Processing method of vitex tea

Abstract

The invention relates to the technical field of processing of vitex tea, and particularly discloses a processing method of vitex tea, which comprises the following process steps: S1, raw material pretreatment, including picking and screening, pesticide residue detection and grading treatment; s2, cleaning treatment including primary cleaning, fine cleaning and color protection cleaning; s3, performing fixation treatment, namely performing fixation by adopting a microwave-steam combined fixation machine; s4, rolling treatment: adopting staged rolling including primary rolling, secondary rolling and strip tidying; s5, drying treatment, wherein a three-stage technology of hot air pre-drying, vacuum freeze drying and hot air secondary drying is adopted; s6, aging treatment, wherein aging is conducted under the condition of constant temperature and constant humidity; s7, quality detection including sensory detection, physical and chemical detection and safety detection; and S8, by-product utilization: performing resource utilization on branches, crushed leaves and cleaning wastewater in the processing process. Compared with the traditional process, the effective components are respectively improved, and the health value of the vitex tea is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of Vitex negundo tea processing technology, and in particular to a Vitex negundo tea processing method that can effectively reduce the loss of effective components. Background Technology

[0002] Vitex negundo is a deciduous shrub or small tree belonging to the genus Vitex of the Verbenaceae family. It is widely distributed in the Yangtze River basin and areas south of it in my country. Its leaves, fruits, and root bark all have medicinal value. The leaves are rich in flavonoids (such as vitexin, isovitexin, apigenin, etc.), volatile oils (mainly composed of α-pinene, limonene, β-caryophyllene, etc.), polysaccharides, amino acids, and various trace elements. It has the effects of clearing heat and relieving summer heat, regulating qi and relieving pain, and eliminating phlegm and relieving cough. It is a commonly used food and medicine raw material in traditional Chinese medicine.

[0003] With the upgrading of health consumption demands, Vitex negundo tea, processed from Vitex negundo leaves, has gradually gained market attention due to its combination of health benefits and drinking value. However, the processing of Vitex negundo tea is still mainly based on traditional coarse processing techniques. Traditional processing often uses methods such as "direct sun-drying of fresh leaves" or "high-temperature pan-frying to kill the green," which, due to prolonged high-temperature treatment, causes a large amount of heat-sensitive active ingredients such as flavonoids and volatile oils in Vitex negundo leaves to decompose or volatilize, significantly reducing the health benefits of Vitex negundo tea.

[0004] The technical problem this application aims to solve is to provide a processing method for Vitex negundo tea that can effectively reduce the loss of its active ingredients. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the purpose of this invention is to provide a processing method for Vitex negundo tea that can effectively reduce the loss of its active ingredients.

[0006] The technical solution adopted in this invention is: a method for processing Vitex negundo tea, comprising the following process steps:

[0007] S1: Raw material pretreatment, including harvesting and screening, pesticide residue testing, and grading;

[0008] S2: Cleaning treatment, including pre-wash, fine wash, and color protection wash;

[0009] S3: Blanching process, using a microwave-steam combined blanching machine;

[0010] S4: Kneading process, which adopts a staged kneading method, including initial kneading, re-kneading, and shaping;

[0011] S5: Drying process, using a three-stage process of hot air pre-drying, vacuum freeze drying, and hot air secondary drying;

[0012] S6: Aging treatment, carried out under constant temperature and humidity conditions;

[0013] S7: Quality inspection, including sensory inspection, physicochemical inspection, and safety inspection;

[0014] S8: By-product utilization, making resource-based use of branches, broken leaves, and washing wastewater during the processing.

[0015] In some implementations, step S1 includes the following steps:

[0016] S1.1: During the picking and screening process, the picking time is from 9:00 to 11:00 am on sunny days from June to August each year. Pick mature Vitex negundo leaves of the current year with a leaf age of 30-45 days and a thickness of 0.2-0.3 mm, and remove yellow leaves, insect-infested leaves, damaged leaves and impurities.

[0017] S1.2: Pesticide residues were detected using high performance liquid chromatography-mass spectrometry, and heavy metal content was detected using atomic absorption spectrophotometry.

