The present invention relates to a process for treating tobacco products with a water-insoluble or slightly water-soluble flavorant. The tobacco products include both smoking tobacco and smokeless tobacco. - In particular, the invention relates to the treatment of tobacco with water-insoluble or slightly water-soluble flavorants, such as menthol for cigarettes and wintergreen for chewing tobacco, by the use of an aqueous dispersion technique and without the need for any volatile and flammable organic solvents.

Certain flavorant substances for tobacco have, heretofore, been applied to tobacco products by dissolving the flavorant in a suitable carrier solvent, such as alcohol. One of the most widely used flavorant substances for smoking tobacco, and particularly for cigarette tobacco, is menthol crystals for imparting a menthol flavor. Traditionally, the menthol crystals are dissolved in alcohol (ethanol) and, thereafter, are applied by spraying the menthol-alcohol solution onto cut tobacco as it is fed through a rotating .cylinder. The treated tobacco is then placed in a controlled environment such that the alcohol will evaporate, leaving the menthol residue on the tobacco, and to maintain the tobacco in a usable condition.

Similarly, the application of water-insoluble flavorants to smokeless or chewing tobacco has traditionally been an alcohol spray process and has comprised a multi-step technique. In the first or casing step, a casing solution is boiled in a kettle. While some flavorants normally found in the casing solution are stable at the boiling temperatures _bf the casing step, others and in particular wintergreen cannot withstand these relatively high processing temperatures and substantially flash-off. Wintergreen flavor is commercially derived from natural wintergreen oil or methyl salicylate (artificial wintergreen flavorant) which are difficult to apply as they are extremely affected by the processing temperatures. The heated casing solution is then applied by conventional techniques to tobacco. The so-called "cased tobacco" is then dried to a desired moisture content. The dried, cased tobacco is then subjected to a recasing step wherein a humectant, such as glycerine, is used to maintain moisture. Further sweeteners are added in the recasing step, such that a sweet taste remains on the tobacco surface for desirable initial, organoleptic properties. In the conventional flavoring processes of the prior art, the flavorant is then imparted to tne recased tooacco oy spraying it witn a solution of the flavorant in alcohol. Where a relatively small volume of alcohol/flavorant solution is used to impart the desired level of flavoring, the flavorant is not uniformly dispersed in the wintergreen application step. It has then been necessary to bulk/blend the treated tobacco in order to achieve a commercially acceptable uniformity of flavoring throughout the tobacco.

The industry has long been aware that the use of ethanol as a carrier solvent in the flavoring of tobacco requires special care and attention. Alcohol has a low flash point (13°C ) and, at concentrations as low as 3.3 percent by volume, it forms an explosive mixture in air that has been reported to auto-ignite. Measurements within the primary spray cylinder have revealed ethanol concentrations approaching 2% in normal and conventional flavorant spray processes,. In order to minimize the hazard, a number of precautionary measures have been taken in the use of solvent based systems, such as explosion proof electrical fixtures and controls, ventilation, extra hazard sprinkler protection, curbs and drains, etc., all of which necessitate considerable added expense.

Efforts have been made to reduce or eliminate the use of ethanol or other flammable and dangerous solvents in the application of water-insoluble or slightly water-soluble flavorants to tobacco. In one technique for mentholation of smoking articles, and particularly as described in the Banks _U.S. Patent Reissue No. 29,298, the menthol is first vaporized, and then sequentially added together with the tobacco to be treated into a pressurized, hot air conduit for processing. This is a costly procedure and otherwise undesirable because of the inability to control accurately the degree and uniformity of menthol application to the tobacco.

Accordingly, there exists a recognized and long felt need for a process for applying water-insoluble or slightly water-soluble flavorants directly to tobacco by techniques which do not involve the use of volatile and combustible organic solvents, such as alcohol.

It is accordingly an object of this invention to provide a process, which may be a continuous process, by means of which controlled levels of a water-insoluble or slightly water-soluble flavorant may be homogeneously and uniformly applied to tobacco during processing without the need for organic solvents, or chemical emulsifiers.

The invention provides a simple process for depositing the water-insoluble or slightly water-soluble flavorants upon tobacco using aqueous dispersion techniques to produce smoking products which possess superior _Qrganoleptic properties.

