Preparation method of radix puerariae coffee concentrated solution

Abstract

The invention discloses a preparation method of a radix puerariae coffee concentrated solution. The method comprises the following steps: (1) crushing, (2) compounding traditional Chinese medicine liquid, (3) extracting, (4) performing enzymolysis, (5) centrifuging, (6) concentrating, (7) adding a stabilizer, (8) performing high-pressure microjet, filling and the like. According to the radix puerariae coffee concentrated solution prepared through the method, the freeze-thaw characteristic of a finished product is good, and the precipitation problem is remarkably solved.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, and in particular to a method for preparing kudzu root coffee concentrate. Background Art

[0002] Coffee, tea and cocoa are known as the world's three major beverage plants. About one-third of the world's population drinks coffee, and the global trade volume of coffee is second only to oil. Coffee is rich in protein, crude fiber, crude fat, caffeine, etc. Because of its unique mellow taste and refreshing and exciting effects, it has gradually become an indispensable daily drink for modern people.

[0003] Coffee concentrate is another important industrial coffee raw material after instant coffee powder and freeze-dried coffee powder. Coffee concentrate can be widely used in dairy products, beverages, ice cream, baking, candy manufacturing and other fields. Coffee concentrates of different concentrations can be used according to the needs of different industries. However, the aromatic substances contained in coffee concentrate are easy to volatilize and decompose at room temperature, resulting in a deterioration of flavor. Therefore, coffee concentrate is usually stored in a refrigerated / frozen manner.

[0004] Industrial frozen coffee concentrate has a large packaging size and may be thawed repeatedly during use, which may cause the flavor of the product to decay and the quality to deteriorate. At the same time, the extracted coffee liquid will precipitate due to the presence of insoluble components such as protein, cellulose, and metal ions. Therefore, there are still obvious deficiencies and difficulties in the technology of coffee concentrate that need to be overcome. The main problems include: 1) The product has poor freeze-thaw characteristics, and the taste and flavor will be significantly reduced after multiple freeze-thaw cycles; 2) The stability of the product needs to be improved, and precipitation will occur after being left for a period of time, affecting consumers' experience of the coffee liquid.

[0005] Therefore, it is of great significance to study and prepare a coffee concentrate with excellent quality. Summary of the invention

[0006] In view of this, the present invention provides a method for preparing a kudzu root coffee concentrate. The kudzu root coffee concentrate prepared by the method has good freeze-thaw properties and the precipitation problem is significantly improved.

[0007] To solve the above problems, the present invention adopts the following technical solutions:

[0008] A method for preparing coffee liquid, the method comprising the following steps:

[0009] (1) Grinding: roasting and grinding the green coffee beans to obtain coffee powder for later use;

[0010] (2) Compounding the Chinese medicine liquid: adding coffee powder to the Pueraria root Chinese medicine liquid, stirring evenly to obtain a mixed liquid for later use;

[0011] (3) Extraction: The mixed liquid is subjected to steam extraction. After the extraction treatment is completed, cold extraction is then performed to lock the aroma of the coffee through low temperature and high pressure treatment. The extract is collected and set aside;

[0012] (4) Enzymatic hydrolysis: 0.01% to 0.03% of disodium ethylenediaminetetraacetate is added to the extract to remove metal ions, followed by filtration and enzymatic hydrolysis by immobilized complex enzyme magnetic microspheres under ultrasonic conditions;

[0013] Disodium EDTA: Disodium EDTA is a powerful chelating agent that can form stable complexes with a variety of metal ions (such as calcium, magnesium, iron, aluminum, copper, etc.) to remove metal ions in the extract and avoid precipitation.

[0014] (5) Centrifugation: The extract obtained after enzymatic hydrolysis is centrifuged to remove the residue, and the centrifugation conditions are: 4000-5000r / min, 10-20min, and then a filter is used for secondary filtration to obtain Pueraria coffee concentrate;

[0015] (6) Concentration: The kudzu root coffee concentrate obtained in step (5) is concentrated by a progressive freeze concentration method. First, the kudzu root coffee concentrate is pre-cooled in a 4-8° C. cold storage for 5-10 hours. The pre-cooled coffee concentrate is pumped into a cold tank and sealed for progressive freeze concentration. Refrigeration is turned on and stirred. The refrigerant temperature is -10 to -30° C., the stirring rate is 100-150 r / min, the freezing time is 1.0 to 2.0 h, and the soluble solid content of the concentrate is 30-45° Brix. Ice cubes are separated to obtain kudzu root coffee liquid.

