Off-line pretreatment process for reducing substance content of cell walls of tobacco stems

Abstract

The invention discloses an off-line pretreatment process for reducing the content of cell wall substances of tobacco stems, which comprises the following steps: adding tobacco stems and a dilute phosphoric acid aqueous solution into a fermentation tank for liquid fermentation; carrying out solid-liquid separation on the fermentation liquor, and carrying out microwave expansion treatment on the obtained fermented solid tobacco stems to obtain treated tobacco stems; and carrying out vacuum concentration on the liquid part obtained by solid-liquid separation, and carrying out Maillard reaction to obtain the tobacco stem enzymolysis Maillard extract. The solid tobacco stems are subjected to acid pretreatment, liquid fermentation and microwave expansion treatment, the content of cell wall substances of the obtained tobacco stems is reduced, aroma components are obviously increased, offensive odor is obviously reduced, and the quality of the tobacco stems is improved; and the liquid part is subjected to concentration and Maillard reaction to obtain the tobacco stem enzymolysis Maillard extract, so that zero emission of water pollution is realized.

Description

Technical Field

[0001] The present application relates to an off-line pretreatment process for reducing the content of tobacco stem cell wall substances, and belongs to the technical field of tobacco stem processing. Background Art

[0002] Tobacco stems account for 25% to 30% of the weight of tobacco leaves. Since tobacco stems have similar components to tobacco leaves and have the functions of improving the structure of cigarettes, reducing costs, and reducing harm and tar, they are an important component of cigarette raw materials. However, the content of cell wall substances in tobacco stems is higher in tobacco stems, accounting for more than 40%. Cell wall substances include cellulose, hemicellulose, pectin, lignin and other substances. After pyrolysis and combustion, pectin will produce pyrolysis products such as methanol, formaldehyde and formic acid. These products not only bring irritation to the smoke and cover up the aroma of cigarettes themselves, but also have certain harm to the human body; lignin is the main cause of the heavy woody smell in the smoke, resulting in strong coughing and burning throat during combustion, interfering with the aroma of the smoke, and pyrolysis of lignin will produce catechol and alkylcatechol, causing astringency and carcinogenic activity, affecting the quality and safety of cigarettes. The presence of tobacco stem cell wall substances will cause irritating coughs and strong woody miscellaneous gases when burning, which will have an adverse effect on the quality of tobacco smoking.

[0003] The Chinese invention patent with application number CN201110132050.1 discloses a "method for processing tobacco stems and shredded stems", which involves first expanding the tobacco stems, then cutting the expanded tobacco stems into stem slices, and then cutting them into shredded stems. The tobacco stem expansion is processed using existing microwave expansion equipment, which is a low-frequency (915MHz) high-power (10KW or more) microwave magnetron and a belt conveyor to complete the microwave expansion process during the tobacco stem transportation process. Although the tobacco stems processed in this application have a certain degree of improvement in fluffiness, the pectin and lignin in the tobacco stems are not well reduced, and a good smoking rating cannot be guaranteed. Summary of the invention

[0004] In order to solve the above problems, an offline pretreatment process for reducing the content of cell wall substances in tobacco stems is provided. The solid tobacco stems are subjected to acid pretreatment, liquid fermentation and microwave expansion treatment, so that the content of cell wall substances in the obtained tobacco stems is reduced, the flavor components are significantly increased, the impurities are significantly reduced, the aftertaste comfort is significantly improved, and the quality of the tobacco stems is improved; the liquid part is concentrated and subjected to the Maillard reaction to obtain tobacco stem enzymatic hydrolysis Maillard extract, thereby realizing multiple utilizations of the tobacco stems and zero discharge of water pollution.

[0005] According to one aspect of the present application, an off-line pretreatment process for reducing the content of tobacco stem cell wall substances is provided, comprising the following steps:

[0006] (1) adding tobacco stems and a dilute phosphoric acid aqueous solution into a fermentation tank, and adding a biocomposite preparation for liquid fermentation;

[0007] (2) separating the fermentation liquid into solid and liquid, and subjecting the obtained fermented solid tobacco stems to microwave expansion treatment to obtain treated tobacco stems;

[0008] (3) concentrating the liquid portion obtained by solid-liquid separation under reduced pressure, adjusting the pH, adding glucose and proline, and performing a Maillard reaction to obtain a tobacco stem enzymatically hydrolyzed Maillard extract;

[0009] The biological composite preparation comprises composite cellulase, pectinase, laccase and ligninase.

[0010] Optionally, the mass ratio of xylanase, pectinase, pectin lyase, pectinesterase, glucanase, laccase, ligninase, cellulase and glucosidase is 2.5-3.5: 1.5-2.5: 0.1-0.3: 0.15-0.25: 0.4-0.6: 4-6: 0.5-1.5: 0.5-2: 0.4-0.65.

[0011] Optionally, the liquid fermentation solid-liquid ratio is (1:8) to (1:10); the liquid fermentation temperature is 43°C to 48°C.

[0012] Optionally, the amount of the biological composite preparation is 0.2% to 0.3% of the mass of the tobacco stem.

[0013] Optionally, the liquid fermentation pH is 6.2-6.7; and the fermentation time of the liquid fermentation is 7-9 hours.

[0014] Optionally, the microwave power of the microwave expansion treatment is 5500W to 6000W; the time of the microwave expansion treatment is 160 to 180s; and the height of the material laid in the microwave expansion treatment is 10 to 15mm.

[0015] Optionally, the moisture content of the fermented solid tobacco stems after microwave expansion treatment is 30% to 40%.

[0016] Optionally, in step (3), the reaction temperature is 105°C to 115°C; and the reaction time is 3 to 4 hours.

[0017] Optionally, in step (3), the pH is 7 to 7.5.

[0018] Optionally, in step (1), the tobacco stems need to be segmented first, and the size of the segments is 3 cm to 8 cm.

[0019] The beneficial effects of this application include but are not limited to:

[0020] 1. According to the offline pretreatment process for reducing tobacco stem cell wall material provided in the present application, the solid tobacco stems are subjected to acid pretreatment, liquid fermentation and microwave expansion treatment, so that the content of tobacco stem cell wall material is reduced, the flavor components are significantly increased, the impurities are significantly reduced, the aftertaste comfort is significantly improved, and the quality of the tobacco stems is improved; the liquid part is concentrated and subjected to the Maillard reaction to obtain tobacco stem enzymatic hydrolysis Maillard extract, thereby realizing multiple utilizations of the tobacco stems and zero discharge of water pollution.

[0021] 2. According to the offline pretreatment process for reducing the cell wall material of tobacco stems provided by the present application, the cut stems are treated with a specific biological composite preparation for liquid fermentation. On the one hand, cellulose and pectin can be degraded and converted into sugar substances, reducing the addition of sugar in the process stage, while reducing the discomfort caused by cellulose and pectin to cigarettes and increasing the blending ratio in cigarettes; on the other hand, in the current situation where the prices of raw and auxiliary materials of cigarettes have risen sharply, enzyme treatment of tobacco stems can reduce the production cost of the tobacco industry, which has important practical significance. In addition, the use of tobacco stems can also increase the economic income of tobacco farmers and make full use of resources.

