Preparation process for fermenting selenium-enriched black tea by naturally fermenting fresh rose petals

Abstract

The invention belongs to the technical field of tea processing, and discloses fermentation and a preparation process of selenium-rich black tea naturally fermented by fresh rose petals. Aiming at the problems of poor flavor fusion, low selenium element utilization rate, insufficient active ingredient synergism and the like of the traditional compound fermented tea, the process comprises the following steps of: taking organic double-petal red rose fresh petals and selenium-enriched black tea (the selenium content is more than or equal to 0.5 mg / kg) at the altitude of 2800-3400m and in a region of northern latitude of 30 + / -1 degrees as compound raw materials; the preparation method comprises the following steps: precise pretreatment of raw materials, gradient synergistic withering, four-stage pressure-controlled rolling, probiotic synergistic fermentation, third-stage temperature-controlled drying and refined aging packaging. Selenium-rich black tea is mixed with fresh rose petals according to an optimized proportion after being subjected to specific pretreatment, and in the fermentation process, rose flavone and polyphenol, black tea polyphenol and selenium element form a synergistic effect; a'rose-black tea 'double-substrate fermentation system is adopted, and directional conversion of compound probiotics is combined, so that not only is the strong fragrance of roses and the mellow taste of black tea reserved, but also the bioavailability of selenium is improved, and the functions of resisting oxidation and regulating intestinal flora are achieved.

Description

Technical Field

[0001] This invention relates to the field of tea processing technology, specifically to a fermentation process and preparation technology of Jinshan rose tea with unique flavor and rich nutrition. Background Technology

[0002] Rose tea is beloved by consumers for its rich aroma and abundant nutrients (such as flavonoids and polyphenols). However, traditional rose tea production processes, which often involve direct sun-drying or simple baking, have significant technical drawbacks: First, the lack of standardization in raw material selection and processing leads to inconsistent product quality; second, the extensive processing methods, such as improper control during withering, rolling, and drying, result in the significant loss of characteristic aroma compounds from the roses, and insufficient release and transformation of core nutrients like flavonoids and polyphenols from the petals; finally, the open processing environment is prone to microbial contamination, posing food safety risks.

[0003] Meanwhile, while selenium-enriched black tea, as a functional beverage, possesses unique health benefits, it also faces technological challenges. The combination of traditional black tea fermentation processes and a selenium-rich environment is difficult to control. On the one hand, improper fermentation can easily produce off-flavors, masking or even destroying the delicate aroma of roses. On the other hand, how to fully transform the tea's internal substances during fermentation to create a mellow black tea flavor, while perfectly blending it with the aroma and nutrients of roses, is a problem that current technology has not yet effectively solved.

[0004] Therefore, how to organically combine the rich fragrance of roses with the mellow and sweet taste of selenium-rich black tea, and solve the problems of easy loss of aroma, insufficient release of nutrients, monotonous flavor and unstable quality that exist in the traditional process, are technical problems that urgently need to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a fermentation process for naturally fermented selenium-enriched black tea made from fresh rose petals, which solves the problems of easy loss of aroma, insufficient release of nutrients, monotonous flavor and unstable quality in traditional processes. This process enables the industrial and standardized production of rose fermented tea, resulting in a high-quality product that combines the rich aroma of roses with the mellow taste of black tea.

