A method for removing the bitter taste of Lichuan red in summer and autumn

Abstract

The invention discloses a method for removing the bitter taste of Lichuanhong in summer and autumn. The method includes the steps of fresh leaf picking, light quality withering, leaf rolling conversion, air withering, rolling, fermentation, primary drying, rolling and frying, oxygen isolation maturation, drying, etc., wherein the light quality induction is yellow light quality withering of fresh leaves in a withering trough or an automatic withering machine; the leaf rolling conversion is to put the light withered leaves into the leaf rolling machine for rolling, and then put the light withered leaves that have been rolled into the green spreading trough for static conversion. During the static conversion process, red light is simultaneously irradiated to the light withered leaves in the green spreading trough; the air withering is to carry out air withering on the converted leaves in the withering trough or the automatic withering machine, and the red light is irradiated at the same time as the air withering; the fried leaves are not cooled, and directly enter the maturation machine for oxygen isolation maturation. The present invention removes the bitter taste of Lichuanhong in summer and autumn, improves the aroma of Lichuanhong in summer and autumn, has a high degree of process mechanization, stable tea making quality, simple operation, and low cost.

Description

Technical Field

[0001] The invention belongs to the technical field of tea making, and in particular relates to a method for removing the bitter taste of Lichuan red tea in summer and autumn. Background Art

[0002] Lichuanhong is a public brand of black tea in Enshi Prefecture. For a long time, it has been mainly produced in spring, with less production in summer and autumn. The income of tea farmers is not high, which is not conducive to the development of the industry. The method of removing the bitter taste of summer and autumn tea is not mentioned in patents and non-patent literature. Patent document (CN201810038911.1) reports a method of reducing the bitter taste of green tea by shaking oolong tea; patent document (CN201510502189.9) reports a method of reducing the bitter taste of green tea by constant temperature rolling; patent document (CN202010589606.9) reports a method of reducing the bitter taste of summer and autumn black tea by strong light irradiation withering and shaking. Non-patent literature (Research Progress on Processing Technology for Reducing the Bitterness of Summer and Autumn Tea, Tea Science and Technology 2014 (2): 1-3) summarizes the use of light withering, introduction of green tea making technology, steam killing, exogenous addition of polyphenol oxidase and other methods to improve the bitter taste of green tea. Most of these studies were conducted on green tea. For different types of tea, the relevant measures are not always effective. The basic processing steps of Lichuan Red are withering-rolling-fermentation-shaping-drying. The specific process of each step will directly affect the formation of tea quality. However, there are no reports on the removal of Lichuan Red in summer and autumn. Summary of the invention

[0003] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a Lichuan black tea processing method for removing the bitter taste of Lichuan black tea in summer and autumn. The method is simple and easy to implement, and the prepared product has the quality of "obvious floral and fruity aroma, mellow taste without bitterness", the product characteristics are obvious, and the economic utilization value of summer and autumn tea is improved.

[0004] In order to solve the above problems, the technical solution adopted by the present invention is:

[0005] A method for removing the bitter taste of Lichuan red in summer and autumn, comprising the steps of picking fresh leaves, light quality withering, rolling leaf conversion, air withering, rolling, fermenting, primary drying, rolling and frying, oxygen isolation maturation, and drying, specifically comprising the following steps:

[0006] (1) Fresh leaf picking: fresh leaves are picked manually according to the standard of one bud with two leaves and / or one bud with three leaves;

[0007] (2) light quality induction: the fresh leaves picked in step (1) are subjected to yellow light quality withering using a withering trough or an automatic withering machine, wherein the yellow light intensity is 230-500 Lx, the temperature is 20-22° C., the relative humidity is 80-85%, the leaf thickness is 5 cm-10 cm, and the withering degree is such that the moisture content of the fresh leaves reaches 68%-70%, thereby obtaining light withered leaves;