[0016] (7) Adding stabilizers: Add 0.05-0.5% sodium carboxymethyl cellulose and 0.1%-0.5% β-cyclodextrin to the kudzu coffee liquid (the cavity structure of β-cyclodextrin can wrap bitter substances such as flavonoids and tannins to form an embedding complex and reduce their unpleasant taste), stir thoroughly, and then adjust the pH value of the kudzu coffee liquid to 4.5-5.5;

[0017] pH adjustment: There is no mandatory requirement for acidity control in existing coffee concentrates. According to statistics on the pH of imported coffee concentrates on the market, such as high-concentrated coffee liquids from OFI, Itochu, HACO and other manufacturers, the basic range is between 4.6-5.3, which is weakly acidic. Combined with frozen storage, it can effectively control the flavor change of coffee concentrate. Therefore, sodium carbonate and dipotassium hydrogen phosphate are added to the coffee concentrate in the above step, and the addition amounts are 0.5%-1.0% and 1.2%-2.0% respectively, to adjust the pH of the concentrate to 4.5-5.5.

[0018] (8) High-pressure microfluidization and filling: The kudzu coffee liquid treated in step (7) is treated with high-pressure microfluidization, and then filled under aseptic conditions. After filling, liquid nitrogen is added and the bottle is sealed to obtain a kudzu coffee concentrate. High-pressure microfluidization before filling can reduce the particle size of the kudzu coffee concentrate on the one hand, and on the other hand, high-pressure microfluidization promotes the formation of disulfide bonds between particles through hydrophobic interaction, resulting in the formation of soluble aggregates, reducing the occurrence of flocculation and stratification, and obtaining a stable coffee concentrate.

[0019] Furthermore, the coffee beans in step (1) are roasted in medium to dark roasting and ground to a particle size of 10-30 mesh.

[0020] Furthermore, the Pueraria root Chinese medicine liquid in step (2) is obtained by the following method: baking the Pueraria root in an oven for 10-20 minutes, taking it out and performing alcohol extraction to obtain a Pueraria root extract, then adding a fermentation agent to the Pueraria root extract, performing a first fermentation at 24-27°C for 1-2 days, and then performing a secondary fermentation at 20-23°C for 3-5 days.

[0021] Furthermore, in step (2), the mass ratio of the Pueraria root Chinese medicine liquid to the coffee powder is 15-18:1.

[0022] Furthermore, the temperature of the cold extraction in step (3) is 4-10°C, the pressure is 100-200 MPa, and the extraction time is 30-100 min.

[0023] Furthermore, the preparation method of the immobilized complex enzyme magnetic microspheres in step (4) is as follows:

[0024] 1) A sodium alginate solution with a concentration of 1.0 to 4.0 wt% and a polyvinyl alcohol solution with a concentration of 8.0 to 12.0 wt% are mixed in equal weight ratios to obtain a mixed solution, 0.4 to 1.3 wt% of Fe3O4 magnetic powder is added based on the weight of the mixed solution, and the mixture is stirred evenly, and then the mixture is injected into a boric acid-calcium chloride solution with a concentration of 0.5 to 1.0 wt% by using a syringe to obtain sodium alginate-polyvinyl alcohol composite microspheres with uniform particles and regular shapes, and then washed with water to neutrality, then washed with acetone, and then vacuum dried at a temperature of 40 to 50° C. to prepare a magnetic gel microsphere carrier;

[0025] 2) adding the dried magnetic gel microspheres to an immobilized complex enzyme solution, wherein the immobilized complex enzyme solution comprises: 0.05-0.3 wt % of papain, 0.5-1.0 wt % of glutamine aminotransferase and 0.2-0.6 wt % of cellulase, and then further dissolving the solution with a phosphate buffer solution, and then adding 1.5-3.0 wt % of glutaraldehyde as a cross-linking agent, incubating and shaking the solution at 25±2° C. and 100-200 rpm / min for 1-2 h; and then washing the magnetic gel microspheres with a phosphate buffer solution to remove free enzymes, thereby obtaining immobilized complex enzyme magnetic microspheres.

