White tea fused with active ingredients and aroma components of bamboo leaves and processing method of white tea

Abstract

The invention relates to the field of tea leaf processing, in particular to white tea fused with active ingredients and aroma components of bamboo leaves and a processing method thereof, and the processing method comprises the following steps: (1) raw material pretreatment; (2) pulse electric field pretreatment; (3) ultrasonic pretreatment; (4) vacuum concentration; (5) performing vacuum impregnation: mixing white tea with the bamboo leaf concentrated solution prepared in the step (4), and performing vacuum impregnation treatment to obtain a white tea mixture; and (6) dynamic baking. The white tea and the processing method thereof have the beneficial effects that according to the white tea integrating the active ingredients and the aroma-producing ingredients of the bamboo leaves and the processing method of the white tea, a pulsed electric field coupling ultrasonic-assisted green efficient extraction technology is adopted in the processing method, and flavonoids, polysaccharides and volatile aroma-producing ingredients in the bamboo leaves are directionally enriched; and a vacuum impregnation process is innovatively introduced, so that the composite functional white tea product which has the background flavor of the white tea and the characteristic fragrance of the bamboo leaves and is high in biological value is prepared.

Description

Technical Field

[0001] The present invention relates to the field of tea processing, and in particular to white tea integrating bamboo leaf active ingredients and aromatic components and a processing method thereof. Background Art

[0002] White tea, a traditional, slightly fermented tea beverage, is one of China's six major tea categories, characterized by its silvery white, covered in white hairs. Its traditional production method involves neither frying nor kneading. Its key qualities include a pale, greenish-white dry tea, a pronounced aroma of hairs, a silvery apricot-yellow tea liquor, a sweet, refreshing flavor, and soft, bright leaves. In recent years, with increasing interest in white tea's diverse physiological benefits, including antioxidant, anti-tumor, and anti-mutagenic properties, its ability to prevent obesity and diabetes, and its ability to protect the liver, white tea has gained popularity among consumers due to its unique health benefits and longevity, resulting in a continuously increasing market share.

[0003] Modern biological research indicates that bamboo is one of the most abundant and optimally balanced natural nutritional reservoirs in the plant kingdom, containing nearly 60 nutritional and functional factors. Among these, bamboo leaf flavonoids are considered to be the most potent natural organic antioxidants in nature, their antioxidant capacity rivaling that of Ganoderma lucidum and American ginseng. Bamboo leaf flavonoids primarily consist of carbonyl glycoside flavonoids (such as isovitexin and vitexin) and phenolic acids (such as p-coumaric acid and chlorogenic acid). These components impart physiological and pharmacological activities such as antioxidant, anti-tumor, antiviral, anticoagulant, and hypoglycemic properties to bamboo leaves. In traditional bamboo processing, bamboo leaves, as waste products, are often discarded or incinerated, resulting in both resource waste and environmental pollution. Currently, no research has been reported on product development and transfer technologies that integrate the key active ingredients of bamboo leaf waste with Zhenghe white tea.

[0004] Current white tea offerings are limited to varieties such as Silver Needle Baihao, White Peony, Gongmei, and Shoumei. These products offer relatively limited aromas and health benefits, resulting in relatively low market demand compared to green and black teas. Furthermore, in traditional bamboo processing, bamboo leaves, as waste, are often discarded or incinerated, resulting in both resource waste and environmental pollution. Furthermore, existing white tea preparation methods present several challenges, such as a bland aroma, dark tea color, and a pure but lacking flavor, which compromise the overall quality of the product.

[0005] In order to further expand the white tea market and meet the needs of different consumers, especially those with special flavor preferences and higher requirements for health care effects, white tea products are gradually developing towards diversification, with new fragrance types and new products with stronger health care effects being introduced. Therefore, there is an urgent need to innovate processing technologies to produce innovative white tea products with new flavors, new forms, and stronger health care effects, so as to meet the changing market demands with a more diversified style. At the same time, how to effectively utilize bamboo leaf resources, improve the extraction rate of active ingredients in bamboo leaves, and organically integrate them with white tea to prepare new white tea products with synergistic effects has also become a hot and difficult point in current research. Summary of the Invention

[0006] The technical problem to be solved by the present invention is that in the prior art, the fragrance types of white tea products are single, the health care effects are limited, and bamboo leaf resources are not fully utilized.

[0007] To solve the above technical problem, the technical solution adopted by the present invention is to provide a processing method for white tea integrating the active ingredients and fragrance components of bamboo leaves, comprising the following steps: (1) Raw material pretreatment: drying and pulverizing bamboo leaves to obtain a bamboo leaf active matrix; (2) Pulsed electric field pretreatment: adding water to the bamboo leaf active matrix obtained in step (1) for pulsed electric field pretreatment to obtain a pulsed treatment solution; (3) Ultrasonic pretreatment: performing ultrasonic pretreatment on the pulsed treatment solution obtained in step (2) to obtain a synergistic treatment solution; (4) Vacuum concentration: performing vacuum concentration on the synergistic treatment solution obtained in step (3) to obtain a bamboo leaf concentrated solution; (5) Vacuum impregnation: mixing white tea with the bamboo leaf concentrated solution obtained in step (4) and performing vacuum impregnation treatment to obtain a white tea mixture; (6) Dynamic baking: subjecting the white tea mixture obtained in step (5) to multi-gradient temperature reduction and temperature control baking to finally obtain white tea integrating the active ingredients and fragrance components of bamboo leaves. Another technical solution provided by the present invention is to provide white tea integrating the active ingredients and fragrance components of bamboo leaves prepared by the above processing method for white tea integrating the active ingredients and fragrance components of bamboo leaves.