[0008] (3) Leaf rolling transformation: the light-withered leaves obtained in step (2) are put into a leaf rolling machine and rolled for 15-20 minutes; then the light-withered leaves that have been rolled are put into a greening tank for static transformation. During the static transformation process, red light is simultaneously used to irradiate the light-withered leaves in the greening tank. The red light intensity is 230-500Lx, the temperature is 22-25°C, the relative humidity of the air is 75-80%, the leaf thickness is 5cm-10cm, and the time is 5h-7h to obtain transformed leaves;

[0009] (4) air withering: using a withering trough or an automatic withering machine to wither the transformed leaves obtained in step (3), and simultaneously using red light irradiation treatment, the red light intensity is 230-500Lx, the leaf thickness is 5cm-10cm, the temperature is 28-30°C, the relative humidity of the air is less than 65%, the time is 3h-4h, and the withering degree is such that the moisture content of the transformed leaves is reduced to 55%-58%, thereby obtaining withered leaves;

[0010] (5) rolling: the withered leaves obtained in step (4) are rehumidified for about 30 minutes, and then rolled using a 6CR-55 tea rolling machine for 80-100 minutes. After rolling, the withered leaves are deblocked to obtain rolled leaves;

[0011] (6) fermentation: fermenting the rolled tea leaves obtained in step (5) using a black tea fermentation machine at a fermentation temperature of 28-30° C., an air relative humidity of more than 85%, a fermentation time of 3 h-3.5 h, and fermenting until the leaves turn yellow-red to obtain fermented tea leaves;

[0012] (7) Primary drying: using a drying machine to perform primary drying on the fermented leaves obtained in step (6) at a drying temperature of 90-95° C., reducing the moisture content of the fermented leaves to 45%-47%, thereby obtaining primary dried leaves;

[0013] (8) tumbling and frying: using a frying machine to fry the primary dried leaves obtained in step (7), wherein the primary dried leaves are not turned over and are tumbled in a rotating centrifugal manner during the frying process, the frying temperature is 180° C., the amount of frying leaves is 6 kg, the frying time is 60-70 min, and the water content is reduced to 35%-37%, thereby obtaining frying leaves;

[0014] (9) Oxygen isolation aging: The stir-fried leaves obtained in step (8) are directly put into an aging machine for oxygen isolation aging without cooling, and the temperature is maintained at 50-60° C. and the relative humidity of the air is above 85%. The oxygen isolation aging time is 30 minutes to obtain aging leaves;

[0015] (10) Drying: the ripe leaves obtained in step (9) are formed into needles, strips or beads, and then dried in a drying machine or an aroma machine, or the ripe leaves obtained in step (9) are directly dried in a drying machine or an aroma machine; the drying temperature is 70-80° C., the leaf thickness is 1-2 cm, and the leaves are dried to a moisture content of 5-6%, thereby obtaining the Lichuan black tea.

[0016] Compared with the prior art, the present invention has the following beneficial effects and advantages:

[0017] 1. The present invention removes the bitter taste of Lichuanhong in summer and autumn: first, through the light quality induction and leaf rolling transformation technology in the withering process, the biosynthesis of terpene alcohols and glycosidic enzymolysis in the withering process are promoted, and these substances with sweet fragrance enter the tea soup, enhancing the sweet and mellow flavor of the taste; second, through the rolling, stewing and oxygen-isolated ripening process, the hydrolysis of proteins and polysaccharides into amino acids and soluble sugars, the degradation of ester-type catechins into simple catechins, and the transformation of flavonoids are promoted, thereby promoting the formation of mellow taste.

[0018] 2. The present invention improves the aroma of summer and autumn Lichuan red: using one bud, two or three leaves as raw material, low temperature yellow light or red light induction is used during the withering process to promote the de novo synthesis of floral and fruity substances such as linalool and geraniol during the withering process; rolling leaf conversion technology is used to promote the hydrolysis of glycosides of terpenes to release floral and fruity components. The summer and autumn Lichuan red processed by this technology has the quality characteristics of floral and fruity aroma.

