Temperature-controlled fermentation process for improving enrichment of aroma substances of flue-cured tobacco
By using a compound fermentation system and a three-stage temperature control strategy, and by coordinating microbial and enzymatic reactions, the enrichment efficiency and quality of aroma substances in flue-cured tobacco have been improved. This has solved the problems of insufficient aroma conversion and poor coordination in existing technologies, and has achieved efficient enrichment of aroma substances and quality improvement.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-05
- Publication Date
- 2026-03-24
AI Technical Summary
Existing flue-cured tobacco fermentation processes cannot simultaneously meet the optimal conditions for microbial metabolism and enzymatic hydrolysis, resulting in insufficient conversion of aroma-producing substances, poor aroma coordination, and difficulty in balancing fermentation cycle and quality improvement.
A compound fermentation system is adopted, combining the dominant agarwood-forming fungi and compound biological enzymes. Through a three-stage gradient temperature control strategy, microbial metabolism and enzymatic reactions are synergistically realized, which destroys the cell wall structure of tobacco leaves, promotes the release of nutrients, and ensures the uniform enrichment of aroma substances through stacking operations.
It increases the total amount and stability of aroma-producing substances, shortens the fermentation cycle, improves the aroma quality and duration, and solves the problem of limited aroma substance enrichment efficiency in traditional processes.
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Figure CN121714062A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of tobacco processing technology, specifically to a temperature-controlled fermentation process for enhancing the enrichment of aroma substances in flue-cured tobacco. Background Technology
[0002] As the main raw material for tobacco products in my country, the aroma quality of flue-cured tobacco directly determines the market competitiveness of cigarette products. Newly harvested flue-cured tobacco often suffers from problems such as a strong grassy and impure aroma, high irritation, and low content of aroma-producing substances, requiring a fermentation and aging process to improve its quality. Currently, flue-cured tobacco fermentation is mainly divided into two categories: microbial fermentation and enzymatic fermentation.
[0003] Microbial fermentation technology often uses Bacillus or yeast from tobacco leaves or soil, or single-source agarwood-forming fungi. While this can shorten the aging cycle, it suffers from insufficient conversion of aroma-producing substances and poor aroma harmony. Enzymatic fermentation technology often uses complex biological enzymes to degrade macromolecules, but single-enzyme systems have narrow adaptability to temperature and humidity, resulting in insufficient stability and short duration of aroma components. Furthermore, existing processes mostly use a single temperature control mode, which cannot simultaneously meet the optimal conditions for microbial metabolism and enzymatic reactions, thus limiting the enrichment efficiency of aroma substances and making it difficult to meet the dual requirements of fermentation cycle and quality improvement.
[0004] Therefore, developing a fermentation process that can synergistically combine microbial and enzymatic hydrolysis to achieve efficient enrichment of aroma compounds through precise temperature control has become an urgent technical problem to be solved in the tobacco processing industry. Summary of the Invention
[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a temperature-controlled fermentation process that enhances the enrichment of aroma substances in flue-cured tobacco, so as to solve the problems mentioned in the background art.
[0006] According to one aspect of this application, a temperature-controlled fermentation process for enhancing the enrichment of aroma substances in flue-cured tobacco includes the following steps:
[0007] Step 1: Pre-treatment of flue-cured tobacco:
[0008] Select upper-layer flue-cured tobacco leaves, prioritizing the second and top leaves. Although these leaves have higher protein and nicotine content, they offer greater potential for aroma enhancement after processing using this method. First, destem and impurity removal is performed to remove stems, dust, and other impurities from the tobacco leaves, preventing interference with fermentation uniformity. Then, the tobacco leaves are placed in a constant temperature and humidity environment (20-24℃, 55-60% relative humidity) for 48 hours to allow the moisture content to become more uniform. The moisture content is then measured to ensure stable conditions for subsequent fermentation.
[0009] After balancing, the tobacco leaves are kneaded and squeezed, applying just enough pressure to allow the juice to overflow, avoiding excessive squeezing that could damage the leaf structure. Following kneading, the leaves are microwaved at 800W power and 2450MHz for 4-6 minutes. Microwave treatment disrupts the cell wall structure of the tobacco leaves, promoting juice release and providing nutrients for subsequent microbial metabolism and enzymatic reactions. It also provides gentle sterilization, reducing contamination by other microorganisms.
[0010] Step 2: Preparation of the compound fermentation system:
[0011] The compound fermentation system is made by mixing the dominant agarwood-forming fungus liquid and compound biological enzymes at a weight ratio of 2-4:1. This ratio can achieve synergistic effects of microbial metabolism and enzymatic hydrolysis.
