GB1585024A

GB1585024A - Process for treating tobacco

Info

Publication number: GB1585024A
Application number: GB1800578A
Authority: GB
Original assignee: Fabriques de Tabac Reunies SA
Current assignee: Philip Morris Products SA
Priority date: 1977-05-06
Filing date: 1978-05-05
Publication date: 1981-02-18
Also published as: FR2389342A1; FR2389342B1; CH634469A5; DE2816427A1; DE2816427C2

Abstract

In a method for upgrading tobacco, the nitrates and nitrites are dissolved out of the tobacco with water, and a pure culture of microorganisms is then applied, in its phase of exponential growth, under nitrogen deficiency conditions or under oxygen deficiency conditions, to the tobacco extract solution obtained until the nitrates and nitrites present therein are sufficiently degraded, whereupon the remaining solution constituents of the tobacco extract solution are again added to the tobacco.

Description

(54) A PROCESS FOR TREATING TOBACCO (71) We, FABRIQUES DE TEBAC REUNIES S.A., a Swiss Corporate body of Quai Jeanrenand 3, CH-2003, Neuchatel, Switzerland do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in by the following statement: The invention relates to a process for treating tobacco through the reduction of nitrates, nitrites and other nitrogenous products contained in the tobacco.

Many tobaccos, for example Burley, contain nitrates and/or nitrites which can produce irritant nitric oxides during smoking. Fermentation processes are known which bring about the reduction of these nitrogen salts enzymatically. However, this only occurs to a very limited extent and only as a secondary effect of other enzymatic reactions.

The object of the invention is to reduce the nitrates and nitrites to an acceptable residual content in order to lower the proportion of nitric oxides in the smoke. As far as possible, the reduction of the nitrates and nitrites should take place selectively, i.e. whilst avoiding to the maximum reactions of the tobacco constituents accompanying the nitrates and the nitrites.

According to the invention, there is provided a process of treating tobacco which comprises aerobically culturing a nitrate and/or nitrite-reducing mico-organism in the presence of at least part of the nitrate and/or nitrite content of the tobacco as an essential nitrogen source for the micro-organism, the micro-organism being at an exponential growth phase when initially contacted with the said content and the reduction being immediately terminated when the desired reduced nitrate and/or nitrite content is reached and at most after 24 hours.

Usually, the reduction will be terminated after 8 to 24 hours. Preferably, an aqueous tobacco extract obtained by washing nitrates, nitrites and other water-soluble components out of the tobacco to be treated is cultured with the micro-organism and the resultant low-nitrate and/or nitrite tobacco extract is added to water-washed tobacco.

Under the conditions of the invention the micro-organisms remain in their exponential growth phase for as long as the necessary requirements of oxygen or nitrogen can be met by the nitrites and nitrates. The microorganisms used are forced during use to cover their nitrogen or oxygen requirements from the nitrates and nitrites to be reduced. so that the latter are reduced.

In the case of nitrogen deficiency conditions, the microorganisms are forced to cover their nitrogen requirements from their nitrates and nitrites to be reduced. The nitrogen in the nitrate or nitrite is used by the microorganisms to build up organic compounds necessary for their life. These compounds are mainly aminoacids and proteins, which do not have a disturbing effect when smoking and can in fact have an advantageous action on the flavour of the smoke. In the case of oxygen deficiency conditions. the microorganisms are forced to cover their oxygen requirements from the nitrates and nitrites to be reduced. so that the latter are reduced to the stage of nitrogen or ammonia. The nitrogen can escape in a harmless manner, and the nitrogen present in the form of ammonium salts. aminoacids and amines does not form nitric oxides during smoking.

The exponential growth of microorganisms under nitrogen deficiency conditions can be brought about in an aerobic ambient by introducing a low-nitrogen nutrient solution. The exponential growth of microorganisms under oxygen deficiency conditions can be brought about in an anaerobic ambient by introducing a solution with limited oxygen sources which are accessible to the microorganisms.

As the added microorganisms culture is already activated, its microorganisms have an advance of several hours compared with other undesired microorganisms which are still in their latent phase. Within the action period of a few hours, the undesired microorganisms are unable to recover this initial advance to the extent that they could exert a significant action. It is thus ensured that the action sought by the invention is selective.

