METHOD AND APPLICATION OF PREPARING SUN-CURED TOBACCO BY IRRADIATION

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of International Pat. Appl. No. PCT/CN2024/091913, filed on May 9, 2024, which claims the benefit of Chinese Pat. Appl. No. 202410558871.9, filed on May 8, 2024, both of which are incorporated herein by reference as if fully set forth herein.

TECHNICAL FIELD

The present invention relates to the technical field of tobacco preparation processes. Specifically, it relates to a technical method and application for improving the quality of sun-cured tobacco using irradiation.

BACKGROUND

The tobacco leaf preparation process is a rather complex physiological and biochemical process. There have been many research reports on tobacco leaf preparation, and the research results are also very significant. These achievements have also played an important role in the production of high-quality and characteristic tobacco. However, there are still many problems in the tobacco leaf preparation process. The tobacco leaf preparation process is not only restricted by its own internal factors, but is also influenced by the external environment such as temperature, humidity, air, and various enzymes and microorganisms. Due to the significant environmental differences, the internal chemical reactions of tobacco leaves are greatly affected when different types of tobacco are prepared by different preparation methods. As a result, the preparation method inevitably has a great impact on the quality of the tobacco leaves, thereby changing the quality of the prepared tobacco leaves and their final usability.

Sun-cured tobacco is obtained by naturally sun-drying fresh tobacco leaves. However, the sun-cured tobacco leaves are green and have a relatively strong mixed smell, with a pungent and irritating flavor, resulting in unsmooth smoke, monotonous aroma quality and insufficient aroma volume, which still do not meet the quality requirements for direct industrial processing. Under suitable natural conditions or artificially fortified conditions, after a period of fermentation, the quality of the original tobacco leaves can be improved to varying degrees. Although fermentation and sun-drying reduce the pungent and irritating taste, the aroma and quantity of the cigarette are insufficient, the strength is weak, and the aftertaste is not pure enough. It still fails to meet the quality requirements for industrial tobacco processing.

The present invention is proposed to solve the above problems.

SUMMARY

To overcome the problems existing in the background technology of sun-cured tobacco, the present invention provides a method of using irradiation to modulate sun-cured tobacco. The method of the present invention involves sun-dried fresh tobacco leaves, then using irradiation to assist in the fermentation of the tobacco leaves, followed by maturation and aging. The resulting tobacco leaves have significantly reduced green and mixed odors, possess a natural sweet and mellow aroma as well as a roasting aroma, have a rich fragrance, a good strength, a significantly improved aroma volume and comfort, a purer smoke taste, a better smoking experience and a higher sense of satisfaction. The quality of cigarettes significantly improves.

The technical solution of the present invention is as follows:

The first aspect of the present invention concerns a method for preparing sun-cured tobacco leaves by irradiation, which comprises the following steps:

• • (1) soaking dried (e.g., fully dried) fresh tobacco leaves in water for a period of time and then sun-drying the soaked tobacco leaves;
  • (2) spraying (e.g., evenly) a pretreatment solution on the soaked and dried tobacco leaves (e.g., on surfaces thereof), sealing the sprayed tobacco leaves (e.g., in a water-tight and/or air-tight container or vessel), and letting the sprayed tobacco leaves ferment naturally for a period of time;
  • (3) sun-drying the fermented tobacco leaves again;
  • (4) irradiating the sun-dried tobacco leaves with a certain dose of gamma (γ) rays; and
  • (5) aging and maturing the irradiated tobacco leaves under certain conditions to obtain the sun-cured tobacco.

Preferably, the moisture content of the tobacco leaves before soaking in step (1) should not exceed 12 wt %, and the soaking time is from 30 to 60 minutes.

Preferably, the steps for preparing the pretreatment solution in step (2) are:

• • (A) Preparing an ethanol solution (e.g., an aqueous ethanol solution) having a concentration (e.g., of ethanol) of 0.5 to 5.0 wt %; and
  • (B) Adding a salt to the ethanol solution in step (A) at a mass ratio of 0.5 to 5.0 wt % and dissolving the salt (e.g., in the ethanol solution) to obtain the pretreatment solution.