[0026] Furthermore, in step (4), the ultrasonic intensity is 3.0 to 6.0 W / cm 2 , the ultrasonic frequency is 10-30KHz, the ultrasonic temperature is 20-40℃, and the ultrasonic time is 10-20min.

[0027] Furthermore, the filtration pore size of the filter in step (5) is 0.3-0.8 μm.

[0028] Furthermore, the concentration endpoint in step (6) is that the soluble solids content of the concentrated liquid is 30-45° Brix.

[0029] Furthermore, in the step (8), the pressure used during the treatment by the high-pressure microfluidizer is 100-150 MPa.

[0030] Furthermore, the fermentation bacteria agent is yeast, and the inoculation amount is 2%-5%. During the second fermentation process, oxygen is added to the fermentation tank every day, and the daily oxygen addition amount is 0.5-0.8 ml / L.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The coffee concentrate of the present application breaks the traditional preparation method of coffee concentrate, adds herbal extracts to woody coffee, increases the flavor and efficacy of coffee, and seeks new breakthroughs on the basis of traditional coffee. After adding the herbal extracts, the applicant found that the freeze-thaw properties of the obtained coffee liquid became worse, and the precipitation phenomenon became more serious. Therefore, the coffee concentrate prepared by the method of the present application can maintain good freeze-thaw properties after adding the herbal extracts, and obtain a coffee concentrate with good health effects, good sensory properties, and not easy to precipitate after freezing and thawing.

[0033] In the prior art, some studies have been conducted on adding Pueraria root to coffee to increase the medicinal value of coffee. However, the applicant found that although adding Pueraria root to the traditional Chinese medicine can increase the medicinal value when preparing coffee liquid, a more serious precipitation problem will occur. After solving the precipitation problem by fermentation, the applicant found that after fermentation, it was considered that the components in the traditional Chinese medicine liquid changed, which unexpectedly led to the problem of poor freeze-thaw properties of the coffee liquid. Specifically, after 3-5 freeze-thaw cycles, the coffee liquid precipitated and the flavor changed. For this reason, the applicant speculated that the freeze-thaw properties were affected by the loss of certain compounds such as terpenoid compounds and the increase in organic acid content. For this reason, the applicant continued to conduct a large number of experiments to explore solutions and found that by combining a primary fermentation with a secondary micro-aerobic fermentation, in the secondary micro-aerobic fermentation process at a lower temperature, it was unexpectedly found that the product stability could be improved, the above-mentioned technical problems were solved, and finally a product with good stability, not easy to precipitate, and the flavor of coffee concentrate could be maintained after multiple freeze-thaw cycles was obtained.

[0034] 2. The present invention adopts self-developed coffee cold extraction equipment, firstly adopts instantaneous steam explosion technology to significantly enhance the aroma of coffee, and then adopts ultra-high pressure and low temperature for extraction, so as to avoid the aroma components in the coffee stock solution from escaping at high temperature, so that the aromatic substances such as furans, pyrazines, aldehydes, ketones and esters in the coffee are fully released during the long-term low-temperature soaking process, and the content of aromatic substances is relatively high, among which furan compounds have caramel aroma, pyrazine compounds show the aroma of dairy and butter, and aldehyde compounds have the aroma of nuts and fruits, thereby making the aroma more intense and the flavor can be maintained for a long time; secondly, compared with the hot extraction process, the ultra-high pressure assisted cold extraction process adopted by the present invention has a lower acidity of the coffee liquid, which is more in line with the drinking habits of domestic coffee consumers; finally, in terms of health factors, compared with hot coffee, the contents of active ingredients trigonelline and chlorogenic acid in cold-brewed coffee are significantly increased.

