this manner, the
resultant microwaved tobacco leaf does not require the use of~a
thrasher machine since the undesirable part cf the stem is
already removed. As a result, the typical loss of tobacco
product associated with thrashing is eliminated, reducing tobacco
waste by approximately 10% to 30%.
The improved tobacco of the present invention can be
substituted in whole or part for normally-cured tobacco in any
tobacco product, including cigarettes, cigars, chewing tobacco,
tobacco chewing gum, tobacco lozenges, tobacco pouches, snuff,
or tobacco flavoring and food additives. For the purposes of
smoking, the present invention provides a less noxious odor while
maintaining good smoking characteristics and providing full
flavor with normal nicotine content. For the purposes of
chewing, snuff, pouch and food additives, the tobacco of the
present invention has a rich, pleasant flavor.
The present invention is now illustrated by reference to the
following examples, which are not intended to limit the scope of
the invention in any manner.
Example 1
Virginia flue tobacco was harvested, and the leaves were
placed in a curing barn at about 100-110°F to begin the flue-
curing process. Samples 1-3 were taken from the barn after the
leaves had turned yellow, about 24-36 hours post-harvest. Sample
1 was a lamina sample, stripped of the midrib, and baked in a
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convection air oven at about 400-500°C for about 1 hour, which
browned the lamina. Sample 2 was a yellow leaf, placed in a
' TM
Goldstar Model MA-1572M microwave oven (2450 MHz), and heated on
the high power setting (1,000 watts) while rotating for about 23~
minutes. Sample 3 was a yellow leaf, untreated, used as a
control. Samples 4 and 5 remained in the curing barn under
elevated temperature of about 180°F, Sample 4 being dried outside
the racks and Sample 5 inside the racks. Sample 6 was a cured,
brown leaf, having underwent the normal flue-cure process.
Analyses were performed on each sample to determine NNN,
NAT, NAB and NNK contents. In this and the following examples,
"TSNA" represents the sum of these four tobacco-specific
nitrosamines. Sample work-up and extraction followed a typical
procedure for analysis of TSNAs (see, for example, Burton et al . ,
"Distribution of Tobacco Constituents in Tobacco Leaf Tissue.
1. Tobacco-specific Nitrosamines, Nitrate, Nitrite and
Alkaloids", J. Agric. Food Chem., Volume 40, No. 6, 1992), and
individual TSNAs were quantified on a Thermedics Inc. T~A Model
TM
543 thermal energy analyzer coupled to a Hewlett-Packard Model
5890A gas chromatograph. The results are shown in Table 1 below.
All data in each table below are presented in micrograms of the
nitrosamine per gram of sample (i . a . , parts per million or ~g/g)
41

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TABLE 1
Sample # NNN NAT + NAB NNK TSNA
1 - yellow 0.0310 0.843 <0.0004 0.1157
baked
lamina
2 - yellow <0.0004 <0.0006 <0.0005 <0.0014
microwaved
3 - yellow 0.0451 0.1253 0.0356 0.2061
control
4 - rapid 0.6241 1.4862 1.2248 3.3351
drying
outside
racks
- rapid 0.7465 1.5993 1.3568 3.7044
dr~ring
inside
racks
6 - 1.0263 1.7107 2.2534 4.9904
regular
flue-cured
Example 2
Virginia flue tobacco was harvested. Sample 7 was a fresh-
cut, green leaf used as a control, while Sample 8 was a fresh-cut
green leaf which was subjected to microwave radiation in a
multimode microwave applicator manufactured by MicroDry of
Louisville, Kentucky, operating at 2450 MHz at 2.5 kilowatts, for
about 20 seconds. Samples 9-12 were made from normally flue-
cured brown tobacco. Sample 9 was tobacco from a formed
cigarette; Sample 10 was loose, shredded tobacco for making
cigarettes; Samples 11 and 12 were the same as Samples 9
(cigarette) and 10 (loose), respectively, except that each was
subjected to the same microwave conditions as Sample 8. TSNA
contents were analyzed in the same manner as in Example 1. The
results are shown in Table 2 below:
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Table 2
Sample # NNN NAT + NAB NNK TSNA
7 - fresh <0.0104 0.126 0.0005 0.126
leaf
control
8 - fresh 0.029 0.135 0.0004 0.164
leaf -
microwaved
9 - 1.997 3.495 2.735 8.226
control
cigarette
- 2.067 3.742 2.982 8.791
control
loose
11 - 2.056 3.499 2.804 8.359
cigarette
microwaved
12 - loose 2.139 3.612 2.957 8.707
microwaved
Example 3
The following cigarette brands shown in Table 3 were
purchased at random at various retailers in Lexington, Kentucky,
and analyzed for TSNA content using the procedure described in
Example 1:
Tab 3
Sample # Code No. NNN NAT + NAB NNK TSNA
13- 288292 3.565 4.538 1.099 9.202
TM
Marlboro
-king-pc
14-~ 288292 4.146 4.992 1.142 10.279
Marlboro
'-king-pc
15- 288292 3.580 4.290 1.106 8.977
Marlboro
i -king=pc
43

CA 02294130 2004-08-26
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Sample # Code No. NNN NAT + NAB NNK TSNA
16- 288292 3.849 4.748 1.130 9.728
Marlboro
-king-pc
17- 288192 4.604 5.662- 1.223 11.489
Marlboro
-lights-
100's-bx
18- 288182 3.471 3.859 1.211 8.541
Marlboro
-lights-
100's-pc
19- 288182 3.488 4.136 1.074 8.698
Marlboro
-lights-
100's-pc
20- 288182 3.566 4.240 1.164 8.970
Marlboro
-lights-
100's-pc
21- TM 123143 2.311 2.968 1.329 6.608
Winston-
100's-pc
.
22- 123103 2.241 2.850 1.256 6.348
Winston-
king
23- 125123 2.162 2.831 1.326 6.319
Wins'ton-
king-bx
24- 123123 2.577 3.130 1.207 6.914
Winston-
king-bx
25- 123103 1.988 2.563 1.234 5.786
Winston-
king-pc
26- 123133 2.161 2.706 1.258 6.124
Winston-
lights-
100's-pc
27- 123133 2.189 2.699 1.262 6.150
Winston-
lights- -
100's-pc
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CA 02294130 2004-08-26
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Sample Code No. NNN NAT + NAB NNK TSNA
#
28- 123133 2.394 3.385 2.330 8.109
Winston-
lights-
100's-pc
Example 4
Virginia flue tobacco was harvested, and the leaves were
placed in a curing barn at about 100-110°F to begin the flue-
curing process. After the leaves turned yellow, about 24-36
hours post-harvest, they were taken out of the barn and
microwaved in Goldstar Model MA-1572M microwave oven (2450 MHz?,
high power setting (1000 watts), for about 2~ minutes while
rotating. The leaves were effectively dried by this procedure,
although they did not turn brown, but instead retained their
golden-yellow color. The leaves were shredded and made into
cigarettes. Samples 29-33 were taken from a batch labeled Red
Full Flavor, while Samples 34-38 were taken from a batch labeled
blue Light. Samples 39-42 were cigarettes purchased at a health
TM
food store, under the brand Natural American Spirit. Samples 29-
42 were analyzed for TSNA content using the procedure described
in Example 1, and the results are shown in Table 4 below:

CA 02294130 2004-08-26
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Table 4
Sample NNN NAT + NAB NNK TSNA
#
29-RED 0.138 0.393 <0.0005 0.532 i
FULL
I
FLAVOR
~M
REP 1
- __ -
I
30-RED 0.192 0.231 <0.0005 0.423
FULL I
FLAVOR
REP 2
31-RED 0.129 0.220 <0.0007 0.349
FULL
FLAVOR
REP 3
32-RED 0.145 0.260 <0.0007 0.406
FULL
FLAVOR
REP 4
33-RED 0.140 0.293 <0.0006 0.434
FULL '
FLAVOR
REP 5
AVG 0.149 0.279 <0.0006 0.429
STD 0.022 0.062 0.0001 0.059
34-BLUE 0.173 0.162 <0.0005 0.335
LIGHT T""
REP 1
35-BLUE 0.046 0.229 <0.0005 0.275
LIGHT
REP 2
36-BLUE 0.096 0.188 <0.0005 0.285
LIGHT
REP 3
37-BLUE 0.067 0.215 <0.0005 0.282
LIGHT
REP 4
38-BLUE 0.122 0.218 <0.0005 0.341
LIGHT
REP 5
AVG 0.101 0.202 <0.0005 0.304
STD 0.044 0.024 0.0000 0.028
39- ~ 0.747 1.815 1.455 4.017
NATURAL
AMERICAN __ _
SPIRIT
46

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Sample # NNN NAT + NAB NNK TSNA
40- 0.762 1.805 1.458 4.025
NATURAL
AMERICAN
SPIRIT
41- 0.749 1.826 1.464 4.039
NATURAL
AMERICAN
SPIRIT
42- 0.749 1.760 1.462 3.971
NATURAL
AMERICAN
SPIRIT
AVG 0.752 1.802 1.460 4.013
STD 0.006 0.025 0.004 0.025
STD in the Tables herein is the standard deviation for the
average of the samples shown.