[0018] S1.3: Grading treatment is divided into first-level, second-level, and third-level based on leaf length.

[0019] In some implementations, step S2 includes the following steps:

[0020] S2.1: For the initial wash, soak in running clean water at 20-25℃ for 5-8 minutes, while simultaneously introducing microbubbles with a diameter of 50-100μm;

[0021] S2.2: Fine cleaning is performed using an ultrasonic cleaner with an ultrasonic power of 200-300W, a temperature of 25-30℃, and a time of 5-8 minutes;

[0022] S2.3: Color protection wash uses a mixed aqueous solution of 0.1%-0.3% vitamin C and 0.05%-0.15% citric acid at a temperature of 20-25℃ for 3-5 minutes, followed by centrifugation to dehydrate to a water content of 75%-80%.

[0023] In some embodiments, the parameters of the microwave-steam combined blanching machine in step S3 are: microwave power 500-700W, steam temperature 110-120℃, blanching time 2-4 minutes, and material conveying speed 0.5-0.8m / min.

[0024] In some implementations, step S4 includes the following steps:

[0025] S4.1: Initial kneading parameters are: pressure 0.1-0.2MPa, rotation speed 20-25r / min, time 5-8 minutes;

[0026] S4.2: The re-kneading parameters are: pressure 0.3-0.4MPa, speed 25-30r / min, time 10-15 minutes;

[0027] S4.3: The parameters for the strip are: temperature 40-50℃, vibration frequency 30-40Hz, and time 3-5 minutes.

[0028] In some implementations, step S5 includes the following steps:

[0029] S5.1: Hot air pre-drying parameters are: temperature 60-70℃, wind speed 1.5-2.0m / s, time 15-20 minutes;

[0030] S5.2: Vacuum freeze drying parameters are: freezing at -40℃ to -30℃ for 2-3 hours, vacuum degree 0.08-0.12MPa, and drying at 30-40℃ for 8-12 hours;

[0031] S5.3: The parameters for hot air secondary drying are: temperature 50-60℃, wind speed 1.0-1.5m / s, and time 10-15 minutes.

[0032] In some embodiments, the parameters for aging in step S6 are: temperature 20-25℃, relative humidity 50%-60%, time 30-60 days, ventilation 1-2 times a day for 30-60 minutes each time, and turning over the pile once every 10 days.

[0033] In some implementations, step S7 includes the following steps:

[0034] S7.1: Sensory testing shall be conducted in accordance with GB / T23776, and the evaluation indicators shall include appearance, color, aroma, taste and liquor color;

[0035] S7.2: In physicochemical testing, the flavonoid content is ≥5% by high performance liquid chromatography, the volatile oil content is ≥0.3% by gas chromatography-mass spectrometry, the moisture content is 5%-8%, and the ash content is ≤6%.

[0036] S7.3: In safety testing, pesticide residues comply with GB2763, heavy metals comply with GB2762, total bacterial count is ≤1000 CFU / g, and mold is ≤50 CFU / g.

[0037] In some implementations, step S8 includes the following steps:

[0038] S8.1: The volatile oil in the branches is extracted by supercritical CO2 extraction with the following parameters: pressure 30-40MPa, temperature 40-50℃, time 2-3 hours. The residue is made into dietary fiber or biomass fuel.

[0039] S8.2: After being sterilized by high-pressure steam at 121℃ for 15-20 minutes, the crushed leaves are made into raw materials for tea bags or health products;

[0040] S8.3: After the cleaning wastewater is filtered by a screen, flavonoids and pigments are adsorbed by AB-8 type macroporous adsorption resin.

[0041] The beneficial effects of this invention are as follows:

[0042] 1. This invention significantly reduces the loss of heat-sensitive components by using a microwave-steam combined fixation process instead of traditional high-temperature fixation, combined with vacuum freeze-drying. Testing shows that the flavonoids and volatile oils in the finished Vitex negundo tea produced by this invention are increased compared to traditional processes, greatly enhancing the health benefits of Vitex negundo tea.

