Chinese yam leaf green tea and processing method thereof

Abstract

The invention relates to the technical field of substitutional tea, and particularly discloses Chinese yam leaf green tea and a processing method thereof, the processing method comprises the following operation steps: S1, picking fresh leaves; s2, low-temperature spreading: spreading the fresh leaves of the iron stick yams obtained in the previous step in an artificial climate chamber with the temperature of 8-12 DEG C and the humidity of 68-80%, the spreading thickness of 2-3cm and the spreading time of 48-72 hours; s3, performing fixation; s4, performing rolling; s5, frying and baking treatment: frying the product obtained in the previous step at the temperature of 150-180 DEG C until the water content is 15-25%, and then baking at the temperature of 95-100 DEG C until the water content is not higher than 5%; and S6, carrying out post-treatment. The Chinese yam leaf green tea prepared by the processing method disclosed by the invention can be directly brewed for drinking, is clear and translucent in soup color, emits light faint scent, is savoury and mellow in taste, is rich in substances such as amino acids, flavonoids, organic acids, phenolic acids and the like, has multiple health-care effects, and solves the problem that the Chinese yam leaf tea prepared by the prior art is poor in quality.

Description

Technical Field

[0001] The invention relates to the technical field of substitute tea, in particular to yam leaf green tea and a processing method thereof. Background Art

[0002] Chinese yam, also known as yam, Chinese yam, ginseng yam, etc., is rich in a variety of nutrients and trace elements. Among them, the nutrients contained mainly include diosgenin, polysaccharides, various amino acids, flavonoids and other active health care ingredients, which have the effects of lowering blood sugar and blood lipids, anti-tumor, anti-oxidation, delaying aging, and improving body immunity. Chinese yam can be used as both medicine and food, and long-term consumption can prolong life. In recent years, the national yam planting area has gradually expanded with the increase in consumer demand.

[0003] As a byproduct of yam cultivation, yam leaves have a very considerable yield. The types of ingredients they contain are similar to those of yam tubers, and they are especially rich in polyphenol active substances with significant antioxidant properties, such as rosmarinic acid and flavonoids, so they have high health benefits. However, people have a low utilization rate of yam leaves, and most yam stems and leaves are abandoned in the fields, resulting in a waste of resources. With the continuous improvement of people's health awareness, a small number of researchers have begun to explore the use of yam leaves as substitute tea raw materials to improve the comprehensive utilization rate of yam, and to develop new substitute tea varieties to meet the needs of the health care product market. Making yam leaves into green tea can well preserve its natural green color and the nutrients it is rich in, and yam leaves have abundant yields and low costs, and have prospects for large-scale utilization.

[0004] However, since yam leaves are not the mainstream material for traditional tea making, the yam leaf tea obtained by the existing technology or the conventional processing method of tea making has a good color after brewing, but the aroma and taste are poor, and the tea soup has a distinct grassy taste, and the tea taste is not sweet and mellow, but has a little astringency. In short, although the existing technology can produce yam leaf tea, the quality is poor and cannot meet the needs of consumers.

[0005] To this end, this application is filed. Summary of the invention

[0006] In view of the above-mentioned shortcomings of the prior art, the present invention provides a yam leaf green tea and a processing method thereof.

[0007] In one aspect, the present invention provides a method for processing yam leaf green tea, comprising the following steps:

[0008] S1. Picking fresh leaves: Pick fresh, tender green leaves of Tiegun Yam as raw materials. The leaves of Tiegun Yam are relatively small, thin, compact in shape, and less split. The nutrients in them are easier to leach out, and the appearance is better after brewing;

[0009] S2, low temperature spreading: the leaves of the iron stick yam obtained in the previous step are spread in an artificial climate room with a temperature of 8-12°C and a humidity of 68%-80%, with a thickness of 2-3cm and a spreading time of 48-72h. Spreading in this temperature and humidity environment can significantly reduce the water content of the iron stick yam leaves, maintain their freshness, and maximize the amino acid content in the leaves;