[0022] 3. According to the offline pretreatment process for reducing the cell wall material of tobacco stems provided in the present application, by making specific limitations on process parameters such as the liquid fermentation solid-liquid ratio, liquid fermentation temperature, time, pH, composition of the biocomposite preparation, and dosage of the biocomposite preparation, the liquid fermentation effect is optimal within the process parameter range provided in the present application, and the cell wall material content is effectively reduced. Under the action of the biocomposite preparation, the internal structure of the tobacco stems is damaged, and the duct tissue is severely deformed. After treatment, the wax layer on the surface of the tobacco stems disappears, part of the structure collapses, the wood fiber structure is hydrolyzed, and the cell wall components of the tobacco stems are hydrolyzed into small molecule flavor components, thereby improving the quality of the tobacco stems.

[0023] 4. According to the offline pretreatment process for reducing the cell wall material of tobacco stems provided in the present application, after the tobacco stems that have undergone liquid fermentation are subjected to microwave expansion treatment at a specific power, time, and laying height, the total cellulose, pectin content, lignin content, and cell wall material content of the tobacco stems are effectively reduced. This is mainly due to the non-thermal effect of microwaves, which causes the molecules of the reactants to be instantly activated under the ultra-high frequency oscillation of microwaves, greatly increasing the chances of collision and friction between molecules, making the reaction complex and rapid, and thus causing thermal degradation of some cell wall materials. Under the action of the microwave electromagnetic field, the polar water molecules in the tobacco stems change from their original random distribution state to an arrangement orientation according to the polarity of the electric field. Under the action of the high-frequency electromagnetic field, the orientation of these polar molecules changes continuously according to the frequency of the alternating electromagnetic field, causing the movement of the molecules to intensify and rub against each other, thereby generating heat. The electromagnetic energy is converted into thermal energy to expand the tobacco stems, resulting in a loosened tissue structure of the tobacco stems, expansion of the duct bundle cavity tissue, uniform arrangement, and an increase in the number and size of the voids; after microwave expansion treatment, the total sugar content is significantly reduced. This is because the microwave-expanded tobacco stems are in a closed state, which can make the internal structure of the tobacco stems reach high temperatures instantly, and the heating is relatively uniform. During the microwave expansion process, the temperature continues to rise, and the sugar substances in the tobacco stems participate in caramelization and sugar thermal cracking reactions, producing many furan derivatives, ketone aldehydes, carboxyl compounds and other aroma components. From the perspective of smoking quality, the tobacco stems treated with the microwave parameters specified in this application are mainly characterized by a significant reduction in impurities and a significant improvement in the comfort of the aftertaste. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0025] Figure 1 This is an analysis diagram of the effect of the solid-liquid ratio on tobacco stem lignin involved in Comparative Example 1 of the present application;

[0026] Figure 2 This is an analysis diagram of the effect of temperature on tobacco stem lignin involved in Comparative Example 1 of the present application;

[0027] Figure 3 This is an analysis diagram of the effect of the dosage of the preparation involved in Comparative Example 1 of the present application on tobacco stem lignin;

[0028] Figure 4 This is an analysis diagram of the effect of pH on tobacco stem lignin involved in Comparative Example 1 of the present application;

[0029] Figure 5 This is an analysis diagram of the effect of fermentation time on tobacco stem lignin involved in Comparative Example 1 of the present application;

[0030] Figure 6The electron microscope scanning cross-section of the original sample A1 and sample A2 tobacco stems;

[0031] Figure 7 The surface images of tobacco stems scanned by electron microscope of original sample B1 and sample B2;

[0032] Figure 8 The longitudinal sections of the tobacco stems of original sample C1 and sample C2 are obtained by scanning electron microscope;

[0033] Fig. 9 This is the effect of microwave power on tobacco stem lignin;

[0034] Fig.10 This is the effect of microwave tobacco stem moisture on tobacco stem lignin;

[0035] Fig.11 This is the effect of microwave laying height on tobacco stem lignin;

[0036] Fig.12 This is the effect of microwave reaction time on tobacco stem lignin;

[0037] Fig.13 The electron microscope scanning cross-section of the original sample A1 and sample A2 tobacco stems;

[0038] Fig.14 The surface images of tobacco stems scanned by electron microscope of original sample B1 and sample B2;

[0039] Fig.15 The longitudinal sections of tobacco stems of original sample C1 and sample C2 are scanned by electron microscope. DETAILED DESCRIPTION

[0040] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0041] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in a conventional manner in the art or in accordance with the product instructions. In addition, any method and material similar or equivalent to the described content can be applied to the method of the present invention. The preferred implementation methods and materials described in this patent are for demonstration purposes only.

[0042] Materials: Experimental tobacco stems from the same batch of the company.

[0043] instrument:

[0044] Continuous microwave drying equipment (Anhui Ruida Microwave Application Technology Co., Ltd.);

[0045] Multifunctional food grinder (Shenzhen Baijie Co., Ltd.);

[0046] Simultaneous distillation and extraction apparatus (homemade);

[0047] AA3 continuous flow analyzer (Seal, Germany);

[0048] 7890-5975 gas chromatograph-mass spectrometer (Agilent, USA);

[0049] Constant temperature and humidity chamber (Binder, Germany);

[0050] 1290Ⅱ, 1290 ultra-high performance liquid chromatograph (Agilent, USA);

[0051] ICS 5000 ion chromatograph (Thermo Fisher Scientific, USA);

[0052] 7890B gas chromatograph (Agilent, USA);

[0053] Steam distillation apparatus (Dalian Yeda Technology Co., Ltd.);

[0054] Analytical balance (Mettler Toledo, Switzerland);

[0055] CNC ultrasonic cleaner (Kunshan Hechuang Ultrasonic Instrument Co., Ltd.);

[0056] UV-visible spectrophotometer (Shanghai Meipuda Instrument Co., Ltd.);

[0057] WH type ozone generator (product of Nanjing Wohuan Technology Industry Co., Ltd.);

[0058] UV-1800 dual light speed UV-visible photometer (Shanghai Xinmao Instrument Co., Ltd.);

[0059] SW-CJ-1D clean bench (Suzhou Purification Equipment Co., Ltd.);

[0060] LRH-1500F biochemical incubator (Shanghai Yiheng Scientific Instrument Co., Ltd.);

[0061] QYC-2012C constant temperature shaker (Shanghai Fuma Experimental Equipment Co., Ltd.);

[0062] Soxhlet extractor (Qingdao Jingcheng Instrument Co., Ltd.);

[0063] Some glass instruments.