[0012] Preparation of dominant agarwood-forming fungal culture: Fusarium and *Pterocarya spp.* were selected as dominant strains and mixed at a weight ratio of 1-3:1-3. This combination can produce honey-like aromatic substances and has the ability to synergistically degrade macromolecules. The seed culture medium contained 20.0g glucose and 200.0g potato per liter, with the remainder being distilled water at its natural pH. It was sterilized at 121℃ for 20 minutes and then cooled to 30-32℃ for later use. Slant cultures of both strains were inoculated into the seed culture medium and cultured at 160-180 rpm and 30-32℃ with constant temperature shaking for 36-40 hours to obtain the seed culture solution. The seed culture solution was centrifuged at 6500-8000 rpm for 15-20 minutes, the supernatant was discarded, and the mycelial sludge was mixed with deionized water to prepare a 5-10% mixed culture solution, ensuring the concentration met the fermentation requirements.
[0013] Preparation of the compound bio-enzyme: Laccase, mesophilic amylase, plant hydrolase, and cellulase were selected and composed in a weight ratio of 1-2:1-2:2-3:2-3. This ratio can synergistically degrade macromolecules such as proteins, starch, and cellulose in tobacco leaves, converting them into small-molecule aroma precursors. The mass concentration of the compound bio-enzyme was 1.2-1.8% laccase, 1.2-1.8% mesophilic amylase, 2.5-3.0% plant hydrolase, and 2.5-3.0% cellulase. The amount of compound bio-enzyme added per gram of pretreated flue-cured tobacco was 6000-9000 U. This amount ensured that the enzymatic hydrolysis reaction proceeded fully while avoiding excessive enzyme intake that would increase costs.
[0014] Step 3: Staged temperature-controlled fermentation:
[0015] The compound fermentation system was evenly sprayed onto the surface of the pretreated flue-cured tobacco, with the material-to-liquid ratio controlled at 1:1.5-2.0 to ensure full contact between the tobacco and the fermentation system. A three-stage gradient temperature control strategy was adopted, with parameters for each stage as follows:
[0016] The first stage is the microbial-dominated fermentation stage, with the temperature controlled at 28-32℃ and the relative humidity at 85-90%. These conditions are the optimal metabolic temperature for the dominant agarwood-forming fungi, promoting rapid growth and reproduction of the strains, producing a large amount of mycelium and primary metabolites, and degrading macromolecular nutrients in the tobacco leaves. Fermentation lasts for 3-4 days. During this period, when the core temperature rises to 35-38℃, the pile is turned over every 12 hours to prevent localized overheating that could inactivate the strains and ensure uniform fermentation.
[0017] The second stage is the enzymatic hydrolysis-dominated reaction stage, where the temperature is raised to 42-46℃ and the relative humidity is 75-80%. This temperature range significantly enhances the activity of the complex biological enzymes, promoting efficient enzymatic hydrolysis and further converting the macromolecular precursors produced by microbial degradation into small-molecule aroma compounds, such as phenylacetaldehyde and megastigmatrienone. This stage of fermentation lasts 2-3 days, until the degradation rate of macromolecular substances in the tobacco leaves reaches over 70%.
[0018] The third stage is the synergistic transformation stage, where the temperature is lowered to 25-28℃ and the relative humidity is 70-75%. These conditions coordinate the activity of microorganisms and enzymes, promote the stable accumulation and transformation of aroma compounds, and reduce the loss of volatile aroma compounds. After fermentation for 1-2 days, when the surface of the flue-cured tobacco is covered with mycelia and there are no obvious water droplets, it enters the drying process.
[0019] The drying process uses hot air circulation drying, with the temperature controlled at 40-45℃ and the drying time at 8-10 hours, drying the flue-cured tobacco to a moisture content of 10-13%. This moisture content can prevent the tobacco leaves from becoming moldy, while retaining an appropriate amount of moisture for subsequent aging reactions.
[0020] Step 4: Post-treatment aging:
[0021] The fermented tobacco leaves are stacked to a height of 100-120cm. Stacking too high can lead to poor ventilation, while stacking too low reduces space utilization. The aging environment temperature is controlled at 20-22℃, and the relative humidity at 62-65%. These conditions promote the continuous degradation of residual macromolecules in the tobacco leaves and the further enrichment of aroma compounds. The stacks are turned every 30 days during aging, maintaining a constant stack height to ensure uniform aging. After 4-6 months of aging, highly aromatic flue-cured tobacco is obtained.