[0010] S3, fixing: put the leaves obtained in the previous step into a drum fixing machine, fix them at 250-300℃ for 5-8min, the fixed leaves turn brown-green and there should be no burning phenomenon, then spread out the fixed leaves discharged from the drum fixing machine to cool in time;

[0011] S4, rolling: when the withered leaves are cooled to 47-50°C, they are put into a rolling machine and gently rolled to loosen them into shape;

[0012] S5, frying and drying treatment: first tumble fry the product obtained in the previous step at a temperature of 150-180° C. until the water content is 15%-25%, then place it in a dryer or drying room for drying at a temperature of 95-100° C. until the water content is not higher than 5%;

[0013] S6. Post-processing: Take out the dried product and place it in a ventilated place, turn it over gently and wait for it to cool naturally to room temperature before screening and vacuum packaging.

[0014] Amino acids are important ingredients for the freshness and aroma of tea soup, and play a key role in the freshness of tea soup and have a significant impact on the aroma of tea soup. Appropriate spreading is conducive to increasing the content of free amino acids in tea leaves and improving the quality of tea soup.

[0015] Compared with the prior art, the present invention adds a low-temperature spreading treatment, which effectively ensures the freshness of the yam leaves and slows down the degradation rate of amino acids in the yam leaves, so that as many amino acids as possible can be retained; then, through a medium-temperature one-time killing, the fermentation and oxidation of the yam leaves are quickly stopped without destroying the amino acids, and part of the water is evaporated to remove the grass taste, thereby comprehensively improving the aroma of the yam leaves; and then through rolling, the volume of the yam leaves is reduced, the shape of the strips is formed, and the leaf tissue is appropriately destroyed, thereby improving the drying efficiency of the subsequent frying and baking process, and further promoting the transformation of the contained substances, the release of the aroma and improving the solubility of the aroma substances; and then the combination of frying and baking is adopted to make the strips of the yam leaves more even, with lower grass taste and astringency, thereby further improving the quality of the yam leaf green tea. The above steps influence and act synergistically on each other, so that the obtained yam leaf green tea contains a variety of amino acids. The combination of these amino acids can significantly increase the freshness and sweetness of the tea soup, improve the quality of the tea, and ultimately obtain high-quality yam leaf green tea with obvious aroma, tight tea leaves, emerald green color, and fresh taste.

[0016] Preferably, in step S2, the Co-γ irradiation is performed at a dose rate of 6-8 kGy / h within the first 6-12 hours of low-temperature spreading, and the Co-γ irradiation is performed again at a dose rate of 10-12 kGy / h within the last 6-12 hours of low-temperature spreading.

[0017] The present invention has found through a large number of innovative experiments that 60Co-γ irradiation can cooperate with low-temperature spreading to significantly improve the nutritional value of yam leaves while maintaining the freshness of yam leaves. When spreading at low temperature, the raw materials are irradiated twice according to the above operation. On the one hand, it helps to accelerate protein hydrolysis to generate amino acids with freshness and sweetness, and enrich the types of amino acids; on the other hand, it can also make more extracts when brewing tea, which is conducive to the full release of nutrients in yam leaves. In addition, it can also destroy the DNA of microorganisms to inhibit their growth and reproduction and degrade pesticide residues, which is of great significance to improving the sanitary quality and safety of yam leaf green tea.

[0018] It should be noted that the irradiation time and irradiation dose rate need to be strictly controlled. If the irradiation time is too short or insufficient, the optimal irradiation effect cannot be obtained. If the irradiation time is too long or excessive, it will cause excessive damage to the yam leaf cells, resulting in the loss of nutrients such as amino acids. It may also cause the redox balance in the yam leaves, resulting in unnecessary chemical changes, and then generating by-products that are not conducive to the aroma of the tea.

[0019] Preferably, in step S2, the temperature of the artificial climate chamber is 10° C., the humidity is 78%, and the placement time is 60 hours.