[0043] 2. Through steps such as grading and screening, staged rolling, and temperature-controlled aging, the finished Vitex negundo tea leaves are tightly rolled and uniform, with a dark green and glossy color. After brewing, the tea soup is clear and yellow-green, with a delicate and lasting aroma, a sweet and mellow taste without bitterness, and excellent sensory evaluation, which is superior to traditional Vitex negundo tea.

[0044] 3. This invention uses a three-stage drying process to control the moisture content of the finished product to 5%-8%. Combined with strict raw material testing and finished product microbial testing, the finished Vitex negundo tea can have a shelf life of 18-24 months under normal temperature and sealed conditions, which is more than twice the shelf life of traditional processes, and there is no risk of pesticide residues, heavy metals and excessive microorganisms. Detailed Implementation

[0045] Example 1

[0046] A method for processing Vitex negundo tea includes the following steps:

[0047] S1: Raw material pretreatment

[0048] S1.1: Harvesting and screening: At 10:00 AM on July 10th, mature leaves of the current year with a leaf age of 35 days, a leaf length of 6-7cm, and a thickness of 0.25mm were harvested from Vitex negundo plants with a growth period of 4 years. Yellowed leaves and insect-damaged leaves were removed, resulting in 1000kg of initial selected leaves.

[0049] S1.2: Pesticide Residue Detection: High performance liquid chromatography-mass spectrometry was used to detect the initial selected leaves. Organophosphorus pesticides were not detected, pyrethroid pesticide content was 0.01 mg / kg (GB2763 limit 0.05 mg / kg), and carbamate pesticides were not detected; lead content was 0.02 mg / kg (GB2762 limit 0.1 mg / kg), and cadmium, mercury, and arsenic were not detected. 980 kg of qualified leaves were obtained.

[0050] S1.3: Grading: 980 kg of first-grade leaves with a leaf length of 6-7 cm were selected for subsequent processing.

[0051] S2: Cleaning process

[0052] S2.1: Initial washing: Put 980kg of first-grade leaves into a flowing clean water tank (water temperature 22℃), soak for 6 minutes, and at the same time introduce microbubbles (diameter 80μm), then take them out and drain the water;

[0053] S2.2: Fine cleaning: Place the blades into an ultrasonic cleaner, add deionized water with pH 6.8 (liquid-to-material ratio 5:1), set the ultrasonic power to 250W and the temperature to 28℃, and ultrasonically clean for 6 minutes.

[0054] S2.3: Color protection wash: Transfer the leaves into a 0.2% vitamin C + 0.1% citric acid mixed solution (temperature 22℃) and soak for 4 minutes, then dehydrate them in a centrifuge (1800r / min) for 2.5 minutes until the leaf moisture content drops to 78%.

[0055] Step 3: Blanching

[0056] A microwave-steam combined blanching machine was used, with the microwave power set at 600W, the steam temperature at 115℃, the material conveying speed at 0.6m / min, and the blanching time at 3 minutes. After blanching, the PPO activity of the leaves was reduced by 95% and the moisture content was reduced to 68%. The leaves were immediately transferred to a cooling device (temperature 28℃) for 4 minutes of cooling.

[0057] S4: Kneading process

[0058] S4.1: Initial kneading: Put the cooled blades into the kneading machine, press lightly (0.15MPa), knead at 22r / min for 6 minutes;

[0059] S4.2: Re-kneading: Adjust to medium pressure (0.35MPa), speed 28r / min, knead for 12 minutes, and check the cell breakage rate at 65%;

[0060] S4.3: Shaping: Transfer to the shaping machine, temperature 45℃, vibration frequency 35Hz, shaping for 4 minutes, after screening the tea strips have a uniformity of 92%.

[0061] S5: Drying process

[0062] S5.1: Hot air pre-drying: hot air temperature 65℃, wind speed 1.8m / s, drying for 18 minutes, moisture content reduced to 42%;

[0063] S5.2: Vacuum freeze drying: Freeze at -35℃ for 2.5 hours, vacuum degree 0.1MPa, heat up to 35℃, dry for 10 hours, and the moisture content is reduced to 18%;

[0064] S5.3: Hot air secondary drying: temperature 55℃, wind speed 1.2m / s, drying for 12 minutes, moisture content reduced to 6.5%.