The low-nitrate tobacco extract solution obtained can be added to the washed tobacco from which the tobacco extract solution was obtained. However, this is not always practicable on an industrial scale. The same result is obtained if the low-nitrate tobacco extract solution obtained from a first tobacco charge is added to a second previously washed tobacco charge, whereby the tobacco charges should as far as possible contain tobacco in the same quantity and quality.

The nitrates and nitrites to be reduced are more accessible to the microoganisms in the tobacco extract solution than in the tobacco. This applies in particular to tobacco stems and the invention is therefore preferably used on separated tobacco stems. The nitrates and nitrites in the leaves or strips (i.e. the parts of the leaves between the stems) can be treated in accordance with a process of the invention without previously washing them.

Advantageously an active slush obtained as residue after treatment of an aqueous tobacco extract by a process of the present invention is used, whereby treatment can commence with a very intense action. According to this embodiment of the invention, the action of the microorganisms on the aqueous tobacco extract is terminated by removing the active slush and the latter is sprayed onto tobacco leaves or strips to be treated and is kept in the exponential growth phase for 8 to 24 hours by an added nutrient solution until reduction is completed and then the action of the microorganisms on the tobacco leaves or strips is immediately terminated.

If the active slush is not required for further reduction purposes, it is appropriately added to the tobacco and deactivated, so that the constituents contained in the active slush are added to the tobacco.

Unfermented, air-dried tobaccos frequently have nitrate contents of approximately 50g/kg of dried weight. In extreme cases, nitrate quantities up to 80g/kg of dry weight are measured. The residual content sought is dependent on the further use of the tobacco. In the case of tobacco varieties which represent a large proportion of the ready-for-smoking tobacco mixture, the desired residual content is at most 5g of nitrate and nitrite anions per kg of dry weight. In the case of tobacco varieties which only represent smaller proportions of the ready-for smoking mixtures, the desired residual content can be somewhat higher. In general, the desired residual content is in the range 3 to 20% and is preferably 5% of the original content of the tobacco to be finished, based on the total weight of nitrate and nitrite anions.

The reduction can be stopped by not maintaining the living conditions of the microorganisms, for example by greatly lowering the temperature, drying or removing the microorganisms, for example by filtering as active slush, when the action takes place in liquid surroundings.

The microorganisms used can be bacteria, for example those of the genus Aerobacter, Pseudomonas, Micrococcus or Echerichia or they may be fungi such as for example of the genus Rhodutorula or Candida.

The invention can be used with particular advantage in conjunction with a pure culture of the bacterium Enterobacter aerogenes, preferably of the standard strain ATCC 13048. Pure cultures of this standard strains can be obtained from the Deutsche Sammlung von Mikroorganismen (German Collection of Microorganisms), Grisebachstrasse 8, Göttingen under DSM No. 30053.

Characteristics of Enterobacter aerogenes; Motile rods 0.3 to 1.5 Fm Gram Gas evolution at 370C Glycerine + Inositol + Andonitol + Voges-Proskauer + Methyl red Phenylaminodesaminase Urease Catalase + Ornithine decarboxylase + Lysine decarboxylase + Hydrolysis of Aesculin + Growth in presence of KCN + on malonate a sole carbon source + The microorganism culture is preferably used as a pure culture, the purity level being sufficient to prevent significant secondary actions.

When frozen in liquid nitrogen, the microorganism culture can be stored and then thawed and reactivated for reuse. When in constant use, it can be stored in the active state in a binstat from which the constantly necessary portions can be removed.

The invention is illustrated hereinafter in a number of Examples.

EXAMPLE 1 Treating tobacco leaves under oxygen deficiency conditions lkg Maryland-tobacco whose nitrates and nitrites are to be reduced is de-stemmed. This yields 250g stems and 750g strips.