Example 5
Virginia flue tobacco was harvested, and the leaves were
placed in a curing barn at about 100-110°F to begin the flue-
curing process. Samples 43-44 were taken from the barn after the
leaves had turned yellow, about 24-36 hours post-harvest, and
subjected to microwave radiation in the MicroDry multimode
applicator described above for about 20 and 30 seconds,
respectively, at a power level of about 6 kilowatts. Samples 43
and 44 were dried, golden-yellow leaves after the microwaving.
Samples 45-51 were made from brown, cured leaves having underwent
the normal flue-cure process. Sample 45 was a control; Samples
46 and 47 were baked in a convection oven preheated to about 400-
500 °F for about 1 and about 3 minutes, respectively; and Samples
48 and 49 were subjected to microwave radiation (915 MHz) in a
Waveguide applicator Model WR-975, a large ~ultimode oven
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manufactured by MicroDry (power settings from 0 - 75 KW) at 50
kilowatts for about 10 and 40 seconds, respectively. Samples 50
and 51 were cut (reconstituted sheet) tobacco made from the flue-
cured leaves. Sample 50 was subjected to microwave radiation in
the Waveguide microwave oven at 50 kilowatts for about 1.5
minutes, while Sample 51 was baked in a convection oven preheated
to about 400-500 °F for about 3 minutes. These samnlP~ G
analyzed for TSNA content using the procedure described in
Example 1, and the results are shown in Table 5 below:
Table 5
Sample # NNN NAT + NAB NNK TSNA
43-20 SEC <0.0106 <0.1068 <0.0007 <0.1181
MICROWAVE
44-30 SEC <0.0103 <0.1065 <0.0004 <0.1172
MICROWAVE
45-CONTROL 0.92 2.05 3.71 6.68
NO MICRO
46-OVEN 1 1.14 2.41 5.10 8.66
MIN
47-OVEN 3 0.89 2.06 2.68 5.64
MIN
48- 1.00 2.31 3.29 6.59
WAVEGUIDE
SEC 50
KW
49- 0.62 1.55 1.69 3.86
WAVEGUIDE
40 SEC 50
KW
50-CUT 4.22 4.91 0.99 10.12
TOBACCO
WAVEGUIDE
1.5 MIN SO
KW
51-CUT 4.76 5.60 1.08 11.44
TOBACCO
OVEN 3 MIN
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Example 6
Virginia flue tobacco was harvested, and the leaves were
placed in a curing bar at about 100-110°F to begin the flue-
curing process. Samples 52-55 were cigarettes made from yellow
tobacco which had been pulled from the barn after about 24-36
hours, and subjected to Microwave radiation in a Goldstar
microwave oven, Model MA-1572M (2450 MHz), for about 2 minutes
on the high power setting (1000 watts). For comparison, Samples
61 and 62 were cigarettes made from leaves which had undergone
the normal flue-cure process, without microwave treatment.