To this end, a process for treating tobacco with a water-insoluble or slightly water-soluble flavorant using an aqueous dispersion technique is characterised by:

• a) mixing the flavorant and water in predetermined proportions;
• b) forming an aqueous dispersion of the flavorant and water under constant agitation conditions;
• c) agitating the dispersion to cause any solid flavorant particles to melt or liquefy and to stabilize the dispersion sufficiently for further processing;
• d) transmitting the aqueous flavorant dispersion to a means for applying the dispersion in a homogeneous and uniform way onto the tobacco to be treated;
• e) applying the aqueous flavorant dispersion to the tobacco, in such a way that the tobacco upon drying uniformly retains the flavorant in a weight proportion corresponding to the predetermined proportion of the flavorant in the dispersion; and
• f) conditioning the treated tobacco as necessary to obtain a desired flavorant equilibrium and moisture content.

In order for the flavorant to be applied homogenously and uniformly to the tobacco, the aqueous flavorant dispersion must be maintained in a stable form throughout processing, and particularly as it is sprayed into a cylinder or other vessel containing the tobacco to be treated. This may be accomplished in a number of ways depending upon the physical state of the flavorants. For example, natural or artificial wintergreen oil as a liquid does not, of course, require any special technique for melting, whereas menthol crystals as solids do require liquefaction. In the preferred embodiment, a high speed mixer-emulsifier is used to create the dispersion at a temperature suitable to maintain the presence of liquefied flavorant. This temperature will vary for the solid flavorants. The temperature for menthol crystals ranges from about 45-55°C. The dispersion is in essence formed by the mechanical action of the high speed mixer-emulsifier and heat. It has been found in the most preferred embodiment that sufficient temperature increases may be generated by the heat of shearing developed by the mixer-emulsifier agitation itself to liquefy any solid flavorant to such an extent that a stable dispersion is maintained throughout processing, and particularly, during application to the tobacco to be treated.

In another embodiment where processing at room or ambient temperature is desired for otherwise solid flavorants without the need for heating, low levels of a suitable solvent/stabilizer may be used to solubilize the flavorant, such as menthol, in the aqueous medium. Where menthol is the desired flavor, propylene glycol is a suitable stabilizer and has been found to contribute favorably to the organol- ieptic characteristics of the product. A significant factor is that the solvent/stabilizer should be one that is not so volatile as to form an explosive mixture in air.

The means for applying the aqueous flavorant dispersion to the tobacco is typically a spray apparatus. In such apparatus, a spray nozzle or nozzles are attached with a supply of compressed air at a pressure of about 25 psi (172 kN/m²) to a tobacco processing tumbler or rotating cylinder.

Suitable flavorants, which are insoluble or only slightly soluble in water, include menthol, anethol, cinnamaldehyde, eugenol, heliotropin, menthone, methyl salicylate, gamma-undecalactone and vanillin.

The process in accordance with the invention completely eliminates the prior costly use of ethanol in the application of water-insoluble flavorants to tobacco while still imparting excellent organoleptic properties in a homegeneous and uniform way. Moreover, at least for smoking tobacco, the use of continuous agitation eliminates the need for chemical emulsifiers which may impart off flavors to the tobacco.

Two examples of processes in accordance with the invention will now be described with reference to the accompanying drawings in which:-

• Figure 1 is a diagram of apparatus for carrying out a preferred example of the process for imparting a menthol flavor to cigarette tobacco; and,
• Figure 2 is a diagram of apparatus for carrying out a preferred example of the process for imparting a wintergreen flavor to smokeless tobacco.

Although applicable to other flavorants which are either water-insoluble or only slightly soluble in water, the invention in its preferred embodiments is described first as a process for imparting a menthol flavor to tobacco, preferably cigarette tobacco and, second, as a process for imparting a wintergreen flavor to unrecased tobacco in the manufacture of a smokeless tobacco product.

Accordingly, the first preferred embodiment of the invention relates to the application of a menthol composition derived from both natural and synthetic sources to cigarette tobacco. Menthol is obtained from either peppermint oil or other mint oils or may be prepared synthetically by hydrogenation of thymol. The menthol obtained from natural sources is generally purified by freeze recrystallization from solutions of the crude product. Crude natural menthol crystals, which are generally obtained in Brazil, Taiwan or Japan, such as Brazilian Arvensis menthol crystals, normally give a cooling sensation in the mouth of the user of the product incorporating the menthol; however, the cooling effect carries with it the medicinal taste of menthol. Generally, the recrystallization of a menthol product from natural menthol crystals creates a lingering cool sensation in the mouth of the user of the tobacco product with little or no detection of the menthol taste. A fifty-fifty blend of naturally occurring and synthetic menthol crystals has been found satisfactory in commercial tobacco products.

