A kind of flat tea of ​​polygonatum tender bud and preparation method thereof

Abstract

The invention discloses a flat tea of ​​young polygonatum buds and a preparation method thereof, wherein the tea is prepared by selecting young polygonatum buds in the early stage of leaf expansion as raw materials. The invention uses young polygonatum buds without leaf expansion as raw materials to make flat tea of ​​young polygonatum buds for the first time, wherein the water extract content of the flat tea of ​​young polygonatum buds is 48% to 49%, the flavonoid content is 16 to 17 mg / g, the tea polyphenol content is 13% to 14%, the soluble sugar content is 14% to 15%, and the free amino acid content is 6.5% to 7.3%. The flat tea of ​​young polygonatum buds has a flat, straight, tender green and oily appearance, the tea soup has a tender green and bright color, a high and refreshing aroma, a sweet and fresh taste, and a mellow and fresh taste, and the leaf bottom is bright and yellow-green and complete.

Description

Technical Field

[0001] The invention belongs to the field of substitute tea, and relates to polygonatum substitute tea and a preparation method of the polygonatum tea. Background Art

[0002] Substitute tea refers to a product that is made from buds, leaves, flowers and buds, fruits (fruits), rhizomes, etc. of plants other than tea that are announced as food by the national administrative department, and is processed and brewed (soaked or boiled) in a similar way to tea for people to drink.

[0003] Drinking tea is a traditional habit of the Chinese people. The inventors have made a preliminary study of substitute teas, mixed teas, and medicinal teas recorded in Chinese and foreign literature before the Song Dynasty. They found that these non-teas or mixed teas had appeared before the Tang Dynasty, complemented tea drinking, and were used in health preservation, health care, and spiritual practice. They are an important part of tea culture and have enriched the remains of Chinese tea culture. Substitute teas have attracted the attention of a large number of consumers with their convenient drinking and varied flavors. Chrysanthemum tea, honeysuckle tea, cassia seed tea, etc. have long been well-known.

[0004] Substitute teas with different functions have been increasingly accepted by people, and more and more people are willing to choose substitute teas, which not only changes people's lifestyles and meets the needs of consumers, but also makes drinking tea a fashion.

[0005] Polygonatum sibiricum is an important plant with medicinal and edible properties. It is recorded in the Pharmacopoeia of the People's Republic of China and is divided into Polygonatum sibiricum Red., Polygonatum kigianum Coll.et Hemsl., and Polygonatum cyrtonema Hua. It is sweet and neutral in nature, and has the effects of nourishing yin and moistening the lungs, tonifying the spleen and replenishing qi, and nourishing the kidneys and replenishing essence. The main medicinal part is the rhizome of Polygonatum sibiricum, which mainly contains active ingredients such as polysaccharides, saponins, lectins, amino acids, alkaloids, and flavonoids. It has functional activities such as anti-aging, anti-oxidation, lowering blood sugar, and enhancing immunity.

[0006] The existing technology has focused more on the rhizomes of Polygonatum sibiricum, but less on the non-medicinal parts of Polygonatum sibiricum, such as Polygonatum sibiricum flowers, Polygonatum sibiricum buds (leaves), Polygonatum sibiricum fruits, and even fewer on the conversion into products.

[0007] In the process of realizing the present invention, the inventors found that there are few reports on the systematic research on the young shoots of Polygonatum sibiricum in the prior art. The young shoots of Polygonatum sibiricum have a long history of application as a traditional edible green dish (pen tube vegetable) in some areas of the folk. In addition to being crisp and delicious, it also has the effects of nourishing yin and moistening dryness, resisting fatigue and aging, and regulating blood sugar. There are no specific reports on the research on it, and there are no reports on the research of making the young shoots of Polygonatum sibiricum into a substitute tea. Summary of the invention

[0008] In view of this, one of the objects of the present invention is to provide a substitute tea made from the tender buds of Polygonatum cyrtonema.

[0009] One of the purposes of the present invention is to provide a method for preparing the substitute tea made from the tender buds of polygonatum.

[0010] The inventor has continuously reformed and innovated through long-term exploration and attempts, as well as multiple experiments and efforts, to solve the above technical problems. The technical solution provided by the present invention is to provide a flat tea of ​​young buds of polygonatum, which is prepared by selecting young buds of polygonatum in the early stage of leaf expansion as raw materials.

[0011] Furthermore, the flat tea of ​​young buds of polygonatum has a flat and straight appearance, is tender green and oily, has a water extract content of 48% to 49%, a flavonoid content of 16 to 17 mg / g, a tea polyphenol content of 13% to 14%, a soluble sugar content of 14% to 15%, and a free amino acid content of 6.5% to 7.3%.

[0012] The invention also provides a preparation method of polygonatum tender bud flat tea, comprising the steps of picking tender buds, cooling for the first time, killing green, cooling for the second time, arranging strips, shaping the strips, drying and shaping, and drying and aroma-enhancing; the killing green is carried out by microwave.