[0064] Example 1

[0065] (1) Cut tobacco stems into small pieces of 3 cm, add them into a fermentation tank together with a dilute phosphoric acid aqueous solution, with a solid-liquid ratio of 1:8, and add 0.2% of the weight of the tobacco stems as a biological composite preparation for liquid fermentation; the liquid fermentation temperature is 43°C, the pH is 6.2, and the fermentation time is 7 hours. The biological composite preparation includes xylanase, pectinase, pectin lyase, pectinesterase, glucanase, laccase, ligninase, cellulase, and glucosidase. The mass ratio of xylanase, pectinase, pectin lyase, pectinesterase, glucanase, laccase, ligninase, cellulase, and glucosidase is 2.5:1.5:0.1:0.15:0.4:4:0.5:0.5:0.4;

[0066] (2) separating the fermentation liquid into solid and liquid, and subjecting the obtained fermented solid tobacco stems to microwave expansion treatment for 160 seconds at a microwave power of 5500 W at a height of 10 mm to obtain treated tobacco stems;

[0067] (3) The liquid portion obtained by solid-liquid separation was concentrated under reduced pressure, the pH was adjusted to 7, glucose and proline were added, and the Maillard reaction was carried out at 105° C. for 3 h to obtain tobacco stem enzymatic hydrolysis Maillard extract.

[0068] Example 2

[0069] (1) Cut tobacco stems into small pieces of 5 cm, add them into a fermentation tank together with a dilute phosphoric acid aqueous solution, with a solid-liquid ratio of 1:9, and add 0.25% of the weight of the tobacco stems as a biological composite preparation for liquid fermentation; the liquid fermentation temperature is 45°C, the pH is 6.5, and the fermentation time is 8 hours. The biological composite preparation includes xylanase, pectinase, pectin lyase, pectinesterase, glucanase, laccase, ligninase, cellulase, and glucosidase. The mass ratio of xylanase, pectinase, pectin lyase, pectinesterase, glucanase, laccase, ligninase, cellulase, and glucosidase is 3.5:2.5:0.3:0.25:0.6:6:1.5:2:0.65;

[0070] (2) separating the fermentation liquid into solid and liquid, and subjecting the obtained fermented solid tobacco stems to microwave expansion treatment for 170 seconds at a microwave power of 5800 W at a height of 12 mm to obtain treated tobacco stems;

[0071] (3) The liquid portion obtained by solid-liquid separation was concentrated under reduced pressure, the pH was adjusted to 7.2, glucose and proline were added, and the Maillard reaction was carried out at 110° C. for 3.5 h to obtain tobacco stem enzymatic hydrolysis Maillard extract.

[0072] Example 3

[0073] (1) Cut tobacco stems into small pieces of 8 cm, add them into a fermentation tank together with a dilute phosphoric acid aqueous solution, with a solid-liquid ratio of 1:10, and add 0.3% of the weight of the tobacco stems as a biological composite preparation for liquid fermentation; the liquid fermentation temperature is 48°C, the pH is 6.7, and the fermentation time is 9 hours. The biological composite preparation includes xylanase, pectinase, pectin lyase, pectinesterase, glucanase, laccase, ligninase, cellulase, and glucosidase. The mass ratio of xylanase, pectinase, pectin lyase, pectinesterase, glucanase, laccase, ligninase, cellulase, and glucosidase is 3:2:0.2:0.2:0.5:5:1:1:0.5;

[0074] (2) separating the fermentation liquid into solid and liquid, and subjecting the obtained fermented solid tobacco stems to microwave expansion treatment for 180 seconds at a microwave power of 6000 W at a height of 15 mm to obtain treated tobacco stems;

[0075] (3) The liquid portion obtained by solid-liquid separation was concentrated under reduced pressure, the pH was adjusted to 7.5, glucose and proline were added, and the Maillard reaction was carried out at 115° C. for 4 h to obtain tobacco stem enzymatic hydrolysis Maillard extract.

[0076] Example 4

[0077] (1) Cut tobacco stems into small pieces of 5 cm, add them into a fermentation tank together with a dilute phosphoric acid aqueous solution, with a solid-liquid ratio of 1:10, and add 0.2% of the weight of the tobacco stems as a biological composite preparation for liquid fermentation; the liquid fermentation temperature is 47° C., the pH is 6.5, and the fermentation time is 8 h. The biological composite preparation includes xylanase, pectinase, pectin lyase, pectinesterase, glucanase, laccase, ligninase, cellulase, and glucosidase. The mass ratio of xylanase, pectinase, pectin lyase, pectinesterase, glucanase, laccase, ligninase, cellulase, and glucosidase is 3:2:0.2:0.2:0.5:5:1:1:0.5;

[0078] (2) separating the fermentation liquid into solid and liquid, and subjecting the obtained fermented solid tobacco stems to microwave expansion treatment for 180 seconds at a microwave power of 6000 W at a height of 10 mm to obtain treated tobacco stems;

[0079] (3) The liquid portion obtained by solid-liquid separation was concentrated under reduced pressure, the pH was adjusted to 7.5, glucose and proline were added, and the Maillard reaction was carried out at 110° C. for 3 h to obtain tobacco stem enzymatic hydrolysis Maillard extract.

[0080] Comparative Example 1 Experiment on pretreatment of tobacco stems by liquid fermentation

[0081] The liquid fermentation solid-liquid ratio was fixed at 1:8, temperature at 44°C, pH at 6, preparation dosage at 0.1%, and fermentation time at 6 h. The single factor liquid fermentation tobacco stem experiment was carried out under different conditions by adjusting the fermentation solid-liquid ratio (1:5, 1:6, 1:8, 1:10, 1:12), temperature (37°C, 41°C, 44°C, 47°C, 50°C), pH (5, 5.5, 6, 6.5, 7), preparation dosage (0.03%, 0.05%, 0.1%, 0.2%, 0.3%) and fermentation time (2h, 4h, 6h, 8h, 10h) to investigate the effect of liquid fermentation conditions on the change of tobacco stem lignin content.

[0082] Experimental Example 1

[0083] 1.1 Effect of solid-liquid ratio on tobacco stem lignin

[0084] The liquid fermentation temperature was fixed at 44°C, pH 6, dosage of preparation was 0.1%, and fermentation time was 6h. The single factor liquid fermentation tobacco stem experiment was carried out under different conditions by adjusting the fermentation solid-liquid ratio to 1:5, 1:6, 1:8, 1:10, and 1:12 to investigate the effect of the solid-liquid ratio on the change of tobacco stem lignin content. Figure 1 The test results show that the solid-liquid ratio of liquid fermented tobacco stems has an effect on the change of tobacco stem lignin, which first decreases and then increases.

[0085] 1.2 Analysis of the effect of temperature on tobacco stem lignin

[0086] The liquid fermentation solid-liquid ratio was fixed at 1:8, pH 6, dosage of preparation 0.1%, and fermentation time 6h. The single factor liquid fermentation tobacco stem test was carried out under different conditions by adjusting the liquid fermentation tobacco stem temperature to 37℃, 41℃, 44℃, 47℃, and 50℃ to investigate the effect of temperature on the change of tobacco stem lignin content. Figure 2 The test results show that the temperature of liquid fermented tobacco stems first decreases and then increases the change of tobacco stem lignin.

[0087] 1.3 Analysis of the effect of preparation dosage on tobacco stem lignin

[0088] The liquid fermentation solid-liquid ratio was fixed at 1:8, the temperature was 44°C, the pH was 6, and the fermentation time was 6h. The single factor liquid fermentation tobacco stem test was carried out under different conditions by adjusting the dosage of liquid fermentation tobacco stem preparation to 0.03%, 0.05%, 0.1%, 0.2%, and 0.3% to investigate the effect of the dosage of preparation on the change of tobacco stem lignin content. Figure 3 The test results show that with the increase in the amount of liquid fermented tobacco stem preparation, the tobacco stem lignin tends to gradually decrease.

