fig1 illustrates the steps of the method of the present invention where tobacco is first expanded by admixing the tobacco with water , the water preferably being at a temperature of at least about 70 ° c . thereafter , the water expanded tobacco is evaporatively frozen and the frozen , expanded tobacco material is freeze - dried while being heated by infrared radiation . the evaporatively freeze - dried tobacco is moisture conditioned before being recovered for use as a tobacco filling material in cigarettes and the like . fig2 and 3 illustrate diagrammatically an apparatus of the present invention . the apparatus includes a vessel 10 within which is disposed at least one perforated shelf 12 onto which tobacco admixed with water 14 is exposed . also included in vessel 10 are sources of infrared radiation such as for example , radiant heat quartz lamps 16 and , if desired , for efficiency purposes , reflectors 18 . the reflectors may be positioned both above and below the water - containing tobacco to more effectively heat the tobacco material . in order to evaporatively freeze - dry the tobacco , cold temperature condenser 20 is positioned in communication with vessel 10 and also in communication with vacuum pump 22 . when vacuum is being drawn on the vessel , evaporatively freeze - drying is initiated . although the apparatus of the present invention is illustrated as a non - continuous processing vessel , it will be apparent that modifications may be made therein such that continuous operation is achieved . in continuous processing , the tobacco containing water is transported through a vessel having means for containing a vacuum heat source or other necessary means to evaporatively freeze - dry the tobacco being processed therein . the method and apparatus of the present invention are also applicable to all tobacco materials , including stems and veins . fig4 illustrates an embodiment apparatus 24 which is similar to the device of fig2 and 3 except that it contains multiple perforated shelves 26 interiorly disposed with regard to an upper perforated shelf 28 and a lower perforated shelf 30 . upper and lower perforated shelves may include sources of infrared radiation such as quartz tubular radiant heaters which may be optionally shielded by reflectors 18 if desired . similarly , lower perforated shelf 30 may include reflectors 18 disposed relative to the heat quartz lamps 16 . because of the positioning of the intermediate perforated shelves 26 , it is found typically unnecessary to include reflectors for heaters 32 since these intermediate heaters radiate energy to the top of one tray and the bottom of the other . it will be apparent that the infrared sources are suitably attached to electrical connections to permit operation . also , control mechanisms not illustrated but commercially available may be included in association with the apparatus of the present invention to permit controlled heating of the tobacco either by directly controlling the temperature of the infrared radiation or , alternatively , if desired , by pulsating the energy received from the radiant heaters . the length of time necessary to achieve evaporatively freeze - drying will vary depending upon the depth of tobacco being processed and the degree of vacuum achieved by pump 22 in association with the temperature of the refrigerated condenser 20 . the method of the invention uses saturated steam and / or hot water . hot water penetrates the waxy natural surface of tobacco tissue more rapidly than cold ater and thus shortens the treating time over that required when using cold water , and provides greater swelling of the tobacco tissue for a given amount of water . in such a treatment , the hot water penetrates the tobacco and causes swelling of the cells and associated colloids . any excess of water beyond that which causes this swelling will be held in the tissue by capillary action as long as the amount of hot water used is limited to that which will be substantially completely abosrbed by the tobacco . although the capillary water may tend to extract some watersoluble material from the tobacco , the extractives are nevertheless held within the capillaries or in interstices and do not come to the surface of the tissue to any significant extent . thus , by essentially eliminating the presence of any standing water in contact with the tobacco being treated , there is considerable reduction of transfer of the hygroscopic extractives to the surface of the tissue where they could cause tackiness of the tissue . the amount of hot water droplets used in practicing the present invention is , therefore , generally restricted to about 1 to about 5 parts by weight of water per part of tobacco ( dry basis ) in order to achieve the desired cell wall swelling , and possibly capillary water accumulation , without any significant amount of free - standing water being present . the temperature of the hot water droplets used in practicing the invention should be at least about 70 ° c . and preferably at least 90 ° c . water at its boiling point , or at temperatures above its boiling point under pressure , can also be used . the high temperature of the treating water , and its use for only a short period of time , as required for effecting the desired expansion pursuant to the invention , has been found not to significantly affect either the manufacturing or the smoking quality of the tobacco . maintenance of the desired treating temperature , and concomitant use of minimum treating time , can be facilitated by the presence of high temperature steam although , as explained hereinbefore , the steam contributes very little to the amount of water available for penetration and swelling of the tobacco cell walls . the hot water droplets may be applied to the tobacco pursuant to the invention in the form of a spray . the spray may be formed by atomization with the assistance of air , but in this case the air should be hot in order not to cool the water droplets . steam can also be used as such or to form the spray by atomization . the water droplets can be applied to the tobacco while the latter is being carried mechanically through a spray - application zone . however , unless the tobacco is spread in a thin layer , the application of water droplets will not be uniform . the presently preferred practice is to effect contact between the tobacco and the water droplets by permitting the tobacco to fall through a zone of water droplets in order to obtain maximum uniformity of contact . the amount of water contacted with the tobacco under such conditions can be readily controlled by the concentration of the spray in the contact zone passes , the length of the contact zone through which the tobacco falls , and the rate at which the tobacco falls through this zone such as effected , for example , by the direction of the spray and by an updraft or downdraft existing intentionally or unavoidably in the contacting vessel . after the tobacco has been contacted with the desired amount of hot water droplets for the requisite time to effect swelling of the tobacco cell walls as aforementioned , the puffed tobacco is frozen by any appropriate conventional means . for example , the puffed tobacco can be frozen by carrying it through or by allowing it to fall through , a refrigeration zone in which freezing is effected . however , a low - vacuum evaporative freezing , such as at pressures between about 5 mm and 0 . 