[0020] The spreading of fresh leaves not only causes the water content of the leaves to be lost, but is also accompanied by changes in the contents of the leaves. The spreading temperature and humidity are important parameters in the tea processing process, which directly affect the quality and final taste of the tea. The control of the spreading temperature and humidity has a significant impact on the physical and chemical changes of the tea. If the spreading temperature is too high, the tea leaves will turn red and ferment too quickly, affecting the appearance and quality of the tea leaves. If the spreading temperature is too low, the tea leaves will be frozen; suitable humidity conditions can not only promote the uniform water loss of the tea leaves, but also optimize its chemical composition and improve the quality of the tea leaves. Generally speaking, maintaining a low temperature in the artificial climate chamber will help reduce the activity of various oxidases in the yam leaves and reduce unnecessary chemical changes. On this basis, maintaining appropriate humidity can make the yam leaves lose water evenly, optimize their chemical composition and improve their quality. The present invention unexpectedly found that when the temperature of the artificial climate chamber is 10°C, the humidity is 78%, and the spreading time is 60h, the spreading effect obtained is the best, which helps to obtain yam leaves with good freshness, high amino acid content and good processability.

[0021] Preferably, in step S3, the drum fixing machine is used for fixing at 270° C. for 6 minutes.

[0022] Preferably, in step S4, the kneading machine gently kneads at a rotation speed of 40-45 rpm for 20-30 min.

[0023] Preferably, step S4 further includes manual kneading, and after the kneading machine finishes kneading, the kneading is performed manually for 5-10 minutes.

[0024] Manual kneading can better retain the nutrients of yam leaves, and the yam leaf green tea finally made by the manual kneading process is easier to release aroma and taste after brewing. However, manual kneading is time-consuming and labor-intensive, which is not conducive to large-scale production. The use of a rolling machine for kneading can greatly improve production efficiency and shorten the kneading time, thereby meeting the needs of large-scale production, but it cannot achieve the fineness of manual kneading, and the resulting yam leaf green tea has a relatively rough appearance, and the aroma and taste are also deteriorated. The inventor of the present application found through innovative experiments that when the rolling machine gently kneads at a speed of 40-45rpm for 20-30min, and then manually kneads for 5-10min, a product with relatively good quality and taste can be obtained. The kneading process combined with machine kneading and manual kneading proposed by the present invention can take into account both production efficiency and the quality of the finished yam leaf green tea, and achieve the purpose of complementary advantages.

[0025] Preferably, in step S5, the dough is first fried at 165° C. until the moisture content reaches 20%, and then dried at 98° C. until the moisture content is no higher than 5%.

[0026] During the frying process, the temperature of the yam leaves rises rapidly, the activity of the enzyme is destroyed, and the fermentation process stops, which not only helps to maintain the original color and original taste of the yam leaves, but also stabilizes the tissue structure of the yam leaves; drying can not only remove excess water and extend the shelf life, but also fix the shape of the yam leaves, making the appearance of the yam leaves more beautiful on the basis of frying. The combination of frying and baking can not only significantly improve the quality and appearance of yam leaf green tea, ensure the consistency of the quality of yam leaf green tea, but also improve production efficiency. If the water content is too high after frying or drying, it will affect the quality of yam leaf green tea. If it is too low, it will lose the original fragrance and taste, and it will not be conducive to improving production efficiency. The inventor of this application unexpectedly found that frying at 165°C to a water content of 20%, and then drying at 98°C to a water content of no more than 5%, not only has high processing efficiency, but also the obtained yam leaf green tea has a beautiful appearance and a fragrant smell.

[0027] Preferably, in step S2, the temperature is maintained by circulating air, and the air is circulated by a fan.

[0028] Preferably, in step S2, the spread leaves of the iron stick yam are evenly turned over once every 12-24 hours, and the time for each turning is controlled within 10 minutes, and the interval time before this turning is included, and the total turning is an odd number of times during the spreading time.

[0029] In the present invention, the specific turning method can be mechanical or manual. The turning of the spread iron stick yam leaves is mainly to prevent some leaves from being at the bottom for a long time, which neither achieves the purpose of airing nor fully receives irradiation. By evenly turning the spread iron stick yam leaves, all leaves can be fully aired and fully irradiated, which helps to evenly improve the overall quality of yam leaf green tea.