[0008] The beneficial effects of the present invention are as follows: The present invention provides a white tea integrating the active ingredients and aroma components of bamboo leaves and its processing method. The processing method significantly improves the sensory quality of the bamboo leaf-scented white tea product by establishing a process chain of "physical field cell wall breaking-vacuum impregnation migration-thermal setting", and increases the contents of biochemical components such as total phenols, flavonoids, and water extracts. At the same time, it introduces functional components such as luteolin, maslinic acid, and β-caryophyllene, as well as aroma components such as theaspirane, indole, and trans-β-damascenone into the white tea, endowing the white tea with a unique fresh aroma, and providing an important chemical substance basis for the formation of the potential health care function and unique flavor quality of the bamboo leaf-scented white tea. Among them, a green and efficient extraction technology coupling pulsed electric field and ultrasonic assistance is adopted to directionally enrich flavonoids, polysaccharides, and volatile aroma components in bamboo leaves, and an innovative vacuum impregnation process is introduced. Using the principle of negative pressure penetration, the active substances in the bamboo leaf extraction concentrate are accurately introduced into the cell gaps of white tea to construct a micro-region embedding system. Through dynamic baking treatment, a multi-stage variable temperature control technology combined with continuous turning mass transfer is adopted to achieve moisture gradient removal, thermal stabilization of active components, and molecular rearrangement of aroma substances, and finally a composite functional white tea product with both the background flavor of white tea and the characteristic aroma of bamboo leaves and high biological potency is prepared. This method can effectively solve the problems of single fragrance type and health care efficacy of white tea products and waste of bamboo leaf resources in the background technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is the PCA diagram (positive and negative ion modes) of the liquid chromatography-mass spectrometry evaluation of bamboo leaf-scented white tea and raw material white tea in Example 4 of the specific embodiment of the present invention; Figure 2 is the OPLS-DA diagram (positive and negative ion modes) of the liquid chromatography-mass spectrometry evaluation of bamboo leaf-scented white tea and raw material white tea in Example 4 of the specific embodiment of the present invention; Figure 3 is the PCA and OPLS-DA diagrams of the gas chromatography-mass spectrometry evaluation of bamboo leaf-scented white tea and raw material white tea in Example 4 of the specific embodiment of the present invention; Figure 4 The heat map of volatile differential components in Example 4 of the specific embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] To describe in detail the technical content, the achieved objectives and the effects of the present invention, the following is described in conjunction with the embodiments and accompanied by the drawings.

[0011] The inventive points of the present application are as follows: 1. The present invention is based on the combined extraction technology of pulsed electric field and ultrasonic assistance. The electroporation effect of the pulsed electric field is utilized to destroy the cell structure of bamboo leaves and promote the release of active substances therein. Meanwhile, combined with the ultrasonic assistance, the cavitation effect generated under its mechanical vibration is used to further accelerate the dissolution of the target extract through the pores formed by the pulsed electric field, thereby significantly improving the extraction rate of active ingredients in bamboo leaves. This combined extraction technology has the advantages of being safe and harmless, low energy consumption, high extraction rate, uniform transfer, and being able to effectively retain the original nutritional components of substances.

[0012] 2. Under vacuum conditions, the present invention impregnates white tea in the bamboo leaf concentrated solution. The vacuum environment can significantly reduce the resistance of atmospheric pressure to liquid penetration and promote the rapid and deep penetration of the bamboo leaf concentrated solution into the interior of white tea leaves. Meanwhile, the vacuum environment can reduce the boiling point of the liquid and accelerate the release and transfer of volatile aroma components in the bamboo leaf concentrated solution. This method can enable white tea to more comprehensively and uniformly adsorb the aroma components and functional components in bamboo leaves, thereby significantly enhancing its flavor quality and health care efficacy.

[0013] 3. The dynamic baking process of the present invention adopts precise temperature control in three stages and combines physical field assistance technology. A gradient cooling strategy is implemented in the shaping stage of bamboo leaf flavored white tea, which not only effectively retains the volatile aroma components formed by impregnation with the bamboo leaf concentrated solution but also forms stable quality characteristics through secondary baking the next day. Meanwhile, the coordinated application of three-dimensional oscillation and infrared monitoring technology effectively solves the problem of uneven heating in traditional static baking and significantly improves the product quality.

[0014] 4. The present invention realizes the synergistic effect of white tea and bamboo leaves by organically integrating the active ingredients of bamboo leaves with white tea, overcomes the shortcomings of single aroma type and single health care efficacy of traditional white tea products, and meets the needs of consumers for multifunctional health care beverages; 5. The technological process of the present invention is simple and controllable, easy to operate, and easy to industrialize production. It can effectively expand the product series of white tea, increase the market competitiveness of white tea, and provide new ideas for the sustainable development of the white tea industry.

[0015] The present invention provides a processing method for white tea integrating the active ingredients and aroma components of bamboo leaves, comprising the following steps: (1) Raw material pretreatment: drying and pulverizing bamboo leaves to obtain a bamboo leaf active matrix; (2) Pulsed electric field pretreatment: adding water to the bamboo leaf active matrix obtained in step (1) for pulsed electric field pretreatment to obtain a pulsed treatment solution; (3) Ultrasonic pretreatment: subjecting the pulsed treatment solution obtained in step (2) to ultrasonic pretreatment to obtain a synergistic treatment solution; (4) Vacuum concentration: subjecting the synergistic treatment solution obtained in step (3) to vacuum concentration to obtain a bamboo leaf concentrated solution; (5) Vacuum impregnation: Mix white tea with the bamboo leaf concentrated liquid obtained in step (4), and perform vacuum impregnation treatment to obtain a white tea mixture. (6) Dynamic baking: Bake the white tea mixture obtained in step (5) with multi-gradient temperature reduction and temperature control, and finally obtain white tea integrated with bamboo leaf active ingredients and aroma components.