Sample 56 was a cured leaf; Sample 57 was post-yellow, not fully
cured; Sample 58 was a cured lamina, while Samples 59 and 60 were
cured midribs. TSNA contents were measured as in Example 1, and
the results are set forth in Table 6 below:
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Table 6
Samble # NNN NAT + NAH NNK TSNA
52- 0.12 0.23 0.03 0.38
Goldsmoke
~'
cigarettes
53- 0.062 0.326 0.016 0.404
Goldsmoke
II, 85 mm
54- 0.128 0.348 0.029 O.S04
Goldsmoke
85 mm
55- 0.166 0.317 0.047 0.531
Goldsmoke
100's
Sample B
56-Sample 3.269 4.751 0.833 8.853
M-M
57-Sample 0.267 0.720 0.954 1.941
B-C
58-Lamina 0.933 1.456 1.968 4.356
M-C
59-WM 0.996 1.028 0.408 2.432
60-SM 1.745 1.753 0.306 3.804
61- 1.954 1.544 0.492 3.990
Goldsmoke
control
62- , 1.952 1.889 0.424 4.265
Goldsmoke
control
Example 7
Virginia flue tobacco was harvested. Samples 63 and 66 were
uncured, fresh-cut green tobacco, although over a week lapsed
before TSNA measurements were taken, so some air-curing had taken
place. The remaining leaves were placed in a curing barn at
about 100-110°F to begin :the flue-curing process . Sample 68 was
a leaf taken from the barn after it had turned yellow, about 24-
36 hours post-harvest, and was subjected to microwave radiation

CA 02294130 1999-12-16
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in the Waveguide multimode applicator described above, for about
40 seconds at 25 kilowatts.
Samples 64/65 h eaves) and 67/70 (reconstituted sheet
tobacco, or "cut" tobacco) demonstrate the effects of the present
invention when cured tobacco is rehydrated, then subjected to
microwave radiation. Samples 64 and 65 were leaf samples having
undergone the normal flue-curing process; however, Sample 64 was
rehydrated by running under an open faucet for about 5-10
seconds. The leaf absorbed significant moisture. Each of
Samples 64 and 65 was then microwaved in the Waveguide multimode
applicator for about 40 seconds at 25 kilowatts. Samples 67 and
70 were reconstituted sheet tobacco samples, made from cured
leaves. Sample 67 was rehydrated by adding water so that a
significant quantity was absorbed, then microwaved under the
conditions described for Sample 64. Sample 70 was not
microwaved. Samples 69, 71 and 72 are additional cured leaf
samples, used as controls. The TSNA contents were measured as
in Example 1, and the results are shown in Table 7 below:
Table 7
Sample # NNN NAT + NAB NNK TSNA
63-CONTROL 0.010 0.263 0.000 0.274
UNCURED
64-CURED 0.737 1.252 1.893 3.882
40 SEC
(WET)
65-CURED 0.767 1.520 2.229 4.516
40 SEC
66-UNCURED 0.010 0.261 0.000 0.272
40 SEC
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Sample # NNN NAT + NAB NNK TSNA
67-CUT 0.769 1.328 0.308 2.405
TOBACCO
CURED 4 0
SEC (WET)
68-UNCURED 0.051 0.244 0.014 0.308
40 SEC 25
KW
WAVEGUIDE
69-CURED 0.866 1.548 2.545 4.960
CONTROL
70-CONTROL 1.872 2.536 0.789 5.197
CUT
TOBACCO
7I-CONTROL 0.230 0.606 0.746 1.582
'AL' WHOLE
LEAF
72-SML 0.413 0.884 1.514 2.810
WHOLE LEAF
Example 8
Virginia flue tobacco was harvested, and the leaves were
placed in a curing barn at about 100-110° F to begin the flue-
curing process. Sample 73 was a leaf taken from the barn after
it turned yellow, about 24-36 hours post-harvest, and microwaved
in a Goldstar Model MA-1572M for about 2 minutes on the high
setting. Samples 74-76 were ~lue-cured in the normal way.
