EP3534728A1

EP3534728A1 - Defibrated tobacco material

Info

Publication number: EP3534728A1
Application number: EP17794305.7A
Authority: EP
Inventors: Lars Björkholm
Original assignee: Winnington AB
Current assignee: British American Tobacco Sweden AB
Priority date: 2016-11-02
Filing date: 2017-11-01
Publication date: 2019-09-11
Anticipated expiration: 2037-11-01
Also published as: DK3534728T3; JP2021184712A; CA3042133C; JP2019533451A; HUE063457T2; CA3042133A1; SE541198C2; JP6954677B2; PL3534728T3; KR20190084253A; SE1651447A1; US20190254337A1; RU2709941C1; EP3534728B1; UA126907C2; WO2018083114A1; FI3534728T3

Abstract

A process for production of bleached tobacco raw material comprising the steps of: (I) mechanical defibrating uncooked tobacco raw material to produce a defibrated tobacco raw material; and (II) treating the defibrated tobacco raw material from step (I) with at least one bleaching agent to produce a treated tobacco raw material. Bleached tobacco raw material obtainable by the process.

Description

Defibrated Tobacco Material

PRODUCTION PROCESS

The present invention relates to a process for production of a tobacco raw material, and to tobacco raw material obtainable by this process.

The invention also relates to a smoking tobacco composition comprising the tobacco raw material, and a smokeless tobacco composition comprising the tobacco raw material.

The invention also relates to nasal snuff and oral smokeless tobacco products comprising the smokeless tobacco composition. Background

Bleached tobacco and production processes therefore are previously known.

US20130276801 discloses chemical pulping of tobacco and bleaching the tobacco pulp to produce a dissolving grade pulp. Bleaching the tobacco pulp may include chlorination of the tobacco pulp with a chlorine dioxide solution, and caustic extraction of the tobacco pulp with a second strong base. Carbohydrate content is not suggested to be reduced or limited, but on the contrary to be protected during the treatments. Fermentation is not discussed in the document. WO2015150506, the disclosure of which is incorporated by reference in its entirety herein, discloses bleached tobacco raw material comprising less than about 4 weight-% fermentable carbohydrates, calculated on the dry total weight of the bleached tobacco raw material. It also discloses a process for production of the bleached tobacco raw material comprising: (a) treating tobacco raw material at acidic pH at about 70°C to about 180°C with sulfite ion; (b) defibrating the tobacco raw material; and (c) treating the defibrated material with a bleaching agent at about 60°C to about 90°C.

Short summary of the invention

There is still need for improved processes for production of bleached tobacco raw materials. There is in particular need for improvements relating to dewatering, specifically drainage, since this property often has a significant impact of the operating speed of the production process.

One object of the present invention is to provide such an improved process for production of bleached tobacco raw materials. Thus, one aspect of the invention relates to a process for production of bleached tobacco raw material comprising the steps of:

(I) mechanically defibrating uncooked tobacco raw material to produce a defibrated tobacco raw material;

and

(II) treating the defibrated tobacco raw material from step (I) with at least one bleaching agent to produce a treated tobacco raw material.

Description of embodiments of the invention

Before the present invention is disclosed and described, it is to be understood that this invention is not limited to the particular configurations, process steps, and materials disclosed herein as such configurations, process steps, and materials may vary somewhat. It is also to be understood that the terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting since the scope of the present invention will be limited only by the appended claims and equivalents thereof.

It must be noted that, as used in this specification and the claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise.

In this specification, unless otherwise stated, the term "about" modifying the quantity of an ingredient in the tobacco raw material, tobacco compositions, or tobacco products of the invention or employed in the methods of the invention refers to variation in the numerical quantity that can occur, for example, through typical measuring and liquid handling procedures used for making concentrates or use solutions in the real world; through inadvertent error in these procedures; through differences in the manufacture, source, or purity of the ingredients employed to make the tobacco raw material, tobacco compositions, or tobacco products, or to carry out the methods; and the like. The term "about" also encompasses amounts that differ due to different equilibrium conditions for a composition resulting from a particular initial mixture. Whether or not modified by the term "about", the claims include equivalents to the quantities.