[0006] The core technical solution of this invention is as follows: Step 1, (1) Accurate selection and pretreatment of composite raw materials: Select double-petaled red roses that grow at an altitude of 2800-3400 meters and latitude of 30°±1° north, irrigated by glacial snow water, cultivated with well-rotted farmyard manure, and with an annual sunshine duration of ≥2242 hours and meet the GB / T 19630 organic standard; pick fresh flowers with complete flower shape, deep pink color and no disease or pests at 3:00-5:00 am every day, complete the petal peeling within 1.5 hours, remove impurities such as sepals and stems, place them in a clean and ventilated stainless steel tray to pre-dry for 1-2 hours to remove surface free moisture and obtain pre-treated petals; (2) Pretreatment of selenium-enriched black tea: Select high-quality black tea with selenium content ≥0.5mg / kg, crush it and pass it through a 40-mesh sieve to remove tea stems, tea dust and other impurities. Add sterile water at 30℃ and soak for 15 minutes (material-liquid ratio 1:5, mass-volume ratio). After draining the water, the pretreated black tea is obtained and set aside. (3) Mixing of compound raw materials: Mix the pretreated petals and pretreated black tea at a mass ratio of 3:1 to 5:1 and stir evenly to obtain compound raw materials; Step two, two-stage gradient withering: The composite raw materials are evenly spread in the intelligent withering equipment. The first stage is set with a temperature of 20-22℃, a relative humidity of 60-70%, and a wind speed of 0.3-0.5m / s, lasting for 8-12 hours. The second stage is adjusted to a temperature of 23-25℃, a relative humidity of 55-65%, and a wind speed of 0.5-0.8m / s, lasting for 16-36 hours, until the moisture content of the petals drops to 65%-85%, thus obtaining the withered composite raw materials. Step 3: Four-stage controlled pressure kneading. The withered petals are fed into a kneading machine with pressure feedback, using a gradient process of "light pressure-medium pressure-heavy pressure-light pressure". The light pressure stage is 0.1-0.2MPa for 5-10 minutes, the medium pressure stage is 0.2-0.3MPa for 10-15 minutes, the heavy pressure stage is 0.3-0.4MPa for 10-20 minutes, and the final light pressure stage is 0.1-0.2MPa for 5-10 minutes. The total kneading time is 30-60 minutes. After kneading, the petals are screened through an 8-10 mesh sieve to remove unbroken clumps and impurities, resulting in the initial composite flower threads (tea threads + rose threads). Step 4: Probiotic-assisted constant temperature and humidity fermentation. The initial compound flower threads are spread evenly on a fermentation tray sterilized with ultraviolet light for 40-60 minutes, with a thickness of 4-6 cm. First, a compound probiotic agent is evenly sprayed onto the compound flower threads at a concentration of 0.5-1.0% of the flower thread mass. This agent is prepared by mixing Saccharomyces cerevisiae and Lactobacillus plantarum in a 1:2 mass ratio. Then, the fermentation tray is placed in a constant temperature and humidity fermentation chamber, controlling the temperature at 25-30℃ and the relative humidity at 90-95%. The layers are turned over every 60-90 minutes, and fermentation continues for 6-9 hours until the flower threads turn reddish-brown and possess a sweet rose aroma and a mellow black tea fragrance, thus obtaining the fermented compound flower threads. Step 5: Three-stage temperature-controlled drying. Immediately transfer the fermented composite filaments to a hot air dryer. In the first stage, treat at 90-100℃ and 1.0-1.5m / s for 10-15 minutes to terminate fermentation. In the second stage, cool down to 80-90℃ and dry at 1.2-1.8m / s for 30-45 minutes. In the third stage, cool down to 60-70℃ and dry at 0.8-1.2m / s for 20-30 minutes, turning the filaments every 15 minutes until the moisture content of the composite filaments is ≤5% (Kal Fischer method), thus obtaining dried composite filaments. Step Six: Refined Post-Processing. The dried rose petals are naturally cooled to 20-25℃ and sieved through a 10-20 mesh stainless steel screen to remove fragments and impurities. Then, they are transferred to an aging room with a temperature of 15-20℃, relative humidity of 40-50%, and dust content ≤0.1mg / m³ for aging for 7-15 days. During the aging period, ventilation is carried out for 30 minutes every 3 days. Finally, the product is vacuum-packed using a food-grade aluminum-plastic composite film to obtain the finished product of naturally fermented selenium-rich black tea made from fresh rose petals.

[0007] Preferably, the selection criteria for double-petaled red roses in step one also include: using a 0-5℃ low-temperature preservation box during the transportation process after harvesting to ensure that the core temperature of the petals does not exceed 8℃.

[0008] Preferably, the total number of live bacteria in the compound probiotic agent in step four is ≥1×10⁻⁶. 8 CFU / g (dilution plating method), the pH value of the filaments was monitored in real time during fermentation, and the pH value was stably controlled between 4.0 and 5.0 by adjusting the ventilation frequency of the fermentation chamber.

[0009] Preferably, after the kneading is completed in step three, a screening step is added: the initial filaments are screened using an 8-10 mesh sieve to remove unbroken petal clumps and impurities.

[0010] Preferably, in step five, the air intake method of the dryer is side air intake and top air outlet, and the temperature fluctuation range of each stage is ≤±2℃, and the humidity fluctuation range is ≤±3%.

[0011] Preferably, the air in the aging chamber in step six is ​​purified by a high-efficiency air filter (HEPA). After aging, the filaments are sterilized by microwave for 30-60 seconds. The total number of colonies in the sterilized filaments is ≤100cfu / g (dilution plating method).

[0012] Preferably, in step two, the intelligent withering equipment is equipped with a temperature and humidity sensor, which samples every 5 minutes. When the actual parameters deviate from the set values ​​by more than ±3℃ or ±5%, the equipment automatically starts the adjustment program.

