Rose tea and preparation method thereof

Abstract

The invention provides rose tea and a preparation method thereof, the preparation method comprises the steps of withering, rolling and fermenting roses, the withering comprises the following steps: irradiating the roses with infrared light at 38 + / -2 DEG C for 3-5 minutes, stopping irradiation, standing for 3-5 minutes, and circulating for 2-3 times; and heating to 42 + / -2 DEG C at a rate of 1-2 DEG C / min, irradiating with infrared light for 3-4 minutes, stopping irradiation, standing for 2-3 minutes, circulating for multiple times until withering is finished, and controlling the total withering time to be 100-110 minutes. A specific withering process is adopted, so that the activity of endogenous enzyme is improved, the generation of aroma components and the conversion of anthocyanin to acylated pyran in the fermentation process are promoted, and the color stability and the aroma richness are improved; the prepared rose tea is complete in petals, black and moist in color and luster with golden hair, red, bright and transparent in liquor color with golden rings, and has the characteristics of high-quality rose tea with continuous color release, layered aroma enhancement, mellowness and astringency reduction characteristics.

Description

Technical Field

[0001] This invention relates to the field of flower tea preparation technology, and in particular to a rose tea and its preparation method. Background Technology

[0002] With the rise of tea culture, people have begun to pursue diversity in tea drinking, leading to the emergence of flower tea. Rose tea, as one of the traditional flower teas, is loved by consumers for its rich aroma and mellow taste.

[0003] Currently, the preparation methods for rose tea mainly include picking, spreading, fixing, rolling, fermentation, and drying. For example, patent application number CN202411157013.X discloses a rose black tea and a method for improving the aroma of rose black tea, which belongs to the field of food processing technology. The specific steps are as follows: (1) Selection of raw materials: On a sunny day when roses are in full bloom, after the dew has disappeared, select edible rose varieties with large flowers and pick healthy rose petals without insect spots; (2) Withering: Spread the picked rose petals evenly and wither them under controlled temperature and humidity to lose water and soften them. The thickness of the spread petals is 1-2 cm; (3) Rolling: Roll the rose petals until they release water and break the cell walls, and the aroma becomes stronger. Observe their shape and use uniform and beautiful strips as the standard; (4) Fermentation: Ferment the rolled rose petals aerobically; (5) Drying: Dry the fermented rose petals in time to obtain rose black tea; (6) Packaging: After the prepared rose black tea has cooled to room temperature, put it into a sealed bag and seal it in a cool place.

[0004] While the above methods can enhance aroma to some extent, the constant temperature and humidity during withering cannot effectively activate the endogenous proteases in roses. This prevents the endogenous proteases from effectively promoting the conversion of anthocyanins to acylated pyranose during fermentation. Furthermore, the side chains of anthocyanins lack acyl protection, making them highly susceptible to C4 ring opening, hydroxyl oxidation, or chalcone isomerization in high-temperature, oxygen-rich, and near-neutral water. After brewing at 90 ℃ for 5 minutes, the absorbance (535 nm) decreases by 30-40%, and the tea liquor becomes almost colorless after three infusions. This results in poor color stability of the tea liquor, severely impacting the drinking experience. Moreover, the color of the tea liquor fluctuates significantly with the pH of the water (6.5-8.2), leading to a very poor consumer experience.

[0005] Therefore, this invention is proposed. Summary of the Invention

[0006] This invention provides a rose tea and its preparation method, which solves the defect of unstable color in existing rose tea. The processed rose tea has intact petals, a dark and lustrous color with golden hairs, and a bright red liquor with a golden ring. It has the characteristics of a new type of fermented flower tea and provides technical support for high-value and branded operation.

[0007] This invention provides a method for preparing rose tea, including the steps of withering, rolling and fermenting rose petals. The withering includes the following steps: first, irradiating the rose petals with infrared light at 38±2℃ for 3-5 min, then stopping the irradiation and letting them stand for 3-5 min, repeating this cycle 2-3 times; then, raising the temperature to 42±2℃ at a rate of 1-2℃ / min, irradiating with infrared light for 3-4 min, then stopping the irradiation and letting them stand for 2-3 min, repeating this cycle multiple times until withering is complete, controlling the total withering time to be 100-110 min.

[0008] This invention employs a specific gradient of intermittent infrared-assisted heating, tailored to the characteristics of rose petals—thin, high-moisture, and prone to volatile oil loss—to more gently activate endogenous enzymes (β-glucosidase, polyphenol oxidase, and peroxidase). Compared to constant-temperature or single continuous infrared irradiation, this method more effectively activates endogenous enzymes in rose petals, significantly enhancing their activity. β-glucosidase hydrolyzes glycoside aroma precursors, releasing volatile aroma components and participating in aroma release. Polyphenol oxidase and peroxidase effectively promote the conversion of anthocyanins to acylated pyranose forms, forming a stable red leaf and red liquor base. The effective activation of these three enzymes provides a fundamental guarantee for the stability of aroma components and color during subsequent fermentation, resulting in rose tea with not only a stable color but also a rich and layered aroma.