[0022] The advantages of this application compared to existing technologies are:
[0023] 1. The composite fermentation system constructed in this invention realizes the synergistic effect of the dominant agarwood-forming fungi and composite biological enzymes. The microorganisms first degrade macromolecular nutrients, and the enzymes further convert them into aroma-producing substances, which solves the problem of insufficient conversion in a single fermentation system and increases the total amount of aroma-producing substances.
[0024] 2. The three-stage gradient temperature control strategy precisely matches the optimal conditions for microbial metabolism and enzymatic hydrolysis. The first stage promotes microbial growth, the second stage enhances enzymatic transformation, and the third stage stabilizes aroma accumulation, shortening the fermentation cycle compared to the traditional single temperature control process.
[0025] 3. Microwave treatment during the pretreatment process disrupts the cell wall structure of tobacco leaves, promotes the release of nutrients, and at the same time, it gently sterilizes, reduces contamination by miscellaneous bacteria, and improves fermentation stability; the turning operation during the post-treatment aging process ensures the uniform enrichment of aroma substances. Attached Figure Description
[0026] Figure 1 This is a flowchart of a temperature-controlled fermentation process for enhancing the enrichment of aroma substances in flue-cured tobacco according to an embodiment of this application. Detailed Implementation
[0027] To make the content of this application easier to understand, the appendices in the embodiments of this application will be described below. Figure 1 The technical solutions in the embodiments of this application will be clearly and completely described.
[0028] Example 1
[0029] Step 1: Pre-treatment of flue-cured tobacco: Select the upper part of Yunnan Yunyan 87 flue-cured tobacco, remove stems and impurities, and equilibrate at 22℃ and 58% relative humidity for 48 hours. The moisture content is measured to be 18%. Knead and squeeze until the juice overflows, and then treat with microwave at 800W and 2450MHz for 5 minutes to obtain pre-treated flue-cured tobacco.
[0030] Step 2: Preparation of the compound fermentation system:
[0031] The dominant agarwood-forming fungus culture was prepared by mixing *Fusarium* and *Pterocarya spp.* in a 2:2 weight ratio. The seed culture medium contained 20.0 g glucose, 200.0 g potato, and the remainder distilled water per liter, with the natural pH value, and was sterilized at 121℃ for 20 minutes. The two strains were separately inoculated into the seed culture medium and cultured at 170 rpm and 31℃ with shaking for 38 hours to obtain the seed culture solution. After centrifugation at 6800 rpm for 18 minutes, the supernatant was discarded, and the mycelial slurry was mixed with deionized water to prepare an 8% mixed culture solution.
[0032] The compound bio-enzyme is composed of laccase, mesophilic amylase, plant hydrolase, and cellulase in a weight ratio of 1.5:1.5:2.8:2.8, with mass concentrations of 1.5%, 1.5%, 2.8%, and 2.8%, respectively. 7500U of the compound bio-enzyme is added per gram of pretreated flue-cured tobacco.
[0033] Compound fermentation system: Mix the above bacterial solution and enzyme solution at a weight ratio of 3:1.
[0034] Step 3: Staged temperature-controlled fermentation: The compound fermentation system is sprayed onto the surface of the pretreated flue-cured tobacco at a material-to-liquid ratio of 1:1.8. The first stage involves fermentation at 29℃ and 88% relative humidity for 3.5 days, turning the pile every 12 hours when the core temperature reaches 36℃. The second stage involves fermentation at 44℃ and 78% relative humidity for 2.5 days. The third stage involves fermentation at 26℃ and 72% relative humidity for 1.5 days. The tobacco is then dried with hot air circulation at 42℃ for 9 hours until the moisture content reaches 12%, yielding fermented flue-cured tobacco.
[0035] Step 4, post-processing aging: Stack the fermented tobacco to a height of 110cm and age it for 5 months at 21℃ and 63% relative humidity, turning the stack over every 30 days.
[0036] Example 2
[0037] Step 1: Pretreatment of flue-cured tobacco: Select upper leaves of B3F flue-cured tobacco from Yongzhou, Hunan Province. After removing stems and impurities, equilibrate at 20℃ and 55% relative humidity for 48 hours, and the moisture content is measured to be 17%. Knead and squeeze until the juice overflows, and microwave at 800W and 2450MHz for 4 minutes to obtain pretreated flue-cured tobacco.
[0038] Step 2: Preparation of the compound fermentation system:
[0039] The dominant agarwood-forming fungus culture: Fusarium and Aster tataricus were mixed at a weight ratio of 1:3. The seed culture medium was the same as in Example 1. The culture was carried out at 160 rpm and 30°C with constant temperature shaking for 36 hours, followed by centrifugation at 6500 rpm for 15 minutes to prepare a 5% mixed culture.
