A harvesting and curing method that highlights the sweet aroma of tobacco leaves

Abstract

This invention discloses a harvesting and curing method that highlights the sweet and fragrant aroma of tobacco leaves. By reducing the maturity of fresh tobacco leaves by 10-20%, harvesting 2-6 days earlier, and employing the "43315" curing process, the curing time is extended by 20-30 hours in the early yellowing stage, 15-20 hours in the middle yellowing stage, 10-15 hours in the middle color-fixing stage, and 5-10 hours in the late color-fixing stage. The curing time in the late yellowing stage, early color-fixing stage, and dry rib stage is shortened by 5-10 hours each. The rate of temperature rise in the dry bulb during the early yellowing stage, late yellowing stage, and early color-fixing stage is slowed down, the degree of yellowing of tobacco leaves in the early color-fixing stage is appropriately reduced, and the wet bulb temperature is controlled during the middle yellowing stage, late yellowing stage, early color-fixing stage, and middle color-fixing stage. The proportion of green tobacco after curing is reasonably controlled, effectively improving the content of sweet and fragrant aroma-characteristic substances and sensory quality of the cured tobacco leaves, and fully highlighting the sweet and fragrant aroma characteristics of tobacco leaves.

Description

Technical Field

[0001] This invention relates to a method for harvesting and curing tobacco leaves that highlights their sweet and fragrant flavor, and belongs to the field of tobacco harvesting and curing technology. Background Technology

[0002] Generally, the characteristics of sweet-aroma tobacco leaves are a prominent sweet aroma and a distinct green fragrance, with a high content of sugars and other chemical components. In recent years, the aroma quality of tobacco leaves from different ecological regions has shown a downward trend, and the aroma characteristics have weakened somewhat. As the cigarette industry places increasingly higher demands on distinctive and high-quality tobacco leaves and their distinctive style, developing high-quality and distinctive tobacco leaves has become an important trend in order to fully highlight the aroma characteristics of tobacco leaves.

[0003] Harvesting maturity and curing process are closely related to the quality and aroma characteristics of tobacco leaves. Currently, tobacco leaves are still harvested using conventional production methods, and curing is still mainly carried out using a three-stage curing process. However, the harvesting maturity and curing process cannot fully bring out the style characteristics of sweet and fragrant tobacco leaves. Therefore, it is necessary to change the traditional production model according to the processing requirements to cure tobacco leaves with the desired aroma, which can improve the value of tobacco leaves.

[0004] Patent document (publication number CN109998145A) discloses a roasting process for ten key stable temperature points of sweet-aroma tobacco leaves. This process promotes the full degradation of macromolecular substances in tobacco leaves and the formation of a large number of small molecules, resulting in thorough softening and wilting of the tobacco leaves. This improves the softness of the tobacco leaves, increases their aroma and oil content, enhances their color, and prevents them from becoming stiff. Patent document (publication number CN114568729A) discloses a method and equipment for roasting sweet-aroma tobacco leaves, which reduces low-temperature yellowing. The process involves adjusting the yellowing temperature, slowing down the heating rate, appropriately extending the color-fixing period, and controlling the temperature during the drying stage to improve baking quality, reduce baking losses, and achieve the desired yellowing, softening, and aroma. Patent document (publication number CN108433164A) discloses a loose-leaf baking process for aromatic tobacco leaves, including the early yellowing stage, middle yellowing stage, late yellowing stage, tip drying stage, leaf drying stage, and stem drying stage. The dry-bulb temperature after the early yellowing stage is raised to 40℃, and the wet-bulb temperature is controlled at 40℃. A small amount of... The process involves dehumidifying the leaves to lower the wet-bulb temperature from 40℃ to 39℃, then maintaining this temperature for 16–18 hours. A further small amount of dehumidification is then performed to lower the wet-bulb temperature to 38℃ or 37℃, maintaining this temperature for 14–16 hours. Next, the dry-bulb temperature is raised to 41℃, and dehumidification is increased to lower the wet-bulb temperature to 37℃ or 36℃, maintaining this temperature for 8–10 hours. This method effectively solves problems such as large apical-to-apical temperature difference and thin leaves in the lower leaves after curing, and severe ash buildup, dark color, and stiffness in the upper leaves. (Patent document publication number CN106174677A) A method for curing tobacco leaves that highlights the characteristics of a light-aroma type is disclosed. This method involves lowering the wet-bulb temperature by 1-2°C at each stage, reducing the yellowing degree of the tobacco leaves by 10%, and increasing the moisture loss by 3%. As a result, the cured tobacco leaves have a predominantly white base color, good gloss, and a high sugar and low alkali content in their internal chemical composition. The aroma components are characterized by fewer carotenoid degradation products, fewer browning reaction products, and more phenolic substances. Ultimately, this method achieves the goal of highlighting the characteristics of a light-aroma type of tobacco leaf and ensuring the quality of the tobacco leaves.