Sample 74 was a cured control. Samples 75 and 76 were rehydrated
as in Example 7 (Sample 64), then each sample was subjected to
microwave radiation in the MicroDry applicator (2450 MHz) for
about 20 seconds (Sample 75) and about 40 seconds (Sample 76),
respectively, at power levels of about 6 kilowatts. Samples 77-
79 were reconstituted sheet tobacco, made from the flue-cured
leaves. Sample 77 was a control, while Samples 78 and 79 were
rehydrated as in Example 7 (Sample 67). Samples 78 and 79 were
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microwaved in the MicroDry applicator for about 30 seconds each;
Sample 78 rested on the oven bottom, while Sample 79 was raised
up several inches by resting the sheet sample on a Styrofoam cup,
which permitted more uniform heating. TSNA contents were
measured as in Example l, and the results are set forth in Table
8 below:
Table 8
Sample # NNN NAT + NAB NNK TSNA
73-yellow/ 0.052 0.260 <0.0004 0.313
microwaved
74-A- 1.168 1.904 1.662 4.734
control
leaf,
cured
75-B- 20 0.791 1.705 1.115 3.611
SECONDS
76-C 40 0.808 1.624 1.160 3.592
SECONDS
77- 4.417 3.697 0.960 9.073
CONTROL-
sheet
78-30 2.755 2.553 0.644 5.952
SECONDS
79-30 1.606 1.732 0.350 3.687
SECONDS
ELEVATED
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Example 9
Samples 80-81 were Redman chewing tobacco purchased at
retail. Sample 80 was a control, while Sample 81 was microwaved
in a Goldstar Model MA-1572M for about 1-2 minutes on the high
power setting. Samples 82-83 were Skoal snuff purchased at
retail. Sample 82 was a control, while Sample 83 was microwaved
in the same manner as for Sample 81. TSNA contents were
measured, and the results are shown in Table 9 below:
Table 9
Sample # NNN NAT + NAB NNK SNA
T
80-CHEWING 0.712 0.927 0.975 1.713
TOBACCO
BEFORE
81-CHEWING 0.856 0.906 0.122 1.884
TOBACCO
AFTER
82-SNUFF 4.896 10.545 1.973 17.414
BEFORE
83-SNUFF 6.860 14.610 1.901 23.370
AFTER
Example 10
To test whether TSNAs accumulate over time even after yellow
tobacco is microwaved in accordance with the present invention,
additional samples (designated -A) of the cigarettes tested in
Example 4, Samples 29, 35 and 39 (control) were retested for TSNA
content more than seven months after the TSNA contents were first
measured, as reported in Example 4. The results are shown below
in Table 10:
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Table 10
Sample # NNN NAT NAB NNK TSNA
29A-RED O.1I09 0.1877 0.1078 0.0015 0.4079
FF REP
#1
35A-BLUE 0.0508 0.1930 0.1075 0.0012 0.3525
LIGHT
REP #2
39A- 0.6151 1.2357 0.1072 0.9302 2.8882
NATURAL
AMERICAN
SPIRIT
REP #1
Example 11
Virginia flue tobacco was harvested, and the leaves were
placed in a curing barn at about 100-110°F to begin the flue-
curing process. After the leaves turned yellow, about 24-36
hours post- harvest, they were taken from the barn and subjected
to microwave radiation in a Goldstar Model MA-1572M microwave
oven for about 2 to 2~ minutes, on the high power setting. Each
of the leaves was a golden-yellow color, and effectively dried.
Certain samples, designated by "ground", were later ground up
into a flour-like substance, which would be useful as, for
example, a gum, lozenge or food additive. After more than six
months from the time the leaves were microwaved, the TSNA content
of the following samples were measured using the procedure
described in Example 1. The results are shown in Table 11 below:
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Table 11
Sample # NNN NAT NAB NNK TSNA
84- 0.0013 0.0018 0.0018 0.0015 0.0064
ground
85- 0.0469 0.0341 0.0011 0.0009 0.0831
ground
86- 0.0009 0.0582 0.0013 0.0011 0.0615
ground
87- 0.0113 0.1078 0.1078 0.0015 0.2284
ground
88- 0.0569 0.1401 0.1071 0.0009 0.3051
ground
89- 0.0109 0.1642 0.1073 0.0011 0.2835
ground
90- 0.0008 0.0011 0.0011 0.0009 0.0038
ground
91- 0.0009 0.0012 0.0012 0.0010 0.0044
ground
92- 0.0012 0.1059 0.0017 0.0014 0.1101
ground
93- 0.0013 0.0529 0.0019 0.0015 0.0576
ground
94- 0.0012 0.0613 0.0017 0.0014 0.0657
ground
95- 0.0506 0.0989 0.0013 0.0010 0.1518
ground
96- 0.0017 0.0894 0.0024 0.0019 0.0954
ground
97- 0.0012 0.0017 0.0017 0.0014 0.0061
ground
98- 0.0016 0.0023 0.0023 0.0019 0.0082
ground
99- 0.0342 0.0016 0.0016 0.0013 0.0386
ground
100- 0.0014 0.0020 0.0020 0.0016 0.0070
ground
101-leaf 0.0013 0.0539 <0.0019 <0.0016 0.0587
102-leaf 0.0009 0.0012 <0.0012 <0.0010 0.0043
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Sample # NNN NAT NAB NNK TSNA
103- 0.0202 0.0327 <0.0007 <0.0006 0.0542
shredded
leaves
Example 12
Virginia flue tobacco was harvested, and the leaves were
placed in a curing barn at about 100-110°F to begin the flue-
curing process. Samples 104 and 105 were leaf samples having
undergone the normal flue-curing process, without microwave
treatment. Sample 104 was a cured midrib, while Sample 105 was
cured a lamina. Sample 106 was yellow tobacco, taken from the
barn after the leaves had turned yellow, about 24-36 hours post
harvest. After being taken from the barn, the leaves were
subjected to microwave radiation in a Goldstar Model MA-1572M
microwave oven for about 2-2~ minutes, on the high power setting.