[0016] Further, in the above-mentioned processing method of white tea integrated with bamboo leaf active ingredients and aroma components, the parameters of pulsed electric field pretreatment in step (2) are: electric field strength 1 - 15 kV / cm, number of pulses 20 - 100 times, and pulse width 10 - 80 μs; the parameters of ultrasonic pretreatment in step (3) are: ultrasonic power 100 - 500 W, ultrasonic time 10 - 60 min, and ultrasonic temperature 30 - 90 °C.

[0017] As described above, by defining the synergistic action range of pulsed electric field and ultrasonic parameters, while ensuring sufficient cell wall disruption, it avoids the damage of heat-sensitive components caused by high temperature. Through the coupling of two physical fields, the extraction rate of active substances is increased and the energy consumption is reduced.

[0018] Further, in the above-mentioned processing method of white tea integrated with bamboo leaf active ingredients and aroma components, the bamboo leaf extract in step (4) is concentrated to 20% - 40% of the original volume.

[0019] As described above, after concentration, the concentration of active ingredients is increased to the adsorption threshold of white tea, avoiding the texture deterioration caused by excessive moisture absorption of white tea during the impregnation process.

[0020] Further, in the above-mentioned processing method of white tea integrated with bamboo leaf active ingredients and aroma components, the white tea in step (5) is Shoumei of Zhenghe white tea.

[0021] As described above, the texture characteristics of the coarse and old leaves of Shoumei of Zhenghe white tea can carry more bamboo leaf extracts (the adsorption amount is higher than that of silver needles, etc.).

[0022] Further, in the above-mentioned processing method of white tea integrated with bamboo leaf active ingredients and aroma components, the parameters of vacuum impregnation treatment in step (5) are: vacuum degree 0.08 - 0.1 MPa, temperature 70 - 90 °C, and impregnation time 20 - 30 min.

[0023] As described above, the above settings promote the migration of bamboo leaf active ingredients and aroma substances into the interior of white tea; reduce the boiling point of the liquid to accelerate the migration of aroma components, and at the same time avoid the oxidation loss of white tea polyphenols caused by high temperature.

[0024] Further, in the above-mentioned processing method of white tea integrated with bamboo leaf active ingredients and aroma components, after breaking the vacuum in step (5), the white tea mixture still needs to be impregnated for 15 min under normal pressure.

[0025] As described above, an atmospheric pressure equilibrium stage is set up, and the material exchange equilibrium inside and outside the cells is achieved through the driving of the pressure difference, solving the problem of local concentration gradient imbalance caused by simple vacuum treatment and improving the uniformity of the distribution of active ingredients.

[0026] Further, in the above-mentioned white tea processing method that combines the active ingredients and aroma components of bamboo leaves, the multi-gradient temperature reduction and temperature control baking in step (6) is carried out in three stages: in the first stage, the initial shaping baking is carried out at 80-90 °C for 0.5 h, and the robotic arm is flipped every 10 min during this period; in the second stage, the temperature is lowered to 70-75 °C and baking continues for 2 h, and the three-dimensional oscillation device is simultaneously turned on to achieve dynamic heating of the material; in the third stage, after the baked material is spread out and cooled to room temperature, it is slowly baked at 55-65 °C for 0.5 h the next day, and the temperature and humidity distribution on the surface of the tea leaves is monitored in real time through an infrared thermal imaging system during the baking process, and the hot air circulation rate is adjusted to reduce the moisture content to 5.5±0.5%.

[0027] Further, in the above-mentioned white tea processing method that combines the active ingredients and aroma components of bamboo leaves, the specific white tea processing method is as follows: (1) Raw material pretreatment: Select tender bamboo leaves without pests and diseases, wash them with clean water and drain the water, place them in an oven at 60 °C for drying for 5 h, and after ultrafine pulverization, pass through a 40-mesh sieve to obtain a bamboo leaf active matrix; (2) Pulsed electric field pretreatment: Take the bamboo leaf active matrix prepared in step (1), add food processing water and mix well according to the solid-liquid ratio of 1:15-1:55 kg / L, and carry out pulsed electric field pretreatment to obtain a pulsed treatment liquid; the parameters of the pulsed electric field pretreatment are: electric field strength 1-15 kV / cm, number of pulses 20-100 times, pulse width 10-80 μs; (3) Ultrasonic pretreatment: Take the pulsed treatment liquid obtained in step (2) and carry out ultrasonic pretreatment to obtain a synergistic treatment liquid; the parameters of the ultrasonic pretreatment are: ultrasonic power 100-500 W, ultrasonic time 10-60 min, ultrasonic temperature 30-90 °C; (4) Vacuum concentration: Take the synergistic treatment liquid obtained in step (3), filter it and carry out vacuum concentration at 60 °C to obtain a bamboo leaf concentrated liquid; (5) Vacuum impregnation: Mix white tea and the bamboo leaf concentrated liquid obtained in step (4) according to the weight ratio of 1:0.5-1:1.5, preheat to 80-90 °C, and then place it in a vacuum tank for vacuum impregnation treatment to promote the migration of the active ingredients and aroma substances of the bamboo leaves into the interior of the white tea; the parameters of the vacuum impregnation treatment are: vacuum degree 0.08-0.1 MPa, temperature 70-90 °C, impregnation time 20-30 min; after breaking the vacuum, the white tea mixture still needs to be impregnated at normal pressure for another 15 min; (6) Dynamic baking: Place the white tea mixture from step (5) in a temperature-adjustable dynamic baking machine for multi-gradient temperature reduction and temperature control baking to obtain white tea integrated with the active ingredients and aroma components of bamboo leaves; The multi-gradient temperature reduction and temperature control baking in step (6) is carried out in three stages: The first stage is the initial shaping baking at 80-90 °C for 0.5 h, during which the robotic arm is used to turn the material every 10 min; The second stage is to lower the temperature to 70-75 °C and continue baking for 2 h, and simultaneously turn on the three-dimensional oscillation device to achieve dynamic heating of the material; In the third stage, after spreading the baked material to room temperature (25-30) °C, perform low-temperature slow baking at 55-65 °C for 0.5 h the next day, and during the baking process, use an infrared thermal imaging system to monitor the temperature and humidity distribution on the surface of the tea leaves in real time, and adjust the hot air circulation rate to reduce the moisture content to 5.5 ± 0.5%.