[0019] 3. The process of the present invention has a high degree of mechanization, controllable process parameters, stable tea quality, simple operation and low cost. The price of summer and autumn Lichuan black tea produced by the technology of the present invention is more than 30% higher than that of traditional products. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with specific embodiments. The technical solutions of the present invention, unless otherwise specified, are conventional solutions in the art, and the reagents or materials, unless otherwise specified, are from commercial channels.

[0021] Example 1

[0022] A method for removing the bitter taste of Lichuan red in summer and autumn, comprising the following steps:

[0023] (1) Fresh leaf picking: The standard is one bud and two or three leaves, picked by hand, without squeezing or damaging the fresh leaves;

[0024] (2) Light quality induction: After the fresh leaves enter the factory, the fresh leaves picked in step (1) are irradiated with yellow light using a withering trough, with a light intensity of 400 Lx, a temperature of 20° C., a relative humidity of 80%, a leaf thickness of 10 cm, and a withering degree of 70% water content in the fresh leaves to obtain light-withered leaves;

[0025] (3) Leaf rolling transformation: the light-withered leaves obtained in step (2) are put into a leaf rolling machine and rolled for 20 minutes; then the light-withered leaves that have been rolled are put into a greening trough for static transformation. During the static transformation process, red light is simultaneously used to irradiate the light-withered leaves in the greening trough, with a red light intensity of 400 Lx, a temperature of 25° C., a relative humidity of 80%, a leaf thickness of 10 cm, and a time of 6 hours to obtain transformed leaves;

[0026] (4) air withering: the transformed leaves obtained in step (3) are subjected to air withering in a withering trough, and red light irradiation is performed during the air withering, with a light intensity of 400 Lx, a leaf thickness of 10 cm, a temperature of 30° C., a relative humidity of 60%, a time of 4 h, and a withering degree of 55% to obtain withered leaves;

[0027] (5) rolling: the withered leaves obtained in step (4) are rehumidified for 30 minutes, and then rolled using a 6CR-55 tea rolling machine for 80 minutes, and the blocks are deblocked after rolling to obtain rolled leaves;

[0028] (6) fermentation: fermenting the rolled tea leaves obtained in step (5) in a black tea fermentation machine at a temperature of 30° C. and an air humidity of 85% for 3 h until the leaves turn yellow-red, thereby obtaining fermented tea leaves;

[0029] (7) Primary drying: using a drying machine to perform primary drying on the fermented leaves obtained in step (6) at a temperature of 95° C., wherein the moisture content of the fermented leaves is reduced to 45%, thereby obtaining primary dried leaves;

[0030] (8) Tumbling and frying: Stir-frying the primary dried leaves obtained in step (7) in a frying machine. During the frying process, the primary dried leaves are not turned over but are tumbled in a rotating centrifugal manner. The frying temperature is 180° C., the amount of frying leaves is 6 kg, and the frying time is 70 min, until the water content is reduced to 35%, thereby obtaining frying leaves;

[0031] (9) Oxygen isolation aging: The stir-fried leaves obtained in step (8) are directly put into an aging machine for oxygen isolation aging without cooling, with the temperature maintained at 60° C. and the relative humidity of the air being above 85% for 30 minutes to obtain aging leaves;

[0032] (10) Drying: The ripened leaves obtained in step (9) can be further formed into needles, strips or beads, and then dried in a drying machine at a drying temperature of 80° C. and a leaf thickness of 1 cm until the moisture content is 5%, thereby obtaining the Lichuan black tea.

[0033] Comparative Example 1: Effect of withering in withering trough on the quality of Lichuanhong in summer and autumn

[0034] The process of Comparative Example 1 is the same as that of Example 1, with the only difference being that steps (2), (3) and (4) in the present invention are changed to withering in a withering trough (i.e., forced air withering) at a temperature of 32°C, and the other implementation steps are the same as those of Example 1.