[0005] However, while the aforementioned solutions can improve the quality and style of sweet-aroma tobacco leaves, the problem of maintaining the sweet-aroma style of tobacco leaves from high-altitude tobacco-growing areas has not been effectively solved. On the one hand, ecological issues in high-altitude tobacco-growing areas lead to lower overall temperatures, resulting in significant differences in the maturity characteristics of tobacco leaves compared to low-altitude areas, and there is still a gap in the accuracy of controlling the harvest maturity. On the other hand, over-curing occurs during the curing process, weakening the sweet-aroma style of the tobacco leaves. Currently, there have been no significant technological breakthroughs in addressing these issues. Summary of the Invention

[0006] Therefore, the purpose of this invention is to provide a harvesting and curing method that highlights the characteristics of sweet and fragrant tobacco leaves, so as to at least solve the problems mentioned in the background art.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for harvesting and curing tobacco leaves that highlights their sweet and fragrant aroma includes the following steps:

[0009] S1, Harvesting: Compared with conventional mature harvesting, the maturity of fresh tobacco leaves is reduced by 10-20%, and harvesting is carried out 2-6 days earlier;

[0010] S2, Tobacco sorting and loading: Fresh tobacco is sorted, sorted, and loaded into the kiln in layers.

[0011] S3 is baked using the "43315" baking process.

[0012] The “4” refers to extending the baking time for the early yellowing stage by 20-30 hours, the baking time for the middle yellowing stage by 15-20 hours, the baking time for the middle color fixing stage by 10-15 hours, and the baking time for the late color fixing stage by 5-10 hours.

[0013] The first "3" refers to appropriately shortening the baking time by 5 to 10 hours each during the later yellowing stage, the earlier color-fixing stage, and the drying stage.

[0014] The second "3" refers to slowing down the rate of increase in dry-bulb temperature during the early yellowing stage, the late yellowing stage, and the early color-fixing stage;

[0015] "1" refers to appropriately reducing the degree of yellowing of tobacco leaves in the early stage of color fixing;

[0016] "5" refers to controlling the wet-bulb temperature during the middle stage of yellowing, the later stage of yellowing, the early stage of color setting, and the middle stage of color setting, as well as controlling the proportion of green smoke after baking to be between 2% and 5%.

[0017] Furthermore, the advance harvesting time for fresh tobacco leaves is as follows: compared to the conventional mature harvesting time, the lower tobacco leaves are harvested 2-3 days earlier, the middle tobacco leaves 3-5 days earlier, and the upper tobacco leaves 4-6 days earlier.

[0018] Furthermore, the maturity characteristics of the lower tobacco leaves harvested are as follows: the leaf surface is mainly green, with a yellowish-green hue, the leaf tip is light greenish-yellow, the leaf surface is 2-3 parts yellow, more than 1 / 2 of the main vein is white, 1 / 4 to 1 / 2 of the branch veins are white, 30% to 50% of the pubescence has fallen off, the leaf surface is slightly wrinkled, and the tobacco leaf SPAD value is 24 to 34.