[0028] The present invention also provides white tea integrated with the active ingredients and aroma components of bamboo leaves obtained by the above-mentioned processing method for white tea integrated with the active ingredients and aroma components of bamboo leaves.

[0029] Example 1 A processing method for white tea integrated with the active ingredients and aroma components of bamboo leaves, comprising the following steps: (1) Raw material pretreatment: Screen the tender bamboo leaves without pests and diseases, wash them with clean water and drain the water, place them in an oven at 60 °C for drying for 5 h, and after ultrafine pulverization, pass through a 40-mesh sieve to obtain the bamboo leaf active matrix; (2) Pulsed electric field pretreatment: Take the bamboo leaf active matrix obtained in step (1), add food processing water and mix evenly according to the material-liquid ratio of 1:25 kg / L, and put it into the extraction treatment chamber of the pulsed electric field equipment. Set the electric field strength at 3 kV / cm, the number of pulses at 40 times, and the pulse width at 40 μs to obtain the pulsed treatment liquid; (3) Ultrasonic pretreatment: Place the pulsed treatment liquid obtained in step (2) in an ultrasonic device for ultrasonic treatment, set the ultrasonic power at 150 W, the ultrasonic time at 30 min, and the ultrasonic temperature at 30 °C to obtain the synergistic treatment liquid; (4) Vacuum concentration: Filter the synergistic treatment liquid obtained in step (3) and place it in a vacuum concentration tank for vacuum concentration at 60 °C to obtain a bamboo leaf concentrated liquid with a concentration ratio of 20%; (5) Vacuum impregnation: Mix Zhenghe white tea and the bamboo leaf concentrated liquid according to the weight ratio of 1:0.5, preheat to 80-90 °C, and then place it in a vacuum tank for vacuum impregnation treatment. Set the vacuum degree at 0.08 MPa, the temperature at 70 °C, and the impregnation time at 20 min. After breaking the vacuum, continue to impregnate the white tea mixture under normal pressure for 15 min; (6) Dynamic baking: Place the white tea mixture processed in step (5) in a temperature-adjustable dynamic baking machine. In the first stage, conduct the initial shaping baking at 80°C for 1 h, and during this period, use a robotic arm to turn it every 10 min to ensure uniform heating. In the second stage, lower the temperature to 70°C and continue baking for 2.5 h, and simultaneously turn on the three-dimensional oscillation device to achieve dynamic heating of the material. In the third stage, after spreading out and cooling the baked material to room temperature, conduct low-temperature slow baking at 55°C for 0.6 h the next day, and during the baking process, use an infrared thermal imaging system to monitor the temperature and humidity distribution on the surface of the tea leaves in real time, and adjust the hot air circulation rate to reduce the moisture content to 5.5 ± 0.5%, thereby obtaining the white tea with bamboo leaf aroma and health care effects.

[0030] Example 2 A processing method for white tea integrating bamboo leaf active ingredients and aroma components, comprising the following steps: (1) Raw material pretreatment: Screen the tender bamboo leaves without pests and diseases, wash and drain them, place them in an oven at 60°C for drying for 5 h, and after ultrafine pulverization, pass through a 40-mesh sieve to obtain the bamboo leaf active matrix. (2) Pulsed electric field pretreatment: Take the bamboo leaf active matrix obtained in step (1), add food processing water and mix well according to a solid-liquid ratio of 1:45 kg / L, and then put it into the extraction treatment chamber of the pulsed electric field equipment. Set the electric field strength at 11 kV / cm, the number of pulses at 80 times, and the pulse width at 60 μs to obtain the pulsed treatment liquid. (3) Ultrasonic pretreatment: Place the pulsed treatment liquid obtained in step (2) in an ultrasonic device for ultrasonic treatment, set the ultrasonic power at 250 W, the ultrasonic time at 50 min, and the ultrasonic temperature at 90°C to obtain the synergistic treatment liquid. (4) Vacuum concentration: Filter the synergistic treatment liquid obtained in step (3) and place it in a vacuum concentration tank, and conduct vacuum concentration at 60°C to obtain a bamboo leaf concentrated liquid with a concentration ratio of 40%. (5) Vacuum impregnation: Mix Zhenghe white tea and the bamboo leaf concentrated liquid according to a weight ratio of 1:1.5, preheat to 80 - 90°C, and then place it in a vacuum tank for vacuum impregnation treatment. Set the vacuum degree at 0.1 MPa, the temperature at 90°C, and the impregnation time at 30 min. After breaking the vacuum, continue to impregnate the white tea mixture at normal pressure for 15 min. (6)Dynamic baking: Place the white tea mixture processed in step (5) in a temperature-adjustable dynamic baking machine. In the first stage, conduct primary shaping baking at 90 °C for 0.5 h, and during this period, use a robotic arm to turn it every 10 min to ensure uniform heating. In the second stage, lower the temperature gradient to 75 °C and continue baking for 1.5 h, and simultaneously turn on a three-dimensional oscillation device to achieve dynamic heating of the material. In the third stage, after spreading out and cooling the baked material to room temperature, conduct low-temperature slow baking at 65 °C for 0.4 h the next day, and during the baking process, use an infrared thermal imaging system to monitor the temperature and humidity distribution on the surface of the tea leaves in real time, and adjust the hot air circulation rate to reduce the moisture content gradient to 5.5 ± 0.5%, thereby obtaining the white tea with bamboo leaf aroma and health care effects.