[0009] Furthermore, the withering process includes the following steps: first, irradiate the rose with infrared light at 38±2℃ for 5 min, then stop the irradiation and let it stand for 5 min, repeating this process 3 times; then, raise the temperature to 42±2℃ at a rate of 1.5℃ / min, irradiate with infrared light for 3 min, then stop the irradiation and let it stand for 2 min, repeating this process multiple times until the withering is complete, controlling the total withering time to be 105 min.

[0010] Furthermore, the wavelength of the infrared light is 2500-4000 nm, and its illumination intensity is 150-250 μmol / (m²). 2 When the parameters of the infrared light are within the above range, a better effect can be achieved in activating β-glucosidase, polyphenol oxidase, and peroxidase.

[0011] Preferably, the withering is carried out using an 8-layer mesh belt withering machine, the thickness of the rose petals is 6-8 cm, and the wind speed of the bottom mesh belt is 0.4-0.6 m / s.

[0012] Furthermore, the kneading process includes: first kneading without kneading for 8-12 minutes, then lightly pressing for 13-17 minutes, then heavily pressing for 8-12 minutes, and finally kneading without kneading for 3-6 minutes; the pressure difference between the heavy pressing and the light pressing is 12-28 kPa.

[0013] This invention employs the aforementioned kneading process, which utilizes a suitable pressure difference between heavy and light pressure. This kneading treatment is specifically designed for delicate petals, achieving moderate cell wall damage while maintaining the integrity of the petal shape. Furthermore, since the tannin content in rose petals can reach 1.2-1.8% of fresh weight, mainly in the form of ester-type catechins and proanthocyanidin dimers, and ester-type catechins have a bitter taste, the moderate kneading process in the above scheme facilitates the release of ester-type catechins. During subsequent fermentation, ester-type catechins are converted into low-bitterness non-ester-type catechins, thereby reducing the content of ester-type catechins in rose tea and significantly reducing its bitterness.

[0014] Preferably, the pressure of the light pressure is 15±3 kPa, and the pressure of the heavy pressure is 35±5 kPa.

[0015] More preferably, the kneading process includes: kneading without kneading for 10 minutes, then pressing lightly for 15 minutes, then pressing heavily for 10 minutes, and finally kneading without kneading for 5 minutes.

[0016] Preferably, the kneading speed is 45-50 r / min, the temperature is 22-24 ℃, and the relative humidity is 85-90%.

[0017] Preferably, the kneading is performed once.

[0018] Preferably, the amount of rose petals used in the kneading process is 30-36 kg.

[0019] Furthermore, the cell wall breakage rate of the roses after the kneading process is 70-80%. A cell wall breakage rate of 70-80% is sufficient to meet the requirements of juice overflow and preservation of shape. An excessively high cell wall breakage rate (>80%) will lead to an increase in the powdering rate of the petals during the drying stage and a decrease in quality.

[0020] Furthermore, the preparation method also includes a drying step, which includes: first drying the fermented roses at 40-45 ℃ to a moisture content of 18-20% to fix the color and enzyme activity; then heating to 65-70 ℃ for a medium-temperature aroma enhancement treatment for 15-20 min to stimulate the honey-sweet fragrance; and then cooling to 50-55 ℃ for drying to a moisture content of ≤7% to maintain the integrity of the flower shape and reduce the breakage rate.

[0021] This invention employs a drying process with the aforementioned characteristics, which not only maximizes the preservation and enhancement of the volatile aroma components of roses, forming a three-tiered aroma structure of rose fragrance, fruity sweetness, and mellow sweetness, but also reduces the moisture content to a safe level, achieving both aroma fixation and shape preservation. Simultaneously, this unique drying process further promotes the conversion of ester-type catechins into non-ester-type catechins, further reducing bitterness and meeting consumers' expectations for a mellow taste.

[0022] Preferably, the drying process further includes a stacking step, wherein the stacking temperature is 18-20°C and the stacking time is more than 2 years.

[0023] Furthermore, the fermentation temperature is 28-32 ℃, the relative humidity is 90-95%, and the time is 3.0-4.0 h.

[0024] This invention does not add any exogenous microorganisms during fermentation, relying entirely on the natural microbial community attached to the rose petals and the endogenous enzyme system for synergistic biotransformation. Controlling the fermentation process within the aforementioned range allows β-glucosidase, polyphenol oxidase, and peroxidase to maintain good activity. The withering process provides more β-glucosidase, polyphenol oxidase, and peroxidase. During fermentation, the synergistic action of polyphenol oxidase (PPO) and peroxidase (POD) converts anthocyanins to acylated pyranose forms, reduces tannin polymerization, and forms a stable red leaf and red liquor base, improving the color stability of rose tea and reducing the risk of color fading after multiple infusions. Under the action of β-glucosidase, more aroma compounds are formed, enriching the aroma layers of rose tea. Simultaneously, the fermentation process also promotes the conversion of ester-type catechins to non-ester-type catechins, reducing bitterness and improving the sensory quality of rose tea.