Preferably, the salt in step (B) includes one or more of sodium chloride, sodium carbonate, sodium lactate, sodium oxalate, sodium alginate, sodium benzoate, potassium citrate (monobasic or tribasic), potassium sorbate, methyl lactate, potassium carbonate and potassium phosphate (monobasic, dibasic and/or tribasic).

Preferably, the sprayed tobacco leaves naturally ferment in step (2) at a temperature of 90 to 100° C. and a fermentation time of 2 to 5 days. The moisture content of the tobacco leaves during the fermentation is not less than 30 wt %.

Preferably, in step (4), the sun-dried tobacco leaves are irradiated with γ radiation from a ⁶⁰Co source for 5 minutes to 120 minutes, the dose is 1.0 to 30.0 kGy, and a moisture content of the sun-dried tobacco leaves is not less than 12 wt %.

Preferably, the moisture content of the irradiated tobacco leaves in step (5) during the aging and maturation is maintained at 12 to 15 wt %.

Preferably, the irradiated tobacco leaves in step (5) are aged and/or matured in air having a relative humidity of 45% to 55%, at room temperature for a duration of no less than 30 days. Room temperature may refer to a temperature of from 15° C. to 30° C., which may be maintained by heating or cooling, or allowed to drift up and/or down within this range without heating or cooling.

The second aspect of the present invention concerns the application of the sun-cured tobacco leaves obtained by the method, to produce cigarettes and, for example, improve the smoke quality thereof.

The beneficial effects of the present invention include:

• • 1. The method of the present invention involves sun-dried fresh tobacco leaves, then using irradiation to assist in the fermentation of the tobacco leaves, sun-drying again, then purifying and aging. The resulting tobacco leaves possess a natural sweet and mellow aroma as well as a roasting aroma. The greenish and impure smell of tobacco leaves is significantly reduced, the aroma is more intense, the amount of aroma and comfort are notably enhanced, the vigor is better, the smoke flavor is purer, the taste is better, and the sense of satisfaction is higher. The smoke quality of cigarettes made from tobacco leaves prepared by the present method significantly improves.
  • 2. The method of the present invention uses a pretreatment solution to spray the soaked tobacco leaves for natural fermentation, which removes the pungent taste and reduces the irritating flavor. The fermentation in the present invention is natural fermentation and does not require the addition of microorganisms.
  • 3. The method of the present invention involves subjecting the irradiated tobacco leaves to a certain period of aging and maturation to obtain sun-cured tobacco, which has a rich aroma, increased aroma volume and comfort, good vigor, pure aftertaste, significantly reduced green impurities, purer smoke flavor, and higher satisfaction.
  • 4. The method of the present invention can not only improve the quality of tobacco leaves but also effectively reduce the nitrogen-containing harmful components in sun-cured tobacco. It can effectively improve the utilization rate of sun-cured tobacco.
  • 5. The method of the present invention provides a new idea for the preparation of sun-cured tobacco.

EXAMPLES

The technical solution of the present invention will be further explained through specific implementation methods below. Those skilled in the art should be aware that the given embodiments are only intended to assist in understanding the present invention and should not be regarded as specific limitations of the present invention. The process, conditions, reagents, experimental methods, etc. of implementation, except for the contents specifically mentioned below, are all common knowledge and common sense in this field. There are no particularly restricted contents in the present invention. For the experimental methods in each embodiment where specific conditions are not specified, the conventional conditions or the conditions recommended by the manufacturer are usually followed. Unless otherwise stated, the meanings of all professional terms and scientific expressions used in this specification are the same as those generally understood by those skilled in the art to which the present invention belongs. However, in case of any conflict, this specification containing the definitions shall prevail.

Example 1

The steps for preparing the pretreatment solution are as follows:

• • (A) Preparing an aqueous ethanol solution with an ethanol concentration of 0.5 to 5.0 wt % (specifically, in a ratio of 1 g of ethanol to 97.5 g of water); and
  • (B) Adding a salt (specifically, sodium chloride) to the ethanol solution in step (A) at a mass ratio of 0.5 to 5.0 wt % (specifically, in a ratio of 1.5 g of sodium chloride to 98.5 g of the ethanol solution), and dissolving the salt in the ethanol solution to obtain the pretreatment solution.