[0013] According to one embodiment of the method for preparing flat tea of ​​young buds of polygonatum sibiricum, the picking of young buds comprises: picking young buds with 15 to 20 leaves and a length of 5 cm to 8 cm.

[0014] According to one embodiment of the method for preparing polygonatum tender bud flat tea of ​​the present invention, in the first cooling step, the tender buds are spread indoors until the water content reaches 68% to 72%.

[0015] According to one embodiment of the method for preparing polygonatum tender bud flat tea of ​​the present invention, in the first cooling step, the tender buds are spread indoors until the water content reaches 70%.

[0016] According to one embodiment of the method for preparing polygonatum tender bud flat tea of ​​the present invention, in the microwave killing step, the microwave power is 500-600W, and the killing time is 5.5-6.5min.

[0017] According to one embodiment of the method for preparing polygonatum tender bud flat tea of ​​the present invention, in the microwave killing step, the microwave power is 550 W and the killing time is 6 min.

[0018] According to one embodiment of the preparation method of flat tea of ​​young buds of polygonatum sibiricum of the present invention, the strip-forming step is: the vibration slot of the vibration strip-forming machine is preheated to 100-115°C, and the young buds of polygonatum sibiricum that have been withered and cooled are placed in it. The reciprocating frequency of the slot wave is medium speed. During the strip-forming process, the surface temperature of the product is maintained at 70-80°C. The reciprocating frequency is adjusted to high speed in the middle, maintained for 30-50 seconds, and then switched back to medium speed to continue strip-forming. The process lasts for 55 minutes.

[0019] According to one embodiment of the preparation method of flat tea of ​​young buds of polygonatum of the present invention, the strip-forming step is as follows: when the strips of the product are further tightened and straightened and the leaves with scattered edges are tentacled, a light pressure rod is added to flatten the product into shape so that the leaves with scattered edges fall off, and the reciprocating frequency is adjusted to a low speed when adding the rod, the strips are flattened and straightened, and the light pressure rod is taken out when the leaves with scattered edges have fallen off, and the rod adding time is 4 minutes.

[0020] According to one embodiment of the method for preparing flat tea of ​​young polygonatum sibiricum buds of the present invention, in the microwave sterilization step, the weight of the young buds sterilized by a single microwave is 300 g.

[0021] According to one embodiment of the method for preparing flat tea of ​​young buds of polygonatum sibiricum of the present invention, in the drying and aroma-enhancing step, the tea is dried at 80° C. until the moisture content is below 7%.

[0022] Compared with the prior art, one of the above technical solutions has the following advantages:

[0023] a) The present invention is the first to use the early stage of leaf expansion of polygonatum sibiricum buds as raw materials to produce polygonatum sibiricum bud flat tea, the polygonatum sibiricum bud flat tea extract content of 48% to 49%, flavonoids content of 16 to 17 mg / g, tea polyphenols content of 13% to 14%, soluble sugar content of 14% to 15%, free amino acid content of 6.5% to 7.3%. Its soluble sugar and free amino acid content is higher than that of ordinary green tea, and its tea polyphenol content is lower than that of ordinary green tea, which is the material basis of its sweet, fresh, mellow and refreshing taste.

[0024] b) The IC50 value of tea extract in removing DPPH· was 12.4ug / ml, and the IC50 value of tea extract in removing ABTS was 12.4ug / ml. + The IC50 value of · is 9.8ug / ml, and the IC50 value of scavenging OH· is 822.6ug / ml, which has good health care function.

[0025] c) The flat tea of ​​young polygonatum buds of the present invention uses young polygonatum buds as raw materials, with stems and unexpanded leaves, so that the finished tea has a flat and straight appearance, is tender green and oily, has no raw green taste, has a bright tender green tea soup color, a high and refreshing aroma, a sweet and fresh taste, and a mellow and fresh taste, and has a bright yellow-green and complete leaf bottom.

[0026] d) In the raw material leaves of the flat-shaped tea of ​​the tender buds of the present invention, the raw materials of the tender buds of the polygonatum cyrtonema have stems and undeveloped leaves, and the contents in the tender buds are continuously transformed during the first cooling process, soluble sugars and free amino acids are accumulated, and aromatic substances are transformed. Through the first cooling and microwave sterilization, the grassy taste of the raw materials of the flat-shaped tea of ​​the tender buds of the polygonatum cyrtonema is effectively eliminated, and the tea leaves show a fresh fragrance.

[0027] Instruction Manual

[0028] Figure 1 This is a real picture of the raw material of the flat tea of ​​polygonatum sibiricum sprouts of the present invention.

[0029] Figure 2 This is a real picture of the finished tea of ​​the flat-shaped tea of ​​polygonatum sibiricum tender buds of the present invention. DETAILED DESCRIPTION

[0030] The following describes the invention in conjunction with specific embodiments.