In this specification, unless otherwise stated, the term "bleached" refers to an object, such as for instance a tobacco raw material, whose visible color has been reduced by any known method for this purpose, such as washing with one or more solvents, or treatment with one or more bleaching agents, or any combination thereof. In this specification, unless otherwise stated, the term "fermentable carbohydrates" refers to carbohydrates that can be metabolically broken down in and by the human body, specifically starch, glucose, fructose and sucrose.

In this specification, unless otherwise stated, the term "oral" in connection to a product refers to the product, in normal use, is suited to be placed somewhere in the oral cavity of the user, for example under the lips, in the same way as moist snuff products are generally used.

In this specification, the term "mechanically defibrating" means methods of separating or releasing tobacco fibers in the uncooked tobacco raw material under the influence of processes such as cutting, tearing, grinding or similar processes where the raw material is subjected to cutting, shearing or grinding forces, or a combination thereof. The defibrating process may include moistening of the raw material, the employment of heat, pressure or steam can be included, as being conventionally used when defibrating fibrous materials. The term mechanically defibrator shall not be limited to a process performed with the defibrator according to US patent 2008892. The defibration according to the present invention may control the results of the dewatering in the process, however, different defibrating methods are conceivable that lead to a suitable dewatering process.

In this specification, the term "a defibrated tobacco raw material" is the material subjected to mechanical defibration as previously defined, comprising separated or release tobacco fibers.

Surprisingly, the inventive production process does not only provide for improvements relating to the dewatering/drainage, but also to the bleaching efficiency of the process.

It should be noted that both of these process improvements relate to the corresponding product improvements, namely the freeness and the bleachability, i.e. the consumption of bleaching agent required to reach a given brightness, respectively, of the obtained bleached tobacco raw material.

In one embodiment of the inventive process for production of bleached tobacco raw material said at least one bleaching agent is chosen among Cl₂, CI0₂, NaOCI, Cl₂0, 0₂, 0₃, Na₂S₂0₄, potassium peroxymonosulfate, dimethyldioxirane, peroxides, peroxy acids, enzymes, and combinations thereof. In one aspect of this embodiment said at least one bleaching agent is chosen among 0₂, 0₃, Na₂S₂0₄, potassium peroxymonosulfate, dimethyldioxirane, peroxides, peroxy acids, enzymes, and combinations thereof. The total amount of added said at least one bleaching agent may, for instance, be about 30 - 250 kg per ton tobacco raw material (calculated as pure bleaching agent), specifically about 50 - 200 kg per ton tobacco raw material.

In one embodiment of the inventive process the treated tobacco raw material from step (II) is - after having been treated with said at least one bleaching agent - additionally treated with at least one second bleaching agent. Said at least one second bleaching agent may be chosen among Cl₂, CI0₂, NaOCI, Cl₂0, 0₂, 0₃, Na₂S₂0₄, potassium peroxymonosulfate,

dimethyldioxirane, peroxides, peroxy acids, enzymes, and combinations thereof. In one aspect of this embodiment said at least one second bleaching agent is chosen among 0₂, 0₃, Na₂S₂0₄, potassium peroxymonosulfate, dimethyldioxirane, peroxides, peroxy acids, enzymes, and combinations thereof.

The total amount of added said at least one second bleaching agent may, for instance, be about 10 - 100 kg per ton tobacco raw material (calculated as pure bleaching agent), specifically about 30 - 90 kg per ton tobacco raw material.

The temperature in the step (I) may, for instance, be above about 10°C, specifically over about 20°C.

