Process for flavoring tobacco

Process for flavoring tobacco by mixing dry cut tobacco with one or more micro-encapsulated flavors as well as with an aqueous adhesive solution containing such quantity of water that said quantity may at least be adsorbed for the most part by the tobacco, continuing the mixing operation till a dry or almost dry product is obtained and then, if necessary, subjecting the obtained product to a drying operation respectively reduction operation.

The invention concerns a process for flavoring tobacco. The invention also 
comprises the products obtained by the process according to the invention. 
Tobacco is mostly flavored before it is made into cigarettes. The most 
important prior art method of flavoring consists of spraying or atomizing 
a liquid flavor, sometimes diluted with a suitable solvent e.g. alcohol, 
over the bulk of the tobacco. The main disadvantage of this method is that 
the flavor, being very finely dispersed over a large surface area, 
evaporates rapidly and is susceptible to oxidative deterioration and, 
consequently, is short lived. 
It has been tried to solve this problem using airtight packaging filled 
with an inert gas, e.g. as described in German Offenlegungsschrift No. 
3,006,092. However, this is an expensive solution and the problem 
reappears as soon as the consumer opens the package. 
It has been tried to solve similar problems for tea by using powdered, more 
specifically micro-encapsulated flavors. However, vibrations and shaking, 
e.g. during packing and transport, cause the fine powdered flavor to 
separate from the much coarser tea leaves. Eventually, one part of the 
package contains mainly powdered flavor and the other part mainly tea 
leaves. To prevent this separation, granulated flavors, with a particle 
size comparable to that of tea leaves have been prepared, as described in 
British Patent No. 1,564,001 and in published British Patent Application, 
No. 2,074,838. However, granulated flavors have to be prepared in a 
separate process, using specialized equipment. Although one could envisage 
similar solutions for the flavoring of tobacco, these would suffer from 
the same disadvantages. 
Thus, there is a need for a process to affix powdered flavors to tobacco. 
The product of this process should consist only of particles of the 
original tobacco, some of them being covered with flavor powder. 
Such a process, again for tea, has been described in the above mentioned 
British Patent Application No. 2,074,838, using .beta.-cyclodextrin/flavor 
inclusion complexes as the powdered flavors. These molecular complexes, 
described by W. Saenger in Angew. Chemie 92 (1982) pp. 343-361 are in most 
cases only poorly soluble in cold water. Therefore, as described in the 
above mentioned British Patent Application, they may be made into a 
suspension in water and dispersed on the tea, without suffering from 
decomposition. However, due to the high price of .beta.-cyclodextrin, 
these flavor inclusion complexes are expensive and, consequently, are 
hardly used in the food industry. 
Micro-encapsulated flavors, on the other hand, are extensively used in the 
food industry, but to date hardly in the tobacco industry. They may be 
produced in several different ways, e.g. as described by L. L. Balassa and 
G. O. Fanger in CRC Critical Reviews in Food Technology, July 1971 pp. 
245-264. 
These microcapsules consist of small droplets of flavor oil with a solid 
envelope of an edible hydrocolloid, such as a vegetable gum, a modified 
starch or gelatin. 
However, such microcapsules cannot be used in the process described in the 
British Patent Application mentioned above. Since they are readily soluble 
in water, they will disintegrate, thereby releasing the flavor oil which 
is thus subject to evaporation and oxidation. 
Surprisingly, a process has now been found to affix micro-encapsulated 
flavors to cut tobacco with retention of the original appearance of the 
tobacco. This process comprises the steps of either thoroughly mixing 
tobacco and micro-encapsulated flavors, followed by finely dividing a 
solution of an adhesive material in water over the mixture while 
continuing the mixing operation, or thoroughly mixing the adhesive 
solution with the vegetable material, immediately followed by the addition 
of the micro-encapsulated flavor while continuing the mixing operation. 
The process also comprises continuing the mixing operation after the three 
components mentioned above have been added until the mixture is almost dry 
or completely dry and, if necessary, drying the mixture further with air 
or an inert gas, which may be warmed if desired. 
