Method for improving quality of low-quality oolong tea

Abstract

The invention relates to a method for improving the quality of low-quality oolong tea. The method comprises the following steps: primary enzymolysis: spraying a cellulase solution on the low-quality oolong tea for enzymolysis; primary baking: putting the oolong tea subjected to primary enzymolysis into a graphene baking cage for primary baking; secondary enzymolysis: continuously spraying a protease solution on the oolong tea subjected to primary baking treatment for enzymolysis; secondary baking: putting the oolong tea subjected to secondary enzymolysis into a graphene baking cage for secondary baking; third-time enzymolysis: continuously spraying a tannase solution on the oolong tea subjected to secondary baking treatment for enzymolysis; baking with fire to improve aroma: baking the oolong tea subjected to the third enzymolysis treatment in graphene far infrared light to obtain the oolong tea with improved quality. According to the method disclosed by the invention, the cellulase, the protease and the tannase are used for performing segmented enzymolysis, the graphene baking cage is used for performing combined baking, the bad-taste aroma components are subjected to precise targeted fermentation and conversion, and finally baking is performed for increasing aroma, so that the quality of the low-quality oolong tea is improved.

Description

Technical Field

[0001] This invention belongs to the field of tea processing technology, specifically relating to a method for improving the quality of low-quality oolong tea. Background Technology

[0002] In the traditional production system of oolong tea, the process from picking fresh leaves to refining finished tea involves many meticulous steps, including sun-drying, withering, oxidation, fixation, rolling, fermentation, and baking. Each step has strict requirements on environmental parameters (such as temperature, humidity, and light intensity), operational sequence (such as oxidation time and shaking frequency), and technological precision (such as control of fermentation and baking temperature curves). However, the production of oolong tea is highly dependent on the synergy of nature and human intervention. In spring, when there is much rain and little sunshine, the moisture content of fresh leaves is prone to be too high, leading to poor water circulation. In the hot and humid environment of summer, the degree of "fermentation" during oxidation is prone to get out of control. Even in the ideal season of clear autumn skies, if the maturity of fresh leaves is uneven during picking (such as an imbalance in the phenol-amino acid ratio of tender leaves or coarse and hard fibers in older leaves), or if there is a slight error in adjusting the parameters of a certain process (such as insufficient fixation temperature or uneven rolling force), it may directly affect the conversion efficiency and coordination of the substances contained in the tea leaves.

[0003] Due to the combined effects of the aforementioned complex factors, approximately 30% of finished oolong tea products fail to meet traditional high-quality standards in actual production and are ultimately classified as "low-quality oolong tea." The core defects of this type of tea are concentrated in its sensory quality: due to insufficient or excessive processing, the conversion of tea polyphenols and catechins is incomplete, resulting in a pronounced and persistent bitterness upon tasting. Simultaneously, the synthesis and accumulation of aromatic substances (such as nerolidol, linalool, and their oxides) are low, leading to a weak, one-dimensional aroma in both the dry tea and the tea liquor, sometimes even exhibiting a grassy or coarse character. Furthermore, some low-quality teas may also be accompanied by a weak flavor, a dark and cloudy liquor, and hard and mixed tea leaves. In the traditional tea market, because this type of tea does not meet the consumption demands of high-end gift boxes and premium teas, it typically only enters the market at a low price as raw material tea or is used as a filler ingredient in blended teas, failing to effectively realize its economic value.

[0004] It is noteworthy that if these low-quality oolong teas remain "unutilized" for an extended period, it will result in a huge waste of resources. At the same time, changes in the consumer market have provided a crucial opportunity for the revaluation of low-quality oolong tea. In recent years, with the popularization of healthy consumption concepts and the diversification of tea consumption scenarios, the market for new tea drinks (such as fruit tea, fresh milk tea, and cold brew tea) and pure tea beverages (such as ready-to-drink oolong tea and sugar-free tea bags) has experienced explosive growth. On the one hand, consumers' demand for tea drinks has shifted from "quenching thirst" to "quality experience," requiring both a refreshing and mellow taste and a harmonious and full aroma, while also expecting consistent and stable flavor (avoiding taste fluctuations caused by batch differences in raw materials). On the other hand, downstream tea drink brands and beverage companies have imposed stricter requirements on raw tea to improve product standardization—it must possess "high purity" (no off-flavors), "high stability" (flavor differences between different batches ≤5%), and "high compatibility" (can be harmoniously integrated with ingredients such as milk, sugar, and fruit).

