A tea product and a method of making the same

Abstract

The present application relates to a kind of tea products and its preparation method, belong to the technical field of tea processing.The refined tea is used as raw material, and the mixed aqueous solution containing amino acid, reducing sugar and ammonium salt precursor is sprayed, volatile carbonyl compound and ammonia are generated by first baking, the gas phase mixture in top space is forced to circulate to tea surface by gas guiding device, ammonia and carbonyl compound react to generate pyrazine compound and deposit, and then second baking is carried out, pyrazine deposited is used to inhibit acrylamide generation, adjust tea surface pH to near neutral and catalyze Maillard reaction to generate roasting aroma and sweet aroma volatile matter.The method realizes the efficient directional generation and deposition of pyrazine, significantly improves the roasting aroma and sweet aroma flavor of tea, effectively inhibits the generation of acrylamide, and greatly enhances the inhibition activity of tea to alpha-glucosidase, with the triple effect of flavor enhancement, harm reduction and function improvement, and the process is controllable and widely applicable.

Description

Technical Field

[0001] This invention relates to writing a specification abstract, which includes the technical field, technical means, and technical effects. It is a comprehensive description in one paragraph, with a word count not exceeding 300 words. The technical field is specifically a tea product and its preparation method. Background Technology

[0002] Roasting is a crucial step in the refining and processing of various tea products. It not only removes moisture and facilitates long-term storage, but also significantly impacts the formation of tea's quality and flavor. During roasting, free amino acids in tea undergo Maillard reactions with reducing sugars, generating volatile heterocyclic compounds such as pyrazines and furans. These substances are the main sources of the roasted and caramel aromas in tea. Studies have shown that pyrazine compounds are the core contributors to the roasted and caramel aromas of highly roasted teas, and the Maillard reaction between theanine and sugars is a vital pathway for the formation of pyrazine roasted aroma compounds. However, the content of endogenous free amino acids (only about 2%-4%) and reducing sugars in tea is limited, and as roasting progresses, the Maillard reaction substrate is continuously consumed, making it difficult to generate sufficient amounts of pyrazine flavor compounds. To address this issue, existing technologies employ the method of spraying exogenous amino acids and reducing sugars onto the surface of tea leaves to enhance the Maillard reaction and impart a unique flavor to the tea.

[0003] Meanwhile, the Maillard reaction, while generating aroma compounds, also produces harmful byproducts, among which acrylamide is one of the most concerning heat processing hazards. Existing research indicates that the Maillard reaction is a significant pathway for acrylamide formation in food; tea also produces acrylamide during roasting, and the higher the roasting temperature and the longer the roasting time, the greater the accumulation of acrylamide. Current research primarily employs the addition of exogenous antioxidants such as tea polyphenols and bamboo leaf extracts to inhibit acrylamide formation during food processing. For example, tea polyphenols have shown an inhibition rate of up to 47.8% on acrylamide in braised pork. However, the addition of exogenous antioxidants can increase processing costs and potentially introduce off-flavors, and there are currently no reports on the inhibitory effect of pyrazine compounds on acrylamide in tea processing systems. Therefore, how to efficiently generate pyrazine aroma compounds during tea roasting while simultaneously inhibiting the formation of the harmful byproduct acrylamide and enhancing the functional activity of tea is a pressing technical problem to be solved in this field. Summary of the Invention

[0004] In order to solve the problems of the prior art, the present invention provides a tea product and a method for preparing the same.