[0019] Furthermore, the maturity characteristics of the central tobacco leaves harvested are as follows: the leaf surface is mainly yellow, with a greenish-yellow hue, the leaf tip is greenish-yellow, the leaf edge and auricle are light greenish-yellow, with light greenish-yellow mature patches, the leaf surface is 40-50% yellow, more than 2 / 3 of the main vein is white, 1 / 2 to 2 / 3 of the branch veins are white, 50%-70% of the pubescence has fallen off, the leaf surface is obviously wrinkled, and the tobacco leaf SPAD value is 20-30.

[0020] Furthermore, the maturity characteristics of the upper tobacco leaves harvested are as follows: the leaf surface is mainly yellow, ranging from light yellow to pale yellow, with yellow leaf tips and edges, and light greenish-yellow or pale greenish-yellow leaf auricles. There are obvious yellow mature patches, with 60-70% of the leaf surface being yellow, the main vein turning white, more than 2 / 3 of the branch veins turning white, more than 70% of the pubescence falling off, and the leaf surface having a strong wrinkled feel. The SPAD value of the tobacco leaves is 10-20.

[0021] Furthermore, the baking process using the "43315" baking technique involves the following steps:

[0022] S3-1, Early Yellowing Stage: After ignition, raise the dry bulb temperature to 29-31℃ and the wet bulb temperature to 28-30℃ at a rate of 1℃ / 1-2h, and bake at a stable temperature for 3-5h. The leaves will soften slightly, initiating the yellowing process of the tobacco leaves. Afterward, raise the dry bulb temperature to 36℃ and the wet bulb temperature to 35℃ at a rate of 1℃ / 1-2h, and bake at a stable temperature for 25-30h. The tobacco leaves will turn 30-50% yellow, and more than 2 / 3 of the leaves will soften.

[0023] S3-2, Mid-yellowing stage: Raise the dry bulb temperature to 38℃ at a heating rate of 1℃ / h, control the wet bulb temperature at 36.5~37.5℃ during the mid-yellowing stage, and bake at a stable temperature for 30~40h. The tobacco leaves will turn 60~70% yellow and become soft.

[0024] S3-3, late yellowing stage: Increase the dry bulb temperature to 40℃ at a rate of 1℃ / 2-3h, control the wet bulb temperature at 35.5-36.5℃, and bake at a stable temperature for 5-6h. The tobacco leaves will turn 70-80% yellow and become wilted and soft. After that, increase the dry bulb temperature to 42℃ at a rate of 1℃ / 3-4h, control the wet bulb temperature at 35-36℃, and bake at a stable temperature for 6-8h. The tobacco leaves will turn 80-90% yellow, fully wilted, and the leaf tips will dry 1-2cm.

[0025] S3-4, Pre-color fixation stage: Raise the dry bulb temperature to 45℃ at a rate of 1℃ / 3~4h, control the wet bulb temperature at 34.5~36.5℃, and bake at a stable temperature for 6~8h until the leaf veins contain 4%~6% green and the leaf tips are dry to 5~10cm.

[0026] S3-5, Mid-stage of color fixation: Increase the dry bulb temperature to 48℃ at a rate of 1℃ / 2h, control the wet bulb temperature at 35.5~37.5℃, and bake at a stable temperature for 20~30h until more than half of the tobacco leaves are dry and more than 1 / 3 of the midrib is dry.

[0027] S3-6, Post-color fixation stage: Raise the dry bulb temperature to 53-55℃ and the wet bulb temperature to 38-39℃ at a rate of 1℃ / 1-2h, and bake at a stable temperature for 20-25h until the tobacco leaves are completely dry and more than 2 / 3 of the main veins are dry.

[0028] S3-7, Drying stage: Raise the dry bulb temperature to 65-68℃ and the wet bulb temperature to 40-41℃ at a heating rate of 1℃ / h, and bake at a stable temperature for 10-15 hours until all the tobacco leaves in the kiln are completely dry.