[0065] S6: Aging Treatment

[0066] It was placed in a constant temperature and humidity aging chamber at 23℃ and 55% relative humidity for 45 days, and turned over once every 10 days. After aging, the flavonoid content was tested to be 5.2%, with a delicate aroma and mellow taste.

[0067] S7: Quality Inspection

[0068] S7.1: Sensory inspection: The appearance is tightly rolled and uniform, the color is dark green and glossy, the aroma is elegant, the taste is sweet and mellow, the soup is clear and yellow-green, and the sensory score is 92 points.

[0069] S7.2: Physicochemical tests: Flavonoid content 5.2%, volatile oil content 0.35%, moisture 6.5%, ash content 5.2%;

[0070] S7.3: Safety test: Pesticide residues and heavy metals were not detected, total bacterial count was 800 CFU / g, mold count was 30 CFU / g, and no pathogenic bacteria were detected.

[0071] The product passed the inspection and yielded 120 kg of finished Vitex negundo tea.

[0072] S8: By-product utilization

[0073] S8.1: Branch utilization: Collect 500kg of branches, crush them to 1.5mm, and extract them using supercritical CO2 extraction (pressure 35MPa, temperature 45℃, time 2.5 hours) to extract 3.5kg of volatile oil. The residue is used to make 120kg of dietary fiber powder.

[0074] S8.2: Utilization of broken leaves: Collect 30kg of broken leaves, sterilize at 121℃ for 18 minutes, and make 28kg of tea bags;

[0075] S8.3: Wastewater utilization: Collect 2000L of cleaning wastewater, filter it with a bar screen, adsorb it with AB-8 resin, wash and dry it to obtain 1.2kg of flavonoid powder, and discharge the wastewater in compliance with standards.

[0076] Example 2

[0077] The difference between this embodiment and Embodiment 1 is that:

[0078] S3 blanching parameters: microwave power 500W, steam temperature 110℃, blanching time 4 minutes, moisture content after blanching 65%;

[0079] S5 drying parameters: hot air pre-drying temperature 60℃, time 20 minutes; vacuum freeze drying time 12 hours; hot air secondary drying temperature 50℃, time 15 minutes, finished product moisture content 7.8%;

[0080] S6 aging time: 60 days.

[0081] Example 3

[0082] The difference between this embodiment and Embodiment 1 is that:

[0083] S1 picking leaf grade: Grade II leaves with a leaf length of 3-5cm;

[0084] S4 kneading parameters: kneading pressure 0.4MPa, time 15 minutes, cell breakage rate 70%;

[0085] S8 by-product utilization: Branch residues are made into biomass fuel, and crushed leaves are used as raw materials for the production of Vitex capsules.

[0086] Comparative Example (Traditional Process)

[0087] The traditional processing method for Vitex negundo tea is adopted: fresh leaves are directly stir-fried in a pan to kill the green (temperature 180℃, time 10 minutes), hand-rolled (15 minutes), and naturally sun-dried (moisture content 15%), without any aging process.

[0088] Active ingredient content detection:

[0089] Detection of flavonoid content (HPLC method)

[0090] Sample pretreatment: Take 1.00g of Vitex negundo tea sample, crush it and pass it through a 40-mesh sieve, add 25mL of 80% methanol solution, and extract it by ultrasonication (300W power, 50℃ temperature, 30min time). Centrifuge (5000r / min, 10min) and take the supernatant. Filter it through a 0.22μm filter membrane before testing.

[0091] Chromatographic conditions: ZORBAX SB-C18 column (4.6 mm × 250 mm, 5 μm), mobile phase methanol-0.1% phosphoric acid aqueous solution (50:50, V / V), flow rate 1.0 mL / min, column temperature 30 ℃, detection wavelength 330 nm, injection volume 10 μL;

[0092] Quantitative method: The external standard method was used to plot a standard curve with vitexin standards (concentrations of 0.1, 0.2, 0.5, 1.0, and 2.0 μg / mL) and calculate the total flavonoid content in the sample.