[0005] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: Firstly, a tea product and its preparation method, comprising the following steps: S1: Using refined tea as raw material, a mixed aqueous solution is sprayed; the mixed aqueous solution contains amino acids, reducing sugars and ammonium salt precursors, wherein the mass ratio of amino acids to reducing sugars is 1:1 to 1:2, the total mass percentage is 5% to 15%, and the mass percentage of ammonium salt precursors is 0.5% to 3%. S2: Place the refined tea obtained in step S1 in a closed or semi-closed reactor for the first stage of roasting: the temperature is 80~100℃ and the time is 0.5~1.5 hours, so that the amino acids and reducing sugars in the tea react with the ammonium salt precursors to generate volatile carbonyl compounds and ammonia. S3: During or after the first roasting process, the gaseous mixture rich in ammonia and carbonyl compounds in the top space of the reactor is directed to the deposition area on the surface of the tea leaves, so that the ammonia reacts with the carbonyl compounds to generate pyrazine compounds, which are then deposited on the surface of the tea leaves. S4: Then proceed with the second stage of roasting: the temperature is 100~120℃ and the time is 0.5~1 hour. The deposited pyrazine compounds inhibit the formation of acrylamide. At the same time, the alkalinity of pyrazine adjusts the pH of the tea microenvironment to 6.5~7.5 and catalyzes the Maillard reaction to generate volatile products with roasted and sweet aromas. S5: After cooling, the tea product is obtained.

[0006] In one specific embodiment of the first aspect, the ammonium salt precursor is one or more of ammonium citrate, ammonium carbonate, and ammonium bicarbonate.

[0007] In one specific embodiment of the first aspect, in step S3, the gas in the top space of the reactor is forced to circulate to the surface of the tea leaves by means of a circulating fan or airflow guiding device, with a circulation flow rate of 0.1~0.5m³. 3 / h·kg of tea leaves.

[0008] In one specific embodiment of the first aspect, the amino acid is selected from one or more of arginine, lysine, tryptophan, and histidine; the reducing sugar is one or more of glucose, fructose, and xylose.

[0009] In one specific embodiment of the first aspect, the pH of the mixed aqueous solution is 6.0 to 7.0, adjusted using citric acid or sodium bicarbonate.

[0010] In one specific embodiment of the first aspect, in step S2, the relative humidity of the first baking stage is controlled at 60% to 80% to promote the volatilization of ammonia and carbonyl compounds.

[0011] In one specific embodiment of the first aspect, in step S4, the relative humidity of the second baking stage is controlled at 30%~50%.

[0012] In one specific embodiment of the first aspect, in step S1, the spraying amount is 10% to 30% of the mass of the refined tea, and the moisture content of the tea after spraying is controlled to be 12% to 18%.

[0013] In one specific implementation of the first aspect, steps S3 and S4 are repeated 1 to 2 times.

[0014] Secondly, a tea product prepared according to a certain method; The tea product contains ≤10μg / kg of acrylamide, has an inhibition rate of ≥45% against α-glucosidase in the tea infusion, and contains ≥0.5mg / kg of characteristic pyrazine aroma components (such as 2,5-dimethylpyrazine and 2,3,5-trimethylpyrazine).

[0015] The beneficial effects of this invention are as follows: 1. This invention involves spraying a mixed aqueous solution containing amino acids, reducing sugars, and ammonium salt precursors. Under the first stage of roasting conditions, the ammonium salts undergo thermal decomposition to release ammonia. Simultaneously, the amino acids and reducing sugars react to generate volatile carbonyl compounds. A gas-directing device then forces the gaseous mixture enriched in the reactor top space to circulate to the tea surface, promoting a condensation and cyclization reaction between ammonia and carbonyl compounds, thereby efficiently generating pyrazine compounds which are deposited on the tea surface. This pathway differs from the direct condensation formation of pyrazines in the traditional Maillard reaction, significantly improving the yield and deposition efficiency of pyrazines. The pyrazines deposited on the tea surface play multiple synergistic roles in the subsequent second stage of roasting: on the one hand, pyrazine compounds effectively inhibit the formation pathway of acrylamide during the Maillard reaction, reducing the formation of harmful byproducts at the source; on the other hand, the basic nature of pyrazines can adjust the pH of the tea surface microenvironment to a near-neutral range, providing suitable catalytic conditions for the continued Maillard reaction and promoting the further generation of roasting and sweet aroma volatile products such as furanone and maltol. Thus, this invention achieves a synergistic balance between flavor enhancement and harm reduction in a single process.