In general, tne level or mentnoi on tobacco in conventional mentholated cigarettes is from about 0.2 to 0.5% by weight of the tobacco. This level may be achieved by the present invention during a single application or spray of the aqueous menthol dispersion to the tobacco to be treated. The weight proportion of menthol in the dispersion may range from about 5 to 40 percent and is predetermined so as to correspond to the final weight percent of flavorant desired in the end product. A primary concern is that the proper level of menthol should be applied to the tobacco not only homogeneously, but also on a reasonably uniform basis throughout a given amount of tobacco being treated either as a batch or on a continuous basis. For example, in order to achieve a mentholation level of from 0.2 to 0.5 percent by weight of the tobacco at equilibrium during a single pass of tobacco through the system, it is preferable to achieve a contact time of tobacco and aqueous menthol dispersion (about 5 to 40 percent menthol) of about 0.5 to 4 hours, preferably about 2 to 4 hours, which is normally accomplished in a suitable covered holding container.

Turning now to Fig. 1 of the drawings, at one end of a rotatable spray cylinder 10 for treating cut tobacco, a suitable container 12 is mounted and connected at its exit end 13 to the spray nozzle 14 of a spray compressor 15 via a valve 16. The mixer head 18 of a high speed mixer-emulsifier unit 20 is positioned within the container 12 to promote optimum emulsification. In a batch process, a predetermined amount of water is added to the container 12, mixer unit 20 is started, and a predetermined amount of menthol is slowly added. In a continuous on-line process, such as that shown in Fig. 1, water at a desired and predetermined rate is transferred from holding tank 22 to the container 12 and the mixer unit 20 is started. The mixer speed is set at about 3000 to 5000 rpm. Menthol crystals from tank 24 are added slowly to the agitated water until a homogeneous dispersion at a predetermined weight proportion is obtained and, thereafter, maintained by a constant feed from tanks 22 and 24 at the desired proportions of menthol to water. However, even on a continuous run it may be more practical to prepare the menthol/water dispersion batchwise while spraying it onto a continuous tobacco flow. In any event, while the heat of shearing caused by the mixer promotes the melting and dispersion of liquefied menthol within the agitated dispersion, the system may be supplementally heated, if necessary, to a temperature between 45 and 55°C to ensure complete liquefaction of the menthol crystals.

_Afte; the dispersion at the desired proportion is formed in container 12, the valve 16 is opened and the dispersion is allowed to flow through the spray compressor 15 to spray nozzle 14 where compressed air at 138 kN/m²atomizes the dispersion for application at a prescribed rate to the tobacco from holding bin 26 supplied with tobacco via conveyor belt feed apparatus 27. The rates of flow of the dispersion and the tobacco into the spray cylinder 10 are regulated and monitored by process control device 25. The spray cylinder 10 is rotated at about 10 to 12 rpm during spray treatment. Bin 26 is positioned at the head of the cylinder 10 adjacent to the spray apparatus. The tobacco is tumbled under the spray for about 1 to 5 minutes. The treated tobacco tumbles within the cylinder 10 at a predetermined rate and is continuously collected in the bin 28 at the opposite end of the spray cylinder. The tobacco collected in bin 28 may be continuously carried off for further processing, treatment, or storage via conveyor 29.

After the valve 16 is opened, the container 12 is fed continuously with predetermined amounts of water and menthol crystals regulated by process control device 13 to achieve and maintain the desired level of flavorant on the tobacco and such that the process may be conducted on a continuous on-line basis. In order to maintain proper control of the menthol concentration, the crystalline menthol is slowly added to the water while stirring and the rate of agitation and any optimal heating element (not shown) is adjusted so as to maintain a dispersion temperature of 45-55°C. With regard to the maintenance of the menthol and water within the aqueous dispersion in specified proportions, it has been found that for every pound of tobacco, 5 ml of water and 1.6 grams of menthol are required to create a dispersion which results in the homogeneous application of approximately 0.3 to 0.4 percent menthol by weight of the tobacco product. For example, in order to achieve a cigarette tobacco product having a 0.35% target mentholation, ;1.5 to 1.7 grams of menthol must be dispersed within 4 to 6 ml of water for each pound (₄₅₃ g) of tobacco.