[0031] Example 3 A processing method for white tea integrating bamboo leaf active ingredients and aroma components, comprising the following steps: (1)Raw material pretreatment: Screen young bamboo leaves without pests and diseases, wash them with clean water and drain the water, place them in an oven at 60 °C for drying for 5 h, and after ultrafine pulverization, pass through a 40-mesh sieve to obtain a bamboo leaf active matrix. (2)Pulsed electric field pretreatment: Take the bamboo leaf active matrix obtained in step (1), add food processing water and mix evenly according to a solid-liquid ratio of 1:35 kg / L, and put it into the extraction treatment chamber of the pulsed electric field equipment. Set the electric field strength at 7 kV / cm, the number of pulses at 60 times, and the pulse width at 50 μs to obtain a pulsed treatment liquid. (3)Ultrasonic pretreatment: Place the pulsed treatment liquid obtained in step (2) in an ultrasonic device for ultrasonic treatment, set the ultrasonic power at 350 W, the ultrasonic time at 40 min, and the ultrasonic temperature at 60 °C to obtain a synergistic treatment liquid. (4)Vacuum concentration: Filter the synergistic treatment liquid obtained in step (3) and place it in a vacuum concentration tank, and conduct vacuum concentration at 60 °C to obtain a bamboo leaf concentrated liquid with a concentration ratio of 30%. (5)Vacuum impregnation: Mix Zhenghe white tea and the bamboo leaf concentrated liquid according to a weight ratio of 1:1, preheat to 80 - 90 °C, and then place it in a vacuum tank for vacuum impregnation treatment. Set the vacuum degree at 0.09 MPa, the temperature at 80 °C, and the impregnation time at 25 min. After breaking the vacuum, continue to impregnate the white tea mixture at normal pressure for 15 min. (6)Dynamic baking: Place the white tea mixture processed in step (5) into a temperature-adjustable dynamic baking machine. In the first stage, conduct primary shaping baking at 85°C for 0.8 h, and during this period, use a robotic arm to turn the mixture every 10 min to ensure uniform heating. In the second stage, lower the temperature to 73°C and continue baking for 2 h, and simultaneously turn on a three-dimensional oscillation device to achieve dynamic heating of the material. In the third stage, after spreading out and cooling the baked material to room temperature, conduct low-temperature slow baking at 60°C for 0.5 h the next day, and during the baking process, use an infrared thermal imaging system to monitor the temperature and humidity distribution on the surface of the tea leaves in real time, and adjust the hot air circulation rate to reduce the moisture content to 5.5±0.5%, thereby obtaining the white tea with bamboo leaf aroma and health care effects.

[0032] Example 4 Quality comparison, analysis and evaluation between white tea with bamboo leaf aroma and raw white tea Select the white tea processed in Example 3 with relatively better conditions among the above Examples 1-3 as the experimental sample, and use the raw white tea not impregnated with bamboo leaf concentrate as the control sample. Comprehensively evaluate the quality differences between the white tea with bamboo leaf aroma and the raw white tea from three dimensions: sensory evaluation, biochemical components and non-targeted metabolomics.

[0033] 4.1 Sensory evaluation Group, conduct sensory evaluation on the white tea with bamboo leaf aroma and the raw white tea from five aspects: appearance, soup color, aroma, taste and leaf bottom. The total score is calculated by weighted average of weights (see Table 1 for details), and the result is retained to one decimal place.

[0034] Table 1 Sensory evaluation results of white tea with bamboo leaf aroma and raw white tea According to the scoring results of the white tea with bamboo leaf aroma and the raw white tea, it can be seen that in the sensory evaluation of the white tea with bamboo leaf aroma prepared by the present invention, the scores of all items except the soup color are higher than those of the raw white tea, and the improvement of the aroma and taste is particularly obvious. The overall performance is that the appearance is uniform, clean and tidy, the soup color is clear and bright, the fragrance is rich and lasting, the taste is mellow and sweet, and the leaf bottom is soft and shiny. Thus, compared with the raw white tea, the white tea with bamboo leaf aroma presents unique quality characteristics, which may be attributed to the interaction between the additional chemical components in the bamboo leaf impregnation liquid and the original components of the tea leaves.

[0035] 4.2 Determination of biochemical component content Refer to GB / T 8313-2018 "Determination Method for the Contents of Tea Polyphenols and Catechins in Tea", GB / T 8312-2013 "Determination of Caffeine in Tea", GB / T 20574-2006 "Determination Method for the Total Flavonoid Content in Propolis", GB / T 8314-2013 "Determination of Total Free Amino Acids in Tea", GB / T 15672-2009 "Determination of Total Sugar Content in Edible Fungi", GB / T 8305-2013 "Determination of Water Extract in Tea" and other standards to detect the contents of tea polyphenols, caffeine, total flavonoids, amino acids, total sugar and water extract respectively (see Table 2 for details).

[0036] Table 2 Comparison of the Contents of Main Biochemical Components between Zhuyexiang White Tea and Raw Material White Tea The water extract, flavonoids, amino acids, soluble sugar, etc. in tea are the key factors determining its quality and function, and the differences in the content and composition of active ingredients constitute the essence of the quality characteristics of tea. Among them, the water extract is an important index for evaluating the content of water-soluble components in tea, directly affecting the taste and concentration of the tea soup; flavonoid compounds are the factors affecting the formation of the color of the tea soup; amino acids, as an important component of the taste of the tea soup, endow the tea soup with a fresh and brisk flavor; soluble sugar can neutralize bitterness and make the tea soup present a sweet and mellow taste; tea polyphenols and caffeine are the main components constituting the bitter and astringent taste of the tea soup. According to the results of the components contained in the tea samples, compared with the raw material white tea, the contents of total phenols, flavonoids, total sugar and water extract in the Zhuyexiang white tea prepared by the present invention are significantly increased, indicating that white tea has a good adsorption effect on the active substances in the bamboo leaf extract, and most of the active ingredients are effectively incorporated into the white tea. Therefore, the inner substances of Zhuyexiang white tea are more abundant, and there are more flavor and aroma substances, thus significantly improving the taste quality of the tea soup, and this result is mutually confirmed with the result of sensory evaluation.