[0089] 1.4 Analysis of the effect of pH on tobacco stem lignin

[0090] The liquid fermentation solid-liquid ratio was fixed at 1:8, the temperature was 44°C, the dosage of the preparation was 0.1%, and the fermentation time was 6h. The single factor liquid fermentation tobacco stem experiment was carried out under different conditions by adjusting the fermentation pH to 5, 5.5, 6, 6.5, and 7 to investigate the effect of pH on the change of tobacco stem lignin content. Figure 4 The test results show that the pH of tobacco stems in liquid fermentation changes tobacco stem lignin firstly decreases and then increases.

[0091] 1.5. Analysis of the effect of fermentation time on tobacco stem lignin

[0092] The liquid fermentation solid-liquid ratio was fixed at 1:8, the temperature was 44°C, the pH was 6, and the dosage of the preparation was 0.1%. The single factor liquid fermentation tobacco stem experiment was carried out under different conditions by adjusting the fermentation time to 1:5, 1:6, 1:8, 1:10, and 1:12 to investigate the effect of fermentation time on the change of tobacco stem lignin content. Figure 5 The test results show that the fermentation time of liquid fermented tobacco stems first decreases and then increases the change of tobacco stem lignin.

[0093] Experimental Example 2

[0094] 1. Experimental Parts

[0095] 1. Uniform Experimental Design

[0096] The same batch of tobacco stems from the main line were taken to design a uniform experiment. The liquid fermentation tobacco stem experiment was designed to detect the effects of different reaction conditions on the changes in tobacco stem lignin. The effects of liquid fermentation tobacco stem parameters on tobacco stem lignin were determined by mathematical regression equations and evaluated. The degree of influence of each liquid fermentation tobacco stem parameter on the change of tobacco stem lignin was determined by significance analysis.

[0097] According to the design principles of uniformity experiment, the following experimental plan is formulated. The uniformity experimental factors are shown in Table 1, and the uniformity experimental design table is shown in Table 2:

[0098] Table 1 Uniform experimental factors

[0099] Factor / Level Solid-liquid ratio Temperature ℃ pH Preparation dosage% Reaction time Level 1 1:5 37 5 0.03 2 Level 2 1:6 41 5.5 0.05 4 Level 3 1:8 44 6 0.1 6 Level 4 1:10 47 6.5 0.2 8 Level 5 1:12 50 7 0.3 10 Level 6 1:14 53 7.2 0.4 12

[0100] Table 2 Uniform experimental design table

[0101] factor Solid-liquid ratio temperature pH Preparation dosage% Reaction time N1 1:8 37 6.5 0.4 4 N2 1:12 53 7.2 0.2 6 N3 1:5 44 7 0.03 8 N4 6 41 6 0.1 10 N5 1:6 50 5.5 0.3 10 N6 1:10 47 5 0.05 2

[0102] 2. Experiment on determination of main chemical components of tobacco stems

[0103] The main chemical components of tobacco leaves are tested according to industry standards. The specific methods include: "Continuous Flow Method for Determination of Water-soluble Sugar in Tobacco and Tobacco Products" (YC / T159-2002); "Continuous Flow Method for Determination of Total Alkaloids in Tobacco and Tobacco Products" (YC / T160-2002); "Continuous Flow Method for Determination of Total Nitrogen in Tobacco and Tobacco Products" (YC / T161-2002); "Continuous Flow Method for Determination of Chlorine in Tobacco and Tobacco Products" (YC / T162-2002); "Determination of Chlorogenic Acid, Scopolamine and Rutin in Tobacco and Tobacco Products" (YC / T202-2006); "Determination of potassium in tobacco and tobacco products - continuous flow method" (YC / T217-2006); "Determination of starch in tobacco and tobacco products - enzymatic hydrolysis-ion chromatography" (YC / T283-2008); "Determination of pectin in tobacco and tobacco products - ion chromatography" (YC / T346-2010); "Determination of neutral detergent fiber and acid detergent fiber acid-washed lignin in tobacco and tobacco products - detergent method" (YC / T347-2010); "Determination of total volatile alkali in tobacco and tobacco products" (YC / T35-1996);

[0104] 3. Determination of cell wall material

[0105] Through two extractions with organic solvents and hot water, water-soluble sugars, organic acids, inorganic salts, phenols, proteins, pigments, starch, lipids, waxes and other substances are removed from the tobacco leaf powder, and the remaining substances are the cell wall substances.

[0106] (1) Extraction with ethanol-benzene mixture: Accurately weigh 7g of tobacco sample, put it into a filter paper bag, place it in a Soxhlet extractor, and add 600ml of ethanol-benzene (1:2) mixture to a round-bottom flask connected to the Soxhlet extractor. Heat with an electric heating mantle and continue to extract for about 24 hours until the extract is colorless. Put the extraction residue into a G-3 glass sand funnel for suction filtration and rinse with ethanol and acetone three times respectively. (2) Hot water extraction: Add about 100 times the weight of water to the tobacco sample residue after ethanol-benzene mixture extraction, install a reflux device, heat in a boiling water bath for 1 hour, and repeat the operation 3-4 times until there is no sugar in the extract. Put the residue after hot water extraction into a G-3 glass sand funnel of known weight for suction filtration and rinse with water, ethanol, and acetone in turn. Dry at 60±1℃ for 4 hours and then weigh it, which is the weight of the cell wall material.

[0107] 4. Determination method of aroma components

[0108] Before the experiment, 350 mL of pH distilled water and 60 mL of CH 2 Cl 2 Distill for 2 hours simultaneously to clean the simultaneous distillation extraction device and ensure the cleanliness of the instrument.

[0109] Weigh 30 g (accurate to 0.1 mg) of tobacco dust sample and put it into a 1000 mL round-bottom flask at one end of the simultaneous distillation extraction device. Add 30 g of sodium chloride and 350 mL of distilled water and heat it with a temperature-controlled electric heating mantle. The other end of the device is filled with 60 mL of CH 2 Cl 2 The extract was concentrated into a concentration bottle and heated in a water bath while distilling and extracting for 2.5 h. After the extraction, 1 mL of internal standard phenylethyl acetate solution (0.4237 mg / mL) was added and concentrated to 1.0 mL, which was transferred to a chromatographic bottle for GC-MS analysis.

[0110] Chromatographic conditions: chromatographic column: HP-5MS (60m×0.25mm×0.25μm); injection port temperature: 280℃; injection volume: 1μL; split ratio: 5:1; carrier gas: He, 1.0mL / min; heating program: 50℃ for 2min, increase the temperature to 200℃ at a rate of 4℃ / min, maintain for 30min, and then increase the temperature to 280℃ at a rate of 4℃ / min and maintain for 20min.

[0111] Mass spectrometry conditions: transfer line temperature: 280°C; EI source electron energy: 70 eV; electron multiplier voltage: 1635 V; mass scanning range: 30-550 amu; ion source temperature: 230°C; quadrupole temperature: 150°C.