[0040] The compound bio-enzyme is composed of laccase, mesophilic amylase, plant hydrolase, and cellulase in a weight ratio of 1:2:2:3, with mass concentrations of 1.2%, 1.8%, 2.5%, and 3.0%, respectively. 6000U of compound bio-enzyme is added per gram of pretreated flue-cured tobacco.
[0041] Compound fermentation system: Mix bacterial solution and enzyme solution at a weight ratio of 2:1.
[0042] Step 3: Staged temperature-controlled fermentation: Spray with a material-to-liquid ratio of 1:1.5. The first stage involves fermentation at 28℃ and 85% relative humidity for 3 days, turning the pile every 12 hours when the core temperature reaches 35℃. The second stage involves fermentation at 42℃ and 75% relative humidity for 2 days. The third stage involves fermentation at 25℃ and 70% relative humidity for 1 day. Dry with hot air circulation at 40℃ for 8 hours until the moisture content reaches 10%, obtaining fermented flue-cured tobacco.
[0043] Step 4, Post-processing aging: Stack the stacks to a height of 100cm and age for 4 months at 20℃ and 62% relative humidity, turning the stacks over every 30 days.
[0044] Example 3
[0045] Step 1: Pre-treatment of flue-cured tobacco: Select upper tobacco leaves from Longyan, Fujian, remove stems and impurities, and equilibrate at 24℃ and 60% relative humidity for 48 hours until the moisture content is 19%. Knead and squeeze until the juice overflows, then microwave at 800W and 2450MHz for 6 minutes to obtain pre-treated flue-cured tobacco.
[0046] Step 2: Preparation of the compound fermentation system:
[0047] The dominant agarwood-forming fungus culture: Fusarium and Pterocarya spp. were mixed at a weight ratio of 3:1. The seed culture medium was the same as in Example 1. The culture was carried out at 180 rpm and 32°C with constant temperature shaking for 40 hours, followed by centrifugation at 8000 rpm for 20 minutes to prepare a 10% mixed culture.
[0048] The compound bio-enzyme is composed of laccase, mesophilic amylase, plant hydrolase, and cellulase in a weight ratio of 2:1:3:2, with mass concentrations of 1.8%, 1.2%, 3.0%, and 2.5%, respectively. 9000U of compound bio-enzyme is added per gram of pretreated flue-cured tobacco.
[0049] Compound fermentation system: Mix bacterial solution and enzyme solution at a weight ratio of 4:1.
[0050] Step 3: Staged temperature-controlled fermentation: Spray with a material-to-liquid ratio of 1:2.0. The first stage involves fermentation at 32℃ and 90% relative humidity for 4 days, turning the pile every 12 hours when the core temperature reaches 38℃. The second stage involves fermentation at 46℃ and 80% relative humidity for 3 days. The third stage involves fermentation at 28℃ and 75% relative humidity for 2 days. Dry with hot air circulation at 45℃ for 10 hours until the moisture content reaches 13%, obtaining fermented flue-cured tobacco.
[0051] Step 4, Post-processing aging: Stack the stacks to a height of 120cm and age for 6 months at 22℃ and 65% relative humidity, turning the stacks over every 30 days.
[0052] Example 4 Effect Test
[0053] The aroma-enriched flue-cured tobacco prepared in Examples 1-3 above and flue-cured tobacco prepared by traditional fermentation process (control group) were compared by detecting the content of aroma-enriching substances and conducting sensory evaluation. The results are as follows:
[0054] Aroma compound content: The contents of megastigmatrienone in Examples 1-3 were 16.2 μg / g, 15.8 μg / g, and 16.5 μg / g, respectively; the contents of neophytadiene were 885 μg / g, 872 μg / g, and 893 μg / g, respectively; and the contents of phenylacetaldehyde were 2.3 μg / g, 2.2 μg / g, and 2.4 μg / g, respectively. All of these were more than 40% higher than the control group (megastigmatrienone 11.5 μg / g, neophytadiene 632 μg / g, phenylacetaldehyde 1.6 μg / g).
[0055] Sensory evaluation: The aroma quality score of Examples 1-3 was 9.2-9.5, the aroma quantity score was 9.0-9.3, the off-odor score was 8.8-9.1, the strength score was 8.7-9.0, the irritation score was 8.8-9.1, the aftertaste score was 9.1-9.4, and the total score was 54.6-55.6, which was significantly improved compared with the control group (total score 48.2). The aroma duration reached 550-580 seconds.