[0035] The experimental results show that compared with the traditional withering method, the bitter taste of summer Lichuan red processed by the new withering method is basically eliminated, the aroma still has floral and fruity fragrance, and the quality is significantly improved. From the analysis of quality components, the new process is conducive to reducing the content of tea polyphenols and increasing the content of soluble sugars, reducing the content of bitter substances and increasing the content of sweet substances. At the same time, it can be seen that the floral and fruity components such as α-farnesene, phenylacetaldehyde, phenylethanol, and cis-jasmone of the summer Lichuan red processed by the withering method of the present invention are significantly increased.

[0036] Table 1 Effect of withering on the sensory quality of summer and autumn Lichuan red

[0037]

[0038] Note: Variety: Enshi local group variety; Fresh leaf tenderness: one bud and two or three leaves (one bud and two leaves account for about 70%); Fresh leaves were harvested on July 13, 2023; Data are the mean ± standard deviation of 3 replicates, different capital letters in the same column indicate extremely significant differences at the p < 0.01 level, lowercase letters indicate significant differences at the p < 0.05 level; Astringency scoring standard: no -1 point, yes -2 points, still strong -3 points, relatively strong -4 points, strong -5 points.

[0039] Table 2 Effect of withering on the basic physical and chemical components of Xiaqiu Lichuanhong (%)

[0040]

[0041] Note: Variety: Enshi local group variety; Fresh leaf tenderness: one bud and two or three leaves (one bud and two leaves account for about 70%); Fresh leaves were harvested on July 13, 2023; Data are the mean ± standard deviation of 3 replicates, different capital letters in the same column indicate extremely significant differences at the p < 0.01 level, and lowercase letters indicate significant differences at the p < 0.05 level.

[0042] Table 3 Effect of withering on the aroma of Lichuanhong in summer and autumn (μg / kg)

[0043]

[0044]

[0045] Note: Variety: Fuding Da Baicha; Fresh leaf tenderness: one bud and two leaves, three leaves (one bud and two leaves account for about 70%); Fresh leaf harvest time is July 13, 2023; Data are the mean ± standard deviation of 3 replicates.

[0046] Comparative Example 2: Effects of red light withering + air blast withering on the quality of Lichuan red in summer and autumn

[0047] Comparative Example 2 is based on Comparative Example 1, and light withering and control treatment are set up: compared with the withering process of Comparative Example 1 which is traditional withering trough withering, Comparative Example 2 is red light withering, first cold air for 1h, and then heated to 32°C for forced air withering, and the other implementation steps are the same as Example 1.

[0048] The experimental results show that compared with the traditional withering in comparative example 1, the bitter taste of summer Lichuanhong processed by light withering is significantly reduced, the aroma is sweet and fragrant, and it also has a floral and fruity aroma, and the quality is significantly improved. From the analysis of quality components, the new process is conducive to reducing the content of tea polyphenols and increasing the content of soluble sugars, reducing the content of bitter substances and increasing the content of sweet substances.

[0049] Table 4 Effect of light withering on sensory quality of summer and autumn Lichuan red

[0050]

[0051] Note: Variety: E-cha No. 10; Fresh leaf tenderness: one bud and two or three leaves (one bud and two leaves account for about 70%); Fresh leaves were harvested on June 25, 2023; Data are the mean ± standard deviation of 3 replicates, different capital letters in the same column indicate extremely significant differences at the p < 0.01 level, lowercase letters indicate significant differences at the p < 0.05 level; Astringency scoring standard: none -1 point, yes -2 points, fairly strong -3 points, relatively strong -4 points, strong -5 points.