The 250g stems are washed with 1250ml warm water of 70"C. This removes nitrates and nitrites contained in the stems together with other water-soluble components. The thus obtained stem-extract solution is drawn off from the stems, placed in a 2 l-Erlenmeyer flask, closed with a porous stopper, cooled to 30"C, mixed with 12.5g of D-glucose. as well as innoculated with 10ml of an activated pure culture of the bacterium Enterobacter aerogenes ATCC 13048.

The innoculated stem-extract solution is incubated at 30"C on a shaker until nitrate and nitrite anions have been reduced to a content of 0.1g/l, which takes 16 hours.

The thus obtained low-nitrate stem-extract solution is then immediately centrifuged, the microorganisms settling and are then removed as active slush. The active slush can be reused, discarded or sprayed in deactivated form onto tobacco so that its constituents are supplied to the tobacco.

The centrifugate from the low-nitrate stem-extract solution which still contains the remaining tobacco constituents dissolved out of the stems is re-added to the predried, washed stems which are then dried to a 20% moisture content. In this way all the tobacco components which have been removed with the nitrates and nitrites from the stems are returned to the stems, so that the stems essentially contain their original components, except for nitrates and nitrites, which have been reduced to 1/6 of their original content.

EXAMPLE 2 Example 1 is repeated except for the sole difference that the centrifugate of the low-nitrate stem-extract solution is not re-added to those stems from which the extract was obtained, but is instead added to other stems which were treated in the same way.

EXAMPLE 3 Treating tobacco leaves under oxygen deficiency conditions lkg Maryland-tobacco whose nitrates and nitrites are to be reduced is de-stemmed. This yields 250g stems and 750g strips. The 250g stems are treated as described in Example 1.

The microorganisms of the thus obtained 150ml active slush are still in their exponential growth phase when the active slush is drawn off and are kept in their growth phase by immediately adding the active slush with 30g D-glucose, 12.9g peptone, 9.6g NaCl, 6.75g KH2PO4 and 35.25g Na2PO4 . 2H20 immediately into 1500ml of water. Thus, a suspension of active microorganisms is obtained, which is then immediately sprayed in an even distribution onto the 750g strips of moisture content 20%. The sprayed strips will then have a moisture content of 50% and are stored at 30"C for 24 hours with air exclusion. During this time the microorganisms reduce the nitrates and nitrites contained in the strips to 1/20 of their original content. The strips with their thus reduced nitrate and nitrite content are dried to a 20% moisture level for further processing.This inactivates any microorganisms still remaining on the strips. The strips are now ready for further processing.

EXAMPLE 4 Treating tobacco leaves under oxygen deficiency conditions Pure culture is obtained as in Example 1]i50ml 1.

250g Burley-tobacco leaves are washed in 1250ml of warm water at 70 C. The resulting tobacco-extract solution is treated in the same manner as the stem-extract solution of Example 1, and the thus ultimately obtained low-nitrate tobacco-extract solution is centrifugally separated from the active slush and readded to the tobacco leaves.

EXAMPLE 5 Treating tobacco stems under nitrogen deficiency conditions lkg of Maryland tobacco in which the nitrates and nitrites are to be reduced is de-stemmed, yielding 250g of stems and 750g of strips.

The 250g of stems are washed with 1250ml of warm water at 700C. Water-soluble nitrogen compounds present in the stems are dissolved out together with other water-soluble constituents. The stem-extract solution obtained in this way is drawn off from the stems added to a 2 litres Erlenmeyer flask closed with a porous stopper, cooled to 30"C, mixed with 12.5g of D-glucose, followed by innoculation with 10ml of an activated pure culture of the bacterium Enterobacter aerogenes ATCC 13048.

The innoculated stem-extract solution is vented at 300C on a shaker under sterile conditions with an air throughput of 1300ml/min and is incubated until nitrate and nitrite anions have been reduced to a content of 0.1g/l, which takes 16 hours. Other nitrogenous compounds are also reduced.

The low-nitrate stem-extract solution obtained in this way is then immediately centrifuged, whereby the microorganisms are deposited and removed as active slush. The active slush can then be further used, discarded or sprayed onto the tobacco in deactivated form in order to feed its constituents to the tobacco.

