CN116918885A

CN116918885A - Original Liupu instant tea and preparation method thereof

Info

Publication number: CN116918885A
Application number: CN202310930580.3A
Authority: CN
Inventors: 何梅珍; 黄进达; 石荣强; 谢陆华; 温立香; 庾艳玲; 农寿华; 张芬; 曹中环; 袁冬寅; 袁旭泽; 林家威
Original assignee: Guangxi Wuzhou Tea Factory Co ltd
Current assignee: Guangxi Wuzhou Tea Factory Co ltd
Priority date: 2023-07-27
Filing date: 2023-07-27
Publication date: 2023-10-24

Abstract

The invention belongs to the technical field of tea processing, and discloses a preparation method of original Liupu instant tea, which comprises the following steps: heating Liupu tea material at 45-60deg.C, baking until water content is below 6%, and pulverizing; adding water extractant into the crushed Liupu tea, and performing ultrasonic closed continuous extraction, wherein the extraction temperature in the first stage is 90-100 ℃, and the extraction time is 5-10min; extracting at 50-70deg.C for 30-50min to obtain extract; and (3) carrying out solid-liquid separation, fine filtration, concentration, sterilization and drying on the extract liquid to obtain the original Liupu instant tea. The original Liupu instant tea soup is clear, red and bright, has high fragrance and mellow taste, and has no difference with the tea soup directly brewed by the original tea in quality such as flavor, aroma, soup color and the like.

Description

Original Liupu instant tea and preparation method thereof

Technical Field

The invention belongs to the technical field of tea processing, and particularly relates to original Liupu instant tea and a preparation method thereof.

Background

Liupu tea belongs to black tea, is a tea product with national geographic marks and strong local features in Guangxi provinces, is also a main fuqiao tea in China, is well known in terms of unique quality characteristics of red, strong, old and mellow and various health care effects, and is especially popular with consumers. In recent years, along with the acceleration of the life rhythm and the younger of consumer groups, the traditional tea brewing and drinking mode can not meet the needs of people, and solid beverages such as instant tea and the like are a new break and development direction for promoting tea drinks to be reproduced from a simple one. Compared with the traditional tea brewing drinking method, the instant tea beverage is more convenient, is convenient to carry, is safe and sanitary, is convenient to brew, and various effective components can be rapidly absorbed by human bodies, so that the instant tea beverage is deeply favored by consumers, especially young people.

The traditional instant tea takes middle-grade and low-grade tea as raw materials, and the processed raw tea has excessive flavor characteristic loss, low fragrance and poor taste. Along with the continuous upgrading of market consumption demands, consumers require instant tea to have the flavor characteristics of fragrance, taste and the like of the original tea as far as possible on the basis of keeping the original advantages of convenience and rapidness. Different tea types such as green tea, black tea, white tea and black tea have different flavor characteristics due to different flavor-developing substance types, contents and aroma compositions. Liupu tea belongs to one of typical representative tea of black tea, has own unique flavor in the aspects of aroma, taste and the like, so that the research on the characteristics of Liupu tea is necessary to furthest maintain the original tea flavor (strong aroma, mellow taste and red and bright soup color) of Liupu tea and develop the original Liupu tea solid beverage.

The Liupu instant tea described in the prior art is a flower-fragrance Liupu instant tea, such as jasmine Liupu instant tea of patent CN109953159A, osmanthus fragrans Liupu instant tea of patent CN109953157A, lilac Liupu instant tea of patent CN109953156A and rose Liupu instant tea of patent CN 109953155A. The instant tea is prepared by enzymolysis and extraction of Liupu tea and reflux extraction of ethanol, the preparation method is complex, the original taste of Liupu tea is covered by flower fragrance, and the original flavor of Liupu tea cannot be completely restored.

Disclosure of Invention

The invention aims to provide original Liupu instant tea and a preparation method thereof, solve the problem that the original tea flavor of the existing Liupu instant beverage is lost, and provide a simple, convenient and quick novel original Liupu instant tea for consumers.