[0013] Preferably, the optimal mass ratio of pretreated petals to pretreated black tea in step one (3) is 4:1.

[0014] Precise selection of raw materials: Select organic double-petal red roses from the plateau region at an altitude of 2800-3400 meters and 30 degrees north latitude. This region has large temperature differences between day and night, few pests and diseases, and is irrigated by glacial meltwater and fertilized with farmyard manure. There is zero industrial pollution and zero pesticide residue. The region also enjoys ≥2242 hours of sunshine per year, ensuring that the raw materials are rich in nutrients and have a strong aroma. The harvesting time is strictly controlled between 3-5 am, when the petals have the right moisture content and the aromatic substances have not volatilized. Pre-processing is completed within 2 hours after harvesting to prevent the raw materials from deteriorating.

[0015] Finished product aging process: After drying, the product undergoes low-temperature and low-humidity aging to achieve a more harmonious flavor and extend its shelf life to more than 18 months.

[0016] Beneficial effects: 1. In terms of raw materials, organic double-petal red roses from specific regions are selected, and the early morning harvesting and rapid pre-processing methods ensure that the raw materials are free of pesticide residues and spoilage, and have sufficient nutritional and aromatic substances. In terms of process, each parameter is precisely controlled through gradient withering, four-stage rolling, constant temperature and humidity fermentation, and staged drying, avoiding the randomness of traditional processes. At the same time, the equipment for each step is easy to obtain and the parameters are easy to control, which not only realizes industrialized and standardized production, but also has strong practicality and broad prospects for large-scale application.

[0017] 2. This product boasts a unique flavor and is both nutritious and safe. During fermentation, the rose aroma and microbial metabolites deeply blend, creating a distinctive flavor profile of "rich rose fragrance + mellow black tea flavor." The high rate of petal cell breakage during fermentation promotes the conversion of nutrients, resulting in a finished product with flavonoid content ≥1.2mg / g (aluminum nitrate method) and polyphenol content ≥3.5mg / g (Folin-phenol method), representing an increase of over 30% compared to traditional rose tea. Furthermore, the aseptic fermentation environment and strict microbial control ensure compliance with national food safety standards, with a moisture content ≤5%. Combined with vacuum packaging, this extends the shelf life to 18 months. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] Example 1: Preparation of Jinshan Rose Fermented Tea using Basic Processes Raw material preparation and pretreatment: Select organic double-petaled red roses with a deep pink color grown in an area with an altitude of 3000 meters and a latitude of 30 degrees north. Pick fresh flowers at 4 am, remove petals within 2 hours, remove sepals and stems, select undamaged petals free from pests and diseases, and place them in a ventilated and clean place to air dry for 1.5 hours to remove surface moisture.

[0020] Gradient withering: The petals are evenly spread in the intelligent withering machine, with an initial temperature of 21℃ and relative humidity of 65%, and maintained for 10 hours; then the temperature is adjusted to 24℃ and relative humidity to 60%, and withering continues for 24 hours. The moisture content of the petals is measured to be 75%, the petals are soft, do not drip when squeezed, and can slowly unfold when released.

[0021] Controlled pressure kneading: The withered petals are fed into a kneading machine and kneaded in four stages: light pressure (0.15MPa) for 10 minutes, medium pressure (0.25MPa) for 12 minutes, heavy pressure (0.35MPa) for 15 minutes, and a final light pressure (0.15MPa) for 8 minutes, for a total kneading time of 45 minutes; after kneading, the petal cell breakage rate is 90%, forming uniform filamentous rose petals.

[0022] Constant temperature and humidity fermentation: Spread the rose filaments evenly on a sterile fermentation tray, and sterilize the fermentation environment with ultraviolet light for 45 minutes; place it in a constant temperature and humidity fermentation chamber, control the temperature at 28℃ and the relative humidity at 92%, and turn it over once every 75 minutes; after 7.5 hours of fermentation, the filaments turn reddish-brown, and the fermentation is stopped.

[0023] Staged temperature-controlled drying: The fermented filaments were sent into a dryer with a wind speed of 1.2 m / s. The first stage was treated at 95°C for 12 minutes, the second stage was dried at 85°C for 38 minutes, and the third stage was dried at 65°C for 25 minutes. During the process, the filaments were turned over every 15 minutes, and the moisture content was measured to be 4.2% (Karl Fischer method).

[0024] Finished product post-processing: naturally cooled to 23℃, sieved through a 15-mesh sieve to remove debris; aged for 10 days at 18℃ and 45% relative humidity, ventilated for 30 minutes every 3 days during this period, and finally vacuum-packed to obtain the finished product.

