CN113826732A

CN113826732A - Extraction process of clarified tea

Info

Publication number: CN113826732A
Application number: CN202010515105.6A
Authority: CN
Inventors: 卢卫国; 孟掉琴; 李树森; 李洪亮
Original assignee: Inner Mongolia Mengniu Dairy Group Co Ltd
Current assignee: Inner Mongolia Mengniu Dairy Group Co Ltd
Priority date: 2020-06-08
Filing date: 2020-06-08
Publication date: 2021-12-24

Abstract

The invention discloses a clarified tea extraction process, which comprises the following steps: obtaining hot tea soup: heating and extracting tea leaves by adopting water to obtain hot tea soup; cooling the hot tea soup: cooling and filtering the hot tea soup to obtain cold tea soup; adding of protein: adding protein 0.01-0.1% of the cold tea soup by weight into the cold tea soup, and stirring for reaction; filtering and centrifuging: controlling the temperature to be lower than 10 ℃, maintaining for more than 30min, and then filtering and centrifuging to obtain clear tea soup. The invention has more excellent effect of improving the shelf life of tea drinks to generate a large amount of precipitates, does not influence the original taste of tea soup and has less burden on the whole cost.

Description

Extraction process of clarified tea

Technical Field

The invention relates to the field of food, in particular to a tea extract liquid treatment process.

Background

Tea beverage is usually made from tea leaves as main raw material through the processes of extraction, filtration, blending, sterilization, filling and the like, and contains a certain amount of tea leaf effective components and is a liquid product with tea flavor. The tea drink often has precipitation phenomenon in shelf life, which affects the appearance quality of the product, is an important technical obstacle in the research and development and production processes of the tea drink, and is also a problem which is concerned and addressed by the industry. The clarification process of tea beverages disclosed in the prior art includes low temperature separation, pH adjustment, trans-dissolution, precipitant method, etc.

The cryogenic separation method is a conventional method in the field, and the basic process is as follows: firstly, tea is extracted to obtain extract liquor, then the tea extract liquor is cooled to generate flocculation precipitation, and then the precipitation is further removed by the modes of filtration, centrifugation and the like. For example: chinese document CN110178941A discloses a tea beverage with the effects of clearing away heart-fire and a preparation method thereof, and specifically discloses a method for preparing the tea beverage, which comprises the following steps: taking broadleaf holly leaf, mesona chinensis benth, lotus seed, bitter gourd, chrysanthemum, liquorice and stevia rebaudiana leaves, carrying out water extraction, filtering the water extraction solution, sequentially adding the black tea powder water solution and sodium hexametaphosphate, and uniformly stirring to obtain a feed liquid; step 2: keeping the temperature of the feed liquid to 80-85 ℃, and keeping the temperature interval for thermal standing for 30-40 min; then cooling to 10-15 ℃, and keeping the temperature interval for cold standing for 30-40 min; filtering, centrifuging to obtain supernatant, diluting to desired volume, and sterilizing to obtain tea beverage. In the document, the steps of filtering, hot standing, cold standing, filtering, centrifuging and the like are combined, and a specific feeding sequence is combined, so that the precipitate in the feed liquid is effectively removed, and the problem of the precipitate in the preparation of the tea beverage by the traditional production process is solved. However, the tea beverage produced by the method often generates floccule precipitates along with the prolonging of the shelf life, which affects the terminal sale of the tea beverage.

The pH adjustment method, which is a method of adjusting the optimum pH value formed by tea milk and then removing the tea milk, has only been confirmed in black tea and seed tea, and is not applicable to all tea leaves.

The dissolving method is to add a dissolving agent into the tea soup to promote the dissolution of the tea milk or increase the viscosity of the tea soup to stabilize the tea soup system. In the research on re-dissolving and recycling of green tea soup sediment based on tannase treatment disclosed in the prior art, in tea science 2015, 35(6), 589-595, tannase is added into tea beverage, ester catechin which is a key chemical component formed by green tea sediment can be effectively hydrolyzed, 98% of ester catechin can be hydrolyzed, and 82% of re-precipitation is reduced. However, the method has the disadvantages that the addition of enzyme is too much, the taste of the tea is not maintained, the tea taste is sour, the operation is complex and the time is long.