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents the selected embodiments of the present invention.

[0032] In the embodiments, the sensory evaluation method of finished tea is based on the method of GB / T 23776-2018 "Tea Sensory Evaluation Method" and is appropriately adjusted. A review team composed of multiple experts conducts sensory evaluation on the processed tea samples. All samples are weighed 3g and brewed with 250mL boiling water for 5min for evaluation. All review experts rinse their mouths with mouthwash between different samples and record their comments.

[0033] Total evaluation score = appearance × 30% + soup color × 10% + aroma × 25% + taste × 25% + tea leaves × 10%.

[0034] Determination of moisture content: Determined according to Method 4, General Rules 0832 of the 2020 edition (Volume 4) of the Pharmacopoeia of the People's Republic of China.

[0035] Determination of polysaccharide content: refer to the 2015 edition of the Chinese Pharmacopoeia and prepare 0.2 mg / mL -1 The anhydrous glucose reference solution was developed with phenol-sulfuric acid and the absorbance was measured at a wavelength of 582 nm.

[0036] Protein content determination: The protein content was determined using the Lowry method. The prepared mass concentration was 0.5 mg / mL -1 The absorbance of BSA standard was measured at 650 nm using an enzyme reader.

[0037] Determination of total phenol content: The total phenol content was determined by Folin phenol colorimetry. The concentration was 0.2 mg / mL. -1 The absorbance of the gallic acid reference solution was measured at 765 nm.

[0038] Determination of amino acid content: refer to GB 5009.124-2016 "National Food Safety Standard Determination of Amino Acids in Food", the concentration is 1μmol·mL -1 The amino acid content of the mixed amino acid standard stock solution was determined by the external standard method.

[0039] DPPH free radical scavenging rate: kit method.

[0040] Determination of water extract content: refer to GB / T 8305-2013 "Determination of tea water extract".

[0041] Determination of free amino acid content: refer to GB / T 8314-2013 "Determination of the total amount of free amino acids in tea".

[0042] Determination of soluble sugar content: refer to the anthrone-sulfuric acid colorimetric method (Zhang Zhengzhu. Tea Biochemistry Experiment Tutorial [M]. China Agriculture Press, 2009: 104-110.).

[0043] Determination of tea polyphenols content: refer to GB / T 8313-2002 "Determination of tea polyphenols".

[0044] Example 1

[0045] The flat tea of ​​young buds of polygonatum described in this embodiment is prepared by selecting young buds of polygonatum in the early stage of leaf expansion as raw materials.

[0046] Specifically, it is prepared by the following steps.

[0047] Picking young shoots: Pick young shoots with 15 to 20 unexpanded leaves, 5 to 8 cm in length, see Figure 1 The length of the tender shoots can be 5, 5.5, 6, 6.5, or 7 cm. The tender shoots do not need to be peeled off from the tender leaves, and can be spread out to cool and proceed with the subsequent steps with the stems.

[0048] First cooling: Spread indoors for 20 hours until the water content is about 70%, and the indoor temperature is 28°C. The tender leaves with stems lose water slowly, and the contents are fully transformed, reducing the raw green taste of the flat tea of ​​Huangjing tender buds, and the fragrance is revealed.

[0049] Fixing: Microwave fixing, medium-high fire, microwave time of 6 minutes, leaf amount of 300g. In this embodiment, the microwave oven model used is Midea M1-L213B, the maximum power is 700W, and the power of medium-high fire is 550W. The grassy taste of the raw material of the flat-shaped tea of ​​the tender buds of the polygonatum sibiricum is obviously eliminated, the oxidase activity in the raw material is passivated, and the color of the flat-shaped tea of ​​the tender buds of the polygonatum sibiricum is ensured to be tender green.

[0050] Second cooling: After the tender buds are withered and cooled, the moisture is further reduced, the grass smell disappears further, and the strips become tighter and thinner before being sorted.

[0051] Striping: Preheat the vibration trough of the vibration striping machine to 100-115℃, put the young buds of Polygonatum cyrtonema after killing and cooling, and the reciprocating frequency of the trough is medium speed. During the striping and shaping process, the surface temperature of the product is kept at 70-80℃. Adjust the reciprocating frequency to high speed in the middle and keep it for 30-50 seconds to achieve the purpose of losing moisture and preventing the product from sticking to the vibration trough, and then switch back to medium speed to continue striping. The process lasts for 55 minutes. After striping, the product is cooled to room temperature for the next step.

[0052] Strip shaping: When the strips of the finished product are further tightened and straightened, the moisture is further lost, and the leaves on the edges are scattered, add light pressure rods. The purpose of adding rods is to flatten the finished product into shape and make the leaves on the edges fall off. When adding rods, adjust the reciprocating frequency to low speed, and the strips become flat and straight. When the leaves on the edges have fallen off, take out the light pressure rods. The rod adding time is 4 minutes. Turn off the machine, take out the finished product, manually sieve to remove the powdery broken leaves, and cool to room temperature.