[0025] Preferably, the material thickness during fermentation is 25-30 cm.

[0026] Furthermore, the mixture is stirred every 20-40 minutes during fermentation to ensure more thorough fermentation. Preferably, it is stirred every 30 minutes.

[0027] Furthermore, after kneading, the clumps of rose petals are broken up by vibration and oxygen is added to prevent anaerobic rancidity.

[0028] The present invention also provides rose tea prepared by the method described above.

[0029] The beneficial effects of the rose tea and its preparation method provided by this invention are as follows: (1) The preparation method of the present invention adopts a specific withering process, which can more gently activate endogenous enzymes and significantly enhance the activity of endogenous enzymes. In the subsequent fermentation process, it can effectively promote the generation of aroma components and the conversion of anthocyanins to acylated pyran types, so as to achieve continuous color release, form a stable red leaf and red soup base, and maintain a bright red color even after 5 consecutive brews, thus improving the color stability and aroma richness of rose tea. (2) The preparation method of the present invention can reduce the degree of polymerization of tannins, so that the conversion rate of ester-type catechins is >45%, which significantly reduces the intensity of bitter aftertaste and meets consumers' expectations for a sweet taste. (3) The process parameters of the preparation method of the present invention are fully quantified. The product of the present invention is brewed for 30 min Δa ✽ With a decrease of less than 30%, the tea remains bright red even after five infusions; the annual key indicator RSD is less than 5%, achieving stable production throughout the year and solving the problem of large fluctuations in traditional processes; it also achieves directional cell wall disruption of petals, enzymatic transformation and stabilization, and cascade release of aroma precursors. The rose tea prepared with this method has intact petals, a dark and lustrous color with golden tips, and a bright red liquor with a golden ring. It possesses the characteristics of high-quality rose tea with continuous color release, layered aroma enhancement, and mellow and reduced astringency, providing technical support for high-value and branded operations. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0031] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0032] The detection methods for each index in the following examples and comparative examples are as follows: Anthocyanin content was determined by pH differential method (GB / T 22244-2008); soup color a ✽ The values ​​were measured using a HunterLab UltraScan PRO colorimeter; Aroma components were analyzed using GC-MS (GB / T 30483-2013); The astringency intensity was determined using an electronic tongue (TS-5000Z, in accordance with GB / T 35810-2018); Sensory evaluation was conducted by 10 trained tea tasters using a double-blind scoring method according to GB / T 23776-2018 Sensory Evaluation Method for Tea. The sample size was n=10. The evaluation criteria included: floral / fruity / honey aroma (0-10 points), astringency intensity (0-10 points, 0 points for no astringency), and liquor color brightness / persistence (0-5 points). The total score was 100 points. The breakage rate was determined by weighing. Determination of catechin content: Following GB / T 8313-2018 "Determination Method of Tea Polyphenols and Catechins in Tea", slight adjustments were made to suit rose samples. 1.00 g of crushed rose petals was accurately weighed, added to 70 mL of 70% methanol aqueous solution, and extracted ultrasonically in a 70 ℃ water bath for 30 min. After cooling, the volume was adjusted to 100 mL and filtered. The filtrate was filtered through a 0.45 μm microporous membrane and analyzed by high-performance liquid chromatography (HPLC). Chromatographic conditions: C18 column (4.6 mm × 250 mm, 5 μm), column temperature 35 ℃, detection wavelength 278 nm, mobile phase: 0.1% formic acid aqueous solution (A) and acetonitrile (B), gradient elution, flow rate 1.0 mL / min. The contents of ester-type catechins (including epigallocatechin gallate EGCG and epigallocatechin gallate ECG) and non-ester-type catechins were quantitatively calculated using the external standard method.

[0033] Example 1: Preparation of Fermented Red Rose Tea in Spring This embodiment provides a method for preparing rose tea, including the following steps: 1. Raw materials and pretreatment Half-open red roses, with a corolla diameter of 4.5-5.5 cm, were picked between 6:00 and 8:00 AM in late April, free from pests, diseases, and dew. The fresh flowers were transported to the workshop via a 4°C cold chain. After being sorted by a grading machine, the sepals, receptacles, and browned petals were manually removed. The flowers were then washed with forced air for 90 seconds and centrifuged to remove water for 30 seconds. They were then spread out on a clean stainless steel mesh at an ambient temperature of 23°C and a relative humidity of 68% for 1.2 hours. During this time, the petals lost 10% of their weight, and most of the surface free water was removed.

[0034] 2. Withering An 8-layer mesh belt withering machine (1.2 m wide and 9 m long) was used. The flower material thickness was 7 cm, and the wind speed of the bottom mesh belt was 0.5 m / s.