[0035] 3. The immobilized composite enzyme magnetic microspheres used in the present invention are an enzymatic hydrolysis process containing composite enzymes such as papain, glutamine aminotransferase, cellulase, etc., which are specially designed for the insoluble protein and cellulose of kudzu coffee concentrate. First, in order to improve the enzymatic hydrolysis efficiency and save production costs, the present invention adopts immobilized composite enzyme magnetic microspheres. The immobilized enzyme has high stability after the enzyme is immobilized, and the specific surface area of ​​the enzyme is increased, thereby increasing the contact area between the enzyme and the substrate, thereby enhancing the enzymatic hydrolysis effect. This is also the main reason for immobilizing the enzyme in the prior art; secondly, the present application adds magnetic powder on the basis of the existing immobilized enzyme. On the one hand, the prepared immobilized enzyme contains magnetism, which facilitates the separation and recycling of the immobilized enzyme from the enzymatic hydrolysis solution. On the other hand, the immobilized enzyme containing magnetism can move in different directions under the action of the external magnetic field, thereby increasing the contact between the immobilized enzyme and the substrate, thereby improving the enzymatic hydrolysis effect; finally, low-intensity ultrasound is used to assist in improving the enzymatic hydrolysis efficiency of the immobilized composite enzyme, mainly utilizing the thermal effect, mechanical mass transfer effect, cavitation effect, etc. of the ultrasound itself to enhance the enzymatic hydrolysis effect.

[0036] 4. The progressive freeze concentration adopted in this application is a low-energy concentration technology, with energy consumption of only 1 / 3-1 / 6 of evaporation concentration, and cost reduction of 27.5%-40%. In addition, concentration under low temperature conditions can also reduce the loss of functional nutrients, color, flavor and heat-sensitive components in Pueraria coffee liquid.

[0037] 5. The present invention adopts high-pressure treatment technology twice. The first time, ultra-high pressure treatment is adopted in the extraction process, that is, cold extraction equipment is adopted, and the pressure is 100-200Mpa. The second time, ultra-high pressure treatment is adopted after adding a stabilizer and adjusting the pH at the end of concentration, and the pressure is 100-150Mpa. The two high-pressure treatments have a better refining effect on the liquid material, reduce the particle size value of the solid particles in the product, and reduce the polymer dispersion coefficient, thereby making the concentrated liquid system more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The Pueraria coffee concentrate after being frozen and thawed five times in Example 1;

[0039] Figure 2 This is the Pueraria coffee concentrate after being frozen and thawed 5 times in Comparative Example 6. DETAILED DESCRIPTION

[0040] The following embodiments may help those skilled in the art to more fully understand the present invention, but shall not limit the present invention in any way.

[0041] Example 1

[0042] This embodiment provides a method for preparing kudzu root coffee concentrate, the method comprising the following steps:

[0043] (1) Grinding: roast the green coffee beans in medium to dark roasting, grind to a particle size of 20 mesh, obtain coffee powder, and set aside;

[0044] (2) Compound Chinese medicine liquid: roast the kudzu root in an oven for 15 minutes, extract it with alcohol, and obtain the kudzu root extract. Then, inoculate 3% yeast into the kudzu root extract, and perform the first fermentation at 25°C for 2 days, and then perform the second fermentation at 20°C for 4 days. During the second fermentation, oxygen is added to the fermentation tank every day, and the daily oxygen addition amount is 0.6 ml / L. Add coffee powder to the kudzu root Chinese medicine liquid at a ratio of 16:1 and stir evenly to obtain a mixed liquid for use;

[0045] (3) Extraction: The mixed liquid is placed in a cold extraction device. First, the mixture is subjected to steam extraction using advanced technologies such as instantaneous steam explosion, with the temperature controlled at 130°C and the processing time at 8s. After the extraction treatment, the mixture is placed in an ultra-high pressure equipment cabin for cold extraction (temperature 8°C, pressure 150MPa, extraction time 60min). After the cold extraction is completed, the extract is collected and set aside.

