A processing technology for tea leaves with low caffeine content

Abstract

The present invention relates to a processing technology for tea leaves with low caffeine content, and belongs to the technical field of tea leaf processing. The present invention discloses a processing technology for tea leaves with low caffeine content, and the specific process steps are as follows: (1) withering fresh tea leaves to form withered leaves; (2) putting the withered leaves into distilled water to heat up and soak, then adding modified montmorillonite to wait for it to be dispersed in water for adsorption, cooling and cleaning; (3) rolling the treated tea leaves into strips; (4) then drying, extracting aroma, and refining to obtain tea leaves with low caffeine content. The present invention uses modified montmorillonite to effectively absorb caffeine in tea leaves, and does not reduce tea polyphenols, amino acids and other substances in the tea leaves. At the same time, dodecyl dimethyl benzyl ammonium chloride is used to modify montmorillonite to improve the adsorption efficiency of caffeine. Therefore, the method can prepare tea leaves with good appearance and strong aroma and low caffeine content.

Description

Technical Field

[0001] The invention belongs to the technical field of tea processing and relates to a processing technology for tea with low caffeine content. Background Art

[0002] Tea is one of the most popular beverages in the world, and it has many physiological effects, such as anti-oxidation, anti-cancer, anti-inflammatory, anti-viral, etc. In addition, tea contains 1% to 5% caffeine, which can relieve fatigue, stimulate central nervous system excitement, and act as a diuretic. However, excessive intake of foods containing caffeine can lead to risks such as sleep disorders, increased blood pressure, and miscarriage. Therefore, research on decaffeination of tea has attracted more and more attention.

[0003] The key to deep processing of low-caffeine tea products is to efficiently remove caffeine from tea leaves while retaining other active ingredients (such as catechins) and flavor components (aroma and taste components). At present, hot water extraction, supercritical CO2 extraction, solvent extraction, adsorption separation, microbial and enzyme degradation, and cultivation of low-caffeine tea trees have been used to remove or reduce the caffeine content in tea leaves. Supercritical carbon dioxide extraction is acidic. During extraction, chlorophyll becomes pheophytin, so the green color fades, which seriously affects the green appearance of green tea. Hot water extraction: Fresh leaves are treated with high-temperature hot water for a short time, which will cause the water-soluble substances (amino acids, etc.) in the tea leaves to leach out, resulting in a decrease in the quality of other components in the tea leaves. Decaffeinated tea leaves are further processed into dry tea leaves, which need to be steam-fixed and rolled and dried, which will cause further loss of other nutrients such as the flavor and color of the tea leaves. Solvent extraction increases impurities, which are difficult to separate, and is not conducive to the dissolution of catechins, reducing the extraction rate of catechins and causing the loss of aromatic substances in green tea. Summary of the invention

[0004] The present invention relates to a processing technology for tea leaves with low caffeine content, and belongs to the technical field of tea leaf processing. The present invention discloses a processing technology for tea leaves with low caffeine content, and the specific process steps are as follows: (1) withering fresh tea leaves to form withered leaves; (2) putting the withered leaves into distilled water to heat up and soak, then adding modified montmorillonite to wait for it to be dispersed in water for adsorption, cooling and cleaning; (3) rolling the treated tea leaves into strips; (4) then drying, extracting aroma, and refining to obtain tea leaves with low caffeine content. The present invention uses modified montmorillonite to effectively absorb caffeine in tea leaves, and does not reduce tea polyphenols, amino acids and other substances in the tea leaves. At the same time, dodecyl dimethyl benzyl ammonium chloride is used to modify montmorillonite to improve the adsorption efficiency of caffeine. Therefore, the method can prepare tea leaves with good appearance and strong aroma and low caffeine content.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A processing technology for tea leaves with low caffeine content, the processing technology for tea leaves with low caffeine content is as follows:

[0007] (1) withering the freshly picked tea leaves to form withered leaves;

[0008] (2) The withered leaves are placed in distilled water to be heated and soaked, and then modified montmorillonite is added, and after the montmorillonite is dispersed in the water for adsorption, the temperature is cooled to room temperature, and the pretreated tea leaves are washed with water;

[0009] (3) pre-treating the tea leaves and rolling them into strips;

[0010] (4) The tea is then fried and dried, and then moved to an aroma machine for further drying and aroma enhancement. After refining, low-caffeine tea can be obtained.