[0035] Withering was achieved using intermittent heating with infrared assistance. The infrared light had a wavelength of 3250 nm and an intensity of 200 μmol / (m²). 2The withering process includes: first, irradiating the roses with infrared light at 36℃ for 5 minutes, then stopping the irradiation and letting them stand for 5 minutes, repeating this process 3 times; then, increasing the temperature to 40℃ at a rate of 1.5℃ / min, irradiating with infrared light for 3 minutes, then stopping the irradiation and letting them stand for 2 minutes, repeating this process multiple times until the withering is complete, controlling the total withering time to be 105 minutes, with an endpoint moisture content of 60%, the fragrance changing from fresh and sharp to sweet and delicate, and the petals remaining intact when folded in half.

[0036] 3. Kneading The 55-type kneading machine was used with a feed rate of 45 kg and a rotation speed of 48 r / min. The room temperature was 23 ℃ and the relative humidity was 87%.

[0037] The kneading process includes: kneading the withered rose petals without air for 10 minutes, then applying light pressure (13 kPa) for 15 minutes, followed by heavy pressure (30 kPa) for 10 minutes, and finally kneading without air for 5 minutes. The petal cell wall breakage rate is 75.1%. Immediately after kneading, the petals are placed in a vibratory de-clumping machine (4 mm amplitude, 20 Hz frequency) to break up the clumps, while simultaneously blowing in 2 m³ of clean air. 3 / min, the temperature drops to 24℃.

[0038] 4. Fermentation The broken flower petals were placed into a food-grade 304 stainless steel fermentation box (internal dimensions 1.0 m × 0.8 m × 0.6 m), with a material thickness of 28 cm, and evenly distributed at the bottom of the box. 3 mm venting holes (open area 1.8%). Fermentation parameters: temperature 28 ℃, relative humidity 90%, stirring every 30 min, fermentation 3.5 h. Endpoint criteria: ① floral aroma transforms into a rich fruity honey aroma; ② petal base color bronze, edges slightly curled; ③ soft and elastic to the touch. At this point, anthocyanin retention rate is 87%, and the average degree of polymerization of tannins decreases from 7.2 to 4.6.

[0039] 5. Drying First, the fermented roses were dried at 45 ℃ for 75 min with a wind speed of 1.0 m / s, reducing the moisture content to 19% to fix the color and enzyme activity. Then, the temperature was raised to 70 ℃ for 18 min of medium-temperature fragrance enhancement with a wind speed of 0.8 m / s to stimulate the sweet honey aroma. The edges of the petals turned bright yellow or light gold due to the high temperature. Finally, the temperature was lowered to 55 ℃ for 50 min, reducing the moisture content to 6.2% to maintain the integrity of the flower shape and reduce the breakage rate to ≤ 3%.

[0040] 6. Picking, Packaging and Stacking After drying, the material is sorted by color sorter (CCD resolution 0.5 mm) to remove browned and scorched petals. Broken stems and fragments are removed by manual sorting. The product is then packaged with nitrogen (nitrogen purity 99.5%) and stored at 18℃ for two years to obtain rose tea. This rose tea can be stored at room temperature (≤25 ℃, ≤ 60 % RH) for 18 months, with the main indicator fluctuation RSD < 5%.

[0041] Example 2: Preparation of Summer Red Rose Fermented Flower Tea This embodiment provides a method for preparing rose tea, including the following steps: 1. Raw materials and pretreatment The harvesting time was changed to mid-July, from 5:30 to 7:30 am. The initial moisture content of the fresh flowers was 86%, the wilting time was extended to 115 min, and the final moisture content was 58%. The fermentation temperature was 30 ℃, the relative humidity was 93%, and the time was shortened to 3.0 h (the enzyme activity of the raw materials is high in summer).

[0042] 2. Withering An 8-layer mesh belt withering machine (1.2 m wide and 9 m long) was used. The flower material thickness was 7 cm, and the wind speed of the bottom mesh belt was 0.5 m / s.

[0043] Withering was achieved using intermittent heating with infrared assistance. The infrared light had a wavelength of 3250 nm and an intensity of 200 μmol / (m²). 2 The withering process includes: first, irradiating the roses with infrared light at 38℃ for 5 minutes, then stopping the irradiation and letting them stand for 5 minutes, repeating this process 3 times; then, increasing the temperature to 42℃ at a rate of 1.5℃ / min, irradiating with infrared light for 3 minutes, then stopping the irradiation and letting them stand for 2 minutes, repeating this process multiple times until the withering is complete, controlling the total withering time to be 105 minutes, during which the fragrance changes from fresh and sharp to sweet and delicate, and the petals remain intact when folded in half.

[0044] 3. Kneading The 55-type kneading machine was used with a feed rate of 45 kg and a rotation speed of 48 r / min. The room temperature was 23 ℃ and the relative humidity was 87%.

[0045] The kneading process includes: kneading the withered rose petals without air for 10 minutes, then lightly pressing (15 kPa) for 15 minutes, then heavily pressing (35 kPa) for 10 minutes, and finally kneading without air for 5 minutes. Immediately after kneading, the petals are placed in a vibratory de-clumping machine (4mm amplitude, 20 Hz frequency) to break up the clumps, while simultaneously blowing in 2 m³ of clean air. 3 / min, the temperature drops to 24 ℃.