[0037] 4.3 Determination of Non-volatile Components in Tea Based on Non-targeted Metabolomics (1) Extraction of Tea Sample Metabolites Grind the tea sample into powder, pass it through a 100-mesh sieve and put it into a 2 mL centrifuge tube, add 600 μL of methanol solution containing 2-chloro-L-phenylalanine, and vortex for 30 s. Then add 100 mg of glass beads, put it into a tissue grinder, and grind it at 60 Hz for 90 s. Then ultrasonically treat the centrifuge tube at room temperature for 15 min. Finally, centrifuge at 12000 rpm and 4 °C for 10 min, take the supernatant and filter it through a 0.22 μm filter membrane, and then transfer the filtrate to a detection bottle for LC-MS detection.

[0038] (2) Detection and Analysis of Tea Samples Chromatographic conditions: An ACQUITY UPLC® HSS T3 (2.1×150 mm, 1.8 µm) column was used, with a flow rate of 0.25 mL / min, a column temperature of 40 °C, and an injection volume of 2 μL. The mobile phase consisted of 0.1% formic acid in acetonitrile solution and 0.1% formic acid in aqueous solution.

[0039] Mass spectrometry conditions: Electrospray ionization source (ESI), collected in positive and negative ion modes respectively. Spray voltage: 3.50 kV in positive ion mode, -2.50 kV in negative ion mode, auxiliary gas flow rate: 10 arb, sheath gas flow rate: 30 arb, capillary temperature: 325 °C.

[0040] 4.4 Determination of volatile components in tea based on untargeted metabolomics (1) Extraction of tea sample metabolites Take 0.5 g of tea sample in a 20 mL headspace vial, add 10 μL of internal standard solution, and incubate the sample at 60 °C for 10 min. Before adsorbing the sample, the SPME extraction head was aged at 270 °C for 10 min. Subsequently, the aged SPME extraction head was transferred to the incubation chamber and the sample was adsorbed at 60 °C for 15 min. After adsorption, the SPME extraction head was transferred to the GC injection port and desorbed at 250 °C for 5 min. After injection, the SPME extraction head was aged again at 270 °C for 10 min. Finally, 10 μL of n-alkanes was added to a 20 mL headspace vial for incubation extraction and injection.

[0041] (2) Detection and analysis of tea samples Chromatographic conditions: A DB-Heavy Wax (30 m × 250 μm × 0.5 μm) (Agilent, USA) column was used, with high-purity helium as the carrier gas and a constant flow rate of 1.0 mL / min. The initial temperature of the column was 50 °C, held for 2 min, then increased to 240 °C at a rate of 5 °C / min and held for 5 min.

[0042] Mass spectrometry conditions: The temperature of the mass spectrometry transfer line was 250 °C, the temperature of the ion source was 250 °C, the acquisition rate was 10 spectra / s, the electron impact source energy was 70 eV, the detector voltage was 1.96 kV, and the mass spectrometry scanning range was m / z 35 - 550.

[0043] 4.5 Processing and analysis of metabolomics data Multivariate statistical analysis method is adopted for data analysis. First, the detected metabolites are analyzed by principal component analysis (PCA) in an unsupervised mode to preliminarily understand the overall metabolic differences between groups and the variability among samples within a group. Then, the predictive ability and reliability of the established model are evaluated by orthogonal partial least squares discriminant analysis (OPLS-DA) in a supervised mode.

[0044] 4.5.1 Analysis of non-volatile components of tea based on untargeted metabolomics Based on the experimental results of liquid chromatography-mass spectrometry (LC-MS) untargeted metabolomics, principal component analysis of tea sample metabolites was performed in positive and negative ion modes respectively. As Figure 1 can be seen, in the positive ion mode, the variance contribution rates of the first principal component (PC1) and the second principal component (PC2) are 86.7% and 3.88% respectively, and the cumulative variance contribution rate is 90.58%; in the negative ion mode, the variance contribution rates of the first principal component (PC1) and the second principal component (PC2) are 86% and 4.17% respectively, and the cumulative variance contribution rate is 90.17%, covering most of the metabolite information in the samples. In both positive and negative ion modes, the distance between the sample points of Zhuyexiang white tea and the raw material white tea is relatively far, indicating that significant changes have occurred in the non-volatile metabolites of white tea after being impregnated with bamboo leaf concentrate.

[0045] Although the PCA method can effectively extract the main information, it is not sensitive to variables with relatively small correlations. The supervised mode of OPLS-DA combines orthogonal signal correction, which can maximize the discrimination between groups and is conducive to finding differential markers. As Figure 2 shown, after OPLS-DA analysis, in both positive and negative ion modes, the horizontal distance between pairwise samples is relatively large and both are within the 95% confidence interval. There is an obvious separation between Zhuyexiang white tea and raw material white tea, indicating that differential metabolites can better explain the quality differences between the two.

[0046] Based on the analysis of differential metabolites in the first-order mass spectrometry, the differential ions were analyzed by second-order mass spectrometry. According to the OPLS-DA results, differential substances with VIP>1 and P value <0.05 were selected for analysis, and a total of 217 differential metabolites were identified. Further, with VIP>1, P <0.001 and FC>1.5 as the screening conditions, 28 significantly differential metabolic components were finally determined (see Table 3 for details).