[0025] Example 2: Optimized process for adding compound probiotics The steps of raw material preparation, gradient withering, and controlled-pressure kneading are the same as in Example 1; Constant temperature and humidity fermentation: Before fermentation, add 0.8% of compound probiotic agent (yeast: lactic acid bacteria = 1:2) to the rose filaments and mix well; the remaining fermentation conditions are the same as in Example 1, and the pH value is monitored to be 4.5 during the fermentation process; The steps of staged temperature-controlled drying and post-processing of finished products are the same as in Example 1.

[0026] Example 3: Optimized process with added screening step The raw material preparation and gradient withering steps are the same as in Example 1; Controlled pressure kneading and sieving: The kneading steps are the same as in Example 1. After kneading, a 9-mesh sieve is used to remove unbroken petal clumps. The constant temperature and humidity fermentation, staged temperature-controlled drying, and finished product post-processing steps are the same as in Example 1.

[0027] Example 4 Raw material quality verification experiment The purpose of the experiment was to verify the superiority of "organic double-petaled red roses grown at an altitude of 2800-3400 meters and 30 degrees north latitude (picked at 3-5 am)" as raw materials, and to compare the differences in basic components (moisture, flavonoids, polyphenols) and aroma substances of roses from different origins and picking times, so as to provide data support for the selection criteria of raw materials.

[0028] Three groups of samples were set up, and each group was sampled in parallel three times (n=3): Experimental group (S1): The raw material specified in this invention (highland organic double-petal red rose, altitude 3000 meters, latitude 30 degrees north, picked at 4 am, pre-treated within 2 hours); Control group 1 (S2): Double-petaled red roses grown in plains (500 meters above sea level, conventional fertilizer cultivation, harvested at 4 am); Control group 2 (S3): Double-petaled red roses from the same origin as the experimental group (picked at 2 PM and pretreated 6 hours later).

[0029] Moisture content determination: Referring to GB 5009.3-2016 "National Food Safety Standard - Determination of Moisture in Food", the initial moisture content of 3 groups of samples was determined by the Karl Fischer method. Each group was measured in parallel 3 times and the average value was taken.

[0030] Flavonoid content determination: Step 1, Sample processing: Take 1.0g of rose petals from each group (dried to constant weight), crush them, add 50mL of 70% ethanol, extract in an 80℃ water bath for 2 hours, filter, and dilute to 100mL to obtain the extract; Step 2, Colorimetric reaction: Take 2mL of the extract, add 0.3mL of 5% sodium nitrite, shake well and let stand for 6 minutes; add 0.3mL of 10% aluminum nitrate, shake well and let stand for 6 minutes; add 4mL of 4% sodium hydroxide, dilute to 10mL with 70% ethanol, and let stand for 15 minutes; Step 3, Measure the absorbance at a specific wavelength, and calculate the flavonoid content (mg / g) according to the rutin standard curve.

[0031] Polyphenol content determination (Folin-phenol method): Step 1, sample processing is the same as the flavonoid extraction step, prepare polyphenol extract; Step 2, colorimetric reaction: take 1 mL of extract, add 0.5 mL of Folin-phenol reagent, shake well and let stand for 3 minutes; add 2 mL of 10% sodium carbonate solution, dilute to 10 mL with distilled water, and react at 30℃ in the dark for 1 hour; Step 3, determination: measure absorbance at a specific wavelength, and calculate polyphenol content (mg / g) according to gallic acid standard curve.

[0032] Aroma analysis (GC-MS): Step 1, aroma extraction: Take 5.0g of fresh petals from each group, place them in a 20mL headspace vial, equilibrate at 60℃ for 30 minutes, adsorb from the extraction head for 40 minutes, and desorb at 250℃ for 5 minutes; Step 2, GC conditions: HP-5MS capillary column, column temperature program: initially 40℃ for 3 minutes, increase to 200℃ at 5℃ / min, hold for 5 minutes, then increase to 250℃ at 10℃ / min, hold for 3 minutes; carrier gas is helium (purity ≥99.999%), flow rate 1.0mL / min, split ratio 10:1; Step 3, MS conditions: electron impact ionization source (EI), ionization energy 70eV, ion source temperature 230℃, mass scan range m / z 35-450, qualitative analysis by NIST 17 library matching, and calculation of the relative content of each aroma compound by peak area normalization.