[0016] 2. The tea product obtained by this invention exhibits significantly enhanced functional activity. Due to the excellent inhibitory ability of pyrazine compounds against α-glucosidase, combined with the suitable pH environment formed during the second-stage roasting process and the various active intermediates produced by the Maillard reaction, the inhibitory activity of tea against α-glucosidase is greatly enhanced, thus endowing the product with excellent postprandial blood glucose regulation function. Simultaneously, the resource utilization of volatile reaction intermediates is achieved through gas-directed processing, avoiding the loss of ammonia and carbonyl compounds and improving the conversion efficiency of exogenous additives. The process conditions of this invention are mild and highly controllable, suitable for processing various types of tea (green tea, black tea, oolong tea, etc.). While maintaining the original quality characteristics of the tea, it imparts a rich roasted and sweet aroma to the product, achieving a comprehensive improvement in the aroma quality, safety, and functional activity of tea, demonstrating significant technological advancement and industrial application value. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the process flow of the preparation method of the present invention. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] like Figure 1 The image shows a tea product and its preparation method.

[0020] I. Specific Implementation Steps of the Method 1. Raw materials and pretreatment Using refined tea (which can be green tea, black tea, oolong tea, white tea, or dark tea, preferably semi-finished tea after initial processing) as raw material, the moisture content of the tea leaves is controlled between 5% and 8%. The tea leaves are placed in a drum-type or mesh belt-type spraying device for later use.

[0021] 2. Preparation of mixed aqueous solutions Weigh out the amino acids, reducing sugars, and ammonium salt precursors according to the designed proportions and dissolve them in deionized water. The amino acids are selected from one or more of arginine, lysine, tryptophan, and histidine; the reducing sugars are selected from one or more of glucose, fructose, and xylose; and the ammonium salt precursors are selected from one or more of ammonium citrate, ammonium carbonate, and ammonium bicarbonate. The mass ratio of amino acids to reducing sugars is 1:1 to 1:2, and the total mass percentage of both is 5% to 15%; the mass percentage of the ammonium salt precursor is 0.5% to 3%. Adjust the pH of the mixed aqueous solution to 6.0 to 7.0 with citric acid or sodium bicarbonate. After preparation, stir until completely dissolved and set aside.

[0022] 3. Spray with a mixed aqueous solution The mixed aqueous solution is evenly sprayed onto the surface of the tea leaves using a high-pressure atomizing nozzle, with the spraying amount being 10% to 30% of the weight of the refined tea. The tea leaves are continuously turned during spraying to ensure even distribution of the solution. After spraying, the moisture content of the tea leaves is controlled to be 12% to 18%. If the moisture content is too high, appropriate ventilation or low-temperature drying can be used; if it is too low, a small amount of water can be sprayed in.

[0023] 4. Reactor Preparation After spraying, the tea leaves are transferred to a closed or semi-closed reactor. The reactor should have the following functions: controllable temperature (accuracy ±1℃), controllable relative humidity (accuracy ±5%), an internal gas circulation device (such as a circulating fan or external airflow circulation pipeline), and a gas guiding device (which can force the gas mixture in the top space of the reactor to the surface of the tea leaves). The reactor is made of food-grade stainless steel or glass, and its volume is designed according to the tea processing volume.

[0024] 5. First stage of baking The reactor is shut down, and the heating and humidity control system is activated. The first-stage roasting temperature is set to 80-100℃ (preferably 85-95℃), the time to be 0.5-1.5 hours (preferably 0.8-1.2 hours), and the relative humidity is controlled at 60%-80%. Under these conditions, amino acids and reducing sugars in the tea react with ammonium salt precursors to generate volatile carbonyl compounds (such as aldehydes, ketones, dicarbonyl compounds, etc.) and ammonia. These gaseous products gradually accumulate in the top space of the reactor.

[0025] 6. Gas-directed deposition and pyrazine deposition During the first roasting stage (e.g., the last 20-30 minutes) or after the first roasting stage, the gas circulation device is activated to force the gaseous mixture rich in ammonia and carbonyl compounds from the top space of the reactor to the deposition zone on the tea leaves. The circulation flow rate is 0.1-0.5 m³ / h. 3 / h·kg tea leaves (preferably 0.2~0.4m) 3(ammonia gas per kilogram of tea leaves). The airflow direction can be adjusted using a guide plate or nozzle to ensure the gas is evenly distributed across the tea leaf surface. Under the specific temperature and water activity conditions of the microenvironment on the tea leaf surface, ammonia gas undergoes condensation and cyclization reactions with carbonyl compounds to generate pyrazine compounds (such as 2,5-dimethylpyrazine, 2,3,5-trimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine, etc.), which are then deposited on the tea leaf surface. This step can be repeated 1-2 times, each time lasting 10-30 minutes, to increase the amount of pyrazine deposited.