The quantity of water, added as a solvent for the adhesive, should be 
sufficient to ensure complete moistening of the tobacco and microcapsules 
with the adhesive solution. On the other hand, the tobacco should be able 
to absorb most of the water, to prevent softening or dissolution of the 
microcapsules to a point where the entrapped flavor oil is released. 
Thus, the maximum allowable quantity of water in the adhesive solution also 
depends on the water absorptive capacity of the tobacco. Tobacco may 
contain up to 15-18% by weight of water before becoming damp, the exact 
FIGURE depending on the kind of tobacco and the treatment it has been 
subjected to before. 
In general the quantity of water added should be so limited that after the 
mixing operation the water content of the mixture is at most 5% by weight 
in excess of the quantity that may be absorbed by the vegetable material. 
This residual water is evaporated with air or an inert gas until the 
mixture has a dry appearance, i.e. until the total water content is 15-18% 
by weight or less. Preferably the quantity of water should not exceed the 
FIGURE that can be completely absorbed by the tobacco, thus obviating the 
need for an additional drying step. The absorptive capacity of any kind of 
tobacco may be easily determined in moistening and drying experiments in a 
vacuum desicator. If necessary the absorptive capacity of the tobacco may 
be increased by predrying. 
The amount of microcapsules to be affixed to a given amount of tobacco, 
using the process of the invention, may vary within wide limits and 
depends on the desired flavor strength in the end product. The maximum 
amount that may be affixed is related to the available surface area of the 
tobacco and is directly proportional to the mean particle size of the 
microcapsules. Using microcapsules with a mean particle size of 80 .mu.m, 
the maximum amount is about 350 g of microcapsules per kg of tobacco. From 
these data, the maximum amounts for microcapsules with other particle 
sizes may be derived by simple arithmetic. 
In most cases sufficiently high flavor strengths are already attaind with 
much lower quantities of microcapsules. In many cases it is even simpler 
and cheaper if only a (small) part of the material to be flavored is 
subjected to the process of the invention. This flavored part is 
thereafter mixed with the bulk of unflavored tobacco. If this mixing is 
done immediately after the flavoring process of the invention, it may 
obviate the need for a separate drying step, even if the flavored tobacco 
is not yet completely dry, since the residual water can easily be absorbed 
by the unflavored bulk. 
The adhesives used in the process of the invention may be film forming 
hydrocolloids, comprising vegetable and microbial gums, such as gum 
arabic, karaya, tragacanth, carragenan etc.; modified starches, such as 
dextrines, esterified starches etc.; cellulose derivatives such as 
hydroxypropylcellulose and carboxymethylcellulose; gletain, casein and 
comparable proteins and polyvinylalcohol. Alternatively, saccharose and 
other saccharides which will form a glass on drying may also be used as 
adhesives. Of course adhesives to be used in the process of the invention 
must be approved for use in tobacco. 
The quantity of adhesive used should be sufficient to secure sufficient 
adhesion of the microcapsules to the tobacco, and the minimum amount 
required depends on its adhesive power. Although 1 g of adhesive per kg of 
microcapsules may be sufficient in some cases, preferably a quantity of 10 
g or more per kg of microcapsules should be used to be on the safe side. 
In order to secure a homogeneous distribution of the adhesive through the 
tobacco, it is advantageous to spray or atomize the adhesive solution over 
the tobacco or the mixture of tobacco and microcapsules. To this end a 
spray head or atomizer, adjusted in or above the mixing chamber or mixing 
vessel may be used. 
When selecting the hydrocolloid adhesive, it must be taken into account 
that many of them form highly viscous solutions even in low 
concentrations. The pressure necessary to disperse a liquid into fine 
droplets increases with increasing viscosity of that liquid. Solutions 
with a maximum viscosity of 400 cP may be used on spray heads with a 
working pressure of 300 Bar. With low pressure spray heads (about 10-15 
Bar max.) the viscosity should preferably not exceed 150 cP. However, care 
should also be taken not to use too diluted solutions to prevent the 
addition of a quantity of water exceeding the absorptive capacity of the 
tobacco. Therefore, adhesives causing only a slight viscosity increase in 
solution, are preferred when a high microcapsules content is desired, to 
obtain a high flavor strength. Examples of such adhesives are gum arabic 
and saccharose. 