The method and steps for preparing sun-cured tobacco by irradiation are as follows:

• • (1) Soaking the sun-dried fresh tobacco leaves (the moisture content of which is reduced to 10 wt %) in water for 40 minutes;
  • (2) Spraying evenly the tobacco leaves that have been dried and soaked in step (1) with a pretreatment solution and fermenting at 90° C. for 2 days, wherein the moisture content of the tobacco leaves during fermentation is 30 wt %;
  • (3) Drying the fermented tobacco leaves in the sun for another 10 days, while maintaining the moisture content of the tobacco leaves at 15 wt %;
  • (4) Irradiating the tobacco leaves after further drying were irradiated with 5 kGy of γ radiation from a ⁶⁰Co source for 15 minutes.
  • (5) The tobacco leaves are sun-dried again, then naturally aged and matured for 30 days, in air at a relative humidity of 50% and a temperature of 30° C. to obtain the aforementioned sun-cured tobacco.
  • Comparison Example 1: follow the same steps as in Example 1, and the difference is that there is no step (2): spraying the pretreatment solution and natural fermentation.
  • Comparison Example 2: follow the same steps as in Example 1, but the difference is that there is no irradiation step (4).
  • Comparison Example 3: follow the same steps as in Example 1, but no pretreatment solution is sprayed in step (2).
  • Comparison Example 4: follow the same steps as in Example 1, but without the natural aging and maturation in step (5).

The sun-cured tobaccos obtained from Example 1 and the Comparison Examples 1˜4 were made into cigarettes, and a 9-point evaluation method was used for evaluation of smoking sensation. The results of the smoking sensation evaluation are shown in Table 1.

From the evaluation results in Table 1, it can be seen that the sensory quality of the sun-cured tobacco obtained in Example 1 is the best, with a better aroma, especially featuring a sweet and mellow aroma and a roasting aroma, which is more intense. The sun-cured tobacco obtained in Example 1 has less impurities, rich aroma, good concentration, moderate intensity, a relatively pure and comfortable aftertaste, a purer smoke flavor, and a higher sense of satisfaction. The tobacco from Comparison Example 1 without spraying the pretreatment solution or the natural fermentation step has a relatively high impurity and irritation, and the concentration is insufficient. The tobacco from Comparison Example 2 without the irradiation step has very obvious impurities, a prominent pungent sensation, and the worst aftertaste. The tobacco from Comparison Example 3 without spraying the pretreatment solution has some unpleasant taste, pungent and relatively poor aftertaste. The tobacco from Comparison Example 4 without aging and maturation steps is also relatively good, but the mellow and sweet aroma of the tobacco is insufficient, and the unpleasant taste and aftertaste are not as good as those of the sun-cured tobacco obtained with the natural aging and maturation steps.

The water-soluble sugar, total nitrogen, total alkaloids, potassium, chloride, nitrate and other chemical component indicators of the tobacco leaves obtained in Example 1 and Comparison Examples 1˜4 were determined. The testing methods and basis are shown in Table 2, and the test results are shown in Table 3.

As can be seen from Table 3, the water-soluble sugar content of the tobacco leaves after irradiation treatment increased significantly, reaching up to 89% at the highest, while there was no significant difference in the contents of total nitrogen, alkaloids, potassium and chlorine before and after irradiation. This indicates that after irradiation, the sugar-base ratio significantly increases, making the tobacco taste more mellow, reducing pungent, and significantly decreasing the green unpleasant taste, thereby improving the smoking experience.

The total nitrogen of the tobacco leaves obtained in Example 1 and Comparison Examples 1-4 was tested, and the results are shown in Table 4.

It can be seen from the conclusion of Table 4 that the TSNA content of the tobacco leaves in Example 1 after irradiation treatment and those in Comparison Examples 1, 3 and 4 is lower than that of the tobacco leaves in Comparison Example 2 without irradiation treatment. Among them, the degradation rate of TSNAs in Example 1 compared with the Comparison Example 2 of tobacco leaves without irradiation treatment reached 57%, and the degradation rate of NNK reached 61%. Therefore, the effect of the present invention on reducing nitrogen-containing harmful components by using irradiation to make sun-cured tobacco is obvious.

The embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can be modified and changed in various ways. Any modification, equivalent substitution, improvement, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.