[0005] Therefore, how to improve the quality and reshape the flavor of low-quality oolong tea and transform it into a high-standard raw material that meets the market demand for new tea drinks and pure tea beverages is a key issue that urgently needs to be addressed. Summary of the Invention

[0006] Therefore, the present invention provides a method for preparing oolong matcha based on secondary enzymatic hydrolysis, which has no astringency, a fresh and crisp taste, and a high degree of fullness and persistence of floral and fruity aroma.

[0007] Unlike existing technologies, the above technical solution provides a method for improving the quality of low-quality oolong tea, the method comprising the following steps: First enzymatic hydrolysis: Spray a 5% cellulase solution onto low-quality oolong tea, and then perform enzymatic hydrolysis for 5-7 hours. The mass of the sprayed cellulase solution is 15%-25% of the mass of the low-quality oolong tea. Initial drying: The oolong tea after the first enzymatic hydrolysis is placed in a graphene roasting cage for initial drying at 90-100℃ under graphene far-infrared light for 0.5-1.5 hours. Second enzymatic hydrolysis: Spray a 2% protease solution onto the oolong tea after the initial drying process, and then perform enzymatic hydrolysis for 5-7 hours. The mass of the sprayed protease solution is 25%-35% of the mass of the low-quality oolong tea. Second drying: The oolong tea after the second enzymatic hydrolysis is placed in a graphene baking cage for a second drying at 90-100℃ under graphene far-infrared light for 0.5-1.5 hours. Third enzymatic hydrolysis: Spray a 2% tannin enzyme solution onto the oolong tea after the second drying process, and then perform enzymatic hydrolysis for 5-7 hours. The mass of the sprayed tannin enzyme solution is 15%-25% of the tea mass. Roasting for aroma enhancement: The oolong tea after the third enzymatic hydrolysis treatment is roasted at 125-135℃ using graphene far-infrared light for 4-6 hours to obtain oolong tea with improved quality. The first enzymatic hydrolysis in this invention degrades cellulose in the cell walls of tea leaves using cellulase, improving the texture and releasing aroma precursors, thereby enhancing the aroma of oolong tea.

[0008] This invention uses initial drying to quickly deactivate cellulase, terminate the enzymatic hydrolysis reaction, and reduce the moisture content in tea leaves, thus preparing them for further enzymatic hydrolysis.

[0009] The second enzymatic hydrolysis of this invention breaks down the proteins in oolong tea through protease, reducing the bitterness caused by proteins and improving the mellowness of the tea soup.

[0010] This invention uses a double drying process to rapidly inactivate proteases, terminate the enzymatic hydrolysis of tannins, and simultaneously reduce the moisture content of tea leaves.

[0011] The third enzymatic hydrolysis of this invention specifically hydrolyzes ester-type catechins in oolong tea using tannin enzymes, significantly reducing the astringency of oolong tea, making the tea taste sweeter and more mellow, and reducing the irritation of tea to the gastrointestinal tract.

[0012] This invention uses a roasting process to enhance aroma, which promotes the Maillard reaction in tea leaves and facilitates the conversion of glycosides in oolong tea. The processed tea leaves possess the characteristic roasted and sweet aroma of oolong tea, achieving a high-quality oolong tea flavor. At the same time, it further reduces the moisture content of the tea leaves, extending their shelf life.

[0013] Preferably, the conditions for the first enzymatic hydrolysis are: 40-50℃ and 75%-85% humidity.

[0014] Preferably, the conditions for the second enzymatic hydrolysis are: 40-50℃ and 75%-85% humidity.

[0015] Preferably, the conditions for the third enzymatic hydrolysis are: 40-55℃ and 75%-85% humidity.