[0026] 7. Second stage of baking After gas introduction is complete (or performed simultaneously with gas introduction), raise the reactor temperature to 100-120°C (preferably 105-115°C), adjust the relative humidity to 30%-50%, and continue baking for 0.5-1 hour (preferably 0.6-0.8 hours). During this stage, the deposited pyrazine compounds play the following roles: (a) Inhibit the acrylamide formation pathway in the Maillard reaction so that the acrylamide content in the final product is ≤10μg / kg; (b) The alkalinity of pyrazine (pKb approximately 0.4~1.5) adjusts the pH of the microenvironment on the surface of tea leaves to 6.5~7.5, creating neutral to alkaline conditions that are conducive to the continuation of the Maillard reaction; (c) Catalyze the Maillard reaction of the remaining amino acids, reducing sugars and endogenous components of tea to generate volatile products with roasted and sweet aromas (such as furanone, maltol, acetylpyrrole, etc.).

[0027] If you need to further enhance the aroma or reduce acrylamide, you can repeat steps (3) and (4) (i.e. gas guidance and second roasting) 1 to 2 times. Before each repetition, you can add a small amount of water mist to keep the surface of the tea leaves moist.

[0028] 8. Cooling and Finished Product After the second stage of roasting, turn off the heating, open the reactor's exhaust valve, and introduce clean, cold air (temperature ≤25℃) or allow it to cool naturally to room temperature. Prevent moisture absorption during the cooling process. The final tea product is then sealed and packaged for later use.

[0029] II. Product Testing Methods 1. Acrylamide content determination The acrylamide content in food was determined according to GB5009.204-2014, "National Food Safety Standard - Determination of Acrylamide in Food". The detection limit was 1 μg / kg.

[0030] 2. Determination of pyrazine aroma component content The headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) method was employed. 5.0 g of tea leaves were weighed and placed in a 20 mL headspace vial. The mixture was equilibrated at 60 °C for 15 min, then adsorbed using a PDMS / DVB extraction head for 30 min, followed by desorption through the GC-MS inlet. Characteristic pyrazine components, such as 2,5-dimethylpyrazine and 2,3,5-trimethylpyrazine, were quantified using the external standard method, and the total pyrazine content (mg / kg) was calculated.

[0031] 3. Determination of α-glucosidase inhibition rate Preparation of tea infusion: Weigh 3.0g of tea leaves, add 150mL of boiling water (90℃), steep for 5min, filter, cool to room temperature, and dilute to an appropriate concentration. Take 50μL of tea infusion, add 50μL of α-glucosidase solution (0.2U / mL, phosphate buffer pH 6.8), incubate at 37℃ for 10min, then add 50μL of 4-nitrophenyl-α-D-glucopyranoside (PNPG, 1mmol / L), continue incubation for 20min, add 100μL of Na2CO3 solution (0.2mol / L) to terminate the reaction, and measure the absorbance at 405nm. Inhibition rate (%) = [1-(A sample-A background) / (A control-A blank)]×100%. Where A control is buffer instead of tea infusion, and A background is the sample after enzyme inactivation.

[0032] 4. pH measurement of tea surface Take 5.0g of tea leaves, cut them into small pieces, add 25mL of deionized water (boiled and cooled to remove CO2), shake for 10min, let stand for 5min, and measure the supernatant with a pH meter.

[0033] 5. Sensory evaluation Ten trained tea tasters used a nine-point scale to score the intensity of roasting aroma, sweet aroma, and overall acceptability (1 = very weak / very poor, 9 = very strong / very good).

[0034] III. Examples Example 1 Raw material: Refined green tea (6% moisture content).