The technical scheme of the invention is as follows:

the invention provides a preparation method of original Liupu instant tea, which comprises the following steps:

(1) Heating Liupu tea material at 45-60deg.C, baking until water content is below 6%, and pulverizing;

(2) Adding water extractant into the crushed Liupu tea, and performing ultrasonic closed continuous extraction, wherein the extraction temperature in the first stage is 90-100 ℃, and the extraction time is 5-10min; extracting at 50-70deg.C for 30-50min to obtain extract;

(3) And (3) carrying out solid-liquid separation, fine filtration, concentration, sterilization and drying on the extract liquid to obtain the original Liupu instant tea.

Preferably, the content of the water extract of the Liupu tea raw material is more than or equal to 30%.

Preferably, the crushed Liupu tea is sieved through a 60-80 mesh sieve.

Preferably, the extracting water agent is added in two stages, and the total feed-liquid ratio is 1:12-1: 20.

preferably, the membrane cut-off molecular weight of the fine filtration is more than 10 ten thousand.

Preferably, the concentration is that the concentrated tea extract is sequentially subjected to RO concentration and vacuum concentration.

Preferably, the RO concentration is performed by a reverse osmosis concentration system comprising an aroma recovery device, and the obtained aroma recovery solution substance is backfilled into the concentrated solution after vacuum concentration.

Preferably, the RO membrane working pressure of the RO concentration is 1.5-3.0MPa, and the working temperature is less than 45 ℃.

Preferably, the vacuum concentration temperature is 40-45 ℃, and the concentration is more than 30% of solid content.

The invention also comprises the original Liupu instant tea prepared by the preparation method.

Compared with the prior art, the invention has the following technical effects:

the preparation method comprises the steps of preprocessing raw materials, crushing, leaching by a two-step method, carrying out rough filtration, fine filtration and concentration at each level, sterilizing and drying to obtain the original Liupu instant tea. The Liupu instant tea prepared by the method has extremely strong instant property, can be rapidly dissolved in cold and hot water within 3 seconds, has no suspended matters visible to naked eyes, and has no additives such as essence, pigment, auxiliary materials and the like. The tea soup after dissolution is clear, red and bright, has high fragrance and mellow taste, has no difference in quality such as taste, fragrance, soup color and the like from the tea soup directly brewed by the original tea, has the tea polyphenol content of more than 12g/100g and has the powder yield of 18.70-25.32 percent.

Detailed Description

The Liupu tea raw material used in the invention is Liupu tea with rich fragrance and taste. Preferably, the content of the water extract of the Liupu tea raw material after uniform blending is more than or equal to 30 percent. Experiments show that the instant tea powder prepared from the raw materials with the water extract content of more than 30% has high yield, and the Liupu tea flavor characteristics of the tea soup prepared by dissolving the instant tea powder in water are more obvious in flavor such as aroma, taste and soup color.

TABLE 1 influence of tea extract content of raw materials on quality and yield of instant tea powder

The Liupu tea raw material is baked by double fire until the moisture content is below 6%. The Liupu tea is different from the conventional red green tea, the water content of the conventional tea is less than 6%, the Liupu tea has aging property, and the water content of a finished product is 10-12% in order to be beneficial to later conversion and quality formation in production (GB/T32719.4 Liupu tea regulation). However, according to the invention, if the moisture content of the Liupu tea raw material is too high, caking and the like are very easy to occur in the crushing process, the later test effect is seriously affected, so that the moisture content is reduced to below 6% on the basis of keeping the aging charm of the Liupu tea by low-temperature double fire treatment, the later crushing is facilitated, the crushed tea powder is not stuck and caked when the moisture content is below 6%, the later leaching and the like are facilitated.

The Liupu tea raw material is subjected to low-temperature re-firing at 45-60 ℃. Because the quality characteristics of Liupu tea are different from those of other tea, the 'old charm' characteristics of Chen Xiangchen taste of the original tea are kept as much as possible in the process of re-firing. The quality characteristics of the Liupu tea such as aroma and taste are easily affected due to the too high re-firing temperature, the old charm is weakened, and the re-firing time is prolonged due to the too low re-firing temperature. The invention further preferably has a re-ignition temperature of 48-57 ℃, more preferably 50-55 ℃.

The Liupu tea raw material is baked by double fire until the moisture content is below 6%. The water content of the Liupu tea finished product is 10-12% (GB/T32719.4 Liupu tea regulation). However, according to the invention, if the moisture content of the Liupu tea raw material is too high, caking and the like are very easy to occur in the crushing process, the later test effect is seriously affected, the moisture content is reduced to below 6% on the basis of keeping the aging charm of the Liupu tea through low-temperature double fire treatment, the later crushing is facilitated, the crushed tea powder is not stuck and agglomerated when the moisture content is below 6%, the later leaching and filtering are facilitated, and the like.