[0053] Drying and shaping: The screened work-in-progress is put into the vibrating stripping machine for drying and shaping. The vibration tank temperature is preheated to 100-115°C, and the reciprocating frequency of the tank wave is medium speed. The surface temperature of the product is maintained at 70-80°C during the drying process. The purpose of drying and shaping is to make the work-in-progress more compact, the surface smoother and oilier, and continue to lose moisture. The shaping and drying time is 45 minutes. After drying and shaping, the work-in-progress will be spread to cool to room temperature.

[0054] Drying and aroma extraction: Dry at 80℃ until the moisture content is below 7%.

[0055] Get the flat and straight appearance of the flat tea of ​​young buds of Polygonatum odoratum, see Figure 2 .

[0056] The flat-shaped tea with young buds of Polygonatum is tender green and oily, the tea soup is tender green and bright, the aroma is refreshing and tender, the taste is sweet, mellow and refreshing, the leaf bottom is bright yellow-green and complete.

[0057] The water extract content of the flat tea of ​​young buds of Polygonatum sibiricum is 48% to 49%, the flavonoids content is 16 to 17 mg / g, the tea polyphenols content is 13% to 14%, the soluble sugar content is 14% to 15%, and the free amino acid content is 6.5% to 7.3%.

[0058] The scavenging ability of the tea extract of Polygonatum cyrtonema bud flat tea on DPPH· gradually increased with the increase of concentration, and the dose-effect relationship was significant. In the concentration range of 0.03125-1mg / ml, the maximum scavenging rate of the tea extract on DPPH· was 57.30%; the IC50 value of scavenging DPPH· was 12.4ug / ml.

[0059] Effect of the extract of Polygonatum cyrtonema bud flat tea on ABTS + The scavenging ability of tea extract on ABTS increased with the increase of concentration, and the dose-effect relationship was significant. + The maximum clearance rate of · was 38.53%; the IC50 value for clearing ABTS+· was 9.8ug / ml.

[0060] The scavenging ability of the tea extract of Polygonatum sibiricum bud flat tea on OH· gradually increased with the increase of concentration, and the dose-effect relationship was significant. In the concentration range of 1-9 mg / ml, the maximum scavenging rate of the tea extract on OH· was 72.05%; the IC50 value of scavenging OH· was 822.6ug / ml.

[0061] It can be known from the test results of main nutrients and functional components that the flat tea of ​​young buds of polygonatum sibiricum has good health care function.

[0062] The parameter settings in the first cooling, fixing, and drying steps have a significant impact on the quality of the flat tea of ​​young buds of Polygonatum odoratum. To illustrate the technical effect of the parameter settings of the present invention, the following is an illustration through comparative tests of Examples 2 to 4. In Examples 2 to 4, except for the comparison factors, the parameters of the other steps are the same as those of Example 1.

[0063] Example 2

[0064] The main purpose of this embodiment is to compare the effects of different first cooling degree settings on the flat tea of ​​young buds of polygonatum, and the optimal cooling leaf content rate is about 70%.

[0065] In this example, four groups of horizontal cooling test data were selected for comparison: no cooling, 80%, 70%, and 60%. The functional component contents of finished tea made from cooling leaves with different water contents are shown in Table 1, and the sensory quality evaluation results of finished tea with different cooling water contents are shown in Table 2.

[0066] Table 1 Content of functional components in finished tea with different cooling water content

[0067]

[0068]

[0069] Table 2 Sensory quality evaluation of finished tea with different moisture content during cooling

[0070]

[0071] 1. Changes in water content

[0072] The leaves of young Polygonatum odoratum buds are thicker and have a higher water content than traditional tea leaves, so the cooling time is longer. As the cooling time increases, the water content in the young buds decreases, the leaves become softer, and the grass smell gradually decreases, making the finished tea taste better. During the cooling process of young Polygonatum odoratum buds, the speed of water reduction is related to the cooling temperature, the drying time, and the young buds themselves.

[0073] In the present embodiment, the tender shoots of polygonatum are naturally spread indoors at about 28°C, and the water content of the tender shoots decreases as the cooling time is extended. From the whole process, the reduction of water content is gradually slowed down. The water content of the tender shoots before cooling is 84.05%. After 5h, 20h, and 45h of cooling, the water content of the tender shoots is reduced to 79.80%, 71.42%, and 61.09%. The water loss rate of the tender shoots of polygonatum is the fastest in 0-5h, and 20h-45h is relatively slow. According to the comparison of the quality of the tender shoots at different cooling times, the water content of the tender shoots of polygonatum cooled for 20h is about 70%, and the tender shoots are soft.

[0074] 2. Changes in water extract content

[0075] Water extract refers to the soluble substances in tea leaves after extraction with boiling water. The amount of water extract is positively correlated with the concentration of tea soup. The higher the content of water extract, the better the quality of tea leaves.