The precipitant method is to remove part of tea polyphenols or caffeine in tea water by using substances such as adsorbent, etc., so as to reduce the generation of precipitate. Such as: adding gelatin with adsorption function, soluble aluminum salt, PVP, polyurethane resin, calcium ion, protein, etc. Such as: the addition of calcium ions to tea soup described in the prior art promotes TP-Ca²⁺Precipitate was formed and separated to remove the precipitate. However, when various adsorbents disclosed in the prior art are applied to the field of food, protein is added most safely and effectively, but more protein is often required to be added for removing more tea polyphenol due to insolubility of protein, and as described in the document of removing tea polyphenol by using soybean protein disclosed in the prior art, the optimal effect of removing tea polyphenol can be achieved only when the addition amount of soybean protein relative to tea soup is 1% -2%. However, in the case of removing tea polyphenols to the maximum by using protein, a lot of floc precipitates are generated in some cases as the shelf life is prolonged, and the generation of floc precipitates in the shelf life is particularly remarkable in the case of clear tea.

Disclosure of Invention

Therefore, the technical problem to be solved by the invention is how to avoid the problem that a large amount of floccule precipitates appear in the clear tea during the shelf life; the invention provides a clear tea extraction process which can solve the technical problems and has simple operation and low process energy consumption.

A clarified tea extraction process comprising:

obtaining hot tea soup: heating and extracting tea leaves by adopting water to obtain hot tea soup;

cooling the hot tea soup: cooling and filtering the hot tea soup to obtain cold tea soup;

adding of protein: adding protein 0.01-0.1% of the cold tea soup by weight into the cold tea soup, and stirring for reaction;

filtering and centrifuging: controlling the temperature to 4-10 deg.C, maintaining for more than 30min, filtering, and centrifuging to obtain clear tea soup.

The protein is one or more of whey protein, soybean protein isolate, animal peptide and plant peptide; further, the protein is whey protein or/and soybean protein isolate.

The mass ratio of the tea leaves to the water is 1: (20-50).

The temperature of the heating extraction is 70-90 ℃, and the time is 2-20 min; the temperature of the cold tea soup is lower than 10 ℃.

In the step of cooling the hot tea soup, the filtering condition is more than 300 meshes.

The time for stirring and reacting the whey protein and the cold tea soup is 10-30 min.

The addition amount of the whey protein is 0.02-0.08% of the weight of the cold tea soup.

The addition amount of the whey protein is 0.03 percent of the weight of the cold tea soup;

the temperature in the filtration and centrifugation step is reduced to 4-10 ℃;

the centrifugation is disc centrifugation, and the rotation speed of the disc centrifugation is 3000-5000 rpm.

The filtration is micron filtration, and the filtration pore size is 1 μm.

The technical scheme of the invention has the following advantages:

1. the invention optimizes the selection of the precipitation aid, and preferably adopts protein as the precipitation aid, so that the protein can be combined with unstable tea polyphenol and the like in tea in a liquid environment to generate natural flocculation.

The protein is used in a trace amount, only 0.01-0.1% of the weight of the cold tea soup, the original taste of the tea soup is not affected, the whole cost burden is small, and detection shows that the protein is used for processing, so that the stability is more excellent although the amount of the total tea polyphenol removed is not large; in addition, the protein is directly added into the cold tea soup and only stirred for reaction, so that the operation is simple.

2. The protein in the invention is preferably whey protein which has certain water solubility and is used as exogenous stimulation after being dissolved in water to promote tea polyphenol and protein to generate more flocculates, so that unstable components in the extract liquor are precipitated in advance in the pretreatment stage, the stability, centrifugal precipitation rate, static stability index and clarification index of the treated extract liquor are all obviously superior to those of untreated tea extract liquor in an acid system, the stability is obviously improved, the phenomenon of mass precipitation generated in the shelf life of tea drinks is effectively improved, the shelf life stability of the final tea drinks is improved, and the whey protein can be widely applied to the field of tea drink processing; and under the same dosage, the stability of the whey protein is obviously superior to that of the soybean protein isolate, and the clarification effect is better.