The pretreated Liupu tea raw materials are subjected to soup-opening and evaluation according to a GB/T23776-2018 tea sensory evaluation method, the tea is rich in aroma, mellow in taste and dark red in soup color, and the Liupu tea raw materials are qualified raw materials. Crushing the qualified raw materials, preferably sieving the crushed raw materials with a 60-80 mesh sieve. The crushing mainly increases the contact surface area of the tea leaves and the solvent, and improves the leaching rate of the soluble matters. However, too high a degree of pulverization, too large a surface area of the sample particles, enhanced adsorption, and an influence on the filtration rate. Through multiple experiments, the crushed granularity of the Liupu tea raw material is determined to be 60-80 meshes.

The invention adds the crushed Liupu tea into the extracting water agent and then carries out ultrasonic closed continuous extraction. As an implementation mode, the invention adopts an ultrasonic-assisted closed continuous extractor for extraction, isolates air, and avoids the aroma loss of Liupu tea and the oxidation of functional substances. The extraction according to the invention is carried out in two steps.

The invention firstly adopts short-time high-temperature leaching to excite characteristic aroma and flavor substances to leach. The characteristic aroma and taste components of Liupu tea are mostly high-boiling point volatile substances and hot water-soluble substances, but the active ingredients in the tea are easily influenced by long-time high-temperature leaching, and chemical components in the tea are easily subjected to physicochemical reactions such as oxidization, complexation, hydrolysis and the like under the high-temperature hydrothermal condition, so the extraction temperature of the first stage is 90-100 ℃, the extraction time is 5-10min, and the extraction temperature of the first stage is 93-98 ℃ and the extraction time is 7-8min.

The invention has the characteristics of high speed, high efficiency and high quality by using ultrasonic extraction. The more the extracted material components, the higher the yield, with increased extraction temperature and time during the second stage extraction. However, too high a temperature and too long a time can cause deterioration of tea soup quality, while too low a temperature can cause insufficient leaching, less leaching of active ingredients, long time consumption and the like. The Liupu tea is post-fermented tea, is fully fermented, and can resist high temperature in daily brewing compared with conventional red green tea. According to the invention, experimental researches prove that the extraction temperature of the second stage is 50-70 ℃, the extraction time is 30-50min, and the extraction time of the second stage is 55-65 ℃ and the extraction time is 35-45min.

The invention takes water as an extractant and is added in two stages. Preferably in the first stage and the second stage, respectively. The total feed liquid ratio is preferably 1:12-1: 20 (g/m L), more preferably 1:14-1:18. filtering while the first stage is hot, adding water, extracting while the second stage is hot, coarse filtering, mixing filtrates, standing, and cooling to obtain extractive solution.

The invention can carry out solid-liquid separation on the obtained extract liquid, and any solid-liquid separation mode in the prior art can be adopted, and the invention is not limited to the method. As one embodiment, the invention uses a high-efficiency butterfly centrifuge with a speed of over 8000r/min to butterfly-divide the extract liquid, and removes fine tea particles or impurities contained in the rough filtered extract liquid.

The fine filtration according to the invention is preferably carried out with ultrafiltration membranes, the membrane cut-off molecular weight of the fine filtration being above 10 ten thousand. Removing macromolecular compounds such as pectin, protein, soluble starch, etc. in tea extractive solution by fine filtration. The molecular weight cut-off of the fine filtration membrane is more than 10 ten thousand, otherwise, the effective components in the Liupu tea extract can be cut-off, such as phenols, caffeine, theaflavin, thearubigin, etc. In addition, the fine filtration can remove impurities and cold insoluble substances, and prevent the RO membrane from being blocked during concentration. The invention is not particularly limited in the kind of ultrafiltration membrane, and the ultrafiltration membrane can be obtained by adopting the existing commercial products, such as polypropylene hollow fiber ultrafiltration membrane. As one embodiment, the working pressure of the ultrafiltration membrane is 0.2-0.3MPa, and the temperature is less than 40 ℃. The invention compares the change of the effective components in the tea soup after fine filtration, and the ratio of the effective components after filtration to the effective components before filtration is shown as the ratio of the effective components such as tea polyphenol, amino acid, caffeine, theaflavin, thearubigin and the like is more than or equal to 0.95, which indicates that the effective components are kept more completely.

