EP0078352B1

EP0078352B1 - Process for expanding cut tobacco

Info

Publication number: EP0078352B1
Application number: EP19810305197
Authority: EP
Inventors: Roger Z. De La Burde; Francis V. Utsch; Patrick E. Aument
Original assignee: Philip Morris USA Inc
Current assignee: Philip Morris Products Inc
Priority date: 1981-10-30
Filing date: 1981-10-30
Publication date: 1986-06-18
Also published as: EP0078352A1; MY8700901A

Description

The present invention relates to a process for expanding cut tobacco in which tobacco is wetted with water to a moisture content OV-basis of at least 30% and the moisture is allowed to penetrate through the tobacco, the moist tobacco is dried for a period of a few seconds in a turbulent steam atmosphere to reduce the moisture content to less than that required for processing and the dried tobacco is then remoisturized to a moisture content desired for processing.
US-A-3 734 104 discloses a process of this kind which is, however, applied to tobacco stems. The cell structure of the stems allows expansion to be achieved by the simple evaporation of moisture so that increases in filling power of 60% or more are achieved even with an exit OV value close to 10%.
The present invention is characterized in that the tobacco is tobacco lamina filled to effect expansion by vaporization of the moisture the drying temperature is not less than 232°C and the drying conditions are such that the moisture content of the dried tobacco is less than 3%.
Thus, in accordance with the invention, to obtain the required increase in filling power of leaf tobacco rapid overdrying to a low moisture content is required.
EP-A-0 073 137 which was published on 2nd March 1983 and has a priority date of 20th August 1981 discloses a process of increasing the filling power of tobacco lamina filler which uses water as the only expansion agent. The filler, which has an initial OV value of 8% to 28%, is rapidly and uniformly heated by contact with a gas containing at least 50% of steam at a temperature of at least 232°C for a contact time of 0.1 to 6 seconds. The final OV value is preferably less than 3%.
To facilitate understanding of the present specification, the following definitions are given:-

Oven Volatiles (OV)

As used herein, oven volatiles is the percent weight loss of tobacco in a circulating air oven in three hours at 100°C. OV is used herein to mean the "moisture content" of the tobacco.

Filling Power

As used herein, filling power is the ability of the material to provide a firm rod. The filling power is the minimum weight of tobacco which will produce a tobacco rod of specified dimensions and firmness and may be measured as the volume occupied by a specified weight of filler in an upright cylinder when a specified piston weight is applied to its top surface, as set forth in "Filling Volume of Cut Tobacco and Cigarette Hardness", H. Wakeham, et al., Tobacco Science xx: 164-167, 1976. Standard equilibrium conditions for measurement of filling power are usually 60% relative humidity (RH) at 75°F (23.9°C).

Cylinder Volume (CV)

As used herein, cylinder volume is a measurement of filling power and is determined by placing 10.0 grams of filler in a standard metal cylinder, 3.358 cm. in diameter, and vibrating the assembly for one-half minute to settle the tobacco column. The tobacco is then compressed under a piston weighing 1875 grams and having a diameter of 3.335 cm, for five minutes and the volume reading is then taken. The standard deviation of the cylinder volume measurement is about 1.5%.
Preferably in the process of the present invention, the moisture content of the tobacco is from 30% to 80%, although moisture contents within the range of 30% to 40% are effectively employed. Moisture contents of 60% to 80% may be effectively employed, but penetration or bulking time will probably increase and drying the tobacco within the desired times and to the desired post-treatment moisture levels will be more expensive and time consuming.
It is desired that the moisture be allowed to substantially uniformly penetrate and be distributed or dispersed throughout the cellular structure of the tobacco being processed, although homogeneous dispersion is not required. The bulking penetration time for satisfactory penetration will depend upon batch size and upon the means of addition of the water and the desired economics. Employing a rotary cylinder and a fine mist spray or other conventional mixing system known in the art for incorporating additives, a penetration time of 4 hours or somewhat less will be sufficient, as is further illustrated in Example 5. The primary criterion is that the time of penetration be sufficient to allow the moisture to be distributed within and absorbed by the tobacco cellular structure of substantial portions of the tobacco. Typically, the overwetted tobacco is bulked from about 1/4 hour to about 4 hours.
As previously stated, after penetration of the moisture throughout the tobacco structure, the tobacco is overdried in a period of a few seconds in a turbulent steam atmosphere.
Rapid drying of the tobacco, preferably within less than 5 seconds, in a turbulent steam atmosphere to a moisture content of less than 3% expands the tobacco as the moisture rapidly escapes the tobacco cellular structure. The cellular structure of the tobacco fibers thereupon stiffen to retain the expanded nature of the tobacco during remoisturization to normal processing moisture contents of about 12% to 21%. Drying to a moisture content of 2% to 3% is particularly preferred. Steam drying versus air drying produces substantial gains in filling power as will be noted from Example 2.
To achieve and retain the desired expansion, it has been found that the more rapid the drying, the more effective the process. In effect, an almost immediate evaporation of the moisture is sought. Drying times of 5 seconds or less are desired to achieve a 2% to 3% moisture content, if not even a lower moisture content. The more rapid the drying step, the more rapid the evolution of the moisture and the more effective the expansion. Residence times longer than 5 seconds do not appear to produce the desired expansion levels.
To rapidly overdry the tobacco, a high turbulence drying unit such as a Proctor & Schwartz dispersion dryer, or a Jetstream@ dryer or other equivalent drying tower, capable of producing a turbulent atmosphere high in steam content, may be utilized. The proportion of steam in the turbulent steam drying atmosphere is desirably at least about 60% and preferably at least about 80% although steam contents of about 60% to about 70% can be effectively employed.
With regard to the treatment temperature, that is, the temperature of the turbulent steam atmosphere in the drying unit, at temperatures of at least about 232°C and employing properly designed and reasonably efficient equipment which allows rapid drying of the moisturized tobacco in a period of seconds, the moisture content of the overwetted tobacco may be reduced to less than about 5% to produce economically significant increases in filling power. Rapid drying in a turbulent steam atmosphere at a treatment temperature of at least about 316°C, and preferably from about 316°C to about 330°C provides substantial increases in filling power. As will be seen in Example 3, treatment temperatures of about 121°C provide little useful increase in filling power; temperatures from about 149°C to about 204°C provide perceptible gains in filling power; temperatures from about 232°C to about 288°C provide moderate increases in filling power, and temperature of from about 288°C to about 316°C provide significant increases in filling power. Further, in accordance with the practice of the present invention, turbulent steam atmospheres having temperatures as high as 500°C. may be successfully utilized.
Subsequent to overdrying, the tobacco is preferably remoisturized under mild conditions, by means and processes well known in the industry for reordering tobacco, such as cylinder reordering, to achieve a processing moisture content of about 12%. The reordering should be at a moderate rate to prevent loss of expanded fiber rigidity.
The following examples present illustrative but non-limiting embodiments of the present invention. Comparative examples are also presented.