Each of the leaves was a golden-yellow color, and effectively
dried. Certain of the dried leaves were further processed in a
conventional manner to form a tobacco extract, which was
designated Sample 107 for purposes of analysis. The TSNA
contents of Samples 104-107 were measured using the procedure
described in Example 1. The results are shown in Table 12 below.
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Table 12
Sample # NNN NAT & NAB NNK TSNA
104 - 0.083 0.180 <0.003 0.266
control
midrib
lOS - 0.928 1.367 2.613 4.908
control
lamina
106 - <0.004 <0.006 <O.OOS <O.O1S
microwaved
leaves
107 - <0.004 <O.OOS <0.004 <0.013
I
' microwaved
extract
Example I3
Virginia flue tobacco was harvested, and the leaves were
placed in a curing barn at about 100-110°F to begin the flue-
curing process. Samples 108 and 109 were leaf samples having
undergone the normal flue-curing process. Sample 108 was a cured
lamina, while sample 109 was a cured midrib. Samples 110 and 111
were yellow tobacco, taken from the barn after the leaves had
turned yellow, about 24-36 hours post-harvest. After being taken
from the barn, Samples 110 and 111 were heated in a circulating
TM
air convection oven, a Sharp Carousel Convection/Microwave Model
No. R-9H84B. Sample 110 was rapidly heated at about 300°F for
between 5-l0 minutes. Sample 111 was more slowly heated at lower
temperatures, starting at about 100°F and being stepped up to
about 150°F after more than 10 minutes, for a total heating time
of over 20 minutes. The TSNA contents of Samples 108-111 were
measured using the procedure described in Example 1. The results
are shown in Table 13 below.
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Table 13
Sample # NNN NAT & NAB NNK TSNA
~~ 108 - 1.267 2.509 1.377 5.153
control .
lamina
109 - <0.004 0.464 <0.004 0.472
control
midrib
lI0 - <0.004 <0.005 <0.004 <0.013
convection-
rapid
111 - <0.003 <0.004 <0.003 <0.010
convection-
slow
Although the convection oven heating was shown to reduce
TSNA levels, the quality of the tobacco was i::ferior to that
obtained upon microwaving in accordance with preferred examples
of the invention. Also, the heating time is necessarily longer
than when using the microwave radiation treatment or other forms
of higher frequency radiation. In particular, the convection
heating was unable to lock the color in at the desired golden-
yellow, and the lamina had a tendency to be over-dried and
therefore brittle, while the veins and midrib were not completely
dried. In contrast, in accordance with the most preferred
embodiments of the invention, the microwaved leaves were
effectively dried and retained a golden-yellow color after being
subjected to treatment, while staying supple and pliable for
further processing, especially as cigarettes. In convection-oven
produced samples, the lamina when dried has a tendency to crumble
into a dust and small tobacco particles.
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Example 14
Kentucky burley tobacco was harvested, and the leaves were
processed as follows after they began to turn yellow, about 24-48
hours post-harvest . Samples 112-117 were leaf samples from this
batch, further processed as follows. Sample 112 was microwaved
under approximately the same conditions as Sample 106 in Example
12. The leaves were a golden-yellow color and effectively dried.
Samples 113, and 114 and 117 were heated in the same circulating
air convection oven as described in Example 13, Sample 113 being
heated under approximately the same conditions as Sample 110,
Sample 114 being heated under approximately the same conditions
as Sample 111, and Sample 117 being heated at about 350°F for
about 20 minutes. The quality of Samples 113, 114 and 117 was
akin to that of Samples 110 and 111, as described in Example 13.