[0046] (4) Enzymatic hydrolysis: First, 0.02% disodium ethylenediaminetetraacetate was added to remove metal ions, and then the mixture was filtered and subjected to ultrasonic treatment (ultrasonic intensity was 3.0 W / cm 2 , ultrasonic frequency is 10KHz, ultrasonic temperature is 20℃, ultrasonic time is 20min), enzymatic hydrolysis is carried out by immobilized composite enzyme magnetic microspheres; wherein, the preparation method of composite enzyme magnetic microspheres is as follows: 1) a sodium alginate solution with a concentration of 1.0wt% and a polyvinyl alcohol solution with a concentration of 8.0wt% are mixed in equal mass ratios to obtain a mixed solution, 0.4wt% Fe3O4 magnetic powder is added according to the mass of the mixed solution, stirred evenly, and then the mixture is injected into a boric acid-calcium chloride solution with a concentration of 0.5wt% by a syringe to obtain sodium alginate-polyvinyl alcohol composite microspheres with uniform particles and regular shapes, and washed with water until neutralization, then washing with acetone, and then vacuum drying at 40°C to prepare a magnetic gel microsphere carrier; 2) taking the dried magnetic gel microspheres and adding them to an immobilized complex enzyme solution, the immobilized complex enzyme solution comprising: 0.05wt% papain, 0.5wt% glutamine aminotransferase and 0.6wt% cellulase, and then further dissolving them with a phosphate buffer solution, and then adding 1.5wt% glutaraldehyde as a cross-linking agent, incubating and shaking at 25°C and 100rpm / min for 1h; then washing the magnetic gel microspheres with a phosphate buffer solution to remove free enzymes, thereby obtaining immobilized complex enzyme magnetic microspheres;

[0047] (5) Centrifugation: First, the fixed complex enzyme is removed, and then the extract is centrifuged to remove the residue. The centrifugation condition is 4500r / min for 15min, and then a 0.45μm filter is used for secondary filtration to obtain the kudzu coffee concentrate;

[0048] (6) Concentration: The Pueraria lobata coffee concentrate after the secondary filtration is concentrated by a progressive freeze concentration method. First, the centrifuged coffee concentrate is pre-cooled in a 6°C cold storage for 8 hours. The pre-cooled coffee concentrate is pumped into a cold tank and sealed for progressive freeze concentration. First, refrigeration is turned on and stirred. The refrigerant temperature is -20°C, the stirring rate is 120 r / min, the freezing time is 1.5 hours, and the soluble solid content of the concentrated solution is 40° Brix. Ice cubes are separated to obtain Pueraria lobata coffee liquid.

[0049] (7) Adding stabilizer: adding 0.2% sodium carboxymethyl cellulose and 0.3% β-cyclodextrin to the kudzu coffee liquid and stirring evenly;

[0050] (8) pH adjustment: adding sodium carbonate and dipotassium hydrogen phosphate to the kudzu coffee concentrate obtained in step (7) to adjust the pH of the kudzu coffee concentrate to 5.0;

[0051] (9) High-pressure microfluidization: The coffee concentrate is subjected to high-pressure microfluidization treatment at a treatment pressure of 120 MPa;

[0052] (10) Liquid nitrogen filling: Aseptic filling, add 0.3 mL of liquid nitrogen after filling, the filling time is 60 ms, and the product is sealed within 3 seconds.

[0053] Example 2

[0054] This embodiment provides a method for preparing coffee liquid, which comprises the following steps:

[0055] (1) Grinding: roast the green coffee beans in medium to dark roasting, grind to a particle size of 10 mesh, obtain coffee powder, and set aside;

[0056] (2) Compound Chinese medicine liquid: roast the kudzu root in an oven for 10 minutes, extract it with alcohol, and obtain the kudzu root extract. Then, inoculate 2% yeast into the kudzu root extract, and perform the first fermentation at 24°C for 2 days, and then perform the second fermentation at 22°C for 5 days. During the second fermentation, oxygen is added to the fermentation tank every day, and the daily oxygen addition amount is 0.5 ml / L. Add coffee powder to the kudzu root Chinese medicine liquid at a ratio of 15:1 and stir evenly to obtain a mixed liquid for use;

[0057] (3) Extraction: The mixed liquid is placed in a cold extraction device. First, the mixture is subjected to steam extraction using advanced technologies such as instantaneous steam explosion. The temperature is controlled at 120°C and the treatment time is 10 seconds. After the extraction treatment, the mixture is placed in an ultra-high pressure equipment cabin for cold extraction (temperature 4°C, pressure 100 MPa, extraction time 100 minutes). After the cold extraction is completed, the extract is collected and set aside.