[0052] Table 5 Effect of light withering on the basic physical and chemical components of summer and autumn Lichuan red (%)

[0053]

[0054] Note: Variety: E-cha No. 10; Fresh leaf tenderness: one bud and two or three leaves (one bud and two leaves account for about 70%); Fresh leaf harvest time is June 25, 2023; Data are the mean ± standard deviation of 3 replicates, different capital letters in the same column indicate extremely significant differences at the p < 0.01 level, and lowercase letters indicate significant differences at the p < 0.05 level.

[0055] Table 6 Effect of red light withering on the aroma of Lichuan red in summer and autumn (ng / g-DW)

[0056]

[0057] Note: Variety: E-cha No. 10; Fresh leaf tenderness: one bud and two leaves, three leaves (one bud and two leaves account for about 70%); Fresh leaf harvest time is June 25, 2023; Data are the mean ± standard deviation of 3 replicates.

[0058] Comparative Example 3: Effect of rolling and stewing on the quality of Lichuanhong in summer and autumn

[0059] The process of Comparative Example 3 is the same as that of Example 1, with the only difference being that step (8) in the present invention is replaced by drying in a conventional drying machine, and the other implementation steps are the same as those of Example 1.

[0060] The experimental results show that compared with traditional drying, the summer Lichuan red processed by rolling and stewing has a lighter bitter taste and significantly improved quality.

[0061] Table 7 Effect of rolling and stewing on sensory quality of summer and autumn Lichuan red

[0062]

[0063] Note: Variety: Enshi local group variety; Fresh leaf tenderness: one bud and two or three leaves (one bud and two leaves account for about 70%); Fresh leaves were harvested on September 5, 2023; Data are the mean ± standard deviation of 3 replicates, different capital letters in the same column indicate extremely significant differences at the p < 0.01 level, lowercase letters indicate significant differences at the p < 0.05 level; Astringency scoring standard: none -1 point, yes -2 points, still strong -3 points, relatively strong -4 points, strong -5 points.

[0064] Comparative Example 4: Effect of oxygen-free aging on the quality of summer and autumn Lichuan red

[0065] The process of Comparative Example 4 is the same as that of Example 1, with the only difference being that the oxygen-isolated aging process in step (9) of the present invention is omitted, and the other implementation steps are the same as those of Example 1.

[0066] The experimental results show that the oxygen-isolated aging process can promote the oxidative degradation of tea polyphenols to form more theabrownins, increase the content of amino acids and soluble sugars, significantly reduce the bitter taste of Lichuan Red in summer, and significantly improve the quality.

[0067] Table 8 Effect of oxygen-free aging on the sensory quality of summer and autumn Lichuan red

[0068]

[0069] Note: Variety: Fuding Dabai group; Fresh leaf tenderness: one bud and two or three leaves (one bud and two leaves account for about 70%); Fresh leaf harvest time September 5, 2023; Data are the mean ± standard deviation of 3 replicates, different capital letters in the same column indicate extremely significant differences at the p < 0.01 level, lowercase letters indicate significant differences at the p < 0.05 level; Astringency scoring standard: none -1 point, yes -2 points, still strong -3 points, relatively strong -4 points, strong -5 points.

[0070] Table 9 Effect of oxygen-free aging on the main physical and chemical components of Xiaqiu Lichuanhong (%)

[0071]

[0072] Note: Variety: Fuding Dabai group; Fresh leaf tenderness: one bud and two or three leaves (one bud and two leaves account for about 70%); Fresh leaf harvest time September 5, 2023; Data are the mean ± standard deviation of 3 replicates, different capital letters in the same column indicate extremely significant differences at the p < 0.01 level, lowercase letters indicate significant differences at the p < 0.05 level; Astringency scoring standard: none -1 point, yes -2 points, still strong -3 points, relatively strong -4 points, strong -5 points.

[0073] Finally, it should be noted that the above embodiments do not limit the present invention in any form. For those skilled in the art, some modifications and improvements can be made to the present invention. Therefore, any modification or improvement made without departing from the spirit of the present invention belongs to the scope of protection claimed in the present invention.