[0112] 5. Methods for determining microstructural changes

[0113] Preparation of electron microscope samples: Select the control sample and the tobacco stem treated with steam explosion at a pressure of 0.8 MPa and a pressure maintenance time of 20 s from the same part, drop a few drops of cold (0-4 ℃) 4% glutaraldehyde fixative on a precooled (0-4 ℃) slide, and cut a 1mm×3mm sample with a sharp blade. The sample was processed in the following order: pre-fixed with 4% glutaraldehyde, washed with 0.1 mol / L phosphate buffer for 3 times, post-fixed with 1% osmium acid, dehydrated once in ethanol series, transitioned with propylene oxide, embedded with Epon812 epoxy resin embedding agent, polymerized at 60 ℃ for 24 hours, then sliced ​​on an LKB ultrathin slicer, double stained with uranyl acetate and lead citrate, and finally observed and photographed under an electron microscope. The samples before and after steam explosion were first glued to the stage, gold-plated with an ion sputtering instrument, and then the cross-section, longitudinal section and tobacco stem surface of the sample were observed and photographed by SEM.

[0114] 2. Experimental Results Analysis

[0115] 2.1 Analysis of uniform experimental results

[0116] On the basis of single factor test, uniform test design was conducted for five factors of liquid fermentation, X1 (solid-liquid ratio), X2 (temperature), X3 (pH), X4 (amount of preparation), and X5 (fermentation time). Taking lignin as the investigation index, the U6 (65) uniform test table was selected, and the test design and results are shown in Table 3.

[0117] Table 3 Uniform test results

[0118]

[0119]

[0120] Table 4. Correlation analysis results of uniform experiment

[0121] Correlation coefficient Y Significant level P X1 0.0015 0.9977 X2 -0.0504 0.9245 X3 -0.1318 0.8035 X4 0.0947 0.8583 X5 -0.0311 0.9533 X1*X1 0.1217 0.8183 X2*X2 -0.0087 0.9869 X3*X3 -0.0981 0.8533 X4*X4 0.316 0.5418 X5*X5 0.139 0.7928 X1*X2 0.0504 0.9245 X1*X3 0.0239 0.9641 X1*X4 0.2201 0.6752 X1*X5 0.1233 0.816 X2*X3 -0.0547 0.918 X2*X4 0.1445 0.7847 X2*X5 0.0324 0.9514 X3*X4 0.1282 0.8088 X3*X5 0.0112 0.9833 X4*X5 0.237 0.6512

[0122] According to the correlation of each factor in the table, it can be inferred that the influence of each factor of tobacco stem liquid fermentation on the lignin content is X3 (pH) > X4 (preparation dosage) > X2 (temperature) > X5 (fermentation time) > X1 (solid-liquid ratio).

[0123] Table 5 Partial correlation test of uniform experiment

[0124] Partial Correlation F-number t-test value p-value r(y,X2)= -0.7997 1.3321 0.3143 r(y,X3*X3)= 0.9192 2.3339 0.1448 r(y,X4*X4)= 0.9953 10.2444 0.0094

[0125] The degree of influence of each parameter of tobacco stem liquid fermentation (including the interaction between each parameter) on tobacco stem lignin can be judged by the relative size of the partial correlation t-test value between each parameter of tobacco stem liquid fermentation and lignin in the regression model. The partial correlation t-test values ​​of each parameter and lignin are shown in Table 5. The confidence probability p-values ​​of each partial correlation test shown in Table 5 are very small, indicating that the regression test results are acceptable at the level of confidence = 0.05, the regression results are credible, and the regression model can be applied. According to the partial correlation t-test value in Table 5, it can be seen that among these influencing factors, the interaction of X3 (temperature) * X4 (time) has the greatest influence on tobacco stem lignin.

[0126] The multi-factor quadratic regression analysis was performed using the data processing software DPS, and the quadratic regression equation was obtained as follows:

[0127] Y=3.291818-0.02545965869*X2+0.0422853162*X3*X3+21.44542984*X4*X4-1.460857983*X3*X4

[0128] (x1-5)*(x1-14) / 14<0

[0129] (x2-37)*(x2-53) / 53<0

[0130] (x3-5)*(x3-7.2) / 7.2<0

[0131] (x4-0.03)*(x4-0.4) / 0.4<0

[0132] (x5-2)*(x5-12) / 12<0

[0133] The correlation coefficient R = 1, the adjusted correlation coefficient Ra = 0.9995, the determination coefficient R2 = 0.9976; F = 264.5916> Df = (4, 1); the significant level p = 0.0461; the residual standard deviation S = 0.0073; the determination coefficient = 0.013; the residual path coefficient = 0.03072. At the same time, the quadratic regression equation is optimized by the nonlinear programming method for the minimum model, and the minimum combination of tobacco stem lignin can also be obtained, that is, X1 (liquid fermentation solid-liquid ratio) = 1:10, X2 (temperature) = 47 ° C, X3 (pH) = 6.5, X4 (preparation dosage) = 0.2%, X5 (fermentation time) = 8h, substituting into the above regression equation, the minimum prediction value of Y (tobacco stem lignin) is 2.3776%. The best solution is: X1 (liquid fermentation solid-liquid ratio) = 1:10, X2 (temperature) = 47°C, X3 (pH) = 6.5, X4 (preparation dosage) = 0.2%, X5 (fermentation time) = 8h, i.e. Example 4.

[0134] 2.2 Verification Experiment

[0135] According to: X1 (liquid fermentation solid-liquid ratio) = 1:10, X2 (temperature) = 47°C, X3 (pH) = 6.5, X4 (preparation dosage) = 0.2%, X5 (fermentation time) = 8h. After the tobacco stem liquid fermentation parameters were adjusted, the lignin content was 2.38%, which was significantly lower than the original sample.

[0136] 2.3 Analysis of the effects of liquid fermentation of tobacco stems on the chemical composition of tobacco stems

[0137] According to the optimal tobacco stem liquid fermentation conditions, that is, Example 4, that is, X1 (liquid fermentation solid-liquid ratio) = 1:10, X2 (temperature) = 47°C, X3 (pH) = 6.5, X4 (preparation dosage) = 0.2%, X5 (fermentation time) = 8h, the experimental study was carried out. The present application treated tobacco stems by liquid fermentation, and the changes in the content of tobacco stem cell wall substances and the changes in the content of tobacco stem chemical components before and after liquid fermentation were investigated as shown in the following table:

[0138] Table 6 Results of changes in cell wall substance content during liquid fermentation of tobacco stems

[0139] Sample Information Full Fiber Pectin Lignin Cell wall material As is 29.7 5.7 3.44 38.84 Liquid fermentation 27.6 5.1 2.38 35.08

[0140] Table 7 Changes in chemical composition of tobacco stems during liquid fermentation

[0141]

[0142]

[0143] From the above analysis results, it can be seen that after liquid fermentation of tobacco stems, the total cellulose of tobacco stems decreased by 7.07%, pectin decreased by 10.52%, lignin decreased by 30.81%, and the content of tobacco stem cell wall substances decreased by 9.68%. Composite cellulase, pectinase, laccase, ligninase, etc. promoted the hydrolysis of them into small molecules under liquid fermentation.