[0058] (4) Enzymatic hydrolysis: First, 0.01% disodium ethylenediaminetetraacetate was added to remove metal ions, and then the mixture was filtered and subjected to ultrasonic treatment (ultrasonic intensity was 4.0 W / cm 2 , ultrasonic frequency is 20KHz, ultrasonic temperature is 30℃, ultrasonic time is 15min), enzymatic hydrolysis is carried out by immobilized composite enzyme magnetic microspheres; wherein, the preparation method of composite enzyme magnetic microspheres is as follows: 1) a sodium alginate solution with a concentration of 3.0wt% and a polyvinyl alcohol solution with a concentration of 10.0wt% are mixed in equal mass ratios to obtain a mixed solution, 1.0wt% Fe3O4 magnetic powder is added according to the mass of the mixed solution, stirred evenly, and then the mixture is injected into a boric acid-calcium chloride solution with a concentration of 0.7wt% by a syringe to obtain sodium alginate-polyvinyl alcohol composite microspheres with uniform particles and regular shapes, and washed with water until neutralization, then washing with acetone, and then vacuum drying at 45°C to prepare a magnetic gel microsphere carrier; 2) taking the dried magnetic gel microspheres and adding them to an immobilized complex enzyme solution, the immobilized complex enzyme solution comprising: 0.2wt% papain, 0.7wt% glutamine aminotransferase and 0.5wt% cellulase, and then further dissolving them with a phosphate buffer solution, and then adding 2.0wt% glutaraldehyde as a cross-linking agent, incubating and shaking at 26°C and 150rpm / min for 1.5h; then washing the magnetic gel microspheres with a phosphate buffer solution to remove free enzymes, thereby obtaining immobilized complex enzyme magnetic microspheres;

[0059] (5) Centrifugation: First, the fixed complex enzyme is removed, and then the extract is centrifuged to remove the residue. The centrifugation condition is 4000r / min for 20min, and then a 0.3μm filter is used for secondary filtration to obtain the kudzu coffee concentrate;

[0060] (6) Concentration: The Pueraria lobata coffee concentrate after the secondary filtration is concentrated by a progressive freeze concentration method. First, the coffee concentrate after centrifugation is pre-cooled in a 4°C cold storage for 5 hours. The pre-cooled coffee concentrate is pumped into a cold tank and sealed for progressive freeze concentration. First, refrigeration is turned on and stirred. The refrigerant temperature is -10°C, the stirring rate is 100 r / min, the freezing time is 2.0 hours, and the soluble solid content of the concentrated solution is 30°Brix. Ice cubes are separated to obtain Pueraria lobata coffee liquid.

[0061] (7) Adding stabilizer: adding 0.05% sodium carboxymethyl cellulose and 0.1% β-cyclodextrin to the kudzu coffee liquid and stirring evenly;

[0062] (8) pH adjustment: Sodium carbonate and dipotassium hydrogen phosphate are added to the kudzu coffee concentrate obtained in step (7) to adjust the pH of the kudzu coffee concentrate to 4.5.

[0063] (9) High-pressure microfluidization: The coffee concentrate is subjected to high-pressure microfluidization treatment at a treatment pressure of 100 MPa;

[0064] (10) Liquid nitrogen filling: Aseptic filling, add 0.1 mL of liquid nitrogen after filling, the filling time is 60 ms, and the product is sealed within 1 s.

[0065] Example 3

[0066] This embodiment provides a method for preparing coffee liquid, which comprises the following steps:

[0067] (1) Grinding: roast the green coffee beans in medium to dark roasting, grind to a particle size of 30 mesh, obtain coffee powder, and set aside;

[0068] (2) Compound Chinese medicine liquid: roast the kudzu root in an oven for 20 minutes, take it out and extract it with alcohol to obtain the kudzu root extract, then inoculate 5% yeast into the kudzu root extract, carry out the first fermentation at 27°C for 1 day, and then carry out the second fermentation at 23°C for 3 days. During the second fermentation, oxygen is added to the fermentation tank every day, and the daily oxygen addition amount is 0.8 ml / L. Add coffee powder to the kudzu root Chinese medicine liquid at a ratio of 16:1 and stir evenly to obtain a mixed liquid for use;

[0069] (3) Extraction: The mixed liquid is placed in a cold extraction device. First, the mixture is subjected to steam extraction using advanced technologies such as instantaneous steam explosion, with the temperature controlled at 135°C and the processing time being 5 seconds. After the extraction treatment, the mixture is placed in an ultra-high pressure equipment cabin for cold extraction (temperature 10°C, pressure 200 MPa, extraction time 30 minutes). After the cold extraction is completed, the extract is collected and set aside.