01 mm of mercury , can be used in either of these handling procedures . when frozen it will be observed that there is a negligible amount of free ice on the expanded tobacco material . the frozen puffed tobacco is then dried by conventional low vacuum technique and moisture conditioned to about 11 - 14 %. a variety of means may be used for moisture conditioning including breaking the final freeze - drying chamber vacuum with steam , steaming the tobacco on a moving conveyer or holding the tobacco in a room or chamber having controlled humidity . the following specific examples are illustrative , but not limitative , of the practice of the invention . in the examples all parts are given by weight unless otherwise indicated . the lamina portion of flue - cured tobacco leaves , after curing and aging , was cut at a shred width of thirty - two cuts / inch and placed into a metal tray at a depth of one - half inch . water at a temperature of 90 ° c . was reduced to spray particles of 0 . 1 - 3 . 0 mm diameter by air pressure and was applied to the tobacco at a ratio of four parts of water to one part of tobacco by weight . a second layer of tobacco was added and sprayed in like manner . the water was imbibed by the tobacco with resultant swelling of the latter . within five minutes of completion of spraying , the tray containing the wetted tobacco was placed in a vacuum chamber and evacuated to a pressure of 2 . 5 mm of mercury which resulted in evaporative freezing . the frozen product was freeze - dried at a pressure of 0 . 5 mm of mercury with the product temperature being increased by indirect heating throughout the cycle to a maximum product temperature of about 180 ° f . the total treating time required for wetting , freezing and drying was about nine hours . the filling power of the tobacco was increased by a factor of 2 . 16 to 1 as measured after moisture equilibration in an atmosphere at 63 % relative humidity and 80 ° f . filling power is determined by placing 20 g of moisture conditioned tobacco in a calibrated cylinder having a diameter of approximately 50 mm . a pressure of 1 . 5 psig is applied during three minutes and the volume is read and compared with the volume of an unexpanded control sample . in the following examples , examples 2 and 3 were duplicate runs . comparing examples 2 and 3 with example 4 shows that with infrared radiation , drying time was decreased by 33 % and the filling power increase was essentially maintained . examples 5 and 6 are for direct comparison . in these runs the tobacco / water ratio was decreased and the effect of adding infrared heat was to decrease drying time by 50 %. differences in filling power increases are within expected experimental variation . an excellent comparison of conventional freeze - drying with the improved method of the present invention using the apparatus illustrated in fig3 - 4 are shown in examples 7 and 8 . for example 7 , the tobacco / water ratio was 1 to 3 , the tray was solid metal , the product was contact frozen and only shelf heat was used . at the same water ratio in example 8 , an open mesh tray was used in conjunction with evaporative freezing and infrared heat . drying time as reduced from six to only two hours and the filling power increase for this particular blend of tobacco was greater than for example 7 . exampls 9 and 10 give additional information about the effect of decreasing the tobacco / water ratio . by this means , drying time was decreased but so was the filling power increase . table i__________________________________________________________________________ freezing method heat source drying filling filling powertype of example tobacco to type of tray contact or shelf , infrared time power increase . sup . ( 3 ) tobacco . sup . ( 1 ) no . water ratio solid or mesh evaporative or both . sup . ( 2 ) ( hrs ) ( cc / g ) (%) __________________________________________________________________________blend a 2 1 + 3 mesh evaporative shelf 3 10 . 50 94 . 3blend a 3 1 + 3 mesh evaporative shelf 3 9 . 70 79 . 6blend a 4 1 + 3 mesh evaporative both 2 9 . 50 75 . 9blend a 5 1 + 2 mesh evaporative shelf 3 8 . 80 63 . 0blend a 6 1 + 2 mesh evaporative both 11 / 2 8 . 60 59 . 3blend b 7 1 + 3 solid contact shelf 6 8 . 00 90 . 5blend b 8 1 + 3 mesh evaporative both 2 8 . 45 101 . 5blend c 9 1 + 3 mesh evaporative both 2 7 . 35 101 . 4blend c 10 1 + 2 mesh evaporative both 11 / 2 5 . 35 46 . 6__________________________________________________________________________ . sup . ( 1 ) blend a : a mixture of flue and aircured tobaccos . blend b : fluecured tobacco . blend c : another blend of fluecured tobacco . . sup . ( 2 ) heat source &# 34 ; both &# 34 ; describes the application of infrared heat t the top of the product with shelf heat applied to tray bottom . . sup . ( 3 ) filling powers of unexpanded tobacco blends : blend a 5 . 40 cc / g blend b 4 . 20 cc / g blend c 3 . 65 cc / g evaporatively freeze - drying as used herein is intended to define the process of vacuum induced , reduced pressure boiling of water which , upon partial evaporation , extracts heat from the water expanded tobacco and , correspondingly , causes the tobacco and remaining absorbed water to freeze the tobacco in the expanded condition . the remaining absorbed water in the frozen state is removed by infrared radiation heating which may be applied to the tobacco at any period of time either during the step of evaporatively freeze - drying or subsequently thereto if desired . while the invention has been described in connection with the preferred embodiments , it is not intended to limit the invention to the particular forms set forth , but , on the contrary , it is intended to cover such alternatives , modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims .
the invention disclosed is an apparatus for increasing the filling capacity of cured tobacco by evaporatively freeze - drying water expanded tobacco and effecting heating of the tobacco by infrared radiation . the treated tobacco has increased filling capacity without suffering disadvantageous results .