[0093] Determination of volatile oil content (GC-MS method)

[0094] Sample pretreatment: Take 5.00g of Vitex negundo tea sample and extract volatile oil by steam distillation (refer to GB / T14455.3-2008) for 2h. After collecting the volatile oil, make up to 1mL with n-hexane and filter through a 0.22μm filter membrane.

[0095] Chromatographic-mass spectrometry conditions: Column: DB-5MS (30m × 0.25mm × 0.25μm); Column temperature program: Initial 40℃ (hold for 3 min), increased to 250℃ at 5℃ / min (hold for 5 min); Carrier gas: Helium (purity ≥99.999%), flow rate: 1.0 mL / min, split ratio: 10:1; Ion source: EI source (70 eV); Scan range: m / z 35-400; Solvent delay: 3 min.

[0096] Quantitative methods: Limonene was used as an internal standard to calculate the total content of volatile oils using the internal standard method. At the same time, the relative contents of the main volatile components (α-pinene, limonene, β-caryophyllene) were identified by NIST mass spectrometry library matching.

[0097] Table 1 shows the relevant data for the detection of effective ingredient content.

[0098]

[0099]

[0100] As shown in Table 1, the flavonoid retention rate was significantly higher in the experimental group (5.0%-5.5%) compared to the control group (2.8%), with a flavonoid content increase of 78.6%-96.4%. The core reason for this is that traditional pan-frying for blanching involves temperatures as high as 180℃ for 10 minutes, which causes thermal degradation of flavonoids (such as vitexin). In contrast, the microwave-steam combined blanching method of this invention (110-120℃, 2-4 minutes) utilizes microwaves for strong penetration and uniform heating, while steam maintains humidity and reduces flavonoid oxidation. Experimental data shows that this step can increase the flavonoid retention rate by more than 40%. Vacuum freeze-drying (freezing at -40℃ to -30℃ + sublimation drying) avoids the high temperatures of traditional sun-drying (open-air temperature 35-40℃, lasting 2-3 days). As shown in Table 1, the volatile oil content in the experimental group (0.32%-0.38%) was 2.1-2.5 times that of the control group (0.15%), further demonstrating that low-temperature drying can reduce the loss of heat-sensitive components. Stability of volatile oil components: The relative contents of the main volatile components (α-pinene, limonene, β-caryophyllene) in the experimental group were significantly higher than those in the control group. Among them, limonene (the main source of fresh aroma) reached 23.1% in Example 2, which is 2.2 times that of the control group (10.5%). The reason is that the microwave-steam blanching time is short (2-4 minutes), which can quickly inactivate volatile oil decomposing enzymes (such as terpene enzymes), while the traditional blanching time is long, and the enzymatic reaction continues to occur, resulting in the loss of volatile oils.

[0101] Sensory quality testing:

[0102] Referring to GB / T23776-2018 "Sensory Evaluation Methods for Tea", a review panel composed of 5 senior tea tasters was formed, and a "100-point system" was used for scoring. The specific indicators and weights are shown in the table below:

[0103]

[0104] Before the evaluation, tea tasters received standardized training to avoid subjective bias; each batch of samples was numbered and then blind-evaluated, with the average score from 5 people taken as the final sensory score.

[0105] Table 2 shows the sensory quality test scoring data.

[0106]

[0107] As shown in Table 2, the optimization of appearance and color: the appearance score of the experimental group (21.8-23.1 points) was 53.5%-62.7% higher than that of the control group (14.2 points). The key is that: the grading treatment in step 1.3 (using leaves of the same grade in the same batch) avoids the unevenness of the tea strips caused by traditional mixed processing; the staged rolling in step 4 (light initial rolling → medium-pressure re-rolling) controls the cell breakage rate at 60%-70%, which ensures that the tea strips are tightly rolled (the uniformity of tea strips in Example 2 is 93%), and avoids the increase of broken pieces caused by excessive rolling; the color protection wash in step 2.3 (vitamin C + citric acid) inhibits the activity of polyphenol oxidase. As can be seen from Table 2, the color score of the experimental group (12.5-13.8 points) is 1.6-1.8 times that of the control group (7.8 points), effectively preventing browning. Aroma and Flavor Improvement: The aroma (20.5-22.5 points) and flavor (21.2-22.8 points) scores of the experimental group were 51.9%-66.7% higher than those of the control group (13.5 points and 12.3 points, respectively). The key factor was the temperature-controlled aging process in step 6 (20-25℃, 30-60 days). During the aging process, the bitter substances (such as tannins) in Vitex negundo leaves undergo oxidation and polymerization reactions to generate small-molecule sweet substances. Experimental data showed that Example 1 (flavor score 22.1 points) aged for 45 days had a significantly lower bitterness than the unaged sample (flavor score 16.5 points). The moderate ventilation during aging promoted the slow release and balance of aroma substances, avoiding the "raw green taste" of fresh Vitex negundo leaves and forming a delicate and lasting aroma.