[0016] Preferably, the method for improving the quality of low-quality oolong tea according to the present invention includes the following steps: First enzymatic hydrolysis: A 5% cellulase solution is sprayed onto low-quality oolong tea, and then enzymatic hydrolysis is carried out for 6 hours at 45℃ and 85% humidity; the mass of the sprayed cellulase solution is 20% of the mass of the low-quality oolong tea. Initial drying: The oolong tea after the first enzymatic hydrolysis is placed in a graphene roasting cage for initial drying, and roasted at 100℃ under graphene far-infrared light for 1 hour; Second enzymatic hydrolysis: A 2% protease solution is sprayed onto the oolong tea after the initial drying treatment, and then enzymatic hydrolysis is carried out for 6 hours at 40℃ and 85% humidity; the mass of the sprayed protease solution is 30% of the mass of the low-quality oolong tea. Second drying: The oolong tea after the second enzymatic hydrolysis is placed in a graphene baking cage for a second drying, and baked at 100℃ with graphene far-infrared light for 1 hour. Third enzymatic hydrolysis: A 2% tannin enzyme solution is sprayed onto the oolong tea after the second drying process, and then enzymatic hydrolysis is carried out for 6 hours at 50℃ and 85% humidity; the mass of the sprayed tannin enzyme solution is 20% of the tea mass. Roasting to enhance aroma: The oolong tea after the third enzymatic hydrolysis is roasted at 130℃ with graphene far-infrared light for 4-6 hours to obtain oolong tea with improved quality.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention utilizes three enzymes—cellulase, protease, and tanninase—for segmented enzymatic hydrolysis, and employs a graphene roasting cage for combined roasting to inhibit enzyme activity and prevent mutual interference. It precisely targets and transforms undesirable flavor and aroma components during fermentation, and finally roasts the tea to enhance its aroma. This invention solves the problems of low-quality oolong tea being bitter, astringent, and lacking aroma.

[0018] 2. This invention applies graphene, a novel heating material, to tea roasting, achieving precise, efficient, and energy-saving tea roasting. Graphene's high far-infrared light penetration characteristics can quickly and evenly inhibit enzymatic hydrolysis; uniform and rapid heating with precise temperature control ensures even heating of the tea leaves, rapidly and efficiently enhancing aroma, forming flavor compounds, and stabilizing quality. Simultaneously, the use of graphene heating results in more efficient temperature rise, solving the problem of slow heating in roasting equipment.

[0019] 3. After being improved by the process of this invention, low-quality oolong tea is blended to form the raw material tea for tea beverages and new tea drinks, and is used in the base tea of ​​tea beverages and blended drinks.

[0020] 4. The enzyme engineering fermentation technology of the present invention has a good effect on improving the quality of oolong tea that is under-fermented and coarse and of low quality. Detailed Implementation

[0021] To explain in detail the technical content, structural features, objectives, and effects of the technical solution, the following detailed description is provided in conjunction with specific embodiments. Example 1

[0022] A method for improving the quality of low-quality oolong tea, comprising the following steps: First enzymatic hydrolysis: A 5% cellulase solution is sprayed onto low-quality oolong tea, and then enzymatic hydrolysis is carried out for 7 hours at 40℃ and 85% humidity. The mass of the sprayed cellulase solution is 15% of the mass of the low-quality oolong tea. Initial drying: The oolong tea after the first enzymatic hydrolysis is placed in a graphene roasting cage for initial drying at 90℃ under graphene far-infrared light for 1.5 hours; Second enzymatic hydrolysis: A 2% protease solution is sprayed onto the oolong tea after the initial drying treatment, and then enzymatic hydrolysis is carried out at 50℃ and 75% humidity for 5 hours. The mass of the sprayed protease solution is 35% of the mass of the low-quality oolong tea. Second drying: The oolong tea after the second enzymatic hydrolysis is placed in a graphene baking cage for a second drying, and baked at 100℃ under graphene far-infrared light for 0.5 hours; Third enzymatic hydrolysis: A 2% tannin enzyme solution is sprayed onto the oolong tea after the second drying process, and then enzymatic hydrolysis is carried out for 7 hours at 40℃ and 75% humidity. The mass of the sprayed tannin enzyme solution is 15% of the tea mass. Roasting to enhance aroma: The oolong tea after the third enzymatic hydrolysis treatment is roasted at 125℃ with graphene far-infrared light for 6 hours to obtain oolong tea with improved quality. Example 2