[0029] Furthermore, by harvesting in advance and using the "43315" curing process, the proportion of green tobacco in different parts of the tobacco leaves is controlled: the proportion of green tobacco in the lower tobacco leaves is controlled at 3% to 5%, and the proportion of green tobacco in the middle and upper tobacco leaves is controlled at 2% to 4%.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] This invention reduces the maturity of fresh tobacco leaves by 10-20%, harvesting them 2-6 days earlier. It employs a "43315" curing process, extending the curing time by 20-30 hours in the early yellowing stage, 15-20 hours in the mid-yellowing stage, 10-15 hours in the mid-color-fixing stage, and 5-10 hours in the late color-fixing stage. It also shortens the curing time in the late yellowing stage, early color-fixing stage, and dry-bulb stage by 5-10 hours each, slowing the rate of temperature rise in the dry bulb during the early, late, and early yellowing stages, appropriately reducing the degree of yellowing in the early color-fixing stage, controlling the wet bulb temperature in the mid, late, early, and mid-color-fixing stages, and rationally controlling the proportion of green tobacco after curing. Firstly, this invention, based on the maturity characteristics of different parts of the tobacco leaf, harvests fresh tobacco leaves earlier, avoiding over-ripening and excessive transformation of characteristic substances, while precisely controlling the harvest maturity, making the operation more convenient and efficient. Secondly, by controlling the roasting process to avoid over-roasting and reasonably controlling the proportion of green smoke after roasting, the content of sweet and fragrant characteristic substances in the roasted tobacco leaves and their sensory quality are effectively improved, fully demonstrating the style characteristics of sweet and fragrant tobacco leaves.

[0032] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] A method for harvesting and curing tobacco leaves that highlights their sweet and fragrant aroma includes the following steps:

[0035] S1, Harvesting: Compared with conventional mature harvesting, the maturity of fresh tobacco leaves is reduced by 10-20%, and harvesting is carried out 2-6 days earlier;

[0036] S2, Tobacco sorting and loading: Fresh tobacco is sorted, sorted, and loaded into the kiln in layers.

[0037] S3 is baked using the "43315" baking process.

[0038] The “4” refers to extending the baking time for the early yellowing stage by 20-30 hours, the baking time for the middle yellowing stage by 15-20 hours, the baking time for the middle color fixing stage by 10-15 hours, and the baking time for the late color fixing stage by 5-10 hours.

[0039] The first "3" refers to appropriately shortening the baking time by 5 to 10 hours each during the later yellowing stage, the earlier color-fixing stage, and the drying stage.

[0040] The second "3" refers to slowing down the rate of increase in dry-bulb temperature during the early yellowing stage, the late yellowing stage, and the early color-fixing stage;

[0041] "1" refers to appropriately reducing the degree of yellowing of tobacco leaves in the early stage of color fixing;

[0042] "5" refers to controlling the wet-bulb temperature during the mid-yellowing stage, late-yellowing stage, early-color-fixing stage, and mid-color-fixing stage, as well as controlling the proportion of green tobacco content after curing to between 2% and 5%. Specifically, this is achieved by harvesting early and using the "43315" curing process to control the proportion of green tobacco content in different parts of the tobacco leaves: the lower leaves have a green tobacco content controlled at 3%–5%, while the upper and middle leaves have a green tobacco content controlled at 2%–4%.