TABLE 2 ratio of the content of main active ingredients in the extract after filtration to before filtration

Class of active ingredients	Tea polyphenols	Amino acids	Caffeine and caffeine	Theaflavin	Thearubigins
						Post/pre filtration	0.97	0.98	0.95	0.98	0.96

The concentration of the invention is that the tea extract after fine filtration is sequentially subjected to RO concentration and vacuum concentration. Preferably, RO concentration is performed by a reverse osmosis concentration system including a fragrance recovery device, and the obtained fragrance recovery solution substance is backfilled into the concentrated solution after vacuum concentration. The reverse osmosis membrane RO concentration has the advantages of low temperature, high efficiency and small loss. Because the tea liquid is non-heated and concentrated, macromolecular aroma components in the tea liquid cannot escape, flavor substances in the tea liquid cannot generate oxidation and browning due to heating, and the escaped micromolecular aroma substances can be recovered by an aroma recovery device and used for aroma backfilling in the later period. As one implementation mode, the RO membrane has the working pressure of 1.5-3.0MPa and the working temperature of less than 45 ℃. Concentrating the RO concentrated solution at 40-45deg.C under vacuum, evaporating water, concentrating the concentrated solution until solid content is above 30%, and backfilling with fragrance.

The sterilization method of the present invention is not particularly limited, and a conventionally known sterilization method may be adopted. As one embodiment, ultra-high temperature transient UHT sterilization is adopted, and the sterilization temperature is 130-138 ℃ and the sterilization time is 3-4s.

The drying is preferably low-temperature freezing and vacuum drying, so that the prepared original Liupu tea instant powder is obtained. Parameters of freeze vacuum drying: the thickness of the spreading material is 3 mm-5 mm, the pre-freezing temperature is minus 30 ℃ to minus 50 ℃, the cold trap temperature is less than or equal to minus 60 ℃, and the absolute vacuum degree is 1 Pa-20 Pa.

The extraction rate of tea polyphenol, amino acid, caffeine, theaflavin and thearubigin which are main flavor substances of the original Liupu instant tea prepared by the invention is more than 80%, and the main volatile substances, aroma, taste and soup color are basically consistent with those of the raw material tea.

The technical scheme of the present invention is described in further detail below with reference to specific embodiments, and the technical scheme of the present invention includes but is not limited to the following embodiments.

Example 1

(1) Pretreatment and crushing of raw materials: liupu tea raw materials with strong fragrance and flavor are selected for blending, and the content of water extract of the Liupu tea raw materials after uniform blending is 30%. And (3) re-heating the mixed raw materials at a low temperature of 45 ℃ until the water content is 6%. Crushing the Liupu tea raw materials meeting the requirements, and sieving the crushed Liupu tea raw materials with a 60-mesh sieve.

(2) Leaching and rough filtering: the ultrasonic-assisted closed continuous extractor is adopted for extraction, and the extraction is carried out in two steps: adding a proper amount of water extraction agent, extracting for 10min at 90 ℃, and filtering; and the second step, adding the water extraction agent continuously, and filtering at the extraction temperature of 60 ℃ for 40 min. The total feed-liquid ratio of the two steps is 1:15 (g/mL), and the crude filtrate is combined.

(3) Butterfly is divided into: and (3) butterfly-separating the coarse filtrate by using a high-efficiency butterfly centrifuge with the speed of over 8000r/min, and removing fine tea particles or impurities contained in the coarse filtrate.

(4) Fine filtering: further fine filtering the separated extractive solution with ultrafiltration membrane with molecular weight cutoff of more than 10 kilodaltons, such as polypropylene hollow fiber ultrafiltration membrane, at working pressure of 0.2-0.3MPa and temperature of less than 40deg.C.

(5) Concentrating RO: the concentrated solution is obtained by concentrating the tea extract after fine filtration by reverse osmosis concentration system containing aroma recovery device (collecting and concentrating the micromolecular aroma substances scattered during concentration process) with RO membrane operating pressure of 1.5-3.0MPa and operating temperature of less than 45deg.C.