[0076] As can be seen from Table 1, with the extension of the cooling time, the water extract content in the finished tea shows an obvious upward trend. The water extract content between the tender bud finished tea and the finished tea with 80% cooling water content is rising slowly, the water extract content between the finished tea with 80% cooling water content and the finished tea with 70% cooling water content is rising fastest, and the water extract content between the finished tea with 70% cooling water content and the finished tea with 60% cooling water content does not change much. Therefore, the cooling water content of about 70% is suitable for the subsequent processing of the flat tea of ​​tender buds of Polygonatum odoratum.

[0077] 3. Changes in flavonoid content

[0078] Flavonoids are a kind of functional nutrients, which have a good therapeutic effect on cardiovascular and cerebrovascular diseases, and have a preventive effect on some common diseases, so it is not advisable to lose too much.

[0079] As can be seen from Table 1, as the cooling time increases, the flavonoid content in the finished tea shows a downward trend. The downward trend of the finished tea with a cooling moisture of 80% and the finished tea with a cooling moisture of 70% is obvious, and the downward trend of the finished tea with a cooling moisture of 70% and the finished tea with a cooling moisture of 60% is slower, and the difference between the two is not significant (P>0.05). Therefore, the cooling moisture of about 70% is suitable for the subsequent processing of the flat tea of ​​the tender buds of Polygonatum odoratum.

[0080] 4. Changes in tea polyphenols content

[0081] Tea polyphenols are a major component of tea flavor and have health benefits.

[0082] As can be seen from Table 1, with the extension of the cooling time, the tea polyphenol content in the finished tea showed an upward trend. The rising trend of the finished tea with a cooling water content of 80% and the finished tea with a cooling water content of 70% was obvious, and the rising trend of the finished tea with a cooling water content of 70% and the finished tea with a cooling water content of 60% was slower, and the difference between the two was not significant (P>0.05). Therefore, the cooling water content of about 70% is suitable for the subsequent processing of the flat tea of ​​the tender buds of Polygonatum odoratum.

[0083] 5. Changes in soluble sugar content

[0084] Sugar has a sweet taste, and its presence helps to improve the bitter taste of tea soup and increase the fragrant flavor of tea.

[0085] As can be seen from Table 1, with the extension of the cooling time, the soluble sugar content in the finished tea shows a trend of first rising and then falling. The soluble sugar content of the finished tea with a cooling water content of 80% and 70% has an obvious upward trend, and the soluble sugar content of the finished tea with a cooling water content of 70% and 60% gradually decreases, so the cooling time should not be too long. Therefore, the cooling water content of about 70% is suitable for the subsequent processing of Polygonatum odoratum bud flat tea.

[0086] 6. Changes in free amino acid content

[0087] Free amino acids are an important component of tea soup, and their content determines the freshness of the tea soup.

[0088] As can be seen from Table 1, with the extension of the cooling time, the free amino acid content in the finished tea shows a trend of first rising and then falling. The free amino acid content of the finished tea with a cooling water content of 80% and 70% is obviously rising, and the free amino acid content of the finished tea with a cooling water content of 70% and 60% is gradually decreasing, so the cooling time should not be too long. Therefore, the cooling water content of about 70% is suitable for the subsequent processing of the flat tea of ​​the tender buds of Polygonatum odoratum.

[0089] 7. Sensory quality evaluation of finished tea with different moisture content

[0090] As shown in Table 2, different cooling water content has obvious differences in the sensory quality of flat tea made from young buds of polygonatum. When the young buds of polygonatum are made into tea directly without cooling, the green smell is strong and the taste is not good. As the cooling water content decreases, the smell of grass in the young buds of polygonatum gradually decreases. When the cooling water content is about 70%, the flat tea made from young buds of polygonatum has a strong and lasting aroma, the grass smell is gone, the tea soup is bright green, and the taste is better. When the cooling water content is about 60%, the finished tea has a poor appearance and is not obviously flat and straight, the aroma is reduced, and the sensory score is also the lowest. Therefore, when the cooling water content is 70%, it is more suitable for making flat tea made from young buds of polygonatum.

[0091] Example 3

[0092] This example compares the effects of different fixing methods and microwave fixing parameter settings on the quality of Polygonatum sibiricum tender bud flat tea.

[0093] The purpose of fixing is to quickly passivate the oxidase activity in the raw material leaves, so that the enzymatic oxidation reaction in the tender buds is suppressed, the tender buds leaves are prevented from turning brown, and the tender buds leaves are softened after being spread for cooling, so as to facilitate subsequent processing and forming, and the green odor of the tender buds themselves is distributed, and the formation of the tender buds fragrance is accelerated. Fixing is the key step in the formation of green tea quality. Peroxidase is a very heat-resistant enzyme. When the peroxidase in fruits and vegetables is inactivated in thermal processing, the possibility that other enzymes (such as polyphenol oxidase) exist in an active form is very small, so in fruit and vegetable processing, peroxidase is often used for the index of whether heat treatment is sufficient. Therefore, the present embodiment adopts peroxidase activity and fixing leaf sensory score as indicators, and the fixing process is optimized, and the purpose is to find a better fixing process, so that the enzyme activity in the fixing leaf is lower and the sensory organ of the fixing leaf is better.