[0043] In step S1, the advance harvesting time of fresh tobacco leaves is as follows: compared with the conventional mature harvesting time, the lower tobacco leaves are harvested 2-3 days earlier, the middle tobacco leaves 3-5 days earlier, and the upper tobacco leaves 4-6 days earlier. Specifically, the maturity characteristics of the lower tobacco leaves are: the leaf surface is mainly green, with a yellowish-green hue, the leaf tip is light yellowish-green, the leaf surface is 2-3 parts yellow, more than 1 / 2 of the main vein is white, 1 / 4 to 1 / 2 of the lateral veins are white, 30% to 50% of the pubescence has fallen off, the leaf surface is slightly wrinkled, and the SPAD value of the tobacco leaves is 24-34; the maturity characteristics of the middle tobacco leaves are: the leaf surface is mainly yellow, with a greenish-yellow hue, the leaf tip is greenish-yellow, the leaf edge and auricle are light yellowish-green, with light yellowish-green mature patches, the leaf surface is 4-5 parts yellow, the main vein is 2 / 3 parts yellow, more than 1 / 4 to 1 / 2 of the lateral veins are white, 30% to 50% of the pubescence has fallen off, the leaf surface is slightly wrinkled, and the SPAD value of the tobacco leaves is 24-34. The upper part of the tobacco leaves is harvested with the following characteristics: the leaves are mainly yellow, ranging from light yellow to pale yellow, with yellow tips and edges, and light greenish-yellow or pale greenish-yellow auricles. There are obvious yellow mature patches, the leaves are 60-70% yellow, the main veins are white, more than 2 / 3 of the branch veins are white, more than 70% of the pubescence has fallen off, the leaves are strongly wrinkled, and the leaves have a SPAD value of 10-20.

[0044] In step S2, fresh tobacco is classified, sorted and bundled (interlocked) according to the "GB / T 23219—2008 Technical Specification for Tobacco Curing" and then loaded into the curing pit in layers according to the classification.

[0045] In step S3, the specific steps for baking using the "43315" baking process are as follows:

[0046] S3-1, Early Yellowing Stage: Slow down the heating rate during the early yellowing stage and extend the baking time by 20-30 hours.

[0047] Specifically, after ignition, the dry bulb temperature is increased to 29-31°C and the wet bulb temperature to 28-30°C at a rate of 1°C / 1-2 hours, and then the temperature is maintained for 3-5 hours until the leaves soften slightly and the tobacco leaves begin to turn yellow. Afterward, the dry bulb temperature is increased to 36°C and the wet bulb temperature to 35°C at a rate of 1°C / 1-2 hours, and then the temperature is maintained for 25-30 hours until the tobacco leaves turn 30-50% yellow and more than 2 / 3 of the leaves soften.

[0048] S3-2, Mid-goldening stage: Extend the baking time for the mid-goldening stage by 15-20 hours and control the wet-bulb temperature during the mid-goldening stage.

[0049] Specifically, the dry bulb temperature is raised to 38℃ at a heating rate of 1℃ / h, the wet bulb temperature is controlled at 36.5~37.5℃ during the mid-yellowing stage, and the temperature is kept stable for 30~40h. The tobacco leaves turn 60~70% yellow and become soft.

[0050] S3-3, Late Yellowing Stage: Slow down the heating rate during the late yellowing stage, control the wet-bulb temperature during the late yellowing stage, and shorten the baking time during the late yellowing stage by 5-10 hours.

[0051] Specifically, the dry bulb temperature is increased to 40℃ at a rate of 1℃ / 2-3h, while the wet bulb temperature is controlled at 35.5-36.5℃. The temperature is maintained for 5-6h, until the tobacco leaves turn 70-80% yellow and become wilted and soft. Then, the dry bulb temperature is increased to 42℃ at a rate of 1℃ / 3-4h, while the wet bulb temperature is controlled at 35-36℃. The temperature is maintained for 6-8h, until the tobacco leaves turn 80-90% yellow, become fully wilted, and the leaf tips dry to 1-2cm.

[0052] S3-4, Early Stage of Color Fixing: Slow down the heating rate during the early stage of color fixing, control the wet-bulb temperature during the early stage of color fixing, shorten the baking time during the early stage of color fixing by 5-10 hours, and appropriately reduce the degree of yellowing of tobacco leaves during the early stage of color fixing.

[0053] Specifically, the dry bulb temperature is raised to 45℃ at a rate of 1℃ / 3~4h, the wet bulb temperature is controlled at 34.5~36.5℃, and the temperature is kept stable for 6~8h until the leaf veins contain 4%~6% green and the leaf tips are dry to 5~10cm.