[0023] A method for improving the quality of low-quality oolong tea, comprising the following steps: First enzymatic hydrolysis: A 5% cellulase solution is sprayed onto low-quality oolong tea, and then enzymatic hydrolysis is carried out for 5 hours at 50℃ and 75% humidity. The mass of the sprayed cellulase solution is 25% of the mass of the low-quality oolong tea. Initial drying: The oolong tea after the first enzymatic hydrolysis is placed in a graphene roasting cage for initial drying at 100℃ under graphene far-infrared light for 0.5 hours; Second enzymatic hydrolysis: A 2% protease solution is sprayed onto the oolong tea after the initial drying treatment, and then enzymatic hydrolysis is carried out at 40℃ and 85% humidity for 7 hours. The mass of the sprayed protease solution is 25% of the mass of the low-quality oolong tea. Second drying: The oolong tea after the second enzymatic hydrolysis is placed in a graphene roasting cage for a second drying, and roasted at 90°C under graphene far-infrared light for 1.5 hours; Third enzymatic hydrolysis: A 2% tannin enzyme solution is sprayed onto the oolong tea after the second drying process, and then enzymatic hydrolysis is carried out at 55℃ and 85% humidity for 5 hours. The mass of the sprayed tannin enzyme solution is 25% of the tea mass. Roasting to enhance aroma: The oolong tea after the third enzymatic hydrolysis is roasted at 135℃ with graphene far-infrared light for 4 hours to obtain oolong tea with improved quality. Example 3

[0024] First enzymatic hydrolysis: A 5% cellulase solution was sprayed onto low-quality oolong tea, and then enzymatically hydrolyzed for 6 hours at 45℃ and 85% humidity; the mass of the sprayed cellulase solution was 20% of the mass of the low-quality oolong tea. Initial drying: The oolong tea after the first enzymatic hydrolysis is placed in a graphene roasting cage for initial drying, and roasted at 100℃ under graphene far-infrared light for 1 hour; Second enzymatic hydrolysis: A 2% protease solution is sprayed onto the oolong tea after the initial drying treatment, and then enzymatic hydrolysis is carried out for 6 hours at 40℃ and 85% humidity; the mass of the sprayed protease solution is 30% of the mass of the low-quality oolong tea. Second drying: The oolong tea after the second enzymatic hydrolysis is placed in a graphene baking cage for a second drying, and baked at 100℃ with graphene far-infrared light for 1 hour. Third enzymatic hydrolysis: A 2% tannin enzyme solution is sprayed onto the oolong tea after the second drying treatment, and then enzymatic hydrolysis is carried out for 6 hours at 50℃ and 85% humidity; the mass of the sprayed tannin enzyme solution is 20% of the tea mass. Roasting to enhance aroma: The oolong tea after the third enzymatic hydrolysis is roasted at 130℃ with graphene far-infrared light for 4-6 hours to obtain oolong tea with improved quality.

[0025] The tea infusions made from the low-quality oolong tea raw material of Example 1 (which was not improved) and the high-quality oolong tea prepared in Example 1 were compared. The comparison results are shown in Table 1 below.

[0026] Table 1. Comparison of tea infusions made from low-quality oolong tea raw materials and high-quality oolong tea obtained in Example 1.

[0027] As can be seen from Table 1, untreated low-quality oolong tea has a weak aroma, strong astringency, a rough and bland taste, a dark and dull liquor color, and a high content of ester-type catechins, reaching 50-60%; the content of soluble solids is low, ≤25%, and the market value is low (20-30 yuan / jin). However, after processing by Example 1 of this invention, the oolong tea prepared has improved aroma persistence, significantly reduced astringency, mellow taste, improved color brightness, significantly reduced ester-type catechin content to below 30%, and the content of soluble solids reaches above 33%, significantly increasing the market value by 30-40 yuan / jin.

[0028] This invention utilizes three enzymes—cellulase, protease, and tanninase—for segmented enzymatic hydrolysis. After each hydrolysis, a graphene roasting cage is used for combined roasting to inhibit enzyme activity and prevent mutual interference. This precisely targets and transforms undesirable flavor and aroma components during fermentation, and finally roasts the tea to enhance its aroma. This invention solves the problems of low-quality oolong tea being bitter, astringent, and lacking aroma, and significantly improves the quality of oolong tea.