[0056] The above embodiments are only used to illustrate the technical solutions of the embodiments of this application, and are not intended to limit them. Although the embodiments of this application have been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features, without departing from the spirit and scope defined by the claims of this application.
Claims
1. A temperature-controlled fermentation process for enhancing the enrichment of aroma substances in flue-cured tobacco, characterized in that, Includes the following steps: Step 1: Pretreatment of flue-cured tobacco: Select the upper flue-cured tobacco, remove the stems and impurities, and equilibrate it for 48 hours at a temperature of 20-24℃ and a relative humidity of 55-60%. After measuring the moisture content, knead and squeeze to allow the juice to overflow, and then microwave it for 4-6 minutes to obtain pretreated flue-cured tobacco. Step 2: Preparation of the compound fermentation system: The compound fermentation system is prepared by mixing the dominant agarwood resin-forming fungus liquid and the compound bio-enzyme at a weight ratio of 2-4:1; the dominant agarwood resin-forming fungus liquid is prepared by compounding Fusarium and Pterocarya spp. at a weight ratio of 1-3:1-3; the compound bio-enzyme is composed of laccase, mesophilic amylase, plant hydrolase and cellulase at a weight ratio of 1-2:1-2:2-3:2-3; Step 3: Staged temperature-controlled fermentation: The compound fermentation system is evenly sprayed onto the surface of the pretreated flue-cured tobacco, controlling the material-to-liquid ratio at 1:1.5-2.0, and three stages of fermentation are carried out sequentially: Stage 1: Temperature 28-32℃, relative humidity 85-90%, fermentation for 3-4 days; Stage 2: Temperature 42-46℃, relative humidity 75-80%, fermentation for 2-3 days; Stage 3: Temperature 25-28℃, relative humidity 70-75%, fermentation for 1-2 days. When the surface of the flue-cured tobacco is covered with mycelium and there are no obvious water droplets, it is dried to a moisture content of 10-13% to obtain fermented flue-cured tobacco. Step 4, Post-processing aging: The fermented flue-cured tobacco is stacked to a height of 100-120cm and aged for 4-6 months at a temperature of 20-22℃ and a relative humidity of 62-65% to obtain flue-cured tobacco with high aroma enrichment.
2. The temperature-controlled fermentation process for enhancing the enrichment of aroma substances in flue-cured tobacco according to claim 1, characterized in that, The microwave processing described in step one has a power of 800W and an operating frequency of 2450MHz.
3. The temperature-controlled fermentation process for enhancing the enrichment of aroma substances in flue-cured tobacco according to claim 1, characterized in that, The preparation method of the agarwood dominant resin-forming fungal culture in step two is as follows: slant strains of Fusarium and Pterocarya spp. are inoculated into seed culture medium and cultured at 160-180 rpm and 30-32℃ for 36-40 hours with constant temperature shaking to obtain two seed culture solutions; the two seed culture solutions are centrifuged at 6500-8000 rpm for 15-20 minutes, the supernatant is discarded, and the fungal mud is mixed in proportion and then deionized water is added to prepare a 5-10% mixed fungal culture solution.
4. The temperature-controlled fermentation process for enhancing the enrichment of aroma substances in flue-cured tobacco according to claim 3, characterized in that, The seed culture medium contains 20.0g of glucose and 200.0g of potato per liter, with the remainder being distilled water. It has a natural pH value and is sterilized at 121°C for 20 minutes.
5. The temperature-controlled fermentation process for enhancing the enrichment of aroma substances in flue-cured tobacco according to claim 1, characterized in that, The mass concentration of the compound bio-enzyme in step two is: laccase 1.2-1.8%, mesophilic amylase 1.2-1.8%, plant hydrolase 2.5-3.0%, and cellulase 2.5-3.0%. The amount of compound bio-enzyme added per gram of pretreated flue-cured tobacco is 6000-9000U.
6. The temperature-controlled fermentation process for enhancing the enrichment of aroma substances in flue-cured tobacco according to claim 1, characterized in that, In the first stage of fermentation in step three, when the core temperature rises to 35-38℃, the pile is turned over once every 12 hours.
7. The temperature-controlled fermentation process for enhancing the enrichment of aroma substances in flue-cured tobacco according to claim 1, characterized in that, In step three, the drying temperature is 40-45℃, the drying time is 8-10 hours, and hot air circulation drying is used.
8. The temperature-controlled fermentation process for enhancing the enrichment of aroma substances in flue-cured tobacco according to claim 1, characterized in that, In step four, during the aging process, the stacked tobacco is turned over every 30 days, while keeping the stack height constant during the turning.