[0047] Table 3 Differential components between Zhuyexiang white tea and raw material white tea in LC-MS untargeted metabolomics According to the screening results, it was found that the relative contents of metabolites such as maslinic acid, β-caryophyllene, nootkatone, methyl linolenate, gibberellin A98, luteolin, and D-pinitol in Zhuyexiang white tea were significantly higher than those in the raw material white tea. Research has shown that maslinic acid is a pentacyclic triterpenoid acid with anti-cancer, anti-inflammatory, and neuroprotective activities; β-caryophyllene, as a CB2R inhibitor, can effectively prevent cognitive impairment caused by neuroinflammation; nootkatone is a natural sesquiterpene extract with various biological activities such as antibacterial, antioxidant, and anti-cancer; methyl linolenate belongs to a class of unsaturated fatty acid methyl esters with high biological activity; gibberellin A98 is an effective anti-cancer compound isolated from medicinal plants and plays a role in regulating important signaling pathways related to colon cancer; luteolin is a polyphenolic plant flavonoid that is widely considered to have important value in food applications and packaging systems due to its potential antibacterial properties; D-pinitol is a pharmacologically active cyclitol, and plants rich in D-pinitol are commonly used in traditional medicine for the treatment of diabetes, inflammation, and cancer.

[0048] In summary, due to the introduction of bamboo leaf concentrate and the synergistic effect of processing, Zhuyexiang white tea significantly enriches active metabolites with anti-cancer, anti-inflammatory, neuroprotective, and metabolic regulatory functions. These major differential metabolites constitute the quality difference between Zhuyexiang white tea and the raw material white tea, providing a scientific material basis for the potential health care functions of Zhuyexiang white tea.

[0049] 4.5.2 Analysis of Tea Volatile Components Based on Untargeted Metabolomics Based on the experimental results of gas chromatography-mass spectrometry (GC-MS) untargeted metabolomics, a total of 90 volatile compounds were detected in the raw material white tea and Zhuyexiang white tea samples. Through principal component analysis of the tea sample metabolites, as Figure 3 shown, the variance contribution rates of the first principal component (PC1) and the second principal component (PC2) were 90.8% and 4.29% respectively, and the cumulative variance contribution rate was 95.09%. The distance between the sample points of Zhuyexiang white tea and the raw material white tea was relatively far, indicating that significant changes had occurred in the volatile metabolites in the white tea impregnated with bamboo leaf concentrate. Figure 3 Shown, two principal components were obtained by orthogonal partial least squares discriminant analysis (OPLS-DA). The horizontal distance between the two samples was large and both were within the 95% confidence interval. There was an obvious separation between Zhuyexiang white tea and the raw material white tea, indicating that the differential metabolites could well explain the quality difference between the two.

[0050] The 90 volatile metabolites were normalized, and a clustering heatmap was drawn to reflect the changes in metabolites. The colors in the figure represent the relative contents. The darker the red, the higher the content, and the darker the blue, the lower the content. As Figure 4It can be seen that Zhuyexiang white tea and the raw material white tea clearly divide 90 differential metabolites into two groups. Compared with the raw material white tea, 34 differential metabolites in Zhuyexiang white tea are significantly up-regulated, specifically including: cumin alcohol, capric acid, 4-(2,6,6-trimethylcyclohex-1,3-dienyl)but-3-en-2-one, o-methoxyphenol, pyrrole-2-carboxaldehyde, 2-acetylpyrrole, mesityl oxide, 4-butyl-3,4-dihydro-5-methylpyrimidine, dimethyl disulfide, 2-ethylfuran, 4-(1,1-dimethylpropyl)phenol, 2-vinyl-6-methylpyrazine, theaspirane, 2-ethyl-1-decene, toluene, 3-methylundecane, 3-methylnonane, n-decane, 5-ethyldecane, 5-methylpentadecane, 2-methylundecane, 4-ethyldecane, 2,4-di-tert-butylphenol, 2-methylfuran, p-methoxyaniline, 4-ethyltoluene, (Z)-2,3-dimethyl-3-heptene, dimethyl phthalate, indole, 4-ethylbenzaldehyde, trans-β-damascenone, isobutylaldehyde trimer, 1,3-trans,5-cis-octatriene, 4-hydroxy-2,2,6-trimethylcyclohexan-1-one (isomer 2). Among them, previous studies have shown that theaspirane is the main contributor to tea aroma and fresh aroma, while indole and trans-β-damascenone are the main contributors to floral aroma, sweet aroma and fresh aroma.

[0051] Further analysis shows that the significant differences in volatile metabolites between Zhuyexiang white tea and the raw material white tea may be the result of the synergistic effect of the migration of natural components in bamboo leaves and chemical transformations (esterification, oxidation and hydrolysis) driven by processing conditions. The formation of the unique aroma of Zhuyexiang white tea (such as tea aroma, floral aroma and fresh aroma) not only benefits from the complementary effect between bamboo leaves and white tea components, but also depends on the precise regulation of the metabolite generation pathway by the processing technology. This mechanism provides an important chemical substance basis for the formation of the unique flavor and quality of Zhuyexiang white tea.

[0052] The above are only embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. All equivalent transformations made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in related technical fields, are equally included in the patent protection scope of the present invention.

Claims

1. A processing method for white tea integrating active ingredients and aroma components of bamboo leaves, characterized in that, It includes the following steps: (1) Raw material pretreatment: Dry and crush bamboo leaves to obtain an active bamboo leaf matrix; (2) Pulsed electric field pretreatment: Take the active bamboo leaf matrix obtained in step (1), add water, and perform pulsed electric field pretreatment to obtain a pulsed treatment solution; (3) Ultrasonic pretreatment: Take the pulsed treatment solution obtained in step (2) and perform ultrasonic pretreatment to obtain a synergistic treatment solution; (4) Vacuum concentration: Take the synergistic treatment solution obtained in step (3) and perform vacuum concentration to obtain a concentrated bamboo leaf solution; (5) Vacuum impregnation: Mix white tea with the concentrated bamboo leaf solution obtained in step (4), perform vacuum impregnation treatment to obtain a white tea mixture; (6) Dynamic baking: Bake the white tea mixture obtained in step (5) with multi-gradient temperature reduction and temperature control to finally obtain white tea incorporating the active components and aroma components of bamboo leaves.