The temperature in the step (II) may, for instance, be above about 30°C, specifically over about 40°C, and more specifically over about 50°C. The pH interval in step (II) may, for instance, be the range of about pH 2-6 or in the range of about pH 8-12, depending on which bleaching agent that is used. The pulp consistency in step (II) may, for instance, be between about 1 and about 40%. The temperature during the optional additionally treatment with at least one second bleaching agent, for instance, be above about 30°C, specifically over about 40°C, and more specifically over about 50°C. The pH interval during said optional additionally treatment may, for instance, be in the range of about pH 2-6 or in the range of about pH 8-12, depending on which bleaching agent that is used. The pulp consistency during said optional additionally treatment may, for instance, be between about 1 and about 40%.

In one embodiment of the inventive process said at least one bleaching agent and/or said at least one second bleaching agent is/are chosen among peroxides, peroxy acids, and combinations thereof. In one embodiment of the inventive process said at least one bleaching agent is peroxyacetic acid.

In one embodiment of the inventive process said at least one second bleaching agent is hydrogen peroxide.

In one embodiment of the inventive process the defibrated tobacco raw material from step (I) is subjected to an acid wash step before entering step (II). One purpose of the acid wash step is to remove inorganic substances, such as metal compounds, from the material. The acid used in the acid wash step may be any suitable acid commonly used in acid wash steps in pulp bleaching processes, such as for instance sulfuric acid.

The total amount of added acid may, for instance, be less than about 10 kg per ton tobacco raw material (calculated as pure acid), specifically less than about 5 kg per ton tobacco raw material. The temperature in the acid wash step may, for instance, be above about 20°C, specifically over about 30°C and more specifically over about 40°C. The pH interval in the acid wash step may, for instance, be about pH 1 to about pH 4. The pulp consistency in the acid wash step may, for instance, be between about 1 and about 15%.

In one embodiment of the inventive process the treated tobacco raw material from step (II) is - after having been treated with said at least one bleaching agent - subjected to a chelation treatment to remove metals before the treated tobacco raw material is treated with said at least one second bleaching agent. The chelating agent used in the chelation treatment may be any suitable chelating agent commonly used in chelation treatment steps in pulp bleaching processes, such as for instance EDTA (ethylene diamine tetraacetic acid), DTPA (diethylene triamine pentaacetic acid), NTA (nitrilotriacetic acid), or DTPMP (diethylene triamine pentamethylene phosphoric acid).

The total amount of added chelating agent may, for instance, be less than about 10 kg per ton tobacco raw material (calculated as pure chelating agent), specifically less than about 2 kg per ton tobacco raw material. The temperature in the chelation treatment step may, for instance, be above about 20°C, specifically over about 30°C, and more specifically over about 40°C. The pH interval in the chelation treatment step may, for instance, be about pH 4 to about pH 7. The pulp consistency in the chelation treatment step may, for instance, be between about 1 and about 40%.

In one embodiment of the inventive process the defibrated tobacco raw material from step (I) is subjected to a cooking step, in which the defibrated tobacco raw material is treated at an acidic or neutral pH and at a temperature range of from about 20°C to about 200°C for a total period of up to about 180 minutes with an aqueous solution comprising sulfite ion and/or bisulfite ion, to produce cooked tobacco raw material, before said cooked tobacco raw material enters into step (II).

In one aspect of this embodiment said cooked tobacco raw material is subjected to an acid wash step before entering step (II).

It was surprisingly found that said cooking step provides for a significantly decreased ash content of the obtained bleached tobacco raw material, which in turn makes it softer or smoother, which is a valuable property for many applications of the bleached tobacco raw material, such as for instance oral use.

As indicated above the process improvements obtained with the inventive process are also associated with corresponding product improvements, such as improved freeness and bleachability, and in some instances also decreased ash content of the obtained bleached tobacco raw material.

Hence, one aspect of the invention relates to bleached tobacco raw material obtainable by any one of the above mentioned embodiments and aspects of the inventive process.

According to one embodiment the bleached tobacco raw material has an ISO brightness that is not less than about 40 as measured according to ISO 2470:1999.