In another preferred embodiment, the invention is used to impart a wintergreen flavor to smokeless tobacco. The flavorant is natural wintergreen oil or methyl salicylate (artificial wintergreen flavorant) which is water insoluble. In accordance with the invention, the flavorant is satisfactorily incorporated into the recasing step, thereby reducing the number of processing steps as well as eliminating the need for any final bulk/blending as presently required in alcohol based processes. The level of wintergreen flavorant on conventional smokeless tobacco generally ranges from about .20 to 1.75 percent by weight of the >tobacco, depending upon the type of tobacco employed and consumer preference. This level may be achieved by the present invention in a continuous process during a single application or spraying of the aqueous wintergreen dispersion to the tobacco to be treated. The weight proportion of wintergreen in the dispersion may range from about 5 to 40 percent and is predetermined so as to achieve the desired final weight percent of flavorant in the end product. To achieve a homogeneous and uniform application of the wintergreen flavorant throughout the tobacco, the contact time of the tobacco and the aqueous dispersion is closely regulated. For example, in order to achieve a minimum wintergreen level from .2 to 1.75 percent by weight of the tobacco at equilibrium in a continuous system, the contact time of tobacco and aqueous dispersion (about 5 to 40 percent methyl salicy- late) is about 1 to 10 minutes, preferably about 2 to 5 minutes, which is normally accomplished in a suitable covered holding container.

Referring to Fig. 2 of the drawings, apparatus for a continuous on-line process is shown wherein a conventional recasing container 50 is filtted witn a nign speed mixer-emulsifier 52 such that the emulsifier head 54 is positioned within the container 50 to promote optimum emulsification or dispersion. The flavorant-recasing composition comprises water, methyl salicylate and glycerine in such proportions as to impart the desired concentration of methyl salicylate and glycerine to the tobacco to be treated. With regard to the maintenance of the recasing ingredients in specified proportions within the aqueous dispersion, it has been found that for each pound of tobacco, about 4.5 ml. of water, about 2.7 gms. of methyl salicylate and about 9.0 gms. of glycerine are required to create a dispersion which results in the homogeneous and uniform application of about .35 to .45% flavorant by weight of the tobacco product. For example, in order to achieve a smokeless tobacco product having .4 per- bent target wintergreen flavorant, about 1.8 gms.-2.72 gms. of wintergreen must be dispersed within about 4 to 5 ml. of water for each pound (453 g) of tobacco

The container 50 may be initially supplied with a specified quantity of the aqueous flavorant and recasing ingredients to treat a certain batch of tobacco, or it may be continuously supplied with the recasing ingredients including the flavorant in the desired proportions for an on-line continuous process. Container 50 is connected via valve 58 to pump 56 which in turn connects to the spray nozzle or nozzles 60 for application of the aqueous flavorant-recasing dispersion to the tobacco as it is fed into and tumbled in spray cylinder 62. Unrecased tobacco, i.e. tobacco which has been subjected to an initial casing treatment and dried, is fed from storage tank 64 via a flow scale and meter arrangement 66 to the spray cylinder 62 for treatment with the aqueous recasing and flavorant dispersion. Process control device 70 together with flow scale 66 and flow meter 68 are used to monitor the amount of flavorant applied to the unrecased tobacco to be treated.

In operation of the invention process according to this embodiment, water, glycerine, methyl salicylate and any other desired recasing ingredients in specified proportions are supplied to container 50 wherein the mixture is agitated to form a homogeneous and stable aqueous dispersion. Once the aqueous dispersion is formed in container 50, valve 58 is opened to enable the dispersion to flow via pump 56 and monitored by meter 68 and process control device 70 to the spray nozzle 60 for application to the unrecased tobacco as it is fed into spray cylinder 62. Simultaneously with the flow of the aqueous flavorant-recasing dispersion, unrecased tobacco from tank 64 is fed via flow scale 66 to the cylinder 62 for treatment. In the practice of the invention, the flow scale 66 monitors the flow rate of the unrecased tobacco and generates a signal which is delivered to the process control device 70. The flow scale signal is multiplied by a predetermined constant in the ratio controller of the process control device 70 which is related to the amount of flavorant 5and recasing desired in the end product. The multiplied signal becomes the set point for control device 70. The flow meter 68 monitors the flow rate of the recasing-flavorant dispersion while the flow scale 66 monitors the flow of unrecased tobacco. The resulting signal is compared to the set point signal, such that process control device 70 regulates the flow speed through pump 56 such that the proper quantity of recasing-flavorant dispersion is fed to spray nozzle 60 in relation to the quantity of unrecased tobacco monitored by flow scale 66, all to achieve the desired end product characteristics.

In processing smokeless tobacco in accordance with this technique, it was found that the wintergreen flavorant is satisfactorily applied in the recasing step to achieve a Uniform and homogenious application without the need for an additional bulk/blending step.