2. The white tea processing method for fusing the active ingredients and aroma components of bamboo leaves according to claim 1, characterized in that In step (2), the parameters for pulsed electric field pretreatment are: electric field strength 1 - 15 kV / cm, number of pulses 20 - 100 times, pulse width 10 - 80 μs; in step (3), the parameters for ultrasonic pretreatment are: ultrasonic power 100 - 500 W, ultrasonic time 10 - 60 min, ultrasonic temperature 30 - 90 °C.

3. The processing method of white tea integrating the active ingredients and aroma components of bamboo leaves according to claim 1, wherein In step (4), the bamboo leaf extract is concentrated to 20% - 40% of the original volume.

4. The processing method of white tea integrating the active components and aroma components of bamboo leaves according to claim 1, characterized in that In step (5), the white tea is Shoumei of Zhenghe white tea.

5. The processing method of white tea integrating the active ingredients and aroma components of bamboo leaves according to claim 1, wherein In step (5), the parameters for vacuum impregnation treatment are: vacuum degree 0.08 - 0.1 MPa, temperature 70 - 90 °C, impregnation time 20 - 30 min.

6. The processing method of white tea integrating the active ingredients and aroma components of bamboo leaves according to claim 1, characterized in that, After breaking the vacuum in step (5), the white tea mixture is continuously impregnated for 15 min under normal pressure.

7. The processing method of white tea integrating active components and aroma components of bamboo leaves according to claim 1, characterized in that In step (6), the multi-gradient temperature reduction and temperature control baking is carried out in three stages: In the first stage, perform initial shaping baking at 80 - 90 °C for 0.5 h, and during this period, the robotic arm is flipped every 10 min; in the second stage, lower the temperature to 70 - 75 °C and continue baking for 2 h, and simultaneously turn on the three-dimensional oscillation device to achieve dynamic heating of the material; in the third stage, after spreading out and airing the baked material to 25 - 30 °C, perform low-temperature slow baking at 55 - 65 °C for 0.5 h the next day, and during the baking process, the temperature and humidity distribution on the surface of the tea leaves is monitored in real time through an infrared thermal imaging system, and the hot air circulation rate is adjusted to make the moisture content drop to 5.5 ± 0.5%.

8. The processing method of white tea integrating the active ingredients and aroma components of bamboo leaves according to claim 1, characterized in that, The specific method for processing white tea is as follows: (1) Raw material pretreatment: Screen tender bamboo leaves without pests and diseases, wash them with clean water and drain the water, place them in an oven at 60 °C for drying for 5 h, and after ultrafine crushing, pass through a 40-mesh sieve to obtain an active bamboo leaf matrix; (2) Pulsed electric field pretreatment: Take the active bamboo leaf matrix obtained in step (1), add food processing water according to the solid-liquid ratio of 1:15 - 1:55 kg / L and mix evenly, and perform pulsed electric field pretreatment to obtain a pulsed treatment solution; the parameters for the pulsed electric field pretreatment are: electric field strength 1 - 15 kV / cm, number of pulses 20 - 100 times, pulse width 10 - 80 μs; (3) Ultrasonic pretreatment: Take the pulsed treatment solution obtained in step (2) and perform ultrasonic pretreatment to obtain a synergistic treatment solution; the parameters for the ultrasonic pretreatment are: ultrasonic power 100 - 500 W, ultrasonic time 10 - 60 min, ultrasonic temperature 30 - 90 °C; (4)Vacuum concentration: Take the co-treated liquid obtained in step (3), filter it, and then perform vacuum concentration at 60 °C to obtain concentrated bamboo leaf liquid. (5)Vacuum impregnation: Mix white tea with the concentrated bamboo leaf liquid obtained in step (4) at a weight ratio of 1:0.5 - 1:1.

5. After preheating to 80 - 90 °C, place it in a vacuum tank for vacuum impregnation treatment to promote the migration of the active ingredients and aroma substances of bamboo leaves into the interior of white tea. The parameters of the vacuum impregnation treatment are: vacuum degree 0.08 - 0.1 MPa, temperature 70 - 90 °C, impregnation time 20 - 30 min. After breaking the vacuum, the white tea mixture continues to be impregnated at normal pressure for 15 min. (6)Dynamic baking: Place the white tea mixture in step (5) in a temperature-adjustable dynamic baking machine for multi-gradient temperature reduction and temperature control baking to obtain white tea integrated with the active ingredients and aroma components of bamboo leaves. The multi-gradient temperature reduction and temperature control baking in step (6) are carried out in three stages: In the first stage, perform initial shaping baking at 80 - 90 °C for 0.5 h, and during this period, the robotic arm flips every 10 min; in the second stage, lower the temperature to 70 - 75 °C and continue baking for 2 h, and simultaneously turn on the three-dimensional oscillation device to achieve dynamic heating of the material; in the third stage, after spreading the baked material to room temperature, use low-temperature slow baking at 55 - 65 °C for 0.5 h the next day, and during the baking process, monitor the temperature and humidity distribution on the surface of the tea leaves in real time through an infrared thermal imaging system, and adjust the hot air circulation rate to reduce the moisture content to 5.5 ± 0.5%.

9. White tea integrated with the active ingredients and aroma components of bamboo leaves obtained by the processing method of white tea integrated with the active ingredients and aroma components of bamboo leaves according to any one of claims 1 - 8.

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