In one aspect of this embodiment said ISO brightness remains substantially unaffected when the bleached tobacco raw material is subjected to fluids having pH values of about pH 7 to about pH 12. The present invention thus provides a tobacco raw material that may be substantially free from undesired substances. One advantage of the inventive bleached tobacco raw material is that it provides for tobacco products that does not discolour the user's fingers, and - in the case of oral smokeless tobacco products - does not discolour the user's teeth. The inventive process may be for the production of, and the inventive product may be, a bleached tobacco raw material comprising less than about 4 weight-% fermentable carbohydrates, calculated on the dry total weight of the bleached tobacco raw material, as disclosed in WO2015150506, the disclosure of which is once again incorporated by reference in its entirety herein, Such a tobacco raw material can easily be provided with such desirable properties as is associated with tobacco fermentation, such as enhanced smell and taste, while not being burdened by the undesired side effects of tobacco fermentation (such as generation of undesired by-products, for instance tobacco-specific nitrosamines (TSNA), which are known to be carcinogens).

In one embodiment the bleached tobacco raw material comprises less than about 2 weight- %, specifically less than about 1 weight-%, of fermentable carbohydrates, calculated on the dry total weight of the bleached tobacco raw material. In one embodiment the bleached tobacco raw material comprises less than about 7.0 mg/kg, specifically less than about 3.5 mg/kg, more specifically less than about 1.0 mg/kg of nitrite, calculated on the dry total weight of the bleached tobacco raw material. In one embodiment the bleached tobacco raw material comprises a combined amount of NNN (N-nitrosonornicotine) and NNK ((4- methylnitrosamino)-1 -(3-pyridyl)-1 -butanone) that is less than about 2.0 mg/kg, specifically less than about .0 mg/kg, more specifically less than about 0.2 mg/kg, calculated on the dry total weight of the bleached tobacco raw material.

In one embodiment the bleached tobacco raw material comprises less than about 10.0 pg/kg, specifically less than about 5.0 pg/kg, more specifically less than about 0.6 pg/kg of NDMA (N-Nitrosodimethylamine), calculated on the dry total weight of the bleached tobacco raw material.

In one embodiment the bleached tobacco raw material comprises less than about 5.0 g/kg, specifically less than about 2.5 pg/kg, more specifically less than about 0.6 g/kg of B(a)P (Benzo(a)pyrene), calculated on the dry total weight of the bleached tobacco raw material.

In one embodiment the bleached tobacco raw material comprises less than about 1.0 mg/kg, specifically less than about 0.5 mg/kg, more specifically less than about 0.1 mg/kg of Cd, calculated on the dry total weight of the bleached tobacco raw material. In one embodiment the bleached tobacco raw material comprises less than about 2.0 mg/kg, specifically less than about 1.0 mg/kg, more specifically less than about 0.1 mg/kg of Pb, calculated on the dry total weight of the bleached tobacco raw material.

In one embodiment the bleached tobacco raw material comprises less than about 0.5 mg/kg, specifically less than about 0.25 mg/kg, more specifically less than about 0.1 mg/kg of As, calculated on the dry total weight of the bleached tobacco raw material. In one embodiment the bleached tobacco raw material comprises less than about 3.0 mg/kg, specifically less than about 1 .5 mg/kg, more specifically less than about 0.1 mg/kg of Ni, calculated on the dry total weight of the bleached tobacco raw material.

In one embodiment the bleached tobacco raw material comprises less than about 4.5 mg/kg, specifically less than about 2.25 mg/kg, more specifically less than about 0.1 mg/kg of Cr, calculated on the dry total weight of the bleached tobacco raw material.

In one embodiment the bleached tobacco raw material comprises less than about 7.0 mg/kg nitrite; less than about 2.0 mg/kg combined amount of NNN (N-nitrosonornicotine) and NNK ((4-methylnitrosamino)-1-(3-pyridyl)-1-butanone); less than about 10.0 pg/kg NDMA (N- Nitrosodimethylamine); less than about 5.0 pg/kg B(a)P (Benzo(a)pyrene); less than about 1 .0 mg/kg Cd; less than about 2.0 mg/kg Pb; less than about 0.5 mg/kg As; less than about 3.0 mg/kg Ni; less than about 4.5 mg/kg Cr; calculated on the dry total weight of the bleached tobacco raw material. In one embodiment the bleached tobacco raw material comprises less than about 3.5 mg/kg nitrite; less than about 1.0 mg/kg combined amount of NNN (N-nitrosonornicotine) and NNK ((4-methylnitrosamino)-1-(3-pyridyl)-1 -butanone); less than about 5.0 pg/kg NDMA (N- Nitrosodimethylamine); less than about 2.5 pg/kg B(a)P (Benzo(a)pyrene);