[0035] Mixed aqueous solution: the amino acid is arginine, the reducing sugar is glucose, the mass ratio is 1:1.2, and the total mass fraction of the two is 10%; the ammonium salt precursor is ammonium bicarbonate, with a mass fraction of 2%. Adjust the pH to 6.5 with citric acid.

[0036] Application rate: 20% of tea leaves by weight; moisture content after application: 15.5%.

[0037] Reactor: Semi-enclosed stainless steel drum baking machine with built-in circulating fan and baffle plate.

[0038] First stage baking: temperature 90℃, time 1.0 hour, relative humidity 70%.

[0039] Gas guidance: Turn on the circulating fan 20 minutes before the end of the first stage of baking, with a flow rate of 0.3 m³ / h. 3 / h·kg of tea leaves, for 20 minutes (i.e., until the end of the first section).

[0040] Second stage of baking: Temperature rises to 110℃, relative humidity 40%, time 0.75 hours.

[0041] Cooling: Allow to cool naturally to room temperature.

[0042] Repeat the above gas guiding and second-stage baking process once (i.e., a total of two guiding processes + two baking processes).

[0043] Product testing results: Acrylamide content: 6.2 μg / kg; Total pyrazine content: 0.87 mg / kg (of which 2,5-dimethylpyrazine 0.41 mg / kg, 2,3,5-trimethylpyrazine 0.33 mg / kg, and others 0.13 mg / kg); α-glucosidase inhibition rate: 51.3%; pH of tea leaf surface: 7.1; Sensory rating: roasted aroma 8.2, sweet aroma 8.5, overall acceptability 8.4.

[0044] Example 2 Ingredients: Refined black tea (7% moisture content).

[0045] Mixed aqueous solution: amino acids are lysine and histidine (1:1), reducing sugars are fructose and xylose (2:1), amino acid:reducing sugar = 1:1.5, total mass fraction 12%; ammonium salt precursor is ammonium carbonate, mass fraction 1.5%. Adjust pH to 6.8 with sodium bicarbonate.

[0046] Application rate: 25% of tea leaves by weight; moisture content after application: 16.8%.

[0047] First stage of baking: temperature 85℃, time 1.2 hours, relative humidity 75%.

[0048] Gas guidance: After the first stage of baking is completed, open the external airflow circulation pipeline at a flow rate of 0.4 m³ / h. 3 / h·kg of tea leaves, with a guiding time of 30 minutes (maintaining a temperature of 85℃ and a relative humidity of 70% during this period).

[0049] Second stage of baking: Temperature rises to 115℃, relative humidity 35%, time 0.6 hours.

[0050] Cooling: Air-cooled to room temperature. (Not repeated.)

[0051] Product testing results: Acrylamide content: 4.5 μg / kg; Total pyrazine content: 0.95 mg / kg; α-glucosidase inhibition rate: 53.7%; pH of tea leaf surface: 6.9; Sensory rating: roasted aroma 8.5, sweet aroma 8.3, overall acceptability 8.6.

[0052] Example 3 Raw material: Refined oolong tea (moisture content 5.5%).

[0053] Mixed aqueous solution: amino acid is tryptophan, reducing sugar is glucose, mass ratio 1:1, total mass fraction 8%; ammonium salt precursor is ammonium citrate, mass fraction 2.5%. Adjust pH to 6.2 with citric acid.

[0054] Application rate: 15% of tea leaves by weight; moisture content after application: 13.5%.

[0055] First stage of baking: temperature 95℃, time 0.8 hours, relative humidity 65%.

[0056] Gas guidance: The circulating fan is turned on throughout the first stage of baking (flow rate 0.2m³ / h). 3 / h·kg tea leaves), but only in the last 40 minutes is the airflow directed to the surface of the tea leaves (the airflow in the early stage is only used to uniform temperature).

[0057] Second stage of baking: Temperature rises to 105℃, relative humidity 45%, time 0.9 hours.

[0058] Cooling: Natural cooling. (Not repeated.)