[0033] Experimental results Conclusions: 1. The initial moisture content of the experimental group (S1) was 82.3%, lower than that of the plain rose (S2, 85.6%), avoiding excessively long withering time; higher than that of the afternoon-harvested sample (S3, 80.1%), ensuring petal softness and facilitating cell breakage during crushing, meeting the process requirements. 2. The flavonoid (2.85 mg / g) and polyphenol (5.36 mg / g) contents of S1 were significantly higher than those of S2 (p<0.05), indicating that the zero-pollution environment of the plateau, glacial meltwater, and farmyard manure can promote the accumulation of nutrients; the higher content of S1 than S3 proves that early morning harvesting (petals not exposed to high temperatures, and nutrients not lost) is the key to high-quality raw materials. 3. Aroma advantage: 38 aroma substances were detected in S1, significantly more than S2 (25 kinds), and the relative content of characteristic aroma substances (citronellol, geraniol, etc., which determine the sweet aroma of roses) reached 42.5%, far higher than the control group, verifying the basic aroma advantage of the raw materials of this invention.

[0034] Example 5: Gradient Wilting Parameter Optimization Experiment Experimental objective: To screen the optimal combination of "initial temperature and humidity - subsequent temperature and humidity - total time" to ensure that the petals have a moisture content of 65%-85% after withering and the highest retention rate of aroma substances.

[0035] Experimental design: Using the experimental group's raw material (S1) as the sample, 5 groups of wilting parameters were set (each group was repeated 3 times), with all other conditions being the same (ventilation, no direct sunlight): Detection method: The total content of characteristic aroma substances (citronellol + geraniol + phenylethyl alcohol) in the petals after wilting was determined by GC-MS, and the retention rate was calculated as (content after wilting / initial content × 100%). Petal condition: sensory observation (softness, no browning).

[0036] Experimental results: Conclusion: Group A2 (initial 21℃ / 65%×10h, subsequent 24℃ / 60%×24h, total 34h) had a post-wither moisture content of 75.3% (in line with 65%-85%), a characteristic aroma retention rate of 92.3% (highest), and soft petals without browning, representing the optimal withering parameters. Excessively high temperatures (A4, 23℃ / 75%) or excessive humidity would lead to slow moisture loss and excessive aroma evaporation; excessively low temperatures (A5, 19℃ / 55%) or excessively low humidity would lead to excessively rapid moisture loss and drier petals, neither of which meet the process requirements.

[0037] Example 6: Optimization Experiment of Controlled-Pressure Kneading Parameters Experimental objective: To optimize the pressure and time of the four-stage kneading process (light-medium-heavy-light) to ensure that the petal cell breakage rate is ≥85% and the filaments are uniform in shape (without clumps).

[0038] Experimental design: Using withered petals (A2 group product) as samples, 4 sets of rolling parameters were set (3 replicates per set): Detection methods and indicators: Cell disruption rate: Take 0.1g of the filaments after kneading, observe under a microscope (400x), and count the number of broken cells / total number of cells × 100%; Filament uniformity: Sieve through a 10-mesh sieve, and calculate the mass of filaments passing through the sieve / total mass × 100%; Flower juice overflow: Weighing method (mass of filaments after kneading - mass of petals before kneading, calculate the percentage difference).

[0039] Experimental Results: In the optimization experiment of controlled pressure kneading parameters, the cell breakage rate of group B1 was 78.5±2.3%, which did not meet the requirement of ≥85%, the filiform uniformity was 82.1±1.9%, and the amount of flower juice overflow was 5.2±0.4%. The cell breakage rate of group B2 reached 90.3±1.8%, which met the index requirements. The filiform uniformity was 93.5±1.5%, which was the highest among all groups, and the amount of flower juice overflow was 8.6±0.5%, which could fully meet the nutritional needs of subsequent fermentation. The cell breakage rate of group B3 was 95.6±1.5%, which was high, but the filiform uniformity was only 88.2±1.7%, and the filiform clumping phenomenon occurred. The amount of flower juice overflow was 9.1±0.6%. The cell breakage rate of group B4 was 85.2±2.0%, which just met the qualified line. The filiform uniformity was 89.7±1.6%, and the amount of flower juice overflow was 7.3±0.5%, which was slightly lower than that of group B2.

[0040] Experimental conclusions: Group B2 (light pressure 0.15MPa / 10min → medium pressure 0.25MPa / 12min → heavy pressure 0.35MPa / 15min → final light pressure 0.15MPa / 8min, total 45min) had a cell breakage rate of 90.3% (≥85%), a filament uniformity of 93.5% (highest), and a sap overflow of 8.6% (meeting the nutritional needs of subsequent fermentation), which are the optimal kneading parameters; too low pressure (B1) resulted in insufficient cell breakage and less sap overflow; too high pressure (B3) resulted in excessive compression and clumping of the filaments, affecting the uniformity of subsequent fermentation.