less than about 0.5 mg/kg Cd; less than about 1.0 mg/kg Pb; less than about 0.25 mg/kg As; less than about 1.5 mg/kg Ni; less than about 2.25 mg/kg Cr; calculated on the dry total weight of the bleached tobacco raw material.

In one embodiment the bleached tobacco raw material comprises less than about 1.0 mg/kg nitrite; less than about 0.2 mg/kg combined amount of NNN (N-nitrosonornicotine) and NNK ((4-methylnitrosamino)-1-(3-pyridyl)-1-butanone); less than about 0.6 pg/kg NDMA (N- nitrosodimethylamine); less than about 0.6 pg/kg B(a)P (benzo(a)pyrene); less than about 0.1 mg/kg Cd; less than about 0.1 mg/kg Pb; less than about 0.1 mg/kg As; less than about 0.1 mg/kg Ni; less than about 0.1 mg/kg Cr; calculated on the dry total weight of the bleached tobacco raw material.

In one embodiment the bleached tobacco raw material comprises a combined amount of aflatoxins B1 , B2, G1 , and G2 that does not exceed 0.01 mg/kg, calculated on the dry total weight of the bleached tobacco raw material.

Another aspect of the invention relates to a smoking tobacco composition comprising the inventive bleached tobacco raw material. In one embodiment the smoking tobacco composition comprises nicotine in addition to any nicotine naturally present in the tobacco. The added nicotine may be natural nicotine, i.e. nicotine extracted from tobacco plants, or synthetic nicotine, or a combination thereof. In one embodiment the tobacco raw material content of the smoking tobacco composition comprises up to about 99 wt-%, specifically up to about 50 wt-%, and more specifically up to about 25 wt-% of unbleached tobacco raw material, calculated on the dry total weight of the tobacco raw material content of the composition. Another aspect of the invention relates to a smokeless tobacco composition comprising the inventive bleached tobacco raw material.

In one embodiment the smokeless tobacco composition comprises nicotine in addition to any nicotine naturally present in the tobacco. The added nicotine may be natural nicotine, i.e. nicotine extracted from tobacco plants, or synthetic nicotine, or a combination thereof.

In one embodiment the tobacco raw material content of the smokeless tobacco composition comprises up to about 99 wt-%, specifically up to about 50 wt-%, and more specifically up to about 25 wt-% of unbleached tobacco raw material, calculated on the dry total weight of the tobacco raw material content of the composition.

Another aspect of the invention relates to nasal snuff, i.e. snuff products suited for nasal administration, which comprises the inventive smokeless tobacco composition. Another aspect of the invention relates to an oral smokeless tobacco product comprising the inventive smokeless tobacco composition. The oral smokeless tobacco product may be, but is not limited to, moist snuff such as snus, chewing tobacco, oral dry snuff, or hard snuff.

A particular advantage of this aspect of the invention is that it the low content of fermentable carbohydrates provides for a greatly reduced risk for dental caries. The oral smokeless tobacco product may comprise additives chosen among - but not limited to - one or more substances belonging to any of the following categories, or combinations thereof: API (active pharmaceutical substances), food additives, natural or synthetic nutrients, flavoring substances, natural medicaments or naturally occurring substances that can have an effect on humans. Examples of such substances are green tea, white tea, caffeine, vitamin B12, vitamin C, vitamin E, bioperin, Q10, selenium, glutathione, liponic acid, folic acid, ginseng, pollen extract, antioxidants, minerals, paracetamol, acetylsalicylic acid, Russian root, and rose root.