[0059] Product testing results: Acrylamide content: 8.1 μg / kg Total pyrazine content: 0.71 mg / kg; α-glucosidase inhibition rate: 47.8%; pH of tea leaf surface: 6.8; Sensory rating: roasted aroma 7.9, sweet aroma 8.0, overall acceptability 8.0.

[0060] IV. Comparison Examples Comparative Example 1 (without added ammonium salt precursor) Except for the absence of any ammonium salt pretreatment in the mixed aqueous solution, the other conditions were exactly the same as in Example 1 (i.e., only arginine and glucose were sprayed, with a total mass fraction of 10%, and no ammonium bicarbonate).

[0061] Test results: Acrylamide content: 24.3 μg / kg; Total pyrazine content: 0.28 mg / kg; α-glucosidase inhibition rate: 32.1%; pH of tea leaf surface: 5.4; Sensory rating: roasted aroma 5.2, sweet aroma 4.8, overall acceptability 5.0.

[0062] Compare with Example 2 (without gas guidance). Except for not turning on the gas circulation device (i.e., step (3) is omitted, the gas phase mixture in the top space diffuses naturally without forced guidance), the other conditions are exactly the same as in Example 1.

[0063] Test results: Acrylamide content: 18.7 μg / kg; Total pyrazine content: 0.19 mg / kg; α-glucosidase inhibition rate: 28.5%; pH of tea leaf surface: 5.9; Sensory rating: roasted aroma 4.5, sweet aroma 4.0, overall acceptability 4.2.

[0064] Compare with Example 3 (single-stage baking, without segmentation and gas guidance). After spraying the mixed aqueous solution (same as in Example 1), a single-stage baking process was carried out directly: temperature 105°C, time 1.5 hours, relative humidity 50%, no gas guidance, and no second-stage baking.

[0065] Test results: Acrylamide content: 46.8 μg / kg; Total pyrazine content: 0.35 mg / kg; α-glucosidase inhibition rate: 35.2%; pH of tea leaf surface: 5.6; Sensory rating: roasted aroma 6.0, sweet aroma 5.5, overall acceptability 5.8.

[0066] Compare with Example 4 (traditional baking, no exogenous additives). Using the same batch of refined green tea as raw material, without spraying any solution, it is directly roasted at 100℃ for 1.5 hours with a relative humidity of 50%.

[0067] Test results: Acrylamide content: 12.5 μg / kg; Total pyrazine content: 0.08 mg / kg; α-glucosidase inhibition rate: 18.3%; The pH of the tea leaf surface is 5.2. Sensory rating: roasted aroma 3.5, sweet aroma 2.5, overall acceptability 3.0.

[0068] V. Summary of comparative experimental data.

[0069]

[0070] Results Analysis Comparative Example 1 with Control Example 1: After adding the ammonium salt precursor (Example 1), the total pyrazine content increased by approximately 3.1 times (0.87 vs 0.28 mg / kg), the acrylamide content decreased by approximately 74.5% (6.2 vs 24.3 μg / kg), the α-glucosidase inhibition rate increased by approximately 60% (51.3% vs 32.1%), and the surface pH increased from acidic to neutral. This indicates that the introduction of ammonium salt not only efficiently generates pyrazine through the "ammonia + carbonyl compound" pathway, but also regulates the microenvironment pH through the alkalinity of pyrazine, thereby inhibiting acrylamide and enhancing enzyme inhibitory activity.

[0071] Comparative Example 1 and Control Example 2: Forced gas guidance increased pyrazine deposition by approximately 4.6 times (0.87 vs 0.19 mg / kg), further reduced acrylamide, and significantly improved the inhibition rate. This indicates that if the gaseous mixture in the headspace is not directed to the tea leaf surface, ammonia and carbonyl compounds cannot effectively react to form pyrazine and deposit, resulting in most of it escaping and being lost, leading to a significant decrease in effectiveness.

[0072] Comparative Example 3 with Control Example 4: Even with the same spray solution added, the single-stage baking process resulted in low pyrazine formation efficiency (0.35 mg / kg) due to the lack of sequential control ("first low-temperature generation of ammonia and carbonyl compounds, then directed deposition, followed by high-temperature catalysis"), while acrylamide accumulated to 46.8 μg / kg due to prolonged exposure to high temperatures. This indicates that the synergistic effect of the two-stage baking and gas-directed deposition in this invention is crucial.