[0041] Example 7: Optimization Experiment of Constant Temperature and Humidity Fermentation Parameters Experimental objective: To screen the optimal combination of fermentation temperature, humidity and time, and to verify the effect of adding compound probiotics (yeast: lactic acid bacteria = 1:2) to ensure that the filaments are reddish-brown and have a significant sweet rose aroma after fermentation, and that flavonoids and polyphenols are fully converted.

[0042] Experimental Design: Using the twisted filaments (product of group B2) as the sample, 6 experimental groups were set up (each group was repeated 3 times). Groups C1-C3 did not contain probiotics, while groups C4-C6 contained 0.8% probiotics (based on filament quality): Group C1: Temperature 25℃, Humidity 90%, Fermentation time 6h, no probiotics added; Group C2: Temperature 28℃, Humidity 92%, Fermentation time 7.5h, no probiotics added; Group C3: Temperature 30℃, Humidity 95%, Fermentation time 9h, no probiotics added; Group C4: Temperature 25℃, Humidity 90%, Fermentation time 6h, probiotics added; Group C5: Temperature 28℃, Humidity 92%, Fermentation time 7.5h, probiotics added; Group C6: Temperature 30℃, Humidity 95%, Fermentation time 9h, probiotics added.

[0043] Test methods: Sensory indicators, color (percentage of reddish-brown), aroma (sweetness intensity, 1-5 points, 5 points being the strongest); Nutritional indicators, flavonoid and polyphenol content (same method as described above); Microbiological indicators: total colony count (GB 4789.2-2022, plate count method).

[0044] Experimental Results: In the constant temperature and humidity fermentation parameter optimization experiment, in the groups without added probiotics, Group C1 had a reddish-brown silk content of 75±3.2%, an aroma score of 3.2±0.3, a flavonoid content of 1.12±0.08 mg / g, and a total bacterial count of 120±15 cfu / g; Group C2 had a reddish-brown silk content of 88±2.5%, an aroma score of 4.1±0.2, a flavonoid content of 1.32±0.09 mg / g, and a total bacterial count of 95±12 cfu / g, all of which were better than Group C1; Group C3 had a reddish-brown silk content of 92±2.1%, an aroma score of 4.3±0.2, and a flavonoid content of 1.28±0.07 mg / g, but the total bacterial count reached 150±18 cfu / g, posing a risk of microbial contamination. Among the groups with added probiotics, group C4 had a reddish-brown color percentage of 80±2.8%, an aroma score of 3.8±0.3, a flavonoid content of 1.35±0.09 mg / g, and a total bacterial count of 85±10 cfu / g; group C5 performed best, with a reddish-brown color percentage of 95±2.0%, an aroma score of 4.8±0.2, a flavonoid content of 1.58±0.10 mg / g, a polyphenol content of 4.21±0.14 mg / g, and a total bacterial count of only 62±8 cfu / g; group C6 had a reddish-brown color percentage of 98±1.5%, an aroma score of 4.5±0.2, a flavonoid content of 1.52±0.08 mg / g, and a total bacterial count of 110±14 cfu / g, slightly higher than group C5.

[0045] Experimental Conclusions: 1. In the group without probiotics, C2 (28℃ / 92% humidity / 7.5h) was the best, meeting the standards for color and nutrition, but its aroma and antibacterial effect were weaker than the group with added probiotics; 2. In the group with added probiotics, C5 (28℃ / 92% humidity / 7.5h, 0.8% probiotics) had the best performance in all aspects—95% reddish-brown color, aroma score of 4.8 (rich and sweet aroma), flavonoids of 1.58mg / g (19.7% higher than C2), polyphenols of 4.21mg / g (15.3% higher than C2), and total bacterial count of 62cfu / g (significantly lower than the control group); 3. The optimal fermentation parameters were 28℃, 92% humidity, and 7.5h, with the addition of 0.8% compound probiotics. Probiotics can promote the conversion of rose nutrients into easily absorbed forms, while inhibiting the growth of miscellaneous bacteria, improving flavor and safety.

[0046] Example 8: Optimization Experiment of Staged Temperature Control Drying Parameters Experimental objective: To screen the temperature and time combination of "high-temperature enzyme sterilization - medium-temperature drying - low-temperature aroma fixation" to ensure that the finished product has a moisture content of ≤5%, and the highest aroma retention rate and the least loss of nutrients.