To prevent differences in color between treated and untreated tobacco a 
suitable food color such as carmel may be added to the adhesive solution. 
The process according to the invention may be further improved by spraying 
a small quantity of water miscible organic solvent over the tobacco or the 
mixture of tobacco and microcapsules as the case may be, and thoroughly 
mixing it through, prior to the addition of the adhesive solution. The 
absorption of water from the adhesive solution by the tobacco is thereby 
slowed down, resulting in a more homogeneous dispersion of the adhesive 
solution through the bulk of the mixture. This prevents the formation of 
conglomerates consisting of particles of tobacco and/or microcapsules, 
before homogeneous dispersion of the adhesive has occurred. 
Suitable solvents have to meet the following conditions: they should not 
dissolve or only slightly dissolve the microcapsules; they must be 
suitable for use in tobacco; they should not have an annoying odor or 
flavor of their own. Examples of such solvents are ethanol, isopropanol, 
propylene glycol, glycerol and benzyl alcohol. 
During the operation of the process of the invention, the organic solvent 
will partly evaporate and partly be absorbed by the tobacco, thereby 
limiting the absorptive capacity available for water absorption. The 
quantity of adhesive solution to be used later should be adapted 
accordingly. So, the quantity of solvent to be added and the quantity of 
adhesive solution to be used are interrelated and both depend on the 
absorptive capacity of the tobacco. Tobacco with a high absorptive 
capacity may tolerate the addition of up to 100 g of organic solvent per 
kg of endproduct, especially when that solvent evaporates easily, as is 
the case with ethanol. However, in most cases 40 g or less per kg end 
product will suffice to obtain the desired improvement of the process. 
The process of the invention may be carried out using mixing equipment 
which is conventional in the food industry. It is preferred to use a type 
of mixer which does not cause undue heating of the mixture or damage to 
the tobacco particles, even on prolonged mixing. In most cases conical 
mixers are very suitable. When using a mixer which may cause heating or 
damage the tobacco particles, it may be advantageous to stop the mixing 
operation before the mixture is dry and thereafter complete drying e.g. 
with warm air. In order to get a desired particle-size distribution, the 
product may be passed through a sieve and the remainder ground to the 
desired particle size. 
This is especially appropriate when drying has been completed after the 
mixing operation, since this may cause the particles to cling together. It 
may even be necessary to break and grind the product before sifting. 
However this does not materially affect the appearance of the end product.

EXAMPLE I 
In a 10 l Hobart mixer 700 g cut tobacco and 150 g microencapsulated cocoa 
flavor were mixed in 30 sec., while spraying with 20 g of ethanol. While 
mixing continued, 50 g of a 14% w/w gum arabic solution was sprayed on the 
tobacco in about 2 min. and after another 2 min. 80 g gum arabic was added 
and mixing continued for a few minutes. 1 kg of dry, strongly flavored, 
cut tobacco was obtained, which was diluted to a flavor level desired for 
consumption by mixing with 150 kg of fresh tobacco. 
EXAMPLE II 
In a 100 l conical blender equipped with a doubly rotating screw, 5.8 kg of 
cut tobacco and 1.2 kg of microencapsulated menthol (menthol content 22 
O/O w/w) were mixed during 5 minutes. Using a spray head fitted in the 
blender, 0.15 kg of ethanol was sprayed over the mixture in about 8 
minutes, followed by 0.55 kg of 15 o/o w/w gum arabic solution in about 15 
minutes, while continuing the mixing. Thereafter 2.3 kg of tobacco was 
added and mixing continued for 15 minutes. 10 Kg of strongly menthol 
flavored tobacco was obtained containing 2.6 o/o menthol. This 10 kg of 
flavored tobacco was mixed with 65 kg of unflavored tobacco to obtain 75 
kg of cigarette tobacco blend containing 0.35 o/o menthol.