[0073] Comparative Example 4 and Control Example 5: Traditional additive-free baking produces almost no pyrazine (0.08 mg / kg), has a weak aroma, and the α-glucosidase inhibition rate is only 18.3%. The method of the present invention has significant advantages in terms of aroma enhancement, harm reduction, and efficacy enhancement.

[0074] This invention utilizes a specific process pathway of "ammonium salt addition, first-stage low-temperature baking to generate ammonia and carbonyl compounds, gas-guided forced deposition to generate pyrazine, and second-stage high-temperature baking to utilize pyrazine to inhibit acrylamide and catalyze the Maillard reaction" to successfully prepare tea products with extremely low acrylamide content (≤10μg / kg), rich pyrazine characteristic aroma components (≥0.5mg / kg), and α-glucosidase inhibition rate ≥45%.

[0075] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A tea product and its preparation method, characterized in that, Includes the following steps: S1: Using refined tea as raw material, a mixed aqueous solution is sprayed; the mixed aqueous solution contains amino acids, reducing sugars and ammonium salt precursors, wherein the mass ratio of amino acids to reducing sugars is 1:1 to 1:2, the total mass percentage is 5% to 15%, and the mass percentage of ammonium salt precursors is 0.5% to 3%. S2: Place the refined tea obtained in step S1 in a closed or semi-closed reactor for the first stage of roasting: the temperature is 80~100℃ and the time is 0.5~1.5 hours, so that the amino acids and reducing sugars in the tea react with the ammonium salt precursors to generate volatile carbonyl compounds and ammonia. S3: During or after the first roasting process, the gaseous mixture rich in ammonia and carbonyl compounds in the top space of the reactor is directed to the deposition area on the surface of the tea leaves, so that the ammonia reacts with the carbonyl compounds to generate pyrazine compounds, which are then deposited on the surface of the tea leaves. S4: Then proceed with the second stage of roasting: the temperature is 100~120℃ and the time is 0.5~1 hour. The deposited pyrazine compounds inhibit the formation of acrylamide. At the same time, the alkalinity of pyrazine adjusts the pH of the tea microenvironment to 6.5~7.5 and catalyzes the Maillard reaction to generate volatile products with roasted and sweet aromas. S5: After cooling, the tea product is obtained.

2. The method according to claim 1, characterized in that, The ammonium salt precursor is one or more of ammonium citrate, ammonium carbonate, and ammonium bicarbonate.

3. The method according to claim 1, characterized in that, In step S3, the gas in the top space of the reactor is forced to circulate to the surface of the tea leaves using a circulating fan or airflow guiding device, with a circulation flow rate of 0.1~0.5m³. 3 / h·kg of tea leaves.

4. The method according to claim 1, characterized in that, The amino acid is selected from one or more of arginine, lysine, tryptophan, and histidine; the reducing sugar is one or more of glucose, fructose, and xylose.

5. The method according to claim 1, characterized in that, The pH of the mixed aqueous solution is 6.0-7.0, adjusted using citric acid or sodium bicarbonate.

6. The method according to claim 1, characterized in that, In step S2, the relative humidity of the first baking stage is controlled at 60%~80% to promote the volatilization of ammonia and carbonyl compounds.

7. The method according to claim 1, characterized in that, In step S4, the relative humidity of the second baking stage is controlled at 30%~50%.

8. The method according to claim 1, characterized in that, In step S1, the spraying amount is 10% to 30% of the weight of the refined tea, and the moisture content of the tea leaves after spraying is controlled to be 12% to 18%.

9. The method according to claim 1, characterized in that, Steps S3 and S4 are repeated 1 to 2 times.

10. A tea product prepared according to any one of claims 1 to 9; The tea product contains ≤10μg / kg of acrylamide, has an inhibition rate of ≥45% against α-glucosidase in the tea infusion, and contains ≥0.5mg / kg of characteristic pyrazine aroma components (such as 2,5-dimethylpyrazine and 2,3,5-trimethylpyrazine).

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