[0047] Experimental design: Using fermented filaments (C5 group product) as samples, four drying parameters were set (each group was replicated three times). The air velocity was 1.2 m / s, and the filaments were turned over every 15 minutes: D1 group: high temperature enzyme inactivation 90℃ / 15min, medium temperature drying 80℃ / 45min, low temperature aroma fixation 60℃ / 30min, total time 90min; D2 group: high temperature enzyme inactivation 95℃ / 12min, medium temperature drying 85℃ / 38min, low temperature aroma fixation 65℃ / 25min, total time 75min; D3 group: high temperature enzyme inactivation 100℃ / 10min, medium temperature drying 90℃ / 30min, low temperature aroma fixation 70℃ / 20min, total time 60min; D4 group: high temperature enzyme inactivation 85℃ / 20min, medium temperature drying 75℃ / 50min, low temperature aroma fixation 55℃ / 35min, total time 105min.

[0048] Test indicators and methods: Moisture content of finished product, Karl Fischer method; Aroma retention rate, GC-MS to determine characteristic aroma substances (as before), calculate the content after drying / content after fermentation × 100%; Nutritional loss rate, flavonoid loss rate = (flavonoids after fermentation - flavonoids after drying) / flavonoids after fermentation × 100%.

[0049] Experimental Results: In the step-by-step temperature-controlled drying parameter optimization experiment, the moisture content of component D1 was 5.8±0.3%, exceeding the standard of ≤5%, with an aroma retention rate of 88.5±2.1% and a flavonoid loss rate of 8.2±0.5%. The moisture content of component D2 was 4.2±0.2%, meeting the standard requirements, with an aroma retention rate of 93.2±1.8%, the highest among all groups, and a flavonoid loss rate of only 5.1±0.4%, showing the best nutritional retention effect. The moisture content of component D3 was 3.5±0.2%, which, although low, resulted in an aroma retention rate of only 75.3±1.9% and a flavonoid loss rate as high as 12.5±0.6%, indicating serious loss of both nutrition and aroma. The moisture content of component D4 was 6.2±0.3%, failing to meet the qualified standard, with an aroma retention rate of 90.1±2.0% and a flavonoid loss rate of 6.8±0.5%, all indicators being lower than those of group D2.

[0050] Analysis conclusions: Group D2 (95℃ / 12min enzyme inactivation → 85℃ / 38min drying → 65℃ / 25min aroma fixation, total 75min) has a finished product moisture content of 4.2% (≤5%), aroma retention rate of 93.2% (highest), and flavonoid loss rate of 5.1% (lowest), which are the optimal drying parameters; excessively high temperature (D3) will lead to pyrolysis of aroma substances and oxidation of flavonoids; excessively low temperature (D4) or insufficient time (D1) will result in insufficient moisture content, which does not meet the process requirements.

Claims

1. A preparation process for naturally fermented selenium-enriched black tea made from fresh rose petals, characterized in that, Includes the following steps: Step 1, (1) Selection and pretreatment of double-petaled red roses: Select double-petaled red roses that grow at an altitude of 2800-3400 meters and latitude of 30°±1° north, irrigated by glacial snowmelt, cultivated with well-rotted farmyard manure, and with an annual sunshine duration of ≥2242 hours and meet the organic standards of GB / T 19630; pick fresh flowers with complete flower shape, deep pink color and no diseases or pests at 3:00-5:00 am every day, complete the petal peeling within 1.5 hours, remove impurities such as sepals and stems, and place them in a clean and ventilated stainless steel tray to pre-dry for 1-2 hours to remove surface free moisture and obtain pre-treated petals; (2) Pretreatment of selenium-enriched black tea: Select high-quality black tea with selenium content ≥0.5mg / kg, crush it and pass it through a 40-mesh sieve to remove tea stems, tea dust and other impurities. Soak it in 30℃ sterile water for 15 minutes, drain the water and obtain pretreated black tea for later use; the material-to-liquid ratio is 1:

5. (3) Mixing of compound raw materials: Mix the pretreated petals and pretreated black tea at a mass ratio of 3:1 to 5:1 and stir evenly to obtain compound raw materials; Step 2, Two-stage gradient withering: The composite raw materials are evenly spread in the intelligent withering equipment. In the first stage, the temperature is set at 20-22℃, the relative humidity at 60-70%, and the wind speed at 0.3-0.5m / s, lasting for 8-12 hours. In the second stage, the temperature is adjusted to 23-25℃, the relative humidity at 55-65%, and the wind speed at 0.5-0.8m / s, lasting for 16-36 hours, until the moisture content of the petals drops to 65%-85%, thus obtaining the withered composite raw materials. Step 3, Four-stage controlled pressure kneading: The withered petals are fed into a kneading machine with pressure feedback, using a gradient process of "light pressure-medium pressure-heavy pressure-light pressure". The light pressure stage is 0.1-0.2 MPa for 5-10 minutes, the medium pressure stage is 0.2-0.3 MPa for 10-15 minutes, the heavy pressure stage is 0.3-0.4 MPa for 10-20 minutes, and the final light pressure stage is 0.1-0.2 MPa for 5-10 minutes. The total kneading time is 30-60 minutes. After kneading, the petals are screened through an 8-10 mesh sieve to remove unbroken clumps and impurities, obtaining the initial composite flower threads; the initial composite flower threads include tea threads and rose threads. Step 4: Probiotic-assisted constant temperature and humidity fermentation: Spread the initial compound flower threads evenly on a fermentation tray sterilized with ultraviolet light for 40-60 minutes, with a thickness of 4-6 cm; first, evenly spray compound probiotic agent onto the compound flower threads, with the amount of agent added being 0.5-1.0% of the flower thread mass. The agent is made by mixing brewer's yeast and Lactobacillus plantarum in a mass ratio of 1:2; then place the fermentation tray in a constant temperature and humidity fermentation chamber, controlling the temperature at 25-30℃ and the relative humidity at 90-95%, and turning the upper and lower layers every 60-90 minutes. Ferment for 6-9 hours until the flower threads turn reddish-brown and have a sweet rose aroma and a mellow black tea aroma, thus obtaining fermented compound flower threads; Step 5, Three-stage temperature-controlled drying: Immediately transfer the fermented composite filaments to a hot air dryer. In the first stage, treat at 90-100℃ and 1.0-1.5m / s for 10-15 minutes to terminate fermentation; in the second stage, cool down to 80-90℃ and dry at 1.2-1.8m / s for 30-45 minutes; in the third stage, cool down to 60-70℃ and dry at 0.8-1.2m / s for 20-30 minutes, turning the filaments every 15 minutes until the moisture content of the composite filaments is ≤5%, thus obtaining dried composite filaments. Step Six: Refined Post-Processing: The dried rose petals are naturally cooled to 20-25℃ and then sieved through a 10-20 mesh stainless steel screen to remove fragments and impurities. They are then transferred to an aging room with a temperature of 15-20℃, relative humidity of 40-50%, and dust content ≤0.1mg / m³ for aging for 7-15 days. During the aging period, ventilation is carried out for 30 minutes every 3 days. Finally, the product is vacuum-packed using a food-grade aluminum-plastic composite film to obtain the finished product of naturally fermented selenium-rich black tea made from fresh rose petals.

2. The preparation process according to claim 1, characterized in that, In step one, the selection criteria for double-petaled red roses also include: using a 0-5℃ low-temperature preservation box during the transportation process after picking to ensure that the average temperature of the petals does not exceed 8℃.

3. The preparation process according to claim 1, characterized in that, In step four, the total number of live bacteria in the compound probiotic agent is ≥1×10⁻⁶. 8 CFU / g, the pH value of the silk was monitored in real time during the fermentation process, and the pH value was stably controlled between 4.0 and 5.0 by adjusting the ventilation frequency of the fermentation chamber.

4. The preparation process according to claim 1, characterized in that, In step three, after kneading, a screening step is added: the initial filaments are screened using an 8-10 mesh sieve to remove unbroken petal clumps and impurities.

5. The preparation process according to claim 1, characterized in that, In step five, the air intake method of the dryer is side air intake and top air outlet, and the temperature fluctuation range of each stage is ≤±2℃, and the humidity fluctuation range is ≤±3%.

6. The preparation process according to claim 1, characterized in that, In step six, the aging chamber uses a high-efficiency air filter for air purification. After aging, the filaments are subjected to microwave sterilization for 30-60 seconds. The total number of colonies in the filaments after sterilization is ≤100cfu / g.

7. The preparation process according to claim 1, characterized in that, In step two, the intelligent withering equipment is equipped with a temperature and humidity sensor, which samples every 5 minutes. When the actual parameters deviate from the set values ​​by more than ±3℃ or ±5%, the equipment automatically starts the adjustment program.

8. The preparation process according to claim 1, characterized in that, In step one (3), the optimal mass ratio of pretreated petals to pretreated black tea is 4:

1.

9. A selenium-enriched black tea made from fresh rose petals, characterized in that, The rose petal-enriched selenium-rich black tea is obtained by the preparation process described in any one of claims 1-8.

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