[0011] Furthermore, the specific method of withering treatment in step (1) is: spread the fresh tea leaves at a temperature of 15-25°C and a relative humidity of 50% with a thickness of 10-15 cm, and then leave them for 6-8 hours, and turn the leaves every 2 hours.

[0012] Furthermore, in step (2), the solid-liquid ratio of the total mass of the withered leaves and the modified montmorillonite to distilled water is 10-25:1-2 g / L, wherein the mass ratio of the withered leaves to the modified montmorillonite is 1:1-2.

[0013] Furthermore, the heating in step (2) refers to heating to 40-45° C., the soaking time is 3-5 hours, and the adsorption time is 2-3 hours.

[0014] Furthermore, the preparation method of the modified montmorillonite in step (2) is: montmorillonite is stirred and mixed with deionized water, then dodecyl dimethyl benzyl ammonium chloride is added and stirred continuously, the precipitate is separated by centrifugation and washed with deionized water, deionized water is added and stirred, and the mixture is placed in a freezer, vacuum freeze-dried, and ground and sieved to obtain the modified montmorillonite.

[0015] Furthermore, the mass ratio of the montmorillonite, deionized water and dodecyl dimethyl benzyl ammonium chloride is 1:20-30:0.2-0.5, the stirring and mixing time is 2-3 hours, and the speed and time of the centrifugal separation are 3000-4000 r / min and 10-20 min, respectively.

[0016] Furthermore, the freeze-drying time and temperature are 60-70h and -20±5°C, respectively; the sieving mesh size is 150-250 mesh; and the mass ratio of the precipitate to deionized water is 1:1.

[0017] Furthermore, the strip forming rate of the strips in the step (3) is 65-70%.

[0018] Furthermore, the moisture content of the tea leaves dried in step (4) is 30-35%, and the moisture content of the tea leaves dried in oven is 3-5%.

[0019] Furthermore, the refining in step (4) specifically includes sieving, air separation, and re-firing, wherein the mesh size of the sieving is 60-80 meshes, and the temperature of the re-firing is 100-120°C.

[0020] Beneficial effects of the present invention:

[0021] 1. The calcium ions released from the middle layer of montmorillonite react with the oxalate ions in green tea to form calcium oxalate precipitates. Through the interlayer effect, Na, K, Mg or NH4 ions replace the calcium ions between the montmorillonite layers, thereby inhibiting the precipitation of calcium oxalate in decaffeinated green tea. The ion-exchanged montmorillonite can separate the caffeine in green tea and maintain the appearance quality of green tea.

[0022] 2. The structure of the dodecyl dimethyl benzyl ammonium chloride molecule enables it to form an organic functional group on the surface of montmorillonite, increasing the affinity for adsorbing caffeine molecules, thereby improving the adsorption capacity and efficiency. At the same time, it can adjust the adsorption characteristics of montmorillonite, making it more selective for caffeine molecules. DETAILED DESCRIPTION

[0023] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with embodiments.

[0024] Example 1

[0025] A processing technology for tea leaves with low caffeine content, the processing technology for tea leaves with low caffeine content is as follows:

[0026] (1) withering the freshly picked tea leaves to form withered leaves;

[0027] (2) The withered leaves are placed in distilled water to be heated and soaked, and then modified montmorillonite is added, and after the montmorillonite is dispersed in the water for adsorption, the temperature is cooled to room temperature, and the pretreated tea leaves are washed with water;

[0028] (3) pre-treating the tea leaves and rolling them into strips;

[0029] (4) The tea is then fried and dried, and then moved to an aroma machine for further drying and aroma enhancement. After refining, low-caffeine tea can be obtained.