[0046] 4. Fermentation The broken flower petals were placed into a food-grade 304 stainless steel fermentation box (internal dimensions 1.0 m × 0.8 m × 0.6 m), with a material thickness of 28 cm, and evenly distributed at the bottom of the box. 3 mm venting holes (open area 1.8%). Fermentation parameters: temperature 30 ℃, relative humidity 92%, stirring every 30 min, fermentation 3.5 h. Endpoint criteria: ① floral aroma transforms into a rich fruity honey aroma; ② petal base color bronze, edges slightly curled; ③ soft and elastic to the touch. At this point, anthocyanin retention rate is 87%, and the average degree of polymerization of tannins decreases from 7.2 to 4.6.

[0047] 5. Drying First, the fermented roses were dried at 45 ℃ for 75 min with a wind speed of 1.0 m / s, reducing the moisture content to 19% to fix the color and enzyme activity. Then, the temperature was raised to 70 ℃ for 18 min of medium-temperature fragrance enhancement with a wind speed of 0.8 m / s to stimulate the sweet honey aroma. The edges of the petals turned bright yellow or light gold due to the high temperature. Finally, the temperature was lowered to 55 ℃ for 50 min, reducing the moisture content to 6.2% to maintain the integrity of the flower shape and reduce the breakage rate to ≤ 3%.

[0048] 6. Picking, Packaging and Stacking After drying, the material is sorted by color sorter (CCD resolution 0.5 mm) to remove browned and scorched petals. Broken stems and fragments are removed by manual sorting. The product is then packaged with nitrogen (nitrogen purity 99.5%) and stored at 19℃ for 2 years to obtain rose tea. This rose tea can be stored at room temperature (≤25 ℃, ≤60 % RH) for 18 months, with the main indicator fluctuation RSD <5%.

[0049] Example 3 This embodiment provides a method for preparing rose tea, including the following steps: 1. Raw materials and pretreatment Half-open red roses, with a corolla diameter of 4.5-5.5 cm, were picked between 6:00 and 8:00 AM in late April, free from pests, diseases, and dew. The fresh flowers were transported to the workshop via a 4°C cold chain. After being sorted by a grading machine, the sepals, receptacles, and browned petals were manually removed. The flowers were then washed with forced air for 90 seconds and centrifuged to remove water for 30 seconds. They were then spread out on a clean stainless steel mesh at an ambient temperature of 23°C and a relative humidity of 68% for 1.2 hours. During this time, the petals lost 10% of their weight, and most of the surface free water was removed.

[0050] 2. Withering An 8-layer mesh belt withering machine (1.2 m wide and 9 m long) was used. The flower material thickness was 7 cm, and the wind speed of the bottom mesh belt was 0.5 m / s.

[0051] Withering was achieved using intermittent heating with infrared assistance. The infrared light had a wavelength of 3250 nm and an intensity of 200 μmol / (m²). 2 The withering process includes: first, irradiating the roses with infrared light at 40℃ for 5 minutes, then stopping the irradiation and letting them stand for 5 minutes, repeating this process 3 times; then, raising the temperature to 44℃ at a rate of 1.5℃ / min, irradiating with infrared light for 3 minutes, then stopping the irradiation and letting them stand for 2 minutes, repeating this process multiple times until the withering is complete, controlling the total withering time to be 105 minutes, during which the fragrance changes from fresh and sharp to sweet and delicate, and the petals remain intact when folded in half.

[0052] 3. Kneading The 55-type kneading machine was used with a feed rate of 45 kg and a rotation speed of 48 r / min. The room temperature was 23 ℃ and the relative humidity was 87%.

[0053] The kneading process includes: kneading the withered rose petals without air for 10 minutes, then lightly pressing (18 kPa) for 15 minutes, then heavily pressing (40 kPa) for 10 minutes, and finally kneading without air for 5 minutes. Immediately after kneading, the petals are placed in a vibratory de-clumping machine (4mm amplitude, 20 Hz frequency) to break up the clumps, while simultaneously blowing in 2 m³ of clean air. 3 / min, the temperature drops to 24 ℃.

[0054] 4. Fermentation The broken flower petals were placed into a food-grade 304 stainless steel fermentation box (internal dimensions 1.0 m × 0.8 m × 0.6 m), with a material thickness of 28 cm, and evenly distributed at the bottom of the box. 3 mm venting holes (open area 1.8%). Fermentation parameters: temperature 32 ℃, relative humidity 94%, stirring every 30 min, fermentation 3.5 h. Endpoint criteria: ① floral aroma transforms into a rich fruity and honey aroma; ② petal base color bronze, edges slightly curled; ③ soft and elastic to the touch. At this point, anthocyanin retention rate is 87%, and the average degree of polymerization of tannins decreases from 7.2 to 4.6.