[0094] Microwave sterilization:

[0095] 300g of young buds of Polygonatum cyrtonema after the first cooling were taken, and withered for 6 minutes at medium-high fire using Midea M1-L213B. The withered leaves were immediately taken out and cooled. The sensory evaluation of the withered leaves was carried out and the peroxidase activity was measured. The components were measured after tea making.

[0096] Steam killing:

[0097] Take 300g of the raw material of young buds of Polygonatum cyrtonema after the first cooling, put it into a steamer that has already generated steam, and wither for 6 minutes. Take it out and cool it immediately. Perform sensory evaluation on the withered leaves and measure their peroxidase activity. After making tea, the ingredients are measured.

[0098] Pan frying:

[0099] Take 300g of the raw material of young Polygonatum cyrtonema after the first cooling, set the pot temperature to 180℃, preheat for 5 minutes, put in the raw leaves, and use shaking, tossing and steaming to wither for 6 minutes, take out and cool immediately, conduct sensory evaluation on the withered leaves and determine their peroxidase activity, and determine the ingredients after tea making.

[0100] The comparison of functional component contents of finished tea obtained by different withering methods is shown in Table 3, the sensory quality evaluation results of finished tea are shown in Table 4, and the relative enzyme activity and sensory score results are shown in Table 5.

[0101] Table 3 Functional component contents of finished teas with different fixing methods

[0102]

[0103] Table 4 Sensory quality evaluation of finished teas with different fixing methods

[0104]

[0105] Table 5 Relative enzyme activity and sensory comparison

[0106] Relative enzyme activity (%) Sensory properties of the green leaves (points) Microwave sterilization 0.32 23.33 Steam Fixing 5.79 15.33 Pan-frying 14.4 7.67 .

[0107] As shown in Table 5, according to the relative enzyme activity analysis, under the same withering time, the enzymes in the microwave-withered leaves are basically inactivated, and the enzyme activity in the withered leaves cannot be completely lost during steam withering. However, during pan-frying with withering, the enzyme activity in the withered leaves reaches 14.4%, which is higher than the first two withering methods.

[0108] As shown in Table 5, in terms of sensory aspects, the microwave-cured leaves are dark green, the surface gloss has basically disappeared, and there is no browning; the vanilla smell has basically disappeared, and the aroma is revealed; the leaves are squeezed into a ball and are not easy to loosen, and the sensory score is 23.33 points. When steam-cured, the cured leaves are heated unevenly, the leaf color is slightly mottled; there is a slight grass smell, and the fragrance is bland; the leaves are slightly hard, the tissue is not easy to break, and the sensory score is slightly low. When pan-fried, the color of the cured leaves is mottled, the browning is large; the grass smell is heavy, and there is basically no aroma; the leaves are hard, easy to loosen and break when pinched, and the sensory score is 7.67 points.

[0109] During microwave sterilization, the enzyme activity in the young buds of Polygonatum cyrtonema can be completely passivated and the heat is evenly distributed, so microwave sterilization is suitable for subsequent processing.

[0110] Comparative analysis of functional components in finished tea products with different fixing methods

[0111] 1. Changes in water extract content

[0112] As shown in Table 3, among the three methods of tea killing, the water extract content in the tea samples of the microwave killing group was the highest, at 48.09%, and the water extract content in the steam killing group was the lowest, at 45.23%, and the difference was significant (P<0.05). The reason for this may be that the condensed water produced during the steam killing process caused the loss of water-soluble substances.

[0113] 2. Changes in flavonoid content

[0114] As shown in Table 3, among the three methods of killing green tea, the flavonoid content in the tea samples of the microwave killing group was the highest, at 16.55 mg / g, and the flavonoid content in the pan-frying killing group was the lowest, at 14.11 mg / g, and the difference was significant (P<0.05). The reason for this may be that during pan-frying, flavonoids were oxidized after being exposed to oxygen over a large area, and the substances were transformed, resulting in a low content. During microwave killing, special microwave utensils were used and the lid was added, which reduced the loss of flavonoids.

[0115] 3. Changes in tea polyphenols content

[0116] As shown in Table 3, among the three methods of killing green tea, the tea polyphenol content in the microwave killing green tea group was the highest, at 13.23%, and the tea polyphenol content in the pan-frying killing green tea group was the lowest, at 10.6%, and the difference was significant (P<0.05). The reason for this may be that the temperature in the pan rises slowly during pan-frying killing green tea, and the tea polyphenols are lost due to isomerization, hydrolysis, etc. due to the influence of moisture and heat.