[0144] Due to the liquid fermentation of tobacco stems, the chemical components of total sugar, total alkaloids, and water-soluble proteins in tobacco stems are seriously lost. The total sugar, total alkaloids, protein, starch, total nitrogen, and total volatile alkalis in tobacco stems are reduced by 5.10%, 48.45%, 14.37%, 29.40%, 16.10%, and 40% respectively. Sensory evaluation shows that after the tobacco stems are processed by biological liquid fermentation, the woody smell is significantly reduced, the stimulation is reduced, there is a slight sweetness, and the burning speed is slightly reduced.

[0145] 2.4 Changes in aroma components of tobacco stems after liquid fermentation

[0146] The present application processes tobacco stems by liquid fermentation of tobacco stems, and investigates the changes in the content of tobacco stem aroma components before and after liquid fermentation as shown in Table 8:

[0147] Table 8 Changes in aroma components of tobacco stems during liquid fermentation

[0148]

[0149]

[0150]

[0151]

[0152] The results of aroma component analysis showed that 73 aroma components were detected in the original tobacco stems before liquid fermentation, while 124 aroma components were detected after liquid fermentation. After liquid fermentation, the components of tobacco stems tended to be hydrolyzed into more small molecule aroma components, including acetoin, 3-methyl-2-(5H)-furanone, 2-methylbutyric acid, 3,4-dihydroxy-3,4-dimethyl-2,5-hexanedione, methylcyclopentenolone, eucalyptol, sorbic acid, terpineol, 2 ,3-dihydrobenzofuran, 5-hydroxymethylfurfural, 2-ethyl-p-cresol and 67 other new aroma components, the total amount of aroma components increased from 94.9279μg / g to 155.6461μg / g, some aroma components such as 2,3-butanedione, furfural, 2-acetylfuran, 5-methylfurfural, phenylethanol, phyton, palmitic acid, etc. have a large increase, these substances will have a positive effect on the formation of the aroma of tobacco stems, thereby further increasing the aroma and taste of the stems.

[0153] GC-MS was used to analyze and classify the chemical components in the content of various compounds before and after liquid fermentation treatment, and the contents of various chemical components such as esters, ketones, heterocyclics, and acids were clarified, as shown in Table 11. After liquid fermentation treatment, aldehydes, acids, ketones, esters, phenols, and heterocyclics increased significantly, alcohols increased by 11.89%, aldehydes increased by 66.70%, acids increased by 176.78%, ketones increased by 34.95%, and esters increased by 176.93%. The results of the smoking test showed that the woody aroma of tobacco stems was significantly reduced after liquid fermentation treatment, and the roasted aroma was significantly increased.

[0154] Table 9 Changes in flavor substances before and after liquid fermentation

[0155]

[0156] 2.5 Effect of liquid fermentation on the physical structure of tobacco stems

[0157] Scanning electron microscope photos of tobacco stems before and after liquid fermentation are shown in Figure 6 to Figure 8 . Figure 6 The electron microscope scanning cross-section of the original sample A1 and the sample A2 tobacco stems. Figure 7 The surface images of the tobacco stems of original sample B1 and sample B2 were scanned by electron microscope. Figure 8 The longitudinal sections of tobacco stems of original sample C1 and sample C2 are scanned by electron microscope.

[0158] Comparative Example 2 Single Factor Experiment of Microwave Treatment of Tobacco Stems

[0159] Weigh 2000g tobacco stems with different moisture content (20%, 25%, 30%, 35%, 40%), set different drying times (60s, 90s, 120s, 150s, 180s), spread the materials to different heights (10mm, 15mm, 20mm, 25mm, 30mm), and dry them in a continuous tunnel microwave dryer at different powers (4000W, 4500W, 5000W, 5500W, 6000W). After drying and expansion, the change in tobacco stem lignin content was detected.

[0160] Experimental Example 3

[0161] 1. Effect of microwave power on tobacco stem lignin

[0162] Depend on Fig. 9 The experimental results show that the lignin content in tobacco stems decreases first and then increases with the increase of microwave power.

[0163] 2. Effect of Microwave Tobacco Stem Moisture on Tobacco Stem Lignin

[0164] Depend on Fig.10 The experimental results show that the lignin content of tobacco stems tends to decrease with the increase of moisture content of microwave tobacco stems.

[0165] 3. Effect of microwave paving height on tobacco stem lignin

[0166] Depend on Fig.11 The experimental results show that the lignin content of tobacco stems tends to decrease with the increase of the height of tobacco stem laying.

[0167] 4. Effect of microwave reaction time on tobacco stem lignin

[0168] Depend on Fig.12 The experimental results show that the lignin content of tobacco stems first decreases with the extension of microwave treatment time.

[0169] Experimental Example 4

[0170] 1. Experimental methods

[0171] 1. Orthogonal experimental design analysis

[0172] According to the preliminary analysis results of the single-factor experiment, four factors, namely A power, B reaction time, C laying height and D tobacco stem moisture, were selected, and the experiment was designed with lignin content as the evaluation index. The factors and levels are shown in the table below.

[0173] Table 10 Orthogonal experimental factors and levels

[0174] level Power W Time Moisture% Paving height (mm) 1 4000 90 20 10 2 5000 120 30 20 3 6000 150 40 30

[0175] Table 11 Orthogonal experimental design table

[0176] factor Power W Time Moisture% Paving height (mm) Test 1 4000 90 20 10 Test 2 4000 120 30 20 Test 3 4000 150 40 30 Test 4 5000 90 30 30 Test 5 5000 120 40 10 Test 6 5000 150 20 20 Test 7 6000 90 40 20 Test 8 6000 120 20 30 Test 9 6000 150 30 10

[0177] 2. The experiment for determining the main chemical components of tobacco stems, the determination of cell wall substances, the determination method of aroma components, and the determination method of microstructural changes are the same as parts 2 to 5 of the first part of Example 2.

[0178] 2. Analysis of Experimental Results

[0179] 1.1 Analysis of orthogonal experimental results

[0180] On the basis of single factor experiment, orthogonal experimental design was conducted for three factors: A temperature, B reaction time and C tobacco stem moisture. Taking the change of tobacco stem lignin content as the investigation index, L9(3 3 )Orthogonal array, the experimental design and results are shown in the table below.

[0181] Table 12L9(3 3 )Orthogonal experimental results

[0182]

[0183] Table 13 Test of between-subject effects

[0184]

[0185] The orthogonal experimental results were subjected to a range analysis, and the size of the range R shows the priority of the influencing factors. From the size of the R value, it can be seen that the degree of influence of the lignin rate under different microwave treatment conditions is different. The order of influencing factors is: power W> time S> moisture %> laying height mm. As can be seen from the above table, there are significant differences in the orthogonal experiment variance analysis. Power, time, moisture, and laying height all have a significant effect on the lignin content of tobacco stems. Comprehensive analysis of the results of single factor and orthogonal experiments shows that the optimal reaction conditions for tobacco stem lignin under different microwave treatment conditions are: power of 6000W, time of 180s, moisture of 40%, and laying height of 10mm.