[0055] 5. Drying First, the fermented roses were dried at 45 ℃ for 75 min with a wind speed of 1.0 m / s, reducing the moisture content to 19% to fix the color and enzyme activity. Then, the temperature was raised to 70 ℃ for 18 min of medium-temperature fragrance enhancement with a wind speed of 0.8 m / s to stimulate the sweet honey aroma. The edges of the petals turned bright yellow or light gold due to the high temperature. Finally, the temperature was lowered to 55 ℃ for 50 min, reducing the moisture content to 6.2% to maintain the integrity of the flower shape and reduce the breakage rate to ≤ 3%.

[0056] 6. Picking, Packaging and Stacking After drying, the material is sorted by color sorter (CCD resolution 0.5 mm) to remove browned and scorched petals. Broken stems and fragments are removed by manual sorting. The product is then packaged with nitrogen (nitrogen purity 99.5%) and stored at 20℃ for 2 years to obtain rose tea. This rose tea can be stored at room temperature (≤25 ℃, ≤ 60 % RH) for 18 months, with the main indicator fluctuation RSD < 5%.

[0057] This invention determined the quality of the rose tea prepared in Examples 1-3 (all samples were rose tea that had been stored for two years). To scientifically evaluate product quality, the following standard testing method was specified: The tea infusion was prepared using the evaluation method (3.0g sample steeped in 150mL boiling water for 5 minutes) and used for the analysis of various indicators. Among them, Δa ✽ The percentage decrease is used to characterize the stability of the soup color, and its calculation formula is as follows: Δa ✽ Percentage decrease / % = [(a ✽ 0- a ✽ 1) / a ✽ 0] × 100%; In the formula, a ✽ 0 is the initial value of a ✽ Value, a ✽ 1 represents a after standing for 30 minutes. ✽ value).

[0058] Anthocyanin dissolution rate refers to the total amount of effective components dissolved per unit mass of dried flowers, calculated using the following formula: Anthocyanin dissolution amount (mg / g) = (Anthocyanin concentration in tea soup (mg / mL) × Tea soup volume (mL) / Mass of dried flower sample (g).

[0059] Aroma persistence was assessed by comparing the aroma intensity of the third infusion with that of the first infusion, calculated as (average aroma score of the third infusion / average aroma score of the first infusion) × 100%. The results are shown in Table 1. Table 1. Quality of rose tea prepared in Examples 1-3

[0060] Comparing the finished tea liquor colors of rose tea made from roses from different seasons, it was found that summer rose tea has a slightly deeper red color and a more prominent fruity and honey aroma. Its total sensory score is 92.8, and all indicators are superior to spring rose tea.

[0061] Comparative Example 1 The difference between this comparative example and Example 2 is that during withering, the rose petals were continuously irradiated with infrared light at 42°C for 105 minutes. The resulting rose tea had slightly curled petal edges, a single aroma profile, and a 22% lower content of honey-sweet aroma components (such as phenylethyl alcohol) compared to Example 2.

[0062] Comparative Example 2 The difference between this comparative example and Example 2 is that during withering, it was continuously irradiated with infrared light at 38°C for 105 minutes.

[0063] Comparative Example 3 The difference between this comparative example and Example 2 is that the withering process included: first, irradiating the roses with infrared light at 38°C for 5 minutes, then stopping the irradiation and letting them stand for 5 minutes, repeating this cycle 3 times; then, increasing the temperature to 50°C at a rate of 1.5°C / min, irradiating with infrared light for 3 minutes, then stopping the irradiation and letting them stand for 2 minutes, repeating this cycle multiple times until withering was complete, controlling the total withering time to be 105 minutes. The prepared rose tea suffered significant loss of floral aroma.

[0064] Comparative Example 4 The difference between this comparative example and Example 2 is that the kneading process includes: kneading the withered rose petals without air for 10 minutes, then applying light pressure (15 kPa) for 15 minutes, and then kneading without air for 5 minutes. The cell wall breakage rate is 58%.

[0065] Comparative Example 5 The difference between this comparative example and Example 2 is that the drying process was carried out at a constant temperature of 80°C until the moisture content reached 6.2%. The prepared rose tea suffered significant aroma loss, with a 30% decrease in the honey-sweetness score and a darker liquor color.

[0066] Comparative Example 6 The difference between this comparative example and Example 2 is that Aspergillus niger was added during fermentation at a concentration of 10 mL / 70 kg (spore concentration of 1×10⁻⁶). 6 (CFU / mL). The prepared rose tea had a prominent fruity aroma and a weak rose aroma, with a floral aroma score of 8.2 and a honey-sweet aroma peak area of ​​only 78% of that in Example 2.

[0067] Comparative Example 7 The difference between this comparative example and Example 2 is that the relative humidity was 80% during fermentation. The prepared rose tea had partially dried edges.