[0108] Microbiological and safety testing:

[0109] Microbiological indicator testing:

[0110] Total bacterial count: Refer to GB4789.2-2022 "National Food Safety Standard - Microbiological Examination of Food - Determination of Total Bacterial Count", use plate counting method, incubation temperature 36℃±1℃, incubation time 48h±2h;

[0111] Molds: According to GB4789.15-2016 "National Food Safety Standard for Microbiological Examination of Food - Counting of Molds and Yeasts", Bengal Red Medium was used, the culture temperature was 28℃±1℃, and the culture time was 5d±1d;

[0112] Pathogenic bacteria (Salmonella, Staphylococcus aureus): Refer to GB4789.4-2020 and GB4789.10-2022, use selective culture media for isolation and culture, and a negative result is considered qualified.

[0113] Detection of pesticide residues and heavy metals:

[0114] Pesticide residues: Referring to GB2763-2021 "National Food Safety Standard Maximum Residue Limits for Pesticides in Food", organophosphates (such as chlorpyrifos), pyrethroids (such as cypermethrin), and carbamates (such as carbofuran) were detected by HPLC-MS / MS, with a detection limit of ≤0.01 mg / kg.

[0115] Heavy metals: In accordance with GB2762-2022 "National Food Safety Standard - Limits of Contaminants in Food", lead (Pb), cadmium (Cd), mercury (Hg), and arsenic (As) were detected using an atomic absorption spectrophotometer. The detection limit for lead was ≤0.02 mg / kg, and for other elements it was ≤0.01 mg / kg.

[0116] Table 3 shows the data related to microbiological and safety testing.

[0117]

[0118]

[0119] As shown in Table 3, the microbial control effect was as follows: the total bacterial count (750-850 CFU / g) and mold count (25-35 CFU / g) in the experimental group were much lower than those in the control group (3200 CFU / g and 180 CFU / g, respectively). This is because the three-stage drying in step 5 reduced the moisture content of the finished product to 5%-8% (6.5% in Example 1), while the moisture content of the control group was 15%. The low moisture environment can significantly inhibit the reproduction of microorganisms. The ultrasonic cleaning in step 2 (200-300W, 5-8 minutes) can remove more than 90% of the attached microorganisms on the leaf surface. Experimental verification showed that after ultrasonic cleaning, the total bacterial count of the leaves could be reduced from the initial 12000 CFU / g to below 2000 CFU / g. Safety compliance: In the experimental group, pesticide residues (such as cypermethrin) and heavy metals (such as Pb) were not detected or were below the national standard limits, while in the control group, cypermethrin (0.03 mg / kg, close to the national standard limit of 0.05 mg / kg) and Pb (0.05 mg / kg) were detected. The difference is due to: the pre-testing of pesticide residues / heavy metals in step 1.2, which eliminated unqualified raw materials in advance; and the ultrasonic cleaning in step 2.2, which can physically remove pesticide residues from the leaf surface. Experiments show that this step can achieve a pesticide residue removal rate of more than 80%.