[0186] 1.2 Verification Experiment

[0187] According to the optimal reaction conditions of tobacco stem lignin under microwave treatment, a verification test was carried out. 2000g of 40% tobacco stems with different moisture content were weighed, the drying time was set to 180s, the material was laid to a height of 10mm, and dried at 6000W in a continuous tunnel microwave dryer. After the drying and expansion, the change in the tobacco stem lignin content was detected. The results showed that after the reaction conditions were adjusted, the tobacco stem lignin content was reduced to 2.12%. Compared with the results of each combination of the orthogonal test, the optimized tobacco stem lignin content was lower than the test results of the experiment. Compared with the lignin content of 3.44% before optimization, adjusting the microwave treatment parameters had a positive effect on the reduction of tobacco stem lignin.

[0188] 1.3 Analysis of the effects of microwave treatment on the chemical composition of tobacco stems

[0189] According to the optimal reaction strip, the experimental study was carried out, that is, Example 4. After the reaction was completed, the present application treated the tobacco stems by microwave treatment, and the changes in the content of tobacco stem cell wall substances and the content of tobacco stem chemical components before and after microwave treatment were investigated as shown in the following table:

[0190] Table 14 Changes in cell wall material content during microwave treatment

[0191] Sample Information Full Fiber Pectin Lignin Cell wall material As is 29.7 5.7 3.44 38.84 Fenton reaction 26.4 4.8 2.12 33.32

[0192] Table 15 Changes in chemical composition content of tobacco stems before and after microwave treatment

[0193] Sample Information As is Microwave treatment Total sugar (%) 20.7 18.5 Total plant alkaloids (%) 0.50 0.52 chlorine(%) 1.98 1.89 Reducing sugar (%) 12.2 10.9 Potassium (%) 5.79 5.54 Total nitrogen (%) 1.69 1.75 protein 10.04 10.35 PH 4.99 5.02 Chlorogenic acid 1.39 1.55 Scopolamine 0.33 0.27 Rutin 0.00 0.00 Total volatile alkali 0.20 0.15 starch 1.7 1.7

[0194] From the above analysis results, it can be seen that after microwave treatment, the total cellulose content of tobacco stems decreased by 11.11%, the pectin content decreased by 15.79%, the lignin content decreased by 38.37%, and the cell wall material content of tobacco stems decreased by 14.21%. The cell wall material content of tobacco stems after microwave expansion decreased, and the evaluation results were consistent with the analysis results. This is mainly due to the non-thermal effect of microwaves, which makes the molecules of the reactants instantly activated under the ultra-high frequency oscillation of microwaves, greatly increasing the chances of collision and friction between molecules, making the reaction complex and rapid, and then causing thermal degradation of some cell wall materials. Under the action of microwave electromagnetic fields, the polar water molecules in tobacco stems change from the original random distribution state to the polar arrangement orientation according to the electric field. Under the action of high-frequency electromagnetic fields, the orientation of these polar molecules changes continuously according to the frequency of alternating electromagnetics, causing the movement of molecules to intensify and rub against each other, thereby generating heat. The expansion of tobacco stems is achieved by converting electromagnetic energy into thermal energy.

[0195] Due to the effect of microwave treatment, the total sugar in the tobacco stems decreased by 10.76%, the reducing sugar decreased by 10.84%, and the total volatile alkali decreased by 20.0%. Other indicators did not change significantly. The total sugar content decreased significantly. This is because the microwave-expanded tobacco stems are in a closed state, which can make the internal structure of the tobacco stems reach high temperature instantly and heat more evenly. During the microwave expansion process, the temperature continues to rise, and the sugar substances in the tobacco stems participate in caramelization and sugar thermal cracking reactions, producing many furan derivatives, ketone aldehydes, carboxyl compounds and other aroma components. From the perspective of smoking quality, the tobacco stems after microwave expansion treatment are mainly characterized by a significant reduction in impurities, a significant improvement in the comfort of the aftertaste, and a slight irritation.

[0196] 1.4 Changes in aroma components after microwave treatment

[0197] The present application uses microwave treatment to treat tobacco stems, and the changes in the content of tobacco stem aroma components before and after microwave treatment are investigated as shown in the following table:

[0198] Table 16 Changes in aroma components during microwave treatment

[0199]

[0200]

[0201]

[0202] From the results of aroma component analysis, it can be seen that 70 aroma components were detected in the original sample before microwave treatment, while 58 aroma components were detected after microwave treatment. The composition of tobacco stems changed greatly after microwave treatment, including the addition of 30 new aroma components such as 1-isopropoxy-2-one, methylcyclopentenol ketone, 2-acetylpyrrole, 2,3-dimethylpyridine, 4,7,9-megatrien-3-one, and 3-hydroxy-damascenone. The total amount of aroma components increased from 94.5244μg / g to 115.1988μg / g. Furfural, cyclopent-4-ene-1,3-dione, 2-acetylfuran, phenylethanol, neophytadiene, palmitic acid, etc. increased significantly. These substances will have a positive effect on the formation of the aroma of tobacco stems, thereby further increasing the aroma and taste of the stems.

[0203] GC-MS was used to analyze and classify the chemical components in the content of various compounds before and after microwave treatment of tobacco, and the content of various chemical components such as esters, ketones, heterocyclics, and acids was clarified. After microwave expansion treatment, esters, ketones, heterocyclics, and acids increased significantly, with esters increasing by 209.33%, acids increasing by 22.04%, ketones increasing by 50.25%, and heterocyclics increasing by 32.83%. The content of neophytadiene increased significantly, increasing by 306.19%. Neophytadiene is a C20 polyisoprene with the highest content in tobacco neutral volatiles and is an important aroma substance in tobacco leaves. Neophytadiene can directly enter the smoke when tobacco is burned, which has the effect of reducing irritation, alcohol, and smoke. As a carrier for capturing aroma substances in smoke aerosols, neophytadiene has the ability to carry volatile aroma substances and aroma components in tobacco leaves into smoke, so it is also an important flavor enhancer for tobacco leaves. In addition, neophytadiene can also undergo oxidation reactions during the aging process and further decompose and transform into low-molecular weight compounds with a pure aroma, such as plant furans. These substances will have a positive effect on the formation of the fragrance of flue-cured tobacco, thereby further increasing the aroma and taste of tobacco leaves.