[0030] The specific method of withering treatment in step (1) is: spread the fresh tea leaves at a temperature of 15° C. and a relative humidity of 50% to a thickness of 10 cm, then leave them for 6 hours, and turn the leaves every 2 hours.

[0031] In the step (2), the solid-liquid ratio of the total mass of the withered leaves and the modified montmorillonite to distilled water is 10:1 g / L, wherein the mass ratio of the withered leaves to the modified montmorillonite is 1:1.

[0032] The heating in step (2) refers to heating to 40° C., the soaking time is 3 hours, and the adsorption time is 2 hours.

[0033] The preparation method of the modified montmorillonite in step (2) is as follows: montmorillonite is stirred and mixed with deionized water, dodecyl dimethyl benzyl ammonium chloride is added and stirred continuously, the precipitate is separated by centrifugation, washed with deionized water, deionized water is added and stirred, and then frozen, vacuum freeze-dried, and ground and sieved to obtain the modified montmorillonite.

[0034] The mass ratio of the montmorillonite, deionized water and dodecyl dimethyl benzyl ammonium chloride is 1:20:0.2, the stirring and mixing time is 2 hours, and the speed and time of the centrifugal separation are 3000 r / min and 10 minutes respectively.

[0035] The freeze-drying time and temperature are 60 h and -25°C respectively, the sieving mesh size is 150 meshes, and the mass ratio of the precipitate to deionized water is 1:1.

[0036] The strip forming rate of the kneaded strips in the step (3) is 65%.

[0037] The moisture content of the tea leaves dried in step (4) is 30%, and the moisture content of the oven-dried tea leaves is 3%.

[0038] The refining in step (4) specifically includes sieving, air separation, and re-firing, wherein the mesh size of the sieving is 60 meshes and the temperature of the re-firing is 100°C.

[0039] The montmorillonite is purchased from: Montmorillonite-Bochuan / 1302-78-9.

[0040] Example 2

[0041] A processing technology for tea leaves with low caffeine content, the processing technology for tea leaves with low caffeine content is as follows:

[0042] (1) withering the freshly picked tea leaves to form withered leaves;

[0043] (2) The withered leaves are placed in distilled water to be heated and soaked, and then modified montmorillonite is added, and after the montmorillonite is dispersed in the water for adsorption, the temperature is cooled to room temperature, and the pretreated tea leaves are washed with water;

[0044] (3) pre-treating the tea leaves and rolling them into strips;

[0045] (4) The tea is then fried and dried, and then moved to an aroma machine for further drying and aroma enhancement. After refining, low-caffeine tea can be obtained.

[0046] The specific method of withering treatment in step (1) is: spread the fresh tea leaves at a temperature of 20° C. and a relative humidity of 50% to a thickness of 12 cm, then leave them for 7 hours, and turn the leaves every 2 hours.

[0047] In the step (2), the solid-liquid ratio of the total mass of the withered leaves and the modified montmorillonite to distilled water is 18:1.5 g / L, wherein the mass ratio of the withered leaves to the modified montmorillonite is 1:1.5.

[0048] The heating in step (2) refers to heating to 42° C., the soaking time is 4 hours, and the adsorption time is 2.5 hours.

[0049] The preparation method of the modified montmorillonite in step (2) is as follows: montmorillonite is stirred and mixed with deionized water, dodecyl dimethyl benzyl ammonium chloride is added and stirred continuously, the precipitate is separated by centrifugation, washed with deionized water, deionized water is added and stirred, and then frozen, vacuum freeze-dried, and ground and sieved to obtain the modified montmorillonite.

[0050] The mass ratio of the montmorillonite, deionized water and dodecyl dimethyl benzyl ammonium chloride is 1:25:0.35, the stirring and mixing time is 2.5 hours, and the rotation speed and time of the centrifugal separation are 3500 r / min and 15 minutes respectively.

[0051] The freeze-drying time and temperature are 65h and -20°C respectively, the sieving mesh is 200 mesh, and the mass ratio of the precipitate to deionized water is 1:1.

[0052] The strip forming rate of the kneaded strips in the step (3) is 65%.