Example 1

Five pounds of bright cut filler were placed in a small rotary cylinder and sprayed with a fine water mist until the moisture content was raised to 30% water by weight. The filler was allowed to bulk for 4 hours and was then dried in a.steam atmosphere in a high turbulence drying tower at 316°C for 4 seconds. The rapidly dried filler was allowed to equilibrate for 18 hours at 21°C and 60% RH after which OV and CV measurements were taken and compared to an untreated control. The results are summarized below in i able 1.

Example 2

Two 5-pound samples of bright cut filler were processed as in Example 1 except that Sample 2 was dried in a tower at 316°C. in the absence of steam. The results are summarized below in Table 2.
It can be seen when comparing a sample dried in a turbulent steam atmosphere with a sample dried in an air atmosphere that significant gains in filling power are achieved employing a turbulent steam atmosphere.

Example 3

50 pounds of bright filler were moisturized and bulked as in Example 1. Samples of the overwetted filler were processed in a steam atmosphere in a high turbulence drying tower at 121°C, 149°C, 177°C, 204°C, 232°C, 260°C. 288°C, 316°C and 330°C in a time period of 4 seconds or less. The results are summarized in Table 3 below and illustrate the significant gains in filling power which are achieved by overdrying the overwetted tobacco at elevated temperatures in a turbulent steam atmosphere.

Example 4

Seven 5-pound samples of bright filler were overwetted and bulked to moisture contents of 15%, 20%, 25%, 30%, 40%, 60% and 80% respectively. Each sample was then processed in a tower dryer containing a turbulent steam atmosphere and at the treatment temperature indicated in Table 4 below to less than about 1.5% OV in the indicated treatment time or less. The moisture levels of 60% and 80% required two passes through the tower to achieve the desired overdrying to a moisture level of 1.5% OV. The results of these runs are summarized below in Table 4 and indicate that the desired increase in filling power are achieved with tobacco overwetted to moisture contents on excess of 20%.

Example 5

Fifty pounds of bright filler were moisturized and equilibrated as in Example 1. The filler was allowed to bulk, and portions were removed after 1/4, 1/2, 1, 2, 3, 4 and 24 hours of bulking. The 7 sample portions were rapidly dried in a tower containing a turbulent steam atmosphere at 316°C. The results are summarized in Table 5 below.
The results indicate that bulking from 4 to 24 hours has no significant effect upon the filling power increases as compared with bulking from 1/4 hour to 4 hours and that bulking is not a critical consideration.

Example 6

Fifty pounds of bright filler were processed as in Example 1. The processed filler, after reordering, had a filling power of 56 cc/10g, corrected to 12% moisture. Cigarettes were made in which 15% of the conventional filler was replaced by the processed filler and the subjective qualities of these cigarettes were compared with those of standard production cigarettes. There were no major subjective differences and the cigarettes containing the 15% expanded tobacco were found to be equally satisfying and to have full flavor.
It will be understood that the particular embodiments of the invention described above in Examples 1 through 6 are only illustrative of the principles of the invention, and that various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.

Claims

1. A process for expanding cut tobacco in which tobacco is wetted with water to a moisture content OV-basis of at least 30% and the moisture is allowed to penetrate through the tobacco, the moist tobacco is dried for a period of a few seconds in a turbulent steam atmosphere to reduce the moisture content to less than that required for processing and the dried tobacco is then remoisturized to a moisture content desired for processing, characterized in that the tobacco is tobacco lamina filler and to effect expansion by vaporization of the moisture the drying temperature is not less than 232°C and the drying conditions are such that the moisture content of the dried tobacco is less than 3%.

2. A process according to claim 1 characterized in that the tobacco is moisturized to a moisture content of from 30% to 80%.

3. A process according to claim 1 or 2 characterized in that the tobacco is dried within 5 seconds.

4. A process according to claim 3 characterized in that the tobacco is moisturized to a moisture content of from 30% to 40%, the temperature is from 232°C to 370°C and the turbulent steam atmosphere comprises at least 60% steam.

5. A process according to claim 1, 2 or 3 characterized in that the temperature is from 232°C to 288°C.

6. A process according to claim 1, 2 or 3 characterized in that the temperature is from 288°C to 316°C.

7. A process according to claim 1, 2, 3 or 4 characterized in that the temperature is from 316°C to 330°C.

8. A process according to claim 1, 2, 3, 5, 6 or 7, characterized in that the steam-containing atmosphere comprises at least 60% steam.