In one embodiment the oral smokeless tobacco product contains an alginate composition of the kind, and in the way described in WO 2010/114445, the contents of which is hereby incorporated by reference. More specifically, the oral smokeless tobacco product according to this embodiment contains an alginate composition, distributed in the product and comprising at least water, alginate and an added substance intended to be released from the product when said product is used, said composition containing an alginate matrix that retains at least a major proportion of the added substance so long as the matrix is intact, and the alginate matrix being formed so as to disintegrate and/or dissolve in the chemical and physical environment that exists in a user's mouth; wherein said alginate contains an alginate salt of monovalent cations and is soluble in cold water.

In one embodiment the oral smokeless tobacco product is chewing tobacco comprising a gum base. The gum base may be chosen among - but is not limited to - commercial chewing gum bases, bubble gum bases, and natural gum base materials.

The oral smokeless tobacco product may be provided in baked or compressed form, from which portions may be punched or pressed in portions, such as lozenges or tablets.

As an alternative, the oral smokeless tobacco product may be provided in loose form or in the form of portion-size sachets. As a further alternative it may have a film-like form. The oral smokeless tobacco product may have a pH of about 7-12, specifically about 8-12, more specifically about 8-9.

The oral smokeless tobacco product may have a water content of about 5 - 55%, specifically about 30 - 55%, more specifically about 45 - 52%.

Another aspect of the invention relates to the inventive bleached tobacco raw material for use in the treatment of nicotine addiction, such as for instance in a pharmaceutical for smoking cessation.

The invention will now be illustrated in closer detail in the following non-limiting examples.

EXAMPLE 1

Step I 10 kg of tobacco raw material was defibrated by way of grinding in a pilot refiner.

Step il

The defibrated tobacco raw material from Step I was subjected to the following, consecutive treatments:

Acid washing stage with sulfuric acid

Pulp concentration: 5%

Temperature: 50°C

Time: 60 minutes

pH 2.5

First bleaching stage with peroxyacetic acid

Pulp concentration: 12%

Temperature: 80°C

Time: 150 minutes

100 kg peroxyacetic acid/tonne of tobacco raw material.

pH: 4-6

Dewatering in centrifuge

Chelation stage with EDTA

Pulp concentration: 5%

Temperature: 70°C

Time: 60 minutes

pH 5.5

5 kg EDTA tonne of tobacco raw material.

Second bleaching stage with hydrogen peroxide

Pulp concentration: 12%

Temperature: 90°C

Time: 240 minutes

50 kg H₂0₂/tonne of tobacco raw material.

pH 10.5-1 1.5 - regulated by means of NaOH.

10 kg MgSCVtonne of tobacco raw material.

Dewatering in centrifuge EXAMPLE 2

Step A

10 kg of tobacco raw material was defibrated by way of grinding in a pilot refiner. Step B

The defibrated tobacco raw material from step A was subjected to a cooking step, in which the defibrated tobacco raw material was treated with an aqueous solution comprising sulfite ion and bisulfite ion at a base charge of 4.7 %, calculated as Na₂0 and on dry tobacco raw material; at pH 4; at a liquid/ tobacco raw material ratio of 5 litres/kg; and at a temperature rising from ambient temperature up to 170°C for a period 120 minutes and then at 170°C for 15 minutes.

The obtained material was washed with water and led to a screen to remove undigested fibres. The remaining material was dewatered to dry content of about 20-25%. Step C

The cooked tobacco raw material from Step B was subjected to the following, consecutive treatments:

Acid washing stage with sulfuric acid

Pulp concentration: 5%

Temperature: 50°C

Time: 60 minutes

pH 2.5 First bleaching stage with peroxyacetic acid

Pulp concentration: 12%

Temperature: 80°C

Time: 150 minutes

50 kg peroxyacetic acid/tonne of tobacco raw material.

pH: 4-6

Dewatering in centrifuge

Chelation stage with EDTA

Pulp concentration: 5%

Temperature: 70°C Time: 60 minutes

pH 5.5

5 kg EDT A/tonne of tobacco raw material.