[0053] The moisture content of the tea leaves dried in step (4) is 33%, and the moisture content of the tea leaves dried in oven is 4%.

[0054] The refining in step (4) specifically includes sieving, air separation, and re-firing, wherein the mesh size of the sieving is 70 meshes and the temperature of the re-firing is 110°C.

[0055] The montmorillonite is purchased from: Montmorillonite-Bochuan / 1302-78-9.

[0056] Example 3

[0057] A processing technology for tea leaves with low caffeine content, the processing technology for tea leaves with low caffeine content is as follows:

[0058] (1) withering the freshly picked tea leaves to form withered leaves;

[0059] (2) The withered leaves are placed in distilled water to be heated and soaked, and then modified montmorillonite is added, and after the montmorillonite is dispersed in the water for adsorption, the temperature is cooled to room temperature, and the pretreated tea leaves are washed with water;

[0060] (3) pre-treating the tea leaves and rolling them into strips;

[0061] (4) The tea is then fried and dried, and then moved to an aroma machine for further drying and aroma enhancement. After refining, low-caffeine tea can be obtained.

[0062] The specific method of withering treatment in step (1) is: spread the fresh tea leaves at a temperature of 25° C. and a relative humidity of 50% to a thickness of 15 cm, then leave them for 8 hours, and turn the leaves every 2 hours.

[0063] In the step (2), the solid-liquid ratio of the total mass of the withered leaves and the modified montmorillonite to distilled water is 25:2 g / L, wherein the mass ratio of the withered leaves to the modified montmorillonite is 1:2.

[0064] The heating in step (2) refers to heating to 45° C., the soaking time is 5 hours, and the adsorption time is 3 hours.

[0065] The preparation method of the modified montmorillonite in step (2) is as follows: montmorillonite is stirred and mixed with deionized water, dodecyl dimethyl benzyl ammonium chloride is added and stirred continuously, the precipitate is separated by centrifugation, washed with deionized water, deionized water is added and stirred, and then frozen, vacuum freeze-dried, and ground and sieved to obtain the modified montmorillonite.

[0066] The mass ratio of the montmorillonite, deionized water and dodecyl dimethyl benzyl ammonium chloride is 1:30:0.5, the stirring and mixing time is 3 hours, and the rotation speed and time of the centrifugal separation are 4000 r / min and 20 min, respectively.

[0067] The freeze-drying time and temperature are 70 h and -15°C, respectively; the sieving mesh size is 250 mesh; and the mass ratio of the precipitate to deionized water is 1:1.

[0068] The strip forming rate of the kneading in the step (3) is 70%.

[0069] The moisture content of the tea leaves dried in step (4) is 35%, and the moisture content of the tea leaves dried in oven is 5%.

[0070] The refining in step (4) specifically includes sieving, air separation, and re-firing, wherein the mesh size of the sieving is 80 meshes and the temperature of the re-firing is 120°C.

[0071] The montmorillonite is purchased from: Montmorillonite-Bochuan / 1302-78-9.

[0072] Comparative Example 1

[0073] Based on Example 2, a processing technology for tea leaves with low caffeine content is provided. The processing technology for tea leaves with low caffeine content is as follows:

[0074] (1) withering the freshly picked tea leaves to form withered leaves;

[0075] (2) placing the withered leaves in distilled water to heat and soak, and removing the distilled water to obtain pretreated tea leaves;

[0076] (3) pre-treating the tea leaves and rolling them into strips;

[0077] (4) The tea is then fried and dried, and then moved to an aroma machine for further drying and aroma enhancement. After refining, low-caffeine tea can be obtained.

[0078] The specific method of withering treatment in step (1) is: spread the fresh tea leaves at a temperature of 20° C. and a relative humidity of 50% to a thickness of 12 cm, then leave them for 7 hours, and turn the leaves every 2 hours.

[0079] In the step (2), the solid-liquid ratio of the withered leaves to distilled water is 7.2:1.5 g / L.

[0080] The heating in step (2) refers to heating to 42° C., and the soaking time is 4 hours.