[0054] S3-5, Mid-stage color fixation: Extend the mid-stage baking time for color fixation by 10-15 hours and control the wet-bulb temperature during the mid-stage color fixation.

[0055] Specifically, the dry bulb temperature is raised to 48℃ at a rate of 1℃ / 2h, the wet bulb temperature is controlled at 35.5~37.5℃, and the temperature is kept stable for 20~30h until more than half of the tobacco leaves are dry and more than 1 / 3 of the main veins are dry.

[0056] S3-6, Post-color setting: Extend the baking time for the post-color setting stage by 5-10 hours.

[0057] Specifically, the dry bulb temperature is raised to 53-55℃ and the wet bulb temperature is 38-39℃ at a heating rate of 1℃ / 1-2h, and the temperature is kept stable for 20-25h until the tobacco leaves are completely dry and more than 2 / 3 of the main veins are dry.

[0058] S3-7, Drying stage: Shorten the baking time during the drying stage by 5-10 hours.

[0059] Specifically, the dry bulb temperature is raised to 65-68℃ and the wet bulb temperature to 40-41℃ at a heating rate of 1℃ / h, and then the temperature is maintained for 10-15 hours until all the tobacco leaves in the kiln are completely dry.

[0060] To verify the effectiveness of the technical solution of this invention, the applicant conducted a comparative experiment from 2021 to 2023 in Weining County, Bijie City, Guizhou Province. The tested flue-cured tobacco variety was Yunyan 87, and the test materials were tobacco leaves from the 4th-5th lower leaves, the 10th-11th middle leaves, and the 16th-17th upper leaves. The tested tobacco leaves were managed according to the local high-quality tobacco production technical regulations, and the tested curing barn was an airflow-type biomass standard intensive curing barn, using a tobacco stick weaving method. The comparative experiment was conducted with the local conventional harvesting and curing operation as a control and the harvesting and curing operation of this invention as a comparative treatment.

[0061] The following evaluation and analysis will be conducted on the tobacco leaves produced by the harvesting and curing method of this invention (treatment) and the conventional harvesting and curing method (control) from the aspects of the proportion of green tobacco leaves after curing, the coordination of chemical components, the content of substances characteristic of sweet tobacco leaves, sensory quality and style characteristics.

[0062] 1. Effects of different treatments on the proportion of green smoke after curing

[0063] Table 1. Effects of different treatments on the proportion of green smoke after curing (%)

[0064]

[0065] Note: Leaves with both green patches and green veins are classified as primary and secondary, based on the proportion of green area; different lowercase letters indicate significant differences at the 5% level, the same applies below.

[0066] As shown in Table 1, the proportion of green tobacco in different parts of the tobacco leaves after curing using the method of the present invention is higher than that of conventional harvesting and curing, but all are within the control range of 2% to 5%, which is consistent with the range of green tobacco proportion that highlights the sweet and fragrant tobacco leaf style.

[0067] 2. Effects of different treatments on sugar content and its balance in flue-cured tobacco leaves

[0068] Table 2. Effects of different treatments on sugar content and sugar-to-glucose ratio of cured tobacco leaves.

[0069]

[0070] Note: A ratio of reducing sugar to total sugar greater than 0.9 is considered more balanced.

[0071] Previous studies have shown that high sugar content in flue-cured tobacco leaves is a typical characteristic of sweet tobacco leaves. As shown in Table 2, the sugar content of flue-cured tobacco leaves from different parts of the plant produced by the method of this invention is higher than that of conventionally harvested and flue-cured tobacco leaves, and the ratio of the two sugars is larger, indicating better coordination of chemical components.

[0072] 3. Effects of different treatments on the content of characteristic substances of sweet aroma in flue-cured tobacco leaves

[0073] Table 3. Effects of different treatments on the content of sweet and aromatic characteristic substances in cured tobacco leaves.