The centrifugate from the low-nitrate stem-extract solution which still contains the other tobacco constituents dissolved out of the stems is re-added to the predried washed stems which are then dried to a 20% residual content. The tobacco constituent previously dissolved out of the stems with the nitrates and nitrites are returned to the stems, so that the latter essentially contain their original constituents, except for the reduced nitrogenous compounds which now only represent 1/6 of their original content.

EXAMPLE 6 Example 5 is repeated with the sole difference that the innoculated stem-extract solution is incubated until 50% of the nicotine originally contained in the stem-extract solution has been reduced, which takes 20 hours. The stem-extract solution then contains at most traces of nitrate and nitrite because the added microorganisms only start nicotine reduction when no further nitrate or nitrite is available.

EXAMPLE 7 Treating tobacco leaves under nitrogen deficiency conditions lkg of Maryland tobacco in which the nitrates and nitrites are to be reduced is de-stemmed, which yields 250g of stems and 750g of strips. The 250g of strips are treated as described in Example 5. The 750g of strips are individually immersed for 20 seconds in 11250ml of warm water at 500C. The water-soluble compounds present in the surface area of the strips are dissolved out. As the nitrates and nitrites present in the strips are mainly contained in the surface areas, they mainly pass into the water.In the thus obtained strip extract solution, which still. contains other nitrogenous compounds, the latter are microbiologicallv reduced in the manner of Example 5 and specifically until the anions nitrate and nitrite are reduced to a content of 0.1g/l. The strip extract solution is then concentrated and sprayed onto the washed strips.

EXAMPLE 8 Treating tobacco leaves under nitrogen deficiency conditions 250g of Burley tobacco leaves are washed with 1250ml of water at 500C. The resulting tobacco extract solution is further treated in the same way as the stem-extract solution of Example 5 and the resulting low-nitrate tobacco extract solution is centrifuged off from the active slush and re-added again to the washed tobacco leaves.

WHAT WE CLAIM IS: 1. A process of treating tobacco which comprises aerobically culturing a nitrate and/or nitrite-reducing micro-organism in the presence of at least part of the nitrate and/or nitrite content of the tobacco as an essential nitrogen source for the micro-organism, the micro-organism being at an exponential growth phase when initially contacted with the said content and the reduction being immediately terminated when the desired reduced nitrate and/or nitrite content is reached and at most after 24 hours.

2. A process as claimed in Claim 1 wherein the reduction is terminated after 8 to 24 hours.

3. A process as claimed in either of the preceding Claims wherein the said desired reduced nitrate and/or nitrite content is within the range 3% to 20% of the original nitrate and/or nitrite content in the tobacco to be treated.

4. A process as claimed in Claim 3 wherein said reduced content is 5% of said original content.

5. A process as claimed in any one of the preceding Claims wherein an aqueous tobacco extract obtained by washing nitrates, nitrites and other water-soluble components out of the tobacco to be treated is cultured with the micro-organism and the resultant low-nitrate and/or nitrite tobacco extract is added to water-washed tobacco.

6. A process as claimed in Claim 5 applied to separated tobacco stems.

7. A process as claimed in any one of Claims 1 to 5 applied to tobacco leaves or strips.

8. A process as claimed in Claim 7 wherein the tobacco leaves or strips to be treated are sprayed with an active slush obtained as a residue after treatment of an aqueous tobacco extract by a process as claimed in Claim 5 or Claim 6.

9. A process as claimed in Claim 5 or Claim 6 wherein the action of the micro-organisms on the tobacco extract solution is terminated by removing.the micro-organism as an active slush residue and the removed active slush is added to the washed tobacco and deactivated.

10. A process as claimed in any onexof the preceding Claims wherein the microorganism is a bacteria of the genus Aerobacter, Pseudomonas, Micro-coccus or Echerichia or a fungi of the genus Rhodutorula or Candida.

11. A process as claimed in Claim 10 wherein the micro-organism is a pure culture of the bacterium Enterobacter aerogenes of strain ATCC 13048.

12. A process of treating tobacco to reduce the nitrate and/or nitrite content thereof substantially as described hereinbefore with reference to the Examples.

13. Tobacco whenever treated by a process as claimed in any one of the preceding

Claims

Claims.