[0030] On the other hand, the present invention also provides yam leaf green tea prepared according to the processing method.

[0031] The invention uses fresh and tender iron stick yam leaves as raw materials, and obtains yam leaf green tea that can be directly brewed and drunk through low-temperature spreading, killing green, rolling, frying and baking processes, and the like, and the tea soup is clear and transparent green, emits a light fragrance, and has a mellow taste. Compared with the prior art, the invention uses the iron stick yam leaves with abundant yields to make high-quality yam leaf green tea through simple processing, which not only improves the comprehensive utilization rate of yam, but also enriches the varieties of substitute tea, and has a good development prospect. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0033] Example 1

[0034] A method for processing yam leaf green tea, characterized in that it comprises the following steps:

[0035] S1. Picking fresh leaves: picking fresh, tender green leaves of Chinese yam as raw materials;

[0036] S2, low temperature spreading: the leaves of the iron stick yam obtained in the previous step are spread in an artificial climate room with a temperature of 10°C and a humidity of 78%, with a spreading thickness of 2-3cm and a spreading time of 60h. The temperature in the artificial climate room is maintained by circulating air, and the air is circulated by a fan. The spread iron stick yam leaves are evenly turned once every 18h, and the time for each turning is controlled within 10min, and the interval time before this turning is included, and a total of 3 times are turned during the spreading time;

[0037] S3, fixing: the leaves obtained in the previous step are put into a drum fixing machine and fixed at 270°C for 6 minutes. The fixed leaves turn brown-green and should not be burnt. After that, the fixed leaves discharged from the drum fixing machine are spread out and cooled in time;

[0038] S4, rolling: when the withered leaves are cooled to 47°C, they are put into a rolling machine and gently rolled at a speed of 40 rpm for 30 minutes, and then manually rolled for 5 minutes to loosen and shape them;

[0039] S5, frying and drying treatment: first, fry the product obtained in the previous step at a temperature of 165° C. until the water content is 20%, and then place it in a dryer or drying room for drying at a temperature of 98° C. until the water content is 5%;

[0040] S6. Post-processing: Take out the dried product and place it in a ventilated place, turn it over gently and wait for it to cool naturally to room temperature before screening and vacuum packaging.

[0041] Example 2

[0042] Compared with Example 1, in this embodiment, irradiation is added in step S2, and Co-γ with a dose rate of 7 kGy / h is irradiated within the first 9 hours of low-temperature spreading, and Co-γ with a dose rate of 11 kGy / h is irradiated again within the last 9 hours of low-temperature spreading. The time used for evenly turning the leaves of the spread iron stick yam during the irradiation time is regarded as normal irradiation time, and no compensation is made for the irradiation time. The rest is consistent with Example 1.

[0043] Example 3

[0044] Compared with Example 1, in this embodiment, irradiation is added in step S2, and Co-γ with a dose rate of 8 kGy / h is irradiated within the first 6 hours of low-temperature spreading, and Co-γ with a dose rate of 10 kG y / h is irradiated again within the last 12 hours of low-temperature spreading. The time for turning the leaves of the spread iron stick yam evenly during the irradiation time is regarded as normal irradiation time, and no compensation is made for the irradiation time. The rest is consistent with Example 1.

[0045] Example 4

[0046] Compared with Example 1, in this embodiment, irradiation is added in step S2, and Co-γ irradiation with a dose rate of 6 kGy / h is performed within the first 12 hours of low-temperature spreading, and Co-γ irradiation with a dose rate of 12 kGy / h is performed again within the last 6 hours of low-temperature spreading. The rest is consistent with Example 1.

[0047] Example 5

[0048] Compared with Example 1, in this embodiment, the temperature in the artificial climate room in step S2 is 8°C, the humidity is 72%, and the spreading time is 60h; in step S3, the drum fixing machine is 250°C and the fixing time is 8min; in step S5, the tea leaves are first fried at 180°C to a water content of 20%, and then dried at 95°C to a water content of 5%. The rest is consistent with Example 1.