Samples 115 and 116 were heated in the Sharp Carousel
Convection/Microwave oven described in Example 13, using the
combined microwave (30%)/convection (300°C) feature until the
leaves were effectively dried to golden-yellow color. The TSNA
contents of Samples 112-117 were measured using the procedure
described in Example 1. The results are shown in Table 14 below:
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Table 14
Sample # NNN NAT & NAB NNK TSNA
112 - <0.007 <0.010 <0.008 <0.025
microwaved
113 - <0.003 <0.004 <0.003 <0.010
convection
114 - <0.012 <0.017 <0.014 <0.043
convection
115 - <0.002 <0.003 <0.003 <0.008
microwave
(30%) /
convection
116 - <0.002 <0.003 <0.002 <0.007
microwave
(30%) /
convection
117 - 0.131 0.156 <0.003 0.290
convection
Example 15
Virginia flue tobacco was harvested, and the leaves were
placed in a curing barn at about 100-110°F to begin the flue-
curing process. Samples 118-120 were leaf samples, taken from
the barn after the onset of yellowing, and shortly thereafter
subjected to microwave radiation in a conventional kitchen-type
microwave oven for about 2 to 2 1/2 minutes until the leaves
were effectively dried to a golden-yellow color, ~r~ithout burning
or charring. Samples 121-123 were samples of Kentucky burley
tobacco, harvested and processed after the onset of yellowing in
each instance as follows. Sample 121 was placed in a
conventional steam tumble dryer typically used in the tobacco
industry, at a temperature of about 200°F, until the leaves had
browned and dried somewhat. Sample 122 was microwaved in the
above-referenced Goldstar microwave on high for about 2 minutes,
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the rehydrated with water and placed ir_ the tumble dryer to
impart a slight browning to the leaves which is believed to
enhance t:-!e flavor. Sample 123 was treated like Sample 122,
except that it was microwaved for 1 minute and was not rehydrated
before being put in the tumble dryer. TSNA contents were
likewise measured as in Example 1, and the results are shown in
Table 15 below:
Table 15
Sample # NNN NAT & NAB NNK TSNA
118 <0.003 0.150 <0.003 0.156
119 <0.003 <0.004 <0.003 <0.010
120 <0.002 <0.003 <0.003 <0.008
121 0.486 1.059 <0.003 1.548
122 <0.004 <0.005 <0.004 <0.013
123 <0.003 <0.004 <0.004 <0.011
Example 16
North Carolina burley tobacco was harvested, and the leaves
were processed as follows after they began to turn yellow, about
2-3 days post-harvest. Sample 118 was a leaf sample which had
been subjected to microwave radiation in the same type of
Goldstar microwave oven described above, on the high power
setting for about 2 minutes. After microwaving the leaves were
a golden yellow color, and effectively dried. The TSNA content
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was measured using the procedure described in Example 1. The
results are shown in Table 16 below:
Table 16
Sample # NNN NAT & NAB NNK TSNA
118 0.024 0.048 <0.001 0.073
Example 17
This example demonstrates the effectiveness of using
electron beam radiation to reduce the content of, or
substantially prevent formation of TSNAs, in yellow tobacco
samples. North Carolina burley tobacco was harvested. Samples
119-122 were leaf samples, air-cured by hanging outside in a
normal manner, until the leaves were effectively dried and brown.