[0120] Accelerated shelf-life testing:

[0121] The "temperature-accelerated method" (referring to GB / T22743-2020 "Guidelines for Predicting Shelf Life of Food") was used. The experimental and control group samples were sealed and packaged, then placed in a constant temperature and humidity chamber at 37℃±1℃ and 75%±5% relative humidity. Samples were taken at 0d, 30d, 60d, and 90d, and the following indicators were measured:

[0122] Sensory quality: Whether there is browning, off-odor, or loose strands;

[0123] Physicochemical indicators: moisture content (whether it is >10%), flavonoid content (whether it has decreased by >15%);

[0124] Microbiological indicators: whether mold was detected (>100 CFU / g);

[0125] The shelf life is calculated at room temperature (25℃) by taking "any indicator exceeding the qualified range" as the end point of the shelf life.

[0126] Table 4 shows the relevant data on shelf life.

[0127] Group Accelerate the shelf life of experiments (d) Calculate the shelf life at room temperature (in months). Example 1 90 20 Example 2 95 24 Example 3 85 18 Comparative Example 30 7

[0128] As shown in Table 4, the estimated shelf life of the experimental group at room temperature (18-24 months) is 2.6-3.4 times that of the control group (7 months). The core logic is that low moisture (5%-8%) and sealed packaging can delay oxidation and accelerate the process. The experiment showed that the flavonoid content in the experimental group decreased by only 5% after 60 days (compared to a 20% decrease in the control group). The "protective layer" formed during the aging process (such as oxidation products of polysaccharides) can further isolate external moisture and oxygen, reducing the risk of microbial contamination.

[0129] Resource utilization rate calculation:

[0130] Resource utilization rate = (quality of finished Vitex negundo tea + quality of by-product recovery) / total quality of Vitex negundo raw materials × 100% Quality of finished Vitex negundo tea: the quality of tea products that pass the inspection after drying;

[0131] By-product recovery quality: quality of volatile oil and dietary fiber extracted from branches, quality of tea bags made from crushed leaves, and quality of flavonoid powder recovered from wastewater;

[0132] Total weight of Vitex negundo raw materials: weight of initial harvested fresh leaves + weight of collected branches.

[0133] Table 5 shows the resource utilization rate data.

[0134]

[0135] As shown in Table 5, the resource utilization rate of the experimental group (94.3%-96.5%) was 15-16 times higher than that of the control group (6.0%). The key lies in the full-chain utilization of by-products: volatile oil is extracted from branches (6-7 kg can be extracted from each ton of branches), and dietary fiber is made from the residue, so that the utilization rate of branches reaches more than 90%; broken leaves are made into tea bags, avoiding the discarding of 20%-30% of broken leaves in the traditional process; flavonoids are recovered from wastewater (0.5-0.6 kg can be extracted from each ton of wastewater), which reduces pollution and creates additional economic value.

[0136] In summary, this invention addresses the core challenges of traditional processes through four key technologies: microwave-steam fixation + vacuum freeze-drying to preserve active ingredients, graded rolling + temperature-controlled aging to optimize sensory quality, pre-processing detection + low moisture control to ensure safety, and full utilization of byproducts to improve resource efficiency. Experimental data show that the finished Vitex negundo tea exhibits a flavonoid retention rate ≥85%, a sensory score ≥90, a shelf life at room temperature ≥18 months, and a resource utilization rate ≥94%, all significantly superior to traditional processes. This provides a feasible technical solution for the large-scale, high-quality production of Vitex negundo tea.

[0137] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for processing Vitex negundo tea, characterized in that, The process includes the following steps: S1: Raw material pretreatment, including harvesting and screening, pesticide residue testing, and grading; S2: Cleaning treatment, including pre-wash, fine wash, and color protection wash; S3: Blanching process, using a microwave-steam combined blanching machine; S4: Kneading process, which adopts a staged kneading method, including initial kneading, re-kneading, and shaping; S5: Drying process, using a three-stage process of hot air pre-drying, vacuum freeze drying, and hot air secondary drying; S6: Aging treatment, carried out under constant temperature and humidity conditions; S7: Quality inspection, including sensory inspection, physicochemical inspection, and safety inspection; S8: By-product utilization, making resource-based use of branches, broken leaves, and washing wastewater during the processing.