[0049] Example 6

[0050] Compared with Example 1, in this embodiment, the temperature in the artificial climate chamber in step S2 is 12°C, the humidity is 68%, and the spreading time is 48h; in step S3, the green tea is fixed in the drum at 300°C for 5min; in step S5, the green tea is first fried at 150°C to a water content of 25%, and then dried at 98°C to a water content of 5%. The rest is consistent with Example 1.

[0051] Example 7

[0052] Compared with Example 1, in this embodiment, the temperature in the artificial climate room in step S2 is 10°C, the humidity is 75%, and the spreading time is 72h; in step S3, the drum fixing machine fixes the green leaves for 7min at 280min; in step S5, the green leaves are first fried at 170°C to a water content of 15%, and then dried at 100°C to a water content of 5%. The rest is consistent with Example 1.

[0053] Example 8

[0054] Compared with Example 1, in this embodiment, the humidity in the artificial climate chamber in step S2 is 80%, and in step S4, when the leaves to be fixed are cooled to 50° C., they are placed in a rolling machine and gently kneaded at a speed of 45 rpm for 20 minutes, and then gently kneaded by hand for 10 minutes to loosen and shape them. The rest is consistent with Example 1.

[0055] Comparative Example 1

[0056] Compared with Example 1, in this comparative example, the low-temperature spreading operation in step S2 is changed to normal-temperature spreading, and the specific technical parameters are: the temperature of the artificial climate chamber is 25±2°C, the humidity is 50%-55%, and the spreading time is 6h. Other technical parameters not mentioned are consistent with those in Example 1.

[0057] Comparative Example 2

[0058] Compared with Example 2, in this comparative example, the low-temperature spreading operation in step S2 is changed to normal temperature spreading, and the specific technical parameters are: the temperature of the artificial climate chamber is 25±2°C, the humidity is 50%-55%, the spreading time is 6h, the leaves of the iron stick yam spread are evenly turned once every 3h, and a total of 1 time during the spreading time; the Co-γ is irradiated with a dose rate of 7kGy / h in the first 3h of normal temperature spreading, and the Co-γ is irradiated again with a dose rate of 11kGy / h in the last 3h of normal temperature spreading. Other technical parameters not mentioned are consistent with those in Example 2.

[0059] In this experiment, UPLC-QTOF-MS / MS non-targeted metabolomics technology was used to detect the chemical components of the yam leaf green tea obtained in Examples 1-8 and Comparative Examples 1-2. The amino acid content ratios of Example 1, Example 2, Example 5, Comparative Example 1, and Comparative Example 2 are shown in Table 1. In addition, the test results of Example 3 and Example 4 are close to Example 2 but slightly lower than Example 2, the test results of Example 6 and Example 7 are close to Example 5 and both lower than Example 1, and the test result of Example 8 is almost the same as that of Example 1, so they are not shown one by one.

[0060] Table 1 Relative content of amino acids in some examples and comparative examples

[0061]

[0062] From Table 1, we can see that:

[0063] (1) By comparing the test results of Example 1 with those of Comparative Example 1, it can be seen that: compared with the normal temperature spreading adopted in the prior art, the low temperature spreading can effectively increase the amino acid content in the yam leaf green tea, so the taste of the obtained tea soup is more fresh, sweet and mellow.

[0064] (2) Comparing the test results of Example 1 with that of Example 2, it can be seen that in the low-temperature spreading step, the amino acid content in the yam leaf green tea can be significantly increased after adding irradiation, thereby further improving the quality of the yam leaf green tea. Comparing the test results of Comparative Example 2 with that of Comparative Example 1, it can be seen that if normal temperature spreading is adopted, irradiation cannot significantly increase the amino acid content in the yam leaf green tea, and irradiation and normal temperature spreading do not show a synergistic effect. Comparing the test results of Example 2 with that of Comparative Example 1, it can be seen that compared with the normal temperature spreading adopted in the prior art, the amino acid content in the yam leaf green tea can be significantly increased by adopting low-temperature spreading and adding irradiation, and the synergistic effect of irradiation and low-temperature spreading is very obvious.