[0081] The strip forming rate of the kneaded strips in the step (3) is 65%.

[0082] The moisture content of the tea leaves dried in step (4) is 33%, and the moisture content of the tea leaves dried in oven is 4%.

[0083] The refining in step (4) specifically includes sieving, air separation, and re-firing, wherein the mesh size of the sieving is 70 meshes and the temperature of the re-firing is 110°C.

[0084] Comparative Example 2

[0085] Based on Example 2, a processing technology for tea leaves with low caffeine content is provided. The processing technology for tea leaves with low caffeine content is as follows:

[0086] (1) withering the freshly picked tea leaves to form withered leaves;

[0087] (2) placing the withered leaves in distilled water to heat and soak, and removing the distilled water to obtain pretreated tea leaves;

[0088] (3) pre-treating the tea leaves and rolling them into strips;

[0089] (4) The tea is then fried and dried, and then moved to an aroma machine for further drying and aroma enhancement. After refining, low-caffeine tea can be obtained.

[0090] The specific method of withering treatment in step (1) is: spread the fresh tea leaves at a temperature of 20° C. and a relative humidity of 50% to a thickness of 12 cm, then leave them for 7 hours, and turn the leaves every 2 hours.

[0091] In the step (2), the solid-liquid ratio of the withered leaves to distilled water is 7.2:1.5 g / L.

[0092] The heating in step (2) refers to heating to 80° C., and the soaking time is 20 minutes.

[0093] The strip forming rate of the kneaded strips in the step (3) is 65%.

[0094] The moisture content of the tea leaves dried in step (4) is 33%, and the moisture content of the tea leaves dried in oven is 4%.

[0095] The refining in step (4) specifically includes sieving, air separation, and re-firing, wherein the mesh size of the sieving is 70 meshes and the temperature of the re-firing is 110°C.

[0096] Comparative Example 3

[0097] Based on Example 2, a processing technology for tea leaves with low caffeine content is provided. The processing technology for tea leaves with low caffeine content is as follows:

[0098] (1) withering the freshly picked tea leaves to form withered leaves;

[0099] (2) placing the withered leaves in distilled water to raise the temperature and soak them, then adding montmorillonite, allowing the montmorillonite to disperse in the water for adsorption and then cool to room temperature, and washing with water to obtain pretreated tea leaves;

[0100] (3) pre-treating the tea leaves and rolling them into strips;

[0101] (4) The tea is then fried and dried, and then moved to an aroma machine for further drying and aroma enhancement. After refining, low-caffeine tea can be obtained.

[0102] The specific method of withering treatment in step (1) is: spread the fresh tea leaves at a temperature of 20° C. and a relative humidity of 50% to a thickness of 12 cm, then leave them for 7 hours, and turn the leaves every 2 hours.

[0103] In the step (2), the solid-liquid ratio of the total mass of the withered leaves and montmorillonite to distilled water is 18:1.5 g / L, wherein the mass ratio of the withered leaves to montmorillonite is 1:1.5.

[0104] The heating in step (2) refers to heating to 42° C., the soaking time is 4 hours, and the adsorption time is 2.5 hours.

[0105] The strip forming rate of the kneaded strips in the step (3) is 65%.

[0106] The moisture content of the tea leaves dried in step (4) is 33%, and the moisture content of the tea leaves dried in oven is 4%.

[0107] The refining in step (4) specifically includes sieving, air separation, and re-firing, wherein the mesh size of the sieving is 70 meshes and the temperature of the re-firing is 110°C.

[0108] The montmorillonite is purchased from: Montmorillonite-Bochuan / 1302-78-9.

[0109] Performance Testing

[0110] 1. According to the conventional method specified in the national standard (caffeine: GB / T8312-2013, tea polyphenols: GB / T8313-2008, catechins: GB / T8313-2008, free amino acids: GB / T8314-2013), the caffeine, tea polyphenols, catechins and free amino acid contents in the tea leaves prepared in the above Examples 1-3 and Comparative Examples 1-3 and fresh tea leaves were tested, and the data of the fresh tea leaves were used as the blank group to obtain the removal rate and retention rate.