Second bleaching stage with hydrogen peroxide

Pulp concentration: 12%

Temperature: 90°C

Time: 240 minutes

50 kg H₂0₂/tonne of tobacco raw material.

pH 10.5-1 1 .5 - regulated by means of NaOH.

10 kg MgSCVtonne of tobacco raw material.

Dewatering in centrifuge

ANALYSIS

Dewatering test

The SR numbers of the bleached tobacco raw materials obtained from Example 1 and Example 2 materials were determined by means of a Schopper Riegler Freeness Tester and following standard method ISO 5267-1. The obtained SR numbers are set forth in Table 1. Table 1

Kappa number and ash content tests

The Kappa numbers of the bleached tobacco raw material obtained from Example 1 and Example 2 were determined according to standard method ISO 302 and the ash contents according to standard method ISO 1762. The obtained values are set forth in Table 2. Table 2

Although the invention has been described with regard to certain embodiments it should be understood that various changes and modifications as would be obvious to one having the ordinary skill in this art may be made without departing from the scope of the invention as set forth in the claims appended hereto.

Claims

1. A process for production of bleached tobacco raw material comprising the steps of:

and

2. The process according to claim 1 , wherein said at least one bleaching agent is chosen among Cl₂, CI0₂, NaOCI, Cl₂0, 0₂, 0₃, Na₂S₂0₄, potassium peroxymonosulfate,

dimethyldioxirane, peroxides, peroxy acids, enzymes, and combinations thereof.

3. The process according to claim 1 , wherein the treated tobacco raw material from step (II), after having been treated with said at least one bleaching agent, is additionally treated with at least one second bleaching agent.

4. The process according to claim 3, wherein said at least one second bleaching agent is chosen among Cl₂, CI0₂, NaOCI, Cl₂0, 0₂, 0₃, Na₂S₂0₄, potassium peroxymonosulfate, dimethyldioxirane, peroxides, peroxy acids, enzymes, and combinations thereof.

5. The process according to claim 1 or 3, wherein said at least one bleaching agent and/or said at least one second bleaching agent is/are chosen among peroxides, peroxy acids, and combinations thereof.

6. The process according to claim 1 , wherein said at least one bleaching agent is

peroxyacetic acid.

7. The process according to claim 6, wherein said at least one second bleaching agent is hydrogen peroxide.

8. The process according to claim 1 , wherein the defibrated tobacco raw material from step (I) is subjected to an acid wash step before entering step (II).

9. The process according to claim 3, wherein the treated tobacco raw material from step (II) after having been treated with said at least one bleaching agent is subjected to a chelation treatment to remove metals before the treated tobacco raw material is treated with said at least one second bleaching agent.

10. The process according to any one of the preceding claims, wherein the defibrated tobacco raw material from step (I) is subjected to a cooking step, in which the defibrated tobacco raw material is treated at an acidic or neutral pH and at a temperature range of from about 20°C to about 200°C for a total period of up to about 180 minutes with an aqueous solution comprising sulfite ion and/or bisulfite ion, to produce cooked tobacco raw material, before said cooked tobacco raw material enters into step (II).

1 1 . The process according to claim 10, wherein said cooked tobacco raw material is subjected to an acid wash step before entering step (II).

12. The process according to claim 10, wherein the defibrated tobacco raw material from step (I) is treated in the cooking step first at a temperature of from about 20°C to about 200°C for a period of about 120 minutes, and then at a temperature of from about 150°C to about 200°C for the remaining part of the treatment in the cooking step.

13. Bleached tobacco raw material obtainable by the process according to any one of the preceding claims,

14. The bleached tobacco raw material according claim 13, where the bleached tobacco raw material has an ISO brightness that is not less than about 40.

15. The bleached tobacco raw material according claim 14, where said ISO brightness remains substantially unaffected when the bleached tobacco raw material is subjected to fluids having pH values of about pH 7 to about pH 12.