(6) Vacuum concentration: concentrating the RO concentrated solution at 40deg.C under vacuum, evaporating pure water, and concentrating the tea RO concentrated solution to solid content of more than 30%.

(7) And (3) aroma backfilling: if the fragrance recovery is performed in the step (5), the fragrance recovery solution material can be backfilled into the concentrated solution.

(8) Sterilizing: the ultra-high temperature transient UHT sterilization is adopted, the sterilization temperature is 135 ℃, and the time is 3s.

(9) And (3) drying: and (3) carrying out low-temperature freezing and vacuum drying to obtain the prepared original Liupu tea instant powder. Parameters of freeze vacuum drying: the thickness of the spreading material is 3 mm-5 mm, the pre-freezing temperature is minus 30 ℃ to minus 50 ℃, the cold trap temperature is less than or equal to minus 60 ℃, and the absolute vacuum degree is 1 Pa-20 Pa.

Example 2

(1) Pretreatment and crushing of raw materials: liupu tea raw materials with strong fragrance and flavor are selected for blending, the water extract content of the Liupu tea raw materials after uniform blending is 32%, the blended raw materials are subjected to re-heating at the low temperature of 52 ℃ and baked until the water content is 5.3%. Crushing the Liupu tea raw materials meeting the requirements, and sieving the crushed Liupu tea raw materials with a 80-mesh sieve.

(2) Leaching and rough filtering: the ultrasonic-assisted closed continuous extractor is adopted for extraction, and the extraction is carried out in two steps: adding a proper amount of water extraction agent, extracting for 7min at the temperature of 95 ℃, and filtering; and the second step, adding the water extraction agent continuously, and filtering at the extraction temperature of 50 ℃ for 30 min. The total feed-liquid ratio of the two steps is 1:12 (g/mL), and the crude filtrate is combined.

(8) Sterilizing: the ultra-high temperature instantaneous UHT sterilization is adopted, the sterilization temperature is 130 ℃, and the time is 4s.

And (3) drying: and (3) carrying out low-temperature freezing and vacuum drying to obtain the prepared original Liupu tea instant powder. Parameters of freeze vacuum drying: the thickness of the spreading material is 3 mm-5 mm, the pre-freezing temperature is minus 30 ℃ to minus 50 ℃, the cold trap temperature is less than or equal to minus 60 ℃, and the absolute vacuum degree is 1 Pa-20 Pa.

Example 3

(1) Pretreatment and crushing of raw materials: liupu tea raw materials with strong fragrance and flavor are selected for blending, the water extract content of the blended Liupu tea raw materials is 35%, the blended raw materials are subjected to re-heating at the low temperature of 60 ℃, and the water content is 4.6%. Crushing the Liupu tea raw materials meeting the requirements, and sieving the crushed Liupu tea raw materials with a 80-mesh sieve.

(2) Leaching and rough filtering: the ultrasonic-assisted closed continuous extractor is adopted for extraction, and the extraction is carried out in two steps: adding a proper amount of water extraction agent, extracting for 5min at 100 ℃, and filtering; and the second step, adding the water extraction agent continuously, and filtering at the extraction temperature of 70 ℃ for 50 min. The total feed-liquid ratio of the two steps is 1:20 (g/mL), and the crude filtrate is combined.

(6) Vacuum concentration: concentrating the RO concentrated solution at 45deg.C under vacuum, evaporating pure water, and concentrating the tea RO concentrated solution to solid content of more than 30%.

(8) Sterilizing: the ultra-high temperature instantaneous UHT sterilization is adopted, the sterilization temperature is 138 ℃, and the time is 3s.

Example 4

Influence of re-firing temperature on quality of raw tea

Different from example 1, the following re-firing temperatures of the Liupu tea raw materials blended in the step (1) are set, and the non-re-firing is used as a reference, and the following part 4 of the black tea is prepared according to GB/T32719.4-2016: liupu tea was subjected to sensory quality evaluation, and the evaluation results are shown in Table 3.

TABLE 3 influence of different re-firing temperatures on raw tea quality

The results in Table 3 show that when the re-firing temperature is 45-75 ℃, the raw materials which are baked to meet the moisture requirement are basically consistent with the raw tea which is in comparison with the raw tea (CK does not re-fire), the flavor and the taste are mellow, the thickness of the raw tea is reduced at 75 ℃, and the fragrance, the flavor, the soup color and the raw tea are greatly different at 75 ℃ or above, which is probably that the re-firing temperature is too high, and certain quality characteristic components which are in fragrance and taste, such as the fragrance and the flavor of Liupu tea, are affected, so that the ageing is weakened.