The glycerine ingredient in the recasing composition acts as an emulsifying agent to promote the formation of a uniform aqueous flavorant/recasing dispersion, as well as a humectant to ensure proper moisture retention in the final product. Hydrogenated glucose syrups and sorbitol have also been found to be useful emulsifying agents. In general, all suitable emulsifying agents and humectants are contemplated, as well as all other additives as may be desired and as are well-known in the art.

The following examples further illustrate the present invention, but are not intended to limit its scope in any way.

EXAMPLES 1A and 1B

Two 50 lb. (22.5kg) batches of a commercial tobacco blend were treated with an aqueous menthol dispersion on a batch basis in apparatus similar to that illustrated in the drawing and described hereinabove. The menthol crystals were a fifty-fifty blend of Brazilian natural and a synthetic variety. The spray cylinder was initially conditioned by spraying 15 lbs (6.8 kg) of scrap tobacco with 100 ml of menthol dispersion formulated at a .35% target concentration. The scrap was removed and the first batch of 50 lbs (22.6 kg) of tobacco blend (Example lA) was processed for a .385% menthol target concentration. To achieve the .385% target concentration, 87.5 grams of aenthol were added to 252 ml of water. The target concentration for the second fifty pound (22.6 kg) batch. (Example 1B) of a tobacco blend, was a .35% which only required 79.5 grams of menthol crystals in the same volume of water. In each case the high speed emulsifier (Ross Mixer Corporation) was set at 5000 rpm and the temperature in the mixing container was maintained at 45-50°C. The dispersion was applied at a spray pressure setting of 20 psi (138 kN/m²) which corresponds to a rate of 3.5 ml per second, and the bulking operation was carried out for 4 hours. The spray cylinder was rotated at a rate of 12 rpm.

In an effort to determine the optimum time for the menthol to become homogeneously dispersed throughout the tobacco, a series of tobacco samples from each concentration level (i.e. both Examples 1A and 1B) were extracted for menthol analysis at both times of 0, 2, and 4 hours. Based upon an analysis of the samples obtained, it was found that a bulk processing time, i.e. bulk storage time in a covered container, of approximately 1 to 4 hours is preferred to obtain uniform homogeneous dispersion of the menthol flavorant throughout the tobacco batch in the process of this example.

Upon removing the tobacco from the cylinder after menthol application in the instances of both Examples 1A and 1B, the samples were placed in a storage bin and covered with a tarp so as to prevent menthol loss. The mentholated tobaccos were stored in a conditioning room at 55% relative humidity and 75° F (23.9°C). The cigarettes were stored for approximately 2 weeks in the conditioning room prior to a test panel evaluation comparing them with a control batch of commercial blend mentholated cigarette tobacco. The control cigarettes had been produced from a 6000 lb (2718 kg) batch of tobacco that had been mentholated by conventional techniques with 21 lbs (9.5 kg) of menthol dissolved in 8 gallons (30.2 1) of ethanol. The cigarettes prepared at the target level of 0.35% were paneled against the ethanol applied control and were found to compare favorably.

EXAMPLE 2

A 1000 pound (453 kg) batch of cased and dried smokeless tobacco is treated with 37 pounds (16.8 kg) of an aqueous methyl salicylate, glycerin, water, and sweetener dispersion on a continuous flow system similar to that illustrated and described in Figure II of the drawing. To achieve a final concentration of 40% methyl salicylate, 20 pounds (9.1 kg) of glycerin, 10 pounds (4.5 kg) of water, 1 pound (453 g) of sweetener, and 6 pounds (2.7 kg) of methyl salicylate are sprayed on 1000 pounds (453 kg) of cased and dried tobacco. In each case the high speed emulsifier (Ross Mixer Corporation) is set at 3500 rpm and mixed for approximately five minutes to achieve a uniform aqueous dispersion. Based on a tobacco flow rate of 100 pounds (45.3 kg.) per minute a constant flow of flavorant recasing solution is pumped (approximately 100 psi (689 kN/m²) and sprayed at a rate of 3.7 pounds (1.68 kg.) per minute. The tobacco is filled into storage containers and covered with a tight fitting cover so as to prevent methyl salicylate and moisture loss.

Based on analytical results using a sample prepared essentially by the process of Example 2, the invention material was found to be of equal uniformity coming out of the spray cylinder when compared to the flavorant-alcohol control after bulk-blending. Organoleptic tests indicated that the aqueous dispersion process of the invention yielded a final product equal to the control.