3. The tea soup of the invention preferably adopts high-quality dairy products as the precipitation aid, not only has a plurality of health effects, but also can maximally precipitate unstable components in a front-end process, and avoid excessive use of a system stabilizer.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a diagram illustrating the content of tea polyphenols in the extract prepared in each example of the present invention;

FIG. 2 is a graph I of the static settling velocity of the extract prepared in different examples and comparative examples of the present invention;

FIG. 3 is a graph II of the static settling velocity of the extract prepared in different examples and comparative examples of the present invention;

FIG. 4 is a graph showing the clarity index of the extracts prepared in the examples and comparative examples of the present invention.

Detailed Description

The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.

The examples do not show the specific experimental steps or conditions, and can be performed according to the conventional experimental steps described in the literature in the field. The reagents or instruments used are not indicated by manufacturers, and are all conventional reagent products which can be obtained commercially.

Example 1

A clear tea extract is prepared by the following steps:

firstly, putting 133Kg of green tea leaves into a hanging basket tank, injecting 3990Kg of water at 70 ℃, soaking and extracting the tea leaves, wherein the extraction time is 10min, and the tea leaves are lifted once every 2 min;

secondly, removing tea residues by a 300-mesh rotary drum centrifuge, cooling tea extract to normal temperature through plate heat exchange, slowly adding 3.99Kg of separated whey protein into tea soup while stirring, wherein the stirring speed is 50rpm, the hydration time is 10min, then continuously cooling to 6 ℃, and continuously cooling in a cooling tank for 30min for flocculate separation;

thirdly, disc centrifugation (3000rpm) and micron filtration (1 micron) are carried out on the tea extract to obtain the extract.

Example 2

A clear tea extract is prepared by the following specific steps:

secondly, removing tea residues by a 300-mesh rotary drum centrifuge, cooling tea extract to normal temperature through plate heat exchange, slowly adding 1.2Kg of separated whey protein into tea soup while stirring, wherein the stirring speed is 100rpm, the hydration time is 20min, then continuously cooling to 6 ℃, and continuously cooling in a cooling tank for 30min for flocculate separation;

thirdly, disc centrifugation (4000rpm) and micron filtration (1 μm) are carried out on the tea extract to obtain the extract.

Example 3

A clear tea extract is prepared by the following specific steps:

secondly, separating by a 300-mesh rotary drum centrifuge to remove tea residues, cooling the tea extract to normal temperature through plate heat exchange, slowly adding 2Kg of separated whey protein into the tea soup while stirring, wherein the stirring speed is 200rpm, the hydration time is 20min, then continuously cooling to 6 ℃, and continuously cooling for 30min in a cooling tank to precipitate flocculates;

thirdly, disc centrifugation (5000rpm) and micron filtration (1 micron) are carried out on the tea extract to obtain the extract.

Example 4

A clear tea extract is prepared by the following specific steps:

secondly, removing tea residues by a 300-mesh rotary drum centrifuge, cooling tea extract to normal temperature through plate heat exchange, slowly adding 3.2Kg of separated whey protein into tea soup while stirring, wherein the stirring speed is 100rpm, the hydration time is 20min, then continuously cooling to 6 ℃, and continuously cooling in a cooling tank for 30min for flocculate separation;

Example 5

A clear tea extract is prepared by the following specific steps:

firstly, feeding 133Kg of Ceylon black tea into a hanging basket tank, injecting 2660Kg of water at 80 ℃, soaking and extracting the tea, wherein the extraction time is 10min, and the tea is lifted once every 2 min;

secondly, removing tea residues by a 300-mesh rotary drum centrifuge, cooling tea extract to normal temperature through plate heat exchange, slowly adding 0.8Kg of separated whey protein into tea soup while stirring, wherein the stirring speed is 100rpm, the hydration time is 20min, then continuously cooling to 4 ℃, and continuously cooling in a cooling tank for 30min for flocculate separation;

Example 6

A clear tea extract is prepared by the following specific steps:

firstly, putting 133Kg of oolong tea into a hanging basket tank, injecting 6650Kg of water at 90 ℃, soaking and extracting the tea, wherein the extraction time is 10min, and the hanging basket is lifted every 2 min;

secondly, separating by a 300-mesh rotary drum centrifuge to remove tea residues, cooling the tea extract to normal temperature through plate heat exchange, slowly adding 2Kg of separated whey protein into the tea soup while stirring, wherein the stirring speed is 100rpm, the hydration time is 20min, then continuously cooling to 10 ℃, and continuously cooling for 30min in a cooling tank to precipitate flocculates;