Example 5

Influence of crushing mesh number on coarse filtration speed and instant tea powder yield

Unlike example 1, the raw materials of Liupu tea in the step (1) are crushed and respectively pass through a 40 mesh sieve, a 60 mesh sieve, a 80 mesh sieve and a 100 mesh sieve, and the filtration speed of rough filtration in the step (2) and the yield of the original Liupu instant tea are measured. The instant tea powder yield is calculated by the ratio of the weight of instant powder obtained after the unit weight of raw materials is treated to the weight of the raw materials.

TABLE 4 influence of the number of crushing meshes on the coarse filtration rate and the yield of instant tea powder

Pulverizing mesh number	Filtration speed (L/min)	Yield of instant tea (%)
			40	105	13.65
60	96	18.70
			80	87	25.32
100	40	26.30

The test data in Table 4 show that when the crushing mesh number is less than 60 meshes, the instant tea powder has higher filtering speed but lower yield; when the crushing mesh number is more than 100 meshes, the yield is higher, but the tea powder is too fine and is easy to deposit and block the holes of the filtering membrane, so that the filtering speed is greatly reduced. Comprehensively considering that when the crushing mesh number is between 60 and 80, the filtering speed is higher, the instant tea yield is higher, and the economic benefit in actual production is higher.

Example 6

Influence of extraction time on yield of instant tea powder

Different from example 1, the second water extraction time in the step (2) is respectively 15min, 20min, 30min, 40min, 50min and 60min, the yield of the original Liupu instant tea is calculated and prepared, and the calculation mode is the same as that of example 5.

TABLE 5 influence of extraction time on instant tea powder yield

As shown in Table 5, in the range of 15-50min, the yield of instant tea powder tended to increase with increasing extraction time, the yield of instant tea powder was 13.0% for 20min, and when the extraction time was 30min, the yield of instant tea powder reached 20.7%, which was far higher than that for 20 min. However, the extraction time is 60min, the yield of the instant tea powder is 26.5%, and the yield of the instant tea powder is slightly reduced and is lower than that of the instant tea powder at the extraction time of 50min, which is probably caused by chemical change of the content of the tea soup extracted for a long time.

Example 7

Influence of extraction temperature on quality and yield of instant tea powder

Unlike example 1, the sensory quality evaluation was performed on the prepared primary taste Liupu instant tea by setting the second water extraction temperature of step (2) to 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃ and 80 ℃ respectively, and the yield was calculated in the same manner as in example 5.

TABLE 6 influence of extraction temperature on quality and yield of instant tea powder

As shown in Table 6, the yield of instant tea increases with increasing extraction temperature, but decreases to 80 deg.C, the extraction yield is relatively high at 40 deg.C and 50 deg.C, the aroma, taste, soup color, etc. of the instant tea powder soup prepared at 50-70 deg.C are prominent, and oxidation degradation reaction of tea soup inner matter, volatile matter, etc. is easy to occur when the extraction temperature is too high for long time, and the soup color is dark red, stale flavor is weak, and stale charm is lost after the instant tea powder is boiled.

Example 8

The invention relates to a contrast evaluation method of original Liupu instant tea and raw material tea

(1) Analysis of extraction yield of mainly flavor-developing substance

The contents and extraction rates of tea polyphenols, amino acids, caffeine, theaflavins and thearubigins which are main flavor substances of raw tea and instant tea prepared by the method are analyzed. The raw materials of tea including tea polyphenols, amino acids, caffeine, theaflavins and thearubigins are measured by referring to GB/T8313 method for measuring the content of tea polyphenols and catechin in tea, GB/T8314 method for measuring the total amount of free amino acids in tea, GB/T8312 method for measuring the content of thearubigins in tea by using high performance liquid chromatography, GB/T30483 method for measuring the content of thearubigins in tea by using high performance liquid chromatography and NY/T3675 method for measuring the content of thearubigins and theabrownins in black tea respectively. The relevant components in the instant tea are prepared into liquid to be tested according to the method in GB/T21727, and then are measured and converted according to the raw material tea test method. The extraction rate of each flavor-imparting substance is expressed as a ratio of the content of the flavor-imparting substance in the instant tea powder obtained per unit mass of the raw material tea to the content of the flavor-imparting substance in the raw material tea per unit mass.