Sample li9 was untreated as a control. Samples 120 and 121 were
subjected to electron beam radiation on a conveyor belt using a
Dynamitron Electron Beam Accelerator, manufactured by Radiation
Dynamics, Inc. of Edgewood, N.Y., at an exposure rate of 1
megerad. Sample 122 was subjected to microwave radiation in the
Goldstar microwave oven for about 2 minutes on the high power
setting. Sample 123 was taken from the tip of a burley leaf
after it had begun to turn yellow. Sample 124 was a leaf stem
portion, taken from the same plant as Sample 123, and was still
somewhat green-colored. Samples 125 and 126 were whole leaf
burley samples, at the yellow stage. Each of Samples 123-126 was
subjected to electron beam radiation using the above-describing
Dynamitron, in the same manner and under the same exposure rate
as Samples 120 and 121, as described above. The above samples
were tested to measure TSNA content according to the procedure
63

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set forth in Example 1, and the results are shown in Table 17
below:
Table 17
Sample # NNN NAT & NAB NNK TSNA
219 - 3.6351 1.0847 0.0470 4.7668
control,
cured
120 - high 6.5718 3.7037 0.4368 10.7123
power,
cured
121 - low 4.4771 1.6112 0.7468 6.8369
power,
cured
122 - 4.8974 1.6393 1.1200 7.6567
microwave,
cured
123 - 0.1812 0.3667 0.0013 0.5492
yellow tip
124 - 0.1918 0.8310 0.0016 1.0243
green stem
125 - 0.0014 0.1019 0.0016 0.1048
whole leaf
126 - 0.0646 0.2465 0.0019 0.3130
whole leaf
Although the above data show chat electron beam radiation
is effective to prevent formation of substantial quantities of
tobacco-specific nitrosamines in the yellow leaf samples tested,
the leaves were not dried as effectively as when leaves in a
similar state post-harvest were subjected to microwave radiation,
as described in other examples of this application. Thus,
commercial applications of the electron beam irradiation process
may require an additional drying step, such as conveying the
irradiated leaves through a conventional drying oven, to
facilitate the curing process.
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Example 18
This example demonstrates that high energy beams produced
by lasers are also effective to achieve the low TSNA goals of the
present invention. A COz laser made by Luxar Corp., Model LX-
20SP, was used to irradiate yellow Virginia flue tobacco leaves,
r~
at about 2-3 days post-harvest. A NovaScan handpiece was used
under the superpulse E program, which determines the speed of
application in patterns per second. A setting of E10 was used,
which delivers 10 patterns per second. Eight subsamples of
leaves, T-1 to T-8, were irradiated according to the following
protocol:
E10 - 2 watts E10 - 4 watts
i
T-1 - 1 pass T-5 - 1 pass
each each side
side i
T-2 - 2 passeseach side T-6 - 2 passeseach side
T-3 3 passes each side T-7 - 3 passeseach side
-
~ passes each side T-8 - 4 passeseach side
T-4 a
-
At 2 watts, approximately 120 mJ of energy is delivered in
each scan or pass, while at 4 watts, approximately 240 mJ is
delivered in each such scan.
Subsamples T-1 to T-4 were mixed and combined together to
form leaf Sample 127, which was evaluated for TSNA content in the
same manner as, described in Example 1. Subsamples T-5 to T-8
were similarly mixed and combined together to form leaf Sample

CA 02294130 1999-12-16
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128, which was likewise evaluated for TSNA content. The results
are shown in Table 18 below:
Table 18
Sample # NNN NAT & NAH NNK TSNA
127 0.1031 0.2025 0.0006 0.3061
128 0.1019 0.1287 0.0010 0.2315
As with the samples described in Example 17, the CO~ laser
irradiated samples were not dried as effectively as the
microwaved samples, although the TSNA contents were low, and
there=ore an additional drying step could be employed to speed
the curing process. Also, after the C0, laser irradiation but
prior to TSNA testing, six of the eight subsamples turned
somewhat brown, with no apparent effect on TSNA content.
Example 19
This example demonstrates that gamma radiation is also
effective in preventing formation of significant amounts of TSNA
in yellow tobacco . Virginia flue tobacco was taken about 2 -3
days post harvest, just after the leaves had turned yellow. Each
of Samples 129-132 was taken from the lamina portion of the
yellow leaves, and subjected in an enclosed chamber to gamma
irradiation of l0 kGrey (1 megarad) at an exposure rate of 8
kGrey (.8 megarad) per hour, for a total exposure time of about
75 minutes. The irradiated samples were subsequently evaluated
as to TSNA content in the same fashion as described above, and
the results are shown below in Table 19:
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Table 19
Sample # NNN NAT & NAB NNK TSNA
129 0.098 0.225 0.057 0.380
130 <0.001 <0.001 <0.001 <0.003
131 <0.001 <0.001 <0.001 <0.003
132 0.033 0.079 <0.001 0.113
It will be apparent to those skilled in the art that various
changes and modifications may be made in the preferred
embodiments without departing from the spirit and scope of the
claimed invention. Therefore, the foregoing description is
intended to be illustrative only and should not be viewed in a
limiting sense.
67
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Representative Drawing