[0029] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Unless otherwise specified, an element defined by the phrase "comprising..." or "including..." does not exclude the presence of additional elements in the process, method, article, or terminal device that includes said element. Additionally, in this document, "greater than," "less than," "exceeding," etc., are understood to exclude the stated number; "above," "below," "within," etc., are understood to include the stated number.

[0030] It should be noted that although the above embodiments have been described herein, this does not limit the scope of patent protection for this invention. Therefore, any changes and modifications made to the embodiments described herein based on the innovative concept of this invention, or any equivalent structural or procedural transformations made using the content of this specification, directly or indirectly applying the above technical solutions to other related technical fields, are all included within the scope of patent protection for this invention.

Claims

1. A method for improving the quality of low-quality oolong tea, characterized in that, The method includes the following steps: First enzymatic hydrolysis: Spray a 5% cellulase solution onto low-quality oolong tea, and then perform enzymatic hydrolysis for 5-7 hours. The mass of the sprayed cellulase solution is 15%-25% of the mass of the low-quality oolong tea. Initial drying: The oolong tea after the first enzymatic hydrolysis is placed in a graphene roasting cage for initial drying at 90-100℃ under graphene far-infrared light for 0.5-1.5 hours. Second enzymatic hydrolysis: Spray a 2% protease solution onto the oolong tea after the initial drying treatment, and then perform enzymatic hydrolysis for 5-7 hours. The mass of the sprayed protease solution is 25%-35% of the mass of the low-quality oolong tea. Second drying: The oolong tea after the second enzymatic hydrolysis is placed in a graphene baking cage for a second drying at 90-100℃ under graphene far-infrared light for 0.5-1.5 hours. Third enzymatic hydrolysis: Spray a 2% tannin enzyme solution onto the oolong tea after the second drying process, and then perform enzymatic hydrolysis for 5-7 hours. The mass of the sprayed tannin enzyme solution is 15%-25% of the tea mass. Roasting to enhance aroma: The oolong tea after the third enzymatic hydrolysis treatment is roasted at 125-135℃ using graphene far-infrared light for 4-6 hours to obtain oolong tea with improved quality.

2. The method for improving the quality of low-quality oolong tea according to claim 1, characterized in that, The conditions for the first enzymatic hydrolysis are: 40-50℃ and 75%-85% humidity.

3. The method for improving the quality of low-quality oolong tea according to claim 1, characterized in that, The conditions for the second enzymatic hydrolysis are: 40-50℃ and 75%-85% humidity.

4. The method for improving the quality of low-quality oolong tea according to claim 1, characterized in that, The conditions for the third enzymatic hydrolysis are: 40-55℃ and 75%-85% humidity.

5. The method for improving the quality of low-quality oolong tea according to any one of claims 1-4, characterized in that, The method includes the following steps: First enzymatic hydrolysis: A 5% cellulase solution was sprayed onto low-quality oolong tea, and then enzymatically hydrolyzed for 6 hours at 45℃ and 85% humidity; the mass of the sprayed cellulase solution was 20% of the mass of the low-quality oolong tea. Initial drying: The oolong tea after the first enzymatic hydrolysis is placed in a graphene roasting cage for initial drying, and roasted at 100℃ under graphene far-infrared light for 1 hour; Second enzymatic hydrolysis: A 2% protease solution is sprayed onto the oolong tea after the initial drying treatment, and then enzymatic hydrolysis is carried out for 6 hours at 40℃ and 85% humidity; the mass of the sprayed protease solution is 30% of the mass of the low-quality oolong tea. Second drying: The oolong tea after the second enzymatic hydrolysis is placed in a graphene baking cage for a second drying, and baked at 100℃ with graphene far-infrared light for 1 hour. Third enzymatic hydrolysis: A 2% tannin enzyme solution is sprayed onto the oolong tea after the second drying treatment, and then enzymatic hydrolysis is carried out for 6 hours at 50℃ and 85% humidity; the mass of the sprayed tannin enzyme solution is 20% of the tea mass. Roasting to enhance aroma: The oolong tea after the third enzymatic hydrolysis is roasted at 130℃ with graphene far-infrared light for 4-6 hours to obtain oolong tea with improved quality.

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