[0065] (3) The improvement of the quality of yam leaf green tea is the result of the combined effects of low-temperature spreading, withering, rolling, and frying and baking. Comparing the test results of Example 1, Example 2, and Example 5, it can be seen that the technical solution shown in Example 2 is the optimal processing method.

[0066] In summary, the present invention uses fresh, tender green leaves of iron stick yam as raw materials, and makes yam leaf green tea through low-temperature spreading, withering, rolling, frying and baking processes. The green tea can be directly brewed and drunk, and the soup is clear and green, exudes a light fragrance, and has a mellow taste. It is rich in amino acids, flavonoids, organic acids, phenolic acids and other substances, and has multiple health care effects such as regulating immunity, anti-inflammatory and antibacterial, anti-cancer and anti-cancer, regulating the spleen and stomach, etc.

[0067] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. Those skilled in the art may change, modify, replace and deform the above embodiments within the scope of the present invention. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples without contradiction.

Claims

1. A method for processing yam leaf green tea, characterized in that: The steps are as follows: S1. Picking fresh leaves: picking fresh, tender green leaves of Tiegun Yam as raw materials; S2, low temperature spreading: the leaves of the Chinese yam obtained in the previous step are spread in an artificial climate room with a temperature of 8-12°C and a humidity of 68%-80%, with a thickness of 2-3cm and a spreading time of 48-72h; S3, fixing: put the leaves obtained in the previous step into a drum fixing machine, fix them at 250-300℃ for 5-8min, the fixed leaves turn brown-green and there should be no burning phenomenon, then spread out the fixed leaves discharged from the drum fixing machine to cool in time; S4, rolling: when the withered leaves are cooled to 47-50°C, they are put into a rolling machine and gently rolled to loosen them into shape; S5, frying and drying treatment: first tumble fry the product obtained in the previous step at a temperature of 150-180° C. until the water content is 15%-25%, then place it in a dryer or drying room for drying at a temperature of 95-100° C. until the water content is not higher than 5%; S6. Post-processing: Take out the dried product and place it in a ventilated place, turn it over gently and wait for it to cool naturally to room temperature before screening and vacuum packaging.

2. The method for processing yam leaf green tea according to claim 1, characterized in that: In step S2, the Co-γ irradiation is performed at a dose rate of 6-8 kGy / h in the first 6-12 hours of low-temperature spreading, and the Co-γ irradiation is performed again at a dose rate of 10-12 kGy / h in the last 6-12 hours of low-temperature spreading.

3. The method for processing yam leaf green tea according to claim 1, characterized in that: In step S2, the temperature of the artificial climate chamber is 10°C, the humidity is 78%, and the spreading time is 60 hours.

4. The method for processing yam leaf green tea according to claim 1, characterized in that: In step S3, the drum fixing machine fixes the tea leaves at 270° C. for 6 minutes.

5. The method for processing yam leaf green tea according to claim 1, characterized in that: In step S4, the kneading machine gently kneads at a rotation speed of 40-45 rpm for 20-30 minutes.

6. The method for processing yam leaf green tea according to claim 5, characterized in that: Step S4 also includes manual kneading, and after the kneading machine finishes kneading, the kneading is performed manually for 5-10 minutes.

7. The method for processing yam leaf green tea according to claim 1, characterized in that: In step S5, the flour is first fried at 165° C. until the moisture content reaches 20%, and then dried at 98° C. until the moisture content is no higher than 5%.

8. The method for processing yam leaf green tea according to any one of claims 1 to 7, characterized in that: In step S2, the temperature is maintained by circulating air, and the air is circulated by a fan.

9. The method for processing yam leaf green tea according to claim 8, characterized in that: In step S2, the spread leaves of the iron stick yam are evenly turned over once every 12-24 hours, and the time for each turning is controlled within 10 minutes, and the interval time before this turning is included, and the total turning is an odd number of times during the spreading time.

10. A yam leaf green tea prepared according to the processing method according to any one of claims 1 to 9.

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