TABLE 7 extraction yield of main active ingredients in instant tea powder

Mainly flavor-developing substance	Tea polyphenols	Amino acids	Caffeine and caffeine	Theaflavin	Thearubigins
						Extraction yield (%)	85	87	91	81	80

The results as shown in table 7: the primary taste Liupu instant tea prepared by the invention has the extraction rate of tea polyphenol, amino acid, caffeine, theaflavin and thearubigin which are main taste substances, which are all more than 80 percent.

(2) Fragrance material type detection and analysis

The method for detecting and analyzing aroma substances of the raw material tea and the original Liupu instant tea comprises the following steps:

(1) pretreatment conditions: by adopting an HS-SPME (headspace solid-phase microextraction) method, 6.0g of tea sample or 1.0g of original Liupu instant tea is placed in a 100mL sample bottle, 30mL of distilled water at 100 ℃ is added in a constant-temperature water bath at 60 ℃ for 5min, an extraction head aged for 5min is inserted, headspace is adsorbed for 50min, the extraction head is directly inserted into a GC-MS sampler for desorption for 5min at 240 ℃, and Thermo-DSQ is started to collect data.

(2) Chromatographic conditions: the gas chromatographic column is a DB-WAX capillary column (60 m multiplied by 0.25 mu m multiplied by 0.32 mm), the carrier gas is high purity helium with 99.999%, the flow rate of the column is 1.5mL/min, and the sample injection mode is manual sample injection without split flow. Programming temperature: keeping at 50deg.C for 5min, heating to 170deg.C at 2deg.C/min for 5min, and heating to 215 deg.C at 5deg.C/min for 5min.

(3) Mass spectrometry conditions: sample inlet 240 deg.c and ion source 230 deg.c. The electron bombardment source EI, electron energy 70eV, scanning mass range 50-650amu.

Qualitative and quantitative methods: and comparing the obtained GC-MS spectrum with a standard mass spectrum provided by a NIST mass spectrum library through computer retrieval, identifying aromatic substances by using the published mass spectrum, calculating relative percentages according to a peak area normalization method, and calculating relative percentages of various aroma components according to the reserved peak areas of the chromatograms.

Table 8 comparison of raw tea with key aroma substances for extraction of instant tea powder

Through detection and analysis, the main volatile substances of the original Liupu instant tea prepared by the method are basically consistent with those of the raw material tea.

(3) Sensory quality contrast

Sensory evaluation was carried out on the raw tea and the original Liupu instant tea according to the invention according to the method of GB/T23776-2018.

Table 9 sensory quality comparison of raw tea and instant tea powder

The results are shown in Table 9: the original Liupu instant tea prepared by the method is similar to the raw material tea in flavor such as aroma, taste and soup color, and is basically consistent.

The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.

Claims

1. The preparation method of the original Liupu instant tea is characterized by comprising the following steps of:

2. The method according to claim 1, wherein the extract content of Liupu tea raw material water is not less than 30%.

3. The method of claim 1 wherein the crushed Liupu tea is sieved through a 60-80 mesh sieve.

4. The method according to claim 1, wherein the aqueous extraction agent is added in two stages, and the total feed-to-liquid ratio is 1:12-1: 20.

5. the method of claim 1, wherein the membrane has a molecular weight cut-off of greater than 10 tens of thousands.

6. The method according to claim 1, wherein the concentration is performed by sequentially subjecting the tea extract after the fine filtration to RO concentration and vacuum concentration.

7. The method according to claim 6, wherein the RO concentration is performed by a reverse osmosis concentration system including a fragrance recovery device, and the fragrance recovery solution is backfilled into the concentrated solution after vacuum concentration.

8. The process of claim 6 or 7, wherein the RO membrane is operated at a pressure of 1.5-3.0MPa and a temperature of < 45 ℃.

9. The method according to claim 6, wherein the vacuum concentration is performed at a temperature of 40-45 ℃ until the solid content is 30% or more.

10. The original taste Liupu instant tea prepared by the method of any one of claims 1-9.