Example 7

A clear tea extract is prepared by the following specific steps:

firstly, putting 133Kg of green tea leaves into a hanging basket tank, injecting 3990Kg of 70 ℃ water, soaking and extracting the tea leaves, wherein the extraction time is 10min, and the tea leaves are lifted once every 2 min;

secondly, separating by a drum centrifuge with 300 meshes to remove tea residues, cooling the tea extract to normal temperature through plate heat exchange, slowly adding 1.2Kg of soybean protein isolate into the tea soup while stirring, continuously cooling to 6 ℃ after the hydration time is 20min, and continuously cooling in a cooling tank for 30min to separate out flocculates;

Comparative example 1

A clear tea extract liquid without any additives except tea leaves and water is prepared by the following specific steps:

secondly, separating and removing tea residues by a 300-mesh rotary drum centrifuge, cooling the tea extract to 6 ℃ through plate type heat exchange, and continuously cooling in a cooling tank for 30min to separate out flocculates;

Comparative example 2

A clear tea extract is prepared by the following steps:

firstly, dissolving 3.99Kg of separated lactalbumin into 3990Kg of normal temperature water, stirring at the rotating speed of 100rpm, hydrating for 20min, and then heating to 70 ℃;

secondly, putting 133Kg of green tea leaves into a hanging basket tank, adding 3994Kg of the aqueous solution of whey protein separated at 70 ℃ prepared in the first step, soaking and extracting the tea leaves for 10min, and carrying out basket lifting once every 2 min;

thirdly, separating and removing tea residues by a 300-mesh rotary drum centrifuge, cooling the tea extract to 6 ℃ through plate type heat exchange, and continuously cooling in a cooling tank for 30min to separate out flocculates;

fourthly, disc centrifugation (4000rpm) and micron filtration (1 micron) are carried out on the tea extract to obtain the extract.

Comparative example 3

A clear tea extract without any additives except for Centan black tea and water is prepared by the following specific steps:

firstly, putting 133Kg of Ceylon black tea leaves into a hanging basket tank, adding 2660Kg of hot water at 80 ℃, soaking and extracting the tea leaves for 10min, and carrying out basket lifting once every 2 min;

secondly, separating and removing tea residues by a drum centrifuge rotating at 300 meshes, and cooling the tea extract to 6 ℃ through plate heat exchange for 30 min;

Comparative example 4

A clear tea extract without any additives except oolong tea and water is prepared by the following steps:

firstly, putting 133Kg of oolong tea leaves into a hanging basket pot, adding 6650Kg of hot water with the temperature of 90 ℃, soaking and extracting the tea leaves, wherein the extraction time is 10min, and the tea leaves are lifted once every 2 min;

Test examples

The tea extract liquid prepared in the above examples and comparative examples was tested, and the test method and test results were as follows:

1. and detecting the content of tea polyphenol in the tea extract.

The detection method adopts appendix A (detection method of tea polyphenol in tea beverage) in GB 21733 tea beverage, and the detection result is shown in figure 1.

The analysis of examples 1, 2, 3 and 4 in fig. 1 shows that: aiming at the same tea, along with the increase of the addition amount of the whey protein, the removed tea polyphenol amount is more, and meanwhile, the whole embodiment is lower than the content of the comparative tea polyphenol, so that the embodiment is proved to have obvious effect on removing unstable tea polyphenol. As can be seen from the comparison between example 5 and comparative example 3, and between example 6 and comparative example 4, the whey protein also has the ability to reduce tea polyphenols in black tea and oolong tea extracts, which means that the whey protein can improve the stability of different types of tea extracts.

2. And detecting the stability, static settling velocity and dynamic settling velocity of an acid system in the tea extract.

2.1, the detection method comprises the following steps: the extracts of the examples and the comparative examples were diluted to a tea polyphenol content of 600ppm, and the pH was adjusted to pH3.0 with citric acid, and the test samples were subjected to the tests of the respective test items. Wherein the content of the first and second substances,

the process of detecting the stability of the acid system comprises the following steps: after the detection sample is sterilized by heat, the detection sample is placed in an environment with the temperature of 37 ℃ for observation for a week, the precipitation condition is observed, and the centrifugal precipitation rate is measured, wherein the centrifugal precipitation rate detection method comprises the following steps: uniformly shaking the sterilized detection sample, centrifuging at 6000rpm for 10min, and analyzing the precipitation amount; the results of the measurements are shown in Table 1 below.