[0074]

[0075]

[0076] Previous studies have shown that four substances—1-(1H-pyrrolo-2-yl)-acetone, phenylacetaldehyde, solanone, and (E)-3-hexen-1-ol—make significant contributions to the development of a sweet and refreshing aroma and can be considered key substances for highlighting the sweet and refreshing aroma of tobacco leaves. Table 3 shows that, compared with conventional harvesting and curing methods, the tobacco leaves cured using the method of this invention have a higher content of characteristic substances that contribute to the sweet and refreshing aroma.

[0077] 4. Effects of different treatments on the style characteristics of flue-cured tobacco leaves

[0078] Table 4. Effects of different treatments on the flavor characteristics of cured tobacco leaves

[0079]

[0080] Note: Each evaluation indicator has a maximum score of 9 points. The higher the score, the more prominent the style characteristics.

[0081] Five to seven domestic experts were organized to evaluate the sensory quality of flue-cured tobacco leaves after different treatments. As shown in Table 4, compared with conventional harvesting and curing, the flue-cured tobacco leaves produced by the method of this invention scored higher in terms of sweet aroma, concentration, and strength; the average values ​​of the three indicators were significantly higher than those of conventional harvesting and curing, and the style characteristics of the flue-cured tobacco leaves were more prominent.

[0082] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments without departing from the technical solution of the present invention and based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for harvesting and curing tobacco leaves that highlights their sweet and fragrant aroma, characterized by: Includes the following steps: S1, Harvesting: Compared with conventional mature harvesting, the maturity of fresh tobacco leaves is reduced by 10-20%, and harvesting is carried out 2-6 days earlier; S2, tobacco sorting and loading: sorting fresh tobacco, sorting tobacco by category, and loading tobacco into the kiln by category and layer; S3 is baked using the "43315" baking process. The "4" refers to extending the baking time for the early yellowing stage by 20-30 hours, the mid-yellowing stage by 15-20 hours, the mid-color-fixing stage by 10-15 hours, and the late-color-fixing stage by 5-10 hours. The first "3" refers to appropriately shortening the baking time by 5-10 hours each during the later yellowing stage, the earlier color-fixing stage, and the drying stage. The second "3" refers to slowing down the rate of increase in dry bulb temperature during the early stage of yellowing, the late stage of yellowing, and the early stage of color fixing; "1" refers to appropriately reducing the degree of yellowing of tobacco leaves in the early stage of color fixing; "5" refers to controlling the wet bulb temperature during the middle stage of yellowing, the later stage of yellowing, the early stage of color setting, and the middle stage of color setting, as well as controlling the proportion of green smoke after baking to be between 2% and 5%. The aforementioned early harvesting time for fresh tobacco leaves is as follows: compared to the conventional mature harvesting time, the lower tobacco leaves are harvested 2-3 days earlier, the middle tobacco leaves 3-5 days earlier, and the upper tobacco leaves 4-6 days earlier. The maturity characteristics of the upper tobacco leaves harvested are as follows: the leaf surface is mainly yellow, in light yellow or pale yellow, the leaf tip and leaf edge are yellow, the leaf auricle is light greenish-yellow or pale greenish-yellow, there are obvious yellow mature patches, the leaf surface is 60-70% yellow, the main vein is white, more than 2 / 3 of the branch veins are white, more than 70% of the hairs have fallen off, the leaf surface has a strong wrinkled feel, and the tobacco leaf SPAD value is 10-20. The baking process using the "43315" baking technique is as follows: S3-1, Early Yellowing Stage: After ignition, raise the dry bulb temperature to 29-31℃ and the wet bulb temperature to 28-30℃ at a rate of 1℃ / 1-2h, and bake at a stable temperature for 3-5h. The leaves will soften slightly, initiating the yellowing process of the tobacco leaves. Afterward, raise the dry bulb temperature to 36℃ and the wet bulb temperature to 35℃ at a rate of 1℃ / 1-2h, and bake at a stable temperature for 25-30h. The tobacco leaves will turn 30-50% yellow, and more than 2 / 3 of the leaves will soften. S3-2, Mid-yellowing stage: Raise the dry bulb temperature to 38℃ at a heating rate of 1℃ / h, control the wet bulb temperature at 36.5~37.5℃ during the mid-yellowing stage, and bake at a stable temperature for 30~40h until the tobacco leaves turn 60~70% yellow and become soft. S3-3, late yellowing stage: Increase the dry bulb temperature to 40℃ at a rate of 1℃ / 2~3h, control the wet bulb temperature at 35.5~36.5℃, and bake at a stable temperature for 5~6h. The tobacco leaves will turn 70~80% yellow and become wilted and soft. After that, increase the dry bulb temperature to 42℃ at a rate of 1℃ / 3~4h, control the wet bulb temperature at 35~36℃, and bake at a stable temperature for 6~8h. The tobacco leaves will turn 80~90% yellow, fully wilted, and the leaf tips will dry 1~2cm. S3-4, Pre-color fixation stage: Raise the dry bulb temperature to 45℃ at a rate of 1℃ / 3~4h, control the wet bulb temperature at 34.5~36.5℃, and bake at a stable temperature for 6~8h until the leaf veins contain 4%~6% green and the leaf tips are dry to 5~10cm. S3-5, Mid-stage of color fixation: Increase the dry bulb temperature to 48℃ at a rate of 1℃ / 2h, control the wet bulb temperature at 35.5~37.5℃, and bake at a stable temperature for 20~30h until the tobacco leaves are more than half dry and the midrib is more than 1 / 3 dry. S3-6, Post-color fixation stage: Raise the dry bulb temperature to 53-55℃ and the wet bulb temperature to 38-39℃ at a rate of 1℃ / 1~2h, and bake at a stable temperature for 20~25h until the tobacco leaves in the whole kiln are completely dry and more than 2 / 3 of the main veins are dry. S3-7, Drying stage: Raise the dry bulb temperature to 65~68℃ and the wet bulb temperature to 40~41℃ at a heating rate of 1℃ / h, and bake at a stable temperature for 10~15h until all the tobacco leaves in the kiln are completely dry.