[0068] The quality of rose tea prepared in Comparative Examples 1-7 (all rose tea samples were obtained by piling up for two years) was determined in this invention, and the results are shown in Table 2: Table 2. Quality of rose tea prepared in Example 1 and Comparative Examples 1-7

[0069] Table 2 systematically reveals the impact of different processes deviating from the core parameters of this invention on the final product quality. Using the optimal Example 2 as a benchmark (total sensory score 92.8), the defects of each comparative example are quantified: the use of constant-temperature infrared light-assisted withering (Comparative Examples 1 and 2) leads to a decrease in anthocyanin conversion rate and aroma persistence, and a deterioration in liquor color stability (Δa in Comparative Examples 1 and 2). ✽ The percentage decreases rose to 42.9% and 41.1% respectively. Although the conversion rate was slightly higher (72%) when high temperature withering was used in the middle and late stages of withering (Comparative Example 3), the aroma was severely damaged (the floral fragrance score was only 7.0), proving that the "high temperature" approach is not advisable. Insufficient kneading force (Comparative Example 4) directly led to inadequate dissolution of key substrates (anthocyanin dissolution was only 24.8 mg / g), which limited subsequent conversion; Excessive drying temperature (Comparative Example 5) caused severe loss of aroma (aroma persistence 57%). The introduction of exogenous bacteria (Comparative Example 6) altered the flavor profile; although the astringency was reduced, the natural rose aroma was weakened. Insufficient fermentation humidity (Comparative Example 7) led to a comprehensive deterioration of all core indicators, with the lowest overall sensory score (78.0).

[0070] Based on the above analysis, the present invention uses a process chain of "dual-gradient intermittent infrared heating withering - moderate rolling - moisture-controlled fermentation - segmented drying" to prepare rose tea. The parameters in this process chain are a precise synergistic system. Any deviation of any single parameter will disrupt this balance and affect the quality of the rose tea, resulting in a decrease in color stability, aroma richness, astringency, and mellowness of the taste.

[0071] The enzyme activities of β-glucosidase, polyphenol oxidase, and peroxidase in rose raw materials and roses after wilting treatment in Examples 2 and Comparative Examples 1-3 were determined in this invention. The results are shown in Table 3. Table 3. Enzyme activities of β-glucosidase, polyphenol oxidase, and peroxidase in rose raw materials and roses after wilting treatment in Examples 2 and Comparative Examples 1-3.

[0072] Table 3 data directly supports the innovative mechanism of this invention from a biochemical perspective. The data shows that after assisted withering using the specific dual-gradient intermittent infrared heating method of this invention (Example 2), the activities of β-glucosidase, polyphenol oxidase (PPO), and peroxidase (POD) in rose petals all reached peak values, increasing by approximately 87%, 79%, and 146% respectively compared to the raw material. This confirms that intermittent infrared heating can more efficiently and gently activate the endogenous enzyme system. In contrast, continuous irradiation at a constant temperature of 42°C (Comparative Example 1) caused significant thermal inactivation, with enzyme activity significantly lower than in Example 2; while the gentle constant temperature of 38°C (Comparative Example 2) resulted in insufficient activation energy; particularly, the scheme using a high temperature of 50°C (Comparative Example 3) showed the lowest enzyme activity among the three schemes, proving that excessively high temperatures can damage enzyme proteins.

[0073] Therefore, Table 3 shows that the withering process of the present invention is not a simple "heating", but a precise regulation technology targeting the enzyme system characteristics of rose petals. The enzyme activity level that it can achieve is unattainable by existing conventional withering methods. This provides a crucial biochemical dynamic basis for the generation of aroma components and the stable conversion of anthocyanins in subsequent fermentation.

[0074] Experiment Example 1: Optimization Experiment of Kneading Process This experimental example, based on Example 2, investigates the effect of different kneading processes on the quality of rose tea. The kneading process is as follows: Group A: kneading once, first kneading without kneading for 10 minutes, then lightly pressing for 10 minutes (15 kPa), and finally kneading without kneading for 5 minutes.

[0075] Group B: Knead once, first knead for 10 minutes without kneading, then press lightly for 15 minutes (15 kPa), then press heavily for 10 minutes (35 kPa), and finally knead without kneading for 5 minutes.

[0076] Group C: Kneading twice. First kneading: Knead for 10 minutes without kneading, then press lightly for 15 minutes (15 kPa), then press heavily for 10 minutes (35 kPa), and finally knead without kneading for 5 minutes. Second kneading: Press heavily for 12 minutes (45 kPa), then press heavily for 8 minutes (55 kPa), and finally knead without kneading for 3 minutes.

[0077] The results are shown in Table 4: Table 4. Effects of different rolling processes on the quality of rose tea

[0078] Table 4 shows that the samples corresponding to pre-fermentation ester-type catechins are rose petals after kneading, and the samples corresponding to post-fermentation ester-type catechins are rose petals after fermentation. As shown in Table 4, with increasing kneading intensity, the cell contents are released more fully, and the extraction amount of pre-fermentation ester-type catechins increases accordingly, providing a richer substrate for subsequent fermentation conversion. Group B (75.1% cell wall breakage rate) achieved a high ester-type catechin conversion rate of 48.1%, significantly reducing bitterness. Simultaneously, this kneading process also kept the drying breakage rate at a low level (3.0%), resulting in good product integrity. In contrast, Group A (65.2% cell wall breakage rate) had the lowest conversion rate (37.9%) due to insufficient cell wall breakage and inadequate substrate release. Group C (84.8% cell wall breakage rate) had the highest conversion rate (52.3%), but excessive mechanical damage led to the destruction of the petal structure, causing a sharp increase in the drying breakage rate to 7.8%, severely affecting the product form and commercial value. In summary, a cell wall breakage rate of 70-80% (corresponding to the kneading process in Group B) represents the optimal balance between achieving efficient biochemical transformation and maintaining excellent product quality.