[0117] 4. Changes in soluble sugar content

[0118] As shown in Table 3, among the three methods of killing green tea, the soluble sugar content in the tea samples of the microwave killing green tea group was the highest, at 14.49%, and the content in the tea samples of the pan-frying killing green tea group was the lowest, at 12.01%, and the difference was significant (P<0.05). The reason for this is that during the pan-frying killing green tea, the soluble sugar undergoes a series of reactions under the condition of long-term contact with air, and is converted into other substances, thereby reducing the content.

[0119] 5. Changes in free amino acid content

[0120] As shown in Table 3, among the three methods of killing green tea, the free amino acid content in the tea samples of the microwave killing green tea group was the highest, at 6.77%, and the content in the tea samples of the pan-frying killing green tea group was the lowest, at 5.48%, and the difference was significant (P<0.05). The reason for this is that when the pan is used for killing green tea, the temperature of the wok is high, and the amino acids participate in the reaction to generate aroma substances, resulting in a large loss of amino acid content, resulting in a lower free amino acid content.

[0121] In summary, the functional components and flavor components of the flat tea of ​​polygonatum sibiricum buds are closely related to the withering methods. Through the comparison of the three withering methods, microwave withering has the advantages of uniform withering, rapid heating and short withering time, which is more conducive to retaining the nutrients and effective components in the polygonatum sibiricum buds.

[0122] Sensory contrast

[0123] As shown in Table 4, the sensory qualities of the finished teas treated by the three methods of killing green tea are different. The finished teas in the microwave killing group scored the highest, with flat and straight, tender green color, lasting aroma, bright green tea soup, and complete leaf bottom; the finished teas in the pan-frying killing group scored the lowest, with unobvious flatness, gray color, bright green tea soup, and less lasting aroma than microwave killing green tea. Therefore, microwave killing green tea is the most suitable killing green tea method for the subsequent processing of Huangjing tender bud flat tea.

[0124] In the process of completing the present invention, the inventors also set up a microwave fixation process optimization test, analyzed the influencing factors of microwave power, microwave time, and leaf amount, and optimized the process parameters. According to the test data analysis and sensory scoring, the primary and secondary factors affecting microwave fixation are leaf amount > microwave power > microwave time. When the microwave power is medium-high (550W), the fixation time is 6min, and the leaf amount is 300g, the score is the highest.

[0125] Under the conditions of 6 min of withering time and 300 g of leaf weight, the score decreased when the microwave power was high. At this time, the withering power was too high, the withering leaves lost too much water, and the color was not good. According to the relative enzyme activity analysis, with the increase of microwave power, the enzyme activity of the withering leaves gradually decreased. When the microwave power was medium, the enzyme activity of the withering leaves was already at a low level, and the activity of the enzyme could be effectively inactivated at medium-high heat. Taking all factors into consideration, medium-high heat is better for microwave withering.

[0126] When the microwave power is medium-high (550W) and the amount of leaves is 300g, the withering time is 6min and 8min, the withered leaves are dark green, basically no browning, the aroma is revealed, the grass smell is basically gone, the leaves are lumped and sticky, which meets the tea withering standard. The sensory score decreases with the extension of the withering time. The analysis reason may be that the tender buds lose too much water, and the chlorophyll loss of the withered leaves is large, and the content of pheophytin increases, which makes the color of the withered leaves turn yellow or even dark brown, and the sensory quality decreases. According to the relative enzyme activity analysis, as the withering time increases, the enzyme activity of the withered leaves decreases rapidly. Under the condition of long-term heating, the enzyme is completely inactivated after 6min of withering. Taking all factors into consideration, the withering time is preferably 6min.

[0127] Under the conditions of medium-high microwave power (550W) and withering time of 6 minutes, the amount of leaves added increased from low to high, the sensory score gradually increased and then decreased, and the sensory score was the highest when the amount of leaves added was 300g. At this time, the withered leaves were dark green, basically without browning, the grassy smell basically disappeared, the aroma was revealed, and the leaves were soft. When the amount of leaves added was more than 300g, the color of the tender buds was mixed, there was browning, a slight grassy smell, and the withering was uneven; according to the relative enzyme activity analysis, after the amount of leaves added increased, the peroxidase was on an upward trend, and too much input of Polygonatum odoratum tender buds was not conducive to the quality of the finished tea. Taking all factors into consideration, the amount of leaves added was preferably 300g.

[0128] Example 4

[0129] This example compares the effects of different drying conditions on the quality of flat tea of ​​young buds of Polygonatum odoratum. Four groups of hot air drying methods at 60, 80, 100, and 120°C are selected to dry the young buds to a moisture content of less than 7%. The soluble sugar content, total free amino acid content, water extract content, total phenol content, flavonoid content, and sensory evaluation are compared. The results of the effects of different drying temperatures on the quality of finished tea are shown in Table 6, and the sensory quality evaluation of finished tea at different drying temperatures is shown in Table 7.