Claims

1. A method for removing the bitter taste of Lichuanhong in summer and autumn, comprising the steps of picking fresh leaves, light quality withering, rolling leaf conversion, air withering, rolling, fermentation, primary drying, rolling and frying, oxygen isolation maturation, and drying, specifically comprising the following steps: Step (1), picking fresh leaves: picking fresh leaves manually according to the standard of one bud with two leaves and / or one bud with three leaves; Step (2), light quality induction: using a withering trough or an automatic withering machine to wither the fresh leaves picked in step (1) with yellow light, wherein the yellow light intensity is 230-500Lx, the temperature is 20-22°C, the relative humidity of the air is 80-85%, the leaf thickness is 5cm-10cm, and the withering degree is such that the water content of the fresh leaves reaches 68%-70%, thereby obtaining light-withered leaves; Step (3), leaf rolling transformation: the light-withered leaves obtained in step (2) are put into a leaf rolling machine for tumbling for 15-20 minutes; the light-withered leaves that have been tumbled are then put into a green spreading trough for static transformation. During the static transformation process, red light is simultaneously used to irradiate the light-withered leaves in the green spreading trough, the red light intensity is 230-500Lx, the temperature is 22-25°C, the relative humidity of the air is 75-80%, and the leaf thickness is 5cm-10cm, so as to obtain transformed leaves; Step (4), air withering: using a withering trough or an automatic withering machine to wither the transformed leaves obtained in step (3), and simultaneously using red light irradiation treatment, the red light intensity is 230-500Lx, the leaf thickness is 5cm-10cm, the temperature is 28-30°C, the relative humidity of the air is less than 65%, the time is 3h-4h, and the withering degree is that the water content of the transformed leaves is reduced to 55%-58%, thereby obtaining withered leaves; Step (5), rolling: the withered leaves obtained in step (4) are rehumidified for about 30 minutes, and then rolled using a 6CR-55 tea rolling machine for 80-100 minutes, and the blocks are deblocked after rolling to obtain rolled leaves; Step (6), fermentation: fermenting the rolled tea leaves obtained in step (5) using a black tea fermentation machine, with the relative humidity of air being above 85%, until the leaves turn yellow-red, thereby obtaining fermented tea leaves; Step (7), primary drying: using a drying machine to perform primary drying on the fermented leaves obtained in step (6), the drying temperature being 90-95° C., the moisture content of the fermented leaves being reduced to 45%-47%, and primary dried leaves being obtained; Step (8), rolling and stewing: using a stewing machine to stew the primary dry leaves obtained in step (7), the stewing temperature is 180° C., the amount of stewed leaves is 6 kg, and the stewing time is 60-70 minutes. During the frying process, the primary dry leaves are not turned over and are rotated centrifugally to reduce the water content to 35%-37%, thereby obtaining stewed leaves; Step (9), oxygen-isolated aging: the stir-fried leaves obtained in step (8) are directly put into an aging machine for oxygen-isolated aging without cooling, the oxygen-isolated aging time is 30 minutes, the temperature is maintained at 50-60° C., and the relative humidity of the air is above 85%, to obtain aging leaves; Step (10), drying: the ripe leaves obtained in step (9) are formed into needles, strips or beads, and then dried in a dryer or an aroma machine, or the ripe leaves obtained in step (9) are directly dried in a dryer or an aroma machine; the drying temperature is 70-80°C, the leaf thickness is 1-2 cm, and the leaves are dried to a moisture content of 5-6%, thereby obtaining the Lichuan black tea.

2. The method according to claim 1, characterized in that: In step (3), the light-withered leaves are placed in the greening trough for treatment for 5 hours to 7 hours.

3. The method according to claim 1, characterized in that: In step (6), the fermentation temperature is 28-30° C. and the fermentation time is 3 h-3.5 h.

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