[0204] Tobacco stems contain polar water molecules, which have the characteristics of strong microwave absorption. When the tobacco stems are treated with microwaves, the water molecules collide and rub violently with the microwaves, which will generate a lot of heat, causing the water in the tobacco stems to evaporate rapidly and generate vapor pressure; when the vapor pressure inside the tobacco stems exceeds the bearing capacity of the fiber tissue structure, this pressure causes the tobacco stems to expand. After microwave treatment, the cell structure of the tobacco stems is broken, and the organic matter in the cells undergoes a series of complex Maillard reactions under a high temperature and high pressure closed environment, thereby promoting the transformation of aromatic compounds in the tobacco stems and the browning reaction process, resulting in an increase in the relative content of aroma substances, and the generation of many substances that are beneficial to improving the aroma of tobacco, harmonizing the aroma, reducing impurities, reducing irritation, improving smoke and taste, and thus improving the smoking quality of the stems. Microwave treatment accelerates the enzymatic browning reaction of phenolic compounds in tobacco stems, reduces phenolic compounds in tobacco stems, and deepens the color, which is conducive to improving the sensory quality of the stems, making the stems taste mellow and increasing the aroma. Ketones are all carbonyl compounds and are also one of the main components of tobacco essential oil. The carbonyl group in the ketone molecular structure is an aroma group that can give tobacco a unique and beautiful aroma. Acidic substances play a role in regulating pH and balancing the acidity and alkalinity in tobacco, making the taste mellow, and can enhance the smoke concentration, indirectly affecting the aroma of tobacco. Heterocyclic substances such as 2,3-dimethylpyridine can increase the sweetness and cherry aroma of tobacco, and 2-acetylfuran in furans gives tobacco a fresh and herbal aroma. The more relative content of aroma substances produced by microwave treatment of tobacco stems, the more obvious the improvement in the quality of stems. The improvement in sensory quality of the detected relative content of aroma substances fully confirms this point.

[0205] Table 17 Contents of various compounds before and after microwave treatment

[0206]

[0207] 1.5 Effect of microwave treatment on the physical structure of tobacco stems

[0208] The scanning electron microscope photos of tobacco stems before and after microwave treatment are shown in the figure below. Fig.13 The electron microscope scanning cross-section of the original sample A1 and the sample A2 tobacco stems. Fig.14 Original sample B1 and sample B2 are the surface images of tobacco stems scanned by electron microscope. Fig.15 The longitudinal sections of tobacco stems of original sample C1 and sample C2 are scanned by electron microscope.

[0209] Example 5

[0210] (1) Cut tobacco stems into small pieces of 4 cm, add them into a fermentation tank together with a dilute phosphoric acid aqueous solution, with a solid-liquid ratio of 1:10, and add 0.2% of the weight of the tobacco stems as a biological composite preparation for liquid fermentation; the liquid fermentation temperature is 45° C., the pH is 6.5, and the fermentation time is 8 hours. The biological composite preparation includes xylanase, pectinase, pectin lyase, pectinesterase, glucanase, laccase, ligninase, cellulase, and glucosidase. The mass ratio of xylanase, pectinase, pectin lyase, pectinesterase, glucanase, laccase, ligninase, cellulase, and glucosidase is 3:2:0.2:0.2:0.5:5:1:1:0.5;

[0211] (2) separating the fermentation liquid into solid and liquid, and subjecting the obtained fermented solid tobacco stems to microwave expansion treatment for 185 seconds at a microwave power of 6000 W at a height of 10 mm to obtain treated tobacco stems;

[0212] (3) The liquid portion obtained by solid-liquid separation was concentrated under reduced pressure, the pH was adjusted to 7.5, glucose and proline were added, and the Maillard reaction was carried out at 112° C. for 3 h to obtain tobacco stem enzymatic hydrolysis Maillard extract.

[0213] Example 6

[0214] (1) Cut tobacco stems into small pieces of 4.5 cm, add them into a fermentation tank together with a dilute phosphoric acid aqueous solution, with a solid-liquid ratio of 1:9.5, and add 0.2% of the weight of the tobacco stems as a biological composite preparation for liquid fermentation; the liquid fermentation temperature is 46°C, the pH is 6.5, and the fermentation time is 8 hours. The biological composite preparation includes xylanase, pectinase, pectin lyase, pectinesterase, glucanase, laccase, ligninase, cellulase, and glucosidase. The mass ratio of xylanase, pectinase, pectin lyase, pectinesterase, glucanase, laccase, ligninase, cellulase, and glucosidase is 3:2:0.2:0.2:0.5:5:1:1:0.5;

[0215] (2) separating the fermentation liquid into solid and liquid, and subjecting the obtained fermented solid tobacco stems to microwave expansion treatment for 180 seconds at a microwave power of 6000 W at a height of 10 mm to obtain treated tobacco stems;

[0216] (3) The liquid portion obtained by solid-liquid separation was concentrated under reduced pressure, the pH was adjusted to 7.5, glucose and proline were added, and the Maillard reaction was carried out at 108° C. for 3 h to obtain tobacco stem enzymatic hydrolysis Maillard extract.

Claims

1. An off-line pretreatment process for reducing the content of tobacco stem cell wall substances, characterized in that: The following steps are involved: (1) adding tobacco stems and a dilute phosphoric acid aqueous solution into a fermentation tank, and adding a biocomposite preparation for liquid fermentation; (2) separating the fermentation liquid into solid and liquid, and subjecting the obtained fermented solid tobacco stems to microwave expansion treatment to obtain treated tobacco stems; (3) concentrating the liquid portion obtained by solid-liquid separation under reduced pressure, adjusting the pH, adding glucose and proline, and performing a Maillard reaction to obtain a tobacco stem enzymatically hydrolyzed Maillard extract; The biological composite preparation comprises xylanase, pectinase, pectin lyase, pectinesterase, glucanase, laccase, ligninase, cellulase and glucosidase.

2. The off-line pretreatment process for reducing the content of tobacco stem cell wall substances according to claim 1, characterized in that: The mass ratio of the xylanase, pectinase, pectin lyase, pectinesterase, glucanase, laccase, ligninase, cellulase and glucosidase is 2.5-3.5: 1.5-2.5: 0.1-0.3: 0.15-0.25: 0.4-0.6: 4-6: 0.5-1.5: 0.5-2: 0.4-0.

65.

3. The off-line pretreatment process for reducing the content of tobacco stem cell wall substances according to claim 1, characterized in that: The liquid fermentation solid-liquid ratio is (1:8) to (1:10); the liquid fermentation temperature is 43°C to 48°C.

4. The off-line pretreatment process for reducing the content of tobacco stem cell wall substances according to claim 1, characterized in that: The dosage of the biological composite preparation is 0.2% to 0.3% of the weight of the tobacco stem.

5. The off-line pretreatment process for reducing the content of tobacco stem cell wall substances according to claim 1, characterized in that: The pH of the liquid fermentation is 6.2-6.7; the fermentation time of the liquid fermentation is 7-9 hours.

6. The off-line pretreatment process for reducing the content of tobacco stem cell wall substances according to claim 1, characterized in that: The microwave power of the microwave expansion treatment is 5500W-6000W; the time of the microwave expansion treatment is 160-180s; and the height of the material to be laid in the microwave expansion treatment is 10-15mm.

7. The off-line pretreatment process for reducing the content of tobacco stem cell wall substances according to claim 1, characterized in that: The moisture content of the fermented solid tobacco stems after microwave expansion treatment is 30% to 40%.

8. The off-line pretreatment process for reducing the content of tobacco stem cell wall substances according to claim 1, characterized in that: In step (3), the reaction temperature is 105°C to 115°C; and the reaction time is 3 to 4 hours.

9. The off-line pretreatment process for reducing the content of tobacco stem cell wall substances according to claim 1, characterized in that: In step (3), the pH is 7 to 7.

5.

10. The off-line pretreatment process for reducing the content of tobacco stem cell wall substances according to claim 1, characterized in that: In the step (1), the tobacco stems need to be segmented and cut into pieces of 3 to 8 cm in size.

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