[0111] The above test results are shown in Table 1.

[0112] Table 1 Test results

[0113]

[0114] From the data analysis in Table 1, it can be concluded that the caffeine removal rates of Examples 1-3 are all greater than those of Comparative Examples 1-3, among which Comparative Example 1 has the lowest removal rate, and the retention rates of tea polyphenols, catechins, and free amino acids in Examples 1-3, Comparative Example 1, and Comparative Example 3 are all greater than those of Comparative Example 2. In Comparative Example 1, no modified montmorillonite is added and the soaking temperature is low, and caffeine will be released during the rolling and drying of tea leaves, so the caffeine removal rate is low; in Comparative Example 2, no modified montmorillonite is added, but caffeine molecules escape into the water after hot water soaking, and its caffeine removal rate is higher than that of Comparative Example 1, but due to the increase in temperature, tea polyphenols, catechins, and amino acids are also removed, so the retention rates of the three are all lower than those of the embodiments.

[0115] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A process for processing tea leaves with low caffeine content, characterized in that: The processing technology of the tea with low caffeine content is as follows: (1) withering the freshly picked tea leaves to form withered leaves; (2) The withered leaves are placed in distilled water to be heated and soaked, and then modified montmorillonite is added, and after the montmorillonite is dispersed in the water for adsorption, the temperature is cooled to room temperature, and the pretreated tea leaves are washed with water; (3) pre-treating the tea leaves and rolling them into strips; (4) The tea is then fried and dried, and then transferred to an aroma machine for further drying and aroma enhancement. After refining, low-caffeine tea can be obtained. In step (2), the temperature is raised to 40-45° C., the soaking time is 3-5 hours, and the adsorption time is 2-3 hours; The preparation method of the modified montmorillonite in step (2) is as follows: montmorillonite is stirred and mixed with deionized water, dodecyl dimethyl benzyl ammonium chloride is added and stirred continuously, the precipitate is separated by centrifugation, washed with deionized water, deionized water is added and stirred, and then frozen, vacuum freeze-dried, and ground and sieved to obtain the modified montmorillonite.

2. The processing technology of tea leaves with low caffeine content according to claim 1, characterized in that: The specific method of withering treatment in step (1) is: spread the fresh tea leaves at a temperature of 15-25°C and a relative humidity of 50% to a thickness of 10-15 cm, then leave them for 6-8 hours, and turn the leaves every 2 hours.

3. The processing technology of tea leaves with low caffeine content according to claim 1, characterized in that: In the step (2), the solid-liquid ratio of the total mass of the withered leaves and the modified montmorillonite to distilled water is 10-25:1-2 g / L, wherein the mass ratio of the withered leaves to the modified montmorillonite is 1:1-2.

4. The processing technology of tea leaves with low caffeine content according to claim 1, characterized in that: The mass ratio of the montmorillonite, deionized water and dodecyl dimethyl benzyl ammonium chloride is 1:20-30:0.2-0.5, the stirring and mixing time is 2-3 hours, and the speed and time of the centrifugal separation are 3000-4000 r / min and 10-20 min, respectively.

5. The processing technology of tea leaves with low caffeine content according to claim 1, characterized in that: The freeze-drying time and temperature are 60-70h and -20±5°C respectively, the sieving mesh size is 150-250 mesh, and the mass ratio of the precipitate to deionized water is 1:

1.

6. The processing technology of tea leaves with low caffeine content according to claim 1, characterized in that: The strip forming rate of the kneading in the step (3) is 65-70%.

7. The processing technology of tea leaves with low caffeine content according to claim 1, characterized in that: The moisture content of the tea leaves dried in step (4) is 30-35%, and the moisture content of the tea leaves dried in oven is 3-5%.

8. The processing technology of tea leaves with low caffeine content according to claim 1, characterized in that: The refining in step (4) specifically includes sieving, air separation, and re-firing, wherein the mesh size of the sieving is 60-80 meshes, and the temperature of the re-firing is 100-120°C.

Images