2. The harvesting and curing method for highlighting the sweet and fragrant aroma of tobacco leaves according to claim 1, characterized in that, The maturity characteristics of the lower tobacco leaves harvested are as follows: the leaf surface is mainly green, with a yellowish-green hue, the leaf tip is light greenish-yellow, the leaf surface is 2-3 parts yellow, more than 1 / 2 of the main vein is white, 1 / 4 to 1 / 2 of the branch veins are white, 30% to 50% of the pubescence has fallen off, the leaf surface is slightly wrinkled, and the tobacco leaf SPAD value is 24 to 34.

3. The harvesting and curing method for highlighting the sweet and fragrant aroma of tobacco leaves according to claim 1, characterized in that, The maturity characteristics of the tobacco leaves harvested in the middle section are as follows: the leaf surface is mainly yellow, with a greenish-yellow hue, the leaf tip is greenish-yellow, the leaf edge and auricle are light greenish-yellow, there are light greenish-yellow mature patches, the leaf surface is 40-50% yellow, more than 2 / 3 of the main vein is white, 1 / 2 to 2 / 3 of the branch veins are white, 50% to 70% of the pubescence has fallen off, the leaf surface is obviously wrinkled, and the SPAD value of the tobacco leaves is 20 to 30.

4. The harvesting and curing method for highlighting the sweet and fragrant aroma of tobacco leaves according to any one of claims 1-3, characterized in that, By harvesting in advance and using the "43315" curing process, the proportion of green tobacco in different parts of the tobacco leaves is controlled: the proportion of green tobacco in the lower tobacco leaves is controlled at 3%~5%, and the proportion of green tobacco in the middle and upper tobacco leaves is controlled at 2%~4%.

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