The detection process of the static settling velocity is as follows: and (3) placing the detection sample into a TURBISAN multiple light scattering instrument to detect the static settling velocity of the detection sample, and obtaining a stability index TSI value, wherein the detection result is shown in figure 3.

The detection process of the dynamic settling velocity is as follows: and (3) placing the detection sample into a LUM dynamic stability analyzer to detect the dynamic sedimentation velocity of the detection sample to obtain a clarification index value, wherein the detection result is shown in figure 4.

2.2, the detection result is as follows:

TABLE 1

As can be seen from table 1 above: the whey protein-treated tea extract is not precipitated in an acidic system, or only a little precipitated. From the perspective of centrifugal precipitation rate, the centrifugal precipitation rate of examples 2, 5 and 6 is low, and 0.3g/Kg whey protein is added in the process, thus the better clarification effect is presented. As can be seen from the examples, the centrifugal precipitation rate tends to increase with the increase of the added amount of whey protein, and white transparent precipitate appears at the bottom of the dilution, meaning that some protein precipitate still occurs with the increase of the observation time for excessive whey protein, so the added amount of whey protein should be controlled as required. From examples 2 and 7, it can be seen that whey protein has a superior ability to remove precipitates than soy protein isolate.

The TSI value is a stability index, and the larger the TSI curve slope, the more unstable the liquid system. As can be seen from fig. 2 and 3: the curves of 13 samples are separated with the increase of the test time, and the examples are generally superior to the comparative examples in view of the whole, and the addition of protein (0.1-1.0g/L) has the effect of improving the stability of the system, and particularly the addition of whey protein (0.3-1.0g/L) has the more obvious effect of improving the stability of the system.

The clarification index value can be used for representing the change of sedimentation, floating, aggregation, condensation and combination phenomena of the sample. The larger the clarification index value is, the more serious the phenomena of sedimentation, floating, aggregation, coagulation and combination occur and the more unstable the sample system is under the influence of centrifugal force and gravity in the process of centrifugal motion. As can be seen from fig. 4: examples 1-7 have a lower clarity index, indicating better dynamic stability, and comparative example 2 has the highest clarity index and the lowest dynamic stability. And comprehensively comparing, wherein the stability of the extract liquid added with the whey protein in the cooling link is superior to that of a comparative example without adding the whey protein.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.

Claims

1. A clarified tea extraction process, comprising:

filtering and centrifuging: cooling to below 10 deg.C, cooling for more than 30min, filtering, and centrifuging to obtain clear tea soup.

2. The clarified tea extraction process of claim 1, wherein the protein is one or more of whey protein, soy protein isolate, animal peptides and vegetable peptides.

3. The extraction process of the clarified tea of claim 1 or 2, wherein the weight ratio of the tea leaves to the water is 1: 20-50.

4. The extraction process of clarified tea as claimed in claim 1, wherein the temperature of said heating extraction is 70-90 ℃ for 2-20 min; the temperature of the cold tea soup is lower than 10 ℃.

5. The extraction process of clarified tea as claimed in claim 4 wherein the step of cooling the hot tea soup is conducted under filtration conditions of 300 mesh or more.

6. The extraction process of the clarified tea of claim 1 wherein the whey protein is reacted with cold tea soup with stirring at 50-200rpm for 10-30min hydration time.

7. The extraction process of clarified tea as claimed in claim 1, wherein the whey protein is added in an amount of 0.02-0.08% by weight of the cold tea soup.

8. The process of claim 6, wherein the whey protein is added in an amount of 0.03% by weight of the cold tea soup.

9. The clarified tea extraction process as claimed in claim 1, wherein the temperature is reduced to 4-10 ℃ in the filtration centrifugation step; the centrifugation is disc centrifugation, and the rotation speed of the disc centrifugation is 3000-5000 rpm.

10. The process of claim 1, wherein the filtration is micron filtration and the filtration pore size is 1 μm.