[0079] Experiment Example 2: Fermentation Time Optimization Experiment This experiment, based on Example 2, investigated the effects of different fermentation times (2.0 h, 3.5 h, 5.0 h) on the quality of rose tea. The results are shown in Table 5: Table 5. Effects of different fermentation times on the quality of rose tea

[0080] The results showed that too short a fermentation time resulted in a strong astringent taste and a lighter color, while too long a fermentation time led to a noticeable sour and musty taste. Considering the overall color, aroma, and taste, a fermentation time of 3.5 hours was deemed optimal.

[0081] Experiment Example 3: Drying Process Optimization Experiment This experimental example, based on Example 2, investigates the effects of different drying processes on the quality of rose tea.

[0082] The drying method is as follows: Control group: The fermented roses were dried at a constant temperature of 60 ℃ for 2.5 h.

[0083] Experimental group: Fermented roses were subjected to low-temperature shaping and drying at 45 ℃ for 75 min with a wind speed of 1.0 m / s, reducing the moisture content to 19% to fix the color and enzyme activity; then the temperature was raised to 70 ℃ for medium-temperature fragrance enhancement treatment for 18 min with a wind speed of 0.8 m / s to stimulate the sweet honey fragrance, and the petal edges showed color due to the high temperature, turning bright yellow or light gold; then the temperature was lowered to 55 ℃ for slow drying for 50 min, reducing the moisture content to 6.2%, maintaining the integrity of the flower shape, reducing the breakage rate to ≤ 3%.

[0084] The results are shown in Table 6: Table 6. Quality of Rose Tea After Drying by Different Methods

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing rose tea, comprising the steps of withering, rolling, and fermenting rose petals, characterized in that, The withering process includes the following steps: first, irradiate the roses with infrared light at 38±2℃ for 3-5 minutes, then stop the irradiation and let them stand for 3-5 minutes, repeating this process 2-3 times; then, raise the temperature to 42±2℃ at a rate of 1-2℃ / min, irradiate with infrared light for 3-4 minutes, then stop the irradiation and let them stand for 2-3 minutes, repeating this process multiple times until the withering is complete, controlling the total withering time to be 100-110 minutes.

2. The method for preparing rose tea according to claim 1, characterized in that, The withering process includes the following steps: first, irradiate the rose with infrared light at 38±2℃ for 5 minutes, then stop the irradiation and let it stand for 5 minutes, repeating this process 3 times; then, raise the temperature to 42±2℃ at a rate of 1.5℃ / min, irradiate with infrared light for 3 minutes, then stop the irradiation and let it stand for 2 minutes, repeating this process multiple times until the withering is complete, controlling the total withering time to be 105 minutes.

3. The method for preparing rose tea according to claim 1 or 2, characterized in that, The infrared light has a wavelength of 2500-4000 nm and an irradiance of 150-250 μmol / (m²). 2 ·s).

4. The method for preparing rose tea according to any one of claims 1-3, characterized in that, The kneading process includes: first kneading without air for 8-12 minutes, then lightly pressing for 13-17 minutes, then heavily pressing for 8-12 minutes, and finally kneading without air for 3-6 minutes; the pressure difference between the heavy pressing and the light pressing is 12-28 kPa. Preferably, the pressure of the light pressure is 15±3 kPa, and the pressure of the heavy pressure is 35±5 kPa; Preferably, the kneading is performed once.

5. The method for preparing rose tea according to claim 4, characterized in that, The cell wall breakage rate of the roses after kneading is 70-80%.

6. The method for preparing rose tea according to any one of claims 1-5, characterized in that, The preparation method further includes a drying step, which comprises: first drying the fermented roses at 40-45 ℃ until the moisture content is 18-20%; then heating to 65-70 ℃ for 15-20 min; and then cooling to 50-55 ℃ for drying until the moisture content is ≤7%. Preferably, the drying process further includes a stacking step, wherein the stacking temperature is 18-20°C and the stacking time is more than 2 years.

7. The method for preparing rose tea according to any one of claims 1-6, characterized in that, The fermentation temperature is 28-32 ℃, the relative humidity is 90-95%, and the time is 3.0-4.0 h; Preferably, the material thickness during fermentation is 25-30 cm.

8. The method for preparing rose tea according to claim 7, characterized in that, During fermentation, the mixture is stirred every 20-40 minutes.

9. The method for preparing rose tea according to any one of claims 1-8, characterized in that, After kneading, the rose petals are broken up by vibration and oxygen is added to prevent anaerobic rancidity.

10. Rose tea prepared by the method according to any one of claims 1-9.

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