[0130] Table 6 Effect of different drying temperatures on the quality of finished tea

[0131]

[0132]

[0133] As shown in Table 6, there are differences in the content of physical and chemical components of tea samples made by hot air drying at different drying temperatures. According to the analysis of water extract content, there is no significant difference when drying at 80℃ and 120℃, and the content is the lowest when drying at 100℃; according to the analysis of flavonoid content, the content is the lowest when drying at 60℃, and the content is the highest when drying at 120℃. The reason may be that the time required for drying at 120℃ is shorter, and the flavonoids are less converted into other substances; according to the analysis of tea polyphenol content, the content is the highest when drying at 80℃, and the content is the lowest when drying at 120℃. The reason may be that the high temperature during drying is not conducive to the retention of tea polyphenols; according to the analysis of soluble sugar content, as the drying temperature increases, the content decreases, but there is no significant difference in the content of tea samples dried at 80℃, 100℃, and 120℃; according to the analysis of free amino acid content, there is no significant difference in the content of tea samples dried at 60℃, 80℃, and 100℃, and the content decreases when drying at 120℃. In summary, it is not advisable to use too high a temperature when drying the flat tea of ​​Polygonatum sibiricum young buds, as high temperature is not conducive to the retention of physical and chemical components.

[0134] Table 7 Sensory quality evaluation of finished tea at different drying temperatures

[0135]

[0136] As shown in Table 7, the tea samples obtained at different drying temperatures have different sensory characteristics. The tea sample dried at 80℃ has the highest sensory score of 96.36. The tea sample dried at 120℃ has the lowest sensory score of only 84.92. The poor scores are mainly in the tea soup color and aroma. The reason for this may be that the tea samples treated at high temperature have a cooked and overcooked taste, a darker color, and the tea soup color is not as bright as that dried at other temperatures, which is not conducive to the formation of sensory quality.

[0137] In summary, the flat tea of ​​young buds of Polygonatum sibiricum dried at 80℃ has the best sensory quality.

[0138] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A flat tea of ​​young buds of polygonatum, characterized in that: The tea is prepared by selecting tender buds of polygonatum sibiricum at the early stage of leaf expansion as raw materials; the water extract content of the flat tea of ​​tender buds of polygonatum sibiricum is 48%-49%, the flavonoids content is 16-17 mg / g, the tea polyphenols content is 13%-14%, the soluble sugar content is 14%-15%, and the free amino acid content is 6.5%-7.3%; The flat tea of ​​polygonatum sibiricum tender buds is prepared by the following steps: The method comprises the steps of picking tender buds, first cooling, microwave sterilization, second cooling, striping, strip shaping, drying and shaping, and drying and fragrance enhancement; in the first cooling step, the tender buds are spread indoors until the moisture content is 68%-72%; in the microwave sterilization step, the microwave power is 500-600W, and the sterilization time is 5.5-6.5min; in the drying and fragrance enhancement step, the buds are dried at 80°C until the moisture content is below 7%.

2. A method for preparing the flat tea of ​​young buds of polygonatum according to claim 1, comprising the steps of picking young buds, first cooling, killing green, second cooling, arranging, shaping, drying and shaping, and drying to improve aroma; characterized in that: The killing process is microwave killing; in the first cooling step, the tender shoots are spread indoors until the water content is 68% to 72%; in the microwave killing step, the microwave power is 500 to 600 W, and the killing time is 5.5 to 6.5 minutes; in the drying and aromatizing step, the shoots are dried at 80° C. until the water content is below 7%.

3. The method according to claim 2, characterized in that The method of picking tender shoots is as follows: picking tender shoots with 15 to 20 tender leaves.

4. The method according to claim 2, characterized in that: The strip-straightening step is as follows: preheating the vibration trough of the vibration strip-straightening machine to 100-115°C, putting in the withered and cooled young leaves of Polygonatum cyrtonema, the reciprocating frequency of the trough wave is medium speed, and the surface temperature of the product is maintained at 70-80°C during the strip-straightening and shaping process. Adjusting the reciprocating frequency to high speed in the middle, maintaining it for 30-50 seconds, and then switching back to medium speed to continue strip-straightening, and the process lasts for 55 minutes.

5. The method according to claim 2, characterized in that: The strip shaping step is as follows: when the product strips are further tightened and straightened and the leaves with scattered edges are tentacled, a light pressure rod is added to flatten the product into shape so that the leaves with scattered edges fall off; when adding the rod, the reciprocating frequency is adjusted to a low speed, and the strips are flattened and straightened; when the leaves with scattered edges have fallen off, the light pressure rod is taken out; and the rod adding time is 4 minutes.

6. The method according to claim 2, characterized in that In the microwave sterilization step, the weight of the tender shoots sterilized by microwave in a single time is 300g.

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