2. The method for processing Vitex negundo tea according to claim 1, characterized in that, Step S1 includes the following steps: S1.1: During the picking and screening process, the picking time is from 9:00 to 11:00 am on sunny days from June to August each year. Pick mature Vitex negundo leaves of the current year with a leaf age of 30-45 days and a thickness of 0.2-0.3 mm, and remove yellow leaves, insect-infested leaves, damaged leaves and impurities. S1.2: Pesticide residues were detected using high performance liquid chromatography-mass spectrometry, and heavy metal content was detected using atomic absorption spectrophotometry. S1.3: Grading treatment is divided into first-level, second-level, and third-level based on leaf length.

3. The method for processing Vitex negundo tea according to claim 1, characterized in that, Step S2 includes the following steps: S2.1: For the initial wash, soak in running clean water at 20-25℃ for 5-8 minutes, while simultaneously introducing microbubbles with a diameter of 50-100μm; S2.2: Fine cleaning is performed using an ultrasonic cleaner with an ultrasonic power of 200-300W, a temperature of 25-30℃, and a time of 5-8 minutes; S2.3: Color protection wash uses a mixed aqueous solution of 0.1%-0.3% vitamin C and 0.05%-0.15% citric acid at a temperature of 20-25℃ for 3-5 minutes, followed by centrifugation to dehydrate to a water content of 75%-80%.

4. The method for processing Vitex negundo tea according to claim 1, characterized in that, In step S3, the parameters of the microwave-steam combined blanching machine are: microwave power 500-700W, steam temperature 110-120℃, blanching time 2-4 minutes, and material conveying speed 0.5-0.8m / min.

5. A method for processing Vitex negundo tea according to claim 1, characterized in that, Step S4 includes the following steps: S4.1: Initial kneading parameters are: pressure 0.1-0.2MPa, rotation speed 20-25r / min, time 5-8 minutes; S4.2: The re-kneading parameters are: pressure 0.3-0.4MPa, speed 25-30r / min, time 10-15 minutes; S4.3: The parameters for the strip are: temperature 40-50℃, vibration frequency 30-40Hz, and time 3-5 minutes.

6. The method for processing Vitex negundo tea according to claim 1, characterized in that, Step S5 includes the following steps: S5.1: Hot air pre-drying parameters are: temperature 60-70℃, wind speed 1.5-2.0m / s, time 15-20 minutes; S5.2: Vacuum freeze drying parameters are: freezing at -40℃ to -30℃ for 2-3 hours, vacuum degree 0.08-0.12MPa, and drying at 30-40℃ for 8-12 hours; S5.3: The parameters for hot air secondary drying are: temperature 50-60℃, wind speed 1.0-1.5m / s, and time 10-15 minutes.

7. The method for processing Vitex negundo tea according to claim 1, characterized in that, The parameters for aging in step S6 are: temperature 20-25℃, relative humidity 50%-60%, time 30-60 days, ventilation 1-2 times a day for 30-60 minutes each time, and turning over the pile once every 10 days.

8. A method for processing Vitex negundo tea according to claim 1, characterized in that, Step S7 includes the following steps: S7.1: Sensory testing shall be conducted in accordance with GB / T23776, and the evaluation indicators shall include appearance, color, aroma, taste and liquor color; S7.2: In physicochemical testing, the flavonoid content is ≥5% by high performance liquid chromatography, the volatile oil content is ≥0.3% by gas chromatography-mass spectrometry, the moisture content is 5%-8%, and the ash content is ≤6%. S7.3: In safety testing, pesticide residues comply with GB2763, heavy metals comply with GB2762, total bacterial count is ≤1000 CFU / g, and mold is ≤50 CFU / g.

9. A method for processing Vitex negundo tea according to claim 1, characterized in that, Step S8 includes the following steps: S8.1: The volatile oil in the branches is extracted by supercritical CO2 extraction with the following parameters: pressure 30-40MPa, temperature 40-50℃, time 2-3 hours. The residue is made into dietary fiber or biomass fuel. S8.2: After being sterilized by high-pressure steam at 121℃ for 15-20 minutes, the crushed leaves are made into raw materials for tea bags or health products; S8.3: After the cleaning wastewater is filtered by a screen, flavonoids and pigments are adsorbed by AB-8 type macroporous adsorption resin.

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