[0070] (4) Enzymatic hydrolysis: First, 0.03% disodium ethylenediaminetetraacetate was added to remove metal ions, and then the mixture was filtered and subjected to ultrasonic treatment (ultrasonic intensity was 6.0 W / cm 2, ultrasonic frequency is 30KHz, ultrasonic temperature is 40℃, ultrasonic time is 10min), enzymatic hydrolysis is carried out by immobilized composite enzyme magnetic microspheres; wherein, the preparation method of composite enzyme magnetic microspheres is as follows: 1) a sodium alginate solution with a concentration of 1.0wt% and a polyvinyl alcohol solution with a concentration of 12.0wt% are mixed in equal mass ratios to obtain a mixed solution, 0.4wt% of Fe3O4 magnetic powder is added according to the mass of the mixed solution, stirred evenly, and then the mixture is injected into a boric acid-calcium chloride solution with a concentration of 0.7wt% by a syringe to obtain sodium alginate-polyvinyl alcohol composite microspheres with uniform particles and regular shapes, and washed with water until neutralization, then washing with acetone, and then vacuum drying at a temperature of 40-50° C. to prepare a magnetic gel microsphere carrier; 2) taking the dried magnetic gel microspheres and adding them to an immobilized complex enzyme solution, the immobilized complex enzyme solution comprising: 0.3wt% papain, 1.0wt% glutamine aminotransferase and 0.2wt% cellulase, and then further dissolving them with a phosphate buffer solution, and then adding 3.0wt% glutaraldehyde as a cross-linking agent, incubating and shaking at 27° C. and 120rpm / min for 2h; then washing the magnetic gel microspheres with a phosphate buffer solution to remove free enzymes, thereby obtaining immobilized complex enzyme magnetic microspheres;

[0071] (5) Centrifugation: First, the fixed complex enzyme is removed, and then the extract is centrifuged to remove the residue. The centrifugation condition is 5000r / min for 10min, and then a 0.8μm filter is used for secondary filtration to obtain the kudzu coffee concentrate;

[0072] (6) Concentration: The Pueraria lobata coffee concentrate after secondary filtration is concentrated by a progressive freeze concentration method. First, the centrifuged coffee concentrate is pre-cooled in an 8°C cold storage for 10 hours. The pre-cooled coffee concentrate is pumped into a cold tank and sealed for progressive freeze concentration. First, refrigeration is turned on and stirring is performed. The refrigerant temperature is -30°C, the stirring rate is 150 r / min, the freezing time is 1.0 h, the soluble solids content of the concentrate is 45°Brix, and the ice cubes are separated to obtain the Pueraria lobata coffee concentrate and the coffee liquid product.

[0073] (7) Adding stabilizers: adding 0.5% sodium carboxymethyl cellulose and 0.5% β-cyclodextrin to the kudzu coffee liquid and stirring evenly;

[0074] (8) pH adjustment: adding sodium carbonate and dipotassium hydrogen phosphate to the kudzu coffee concentrate obtained in step (7) to adjust the pH of the kudzu coffee concentrate to 5.5;

[0075] (9) High-pressure microfluidization: The coffee concentrate is subjected to high-pressure microfluidization treatment at a treatment pressure of 150 MPa;

[0076] (10) Liquid nitrogen filling: Aseptic filling, add 0.5 mL of liquid nitrogen after filling, the filling time is 60 ms, and the product is sealed within 4 seconds.

[0077] In order to illustrate the technical effect of the present application, the present application also conducted the following experiments:

[0078] Test example:

[0079] Comparative Example 1: Comparison between hot brew and cold brew

[0080] The difference from Example 1 is that the mixed liquid is not extracted by cold extraction equipment, but by hot extraction method, with extraction at 90±2°C for 10 minutes. The other steps and parameters are the same as those in Example 1.

[0081] Comparative Example 2: Comparison of the effects of repeated use of immobilized complex enzymes

[0082] The difference from Example 1 is that the enzymatic hydrolysis process uses an immobilized complex enzyme that is reused 6 times, and the other steps and parameters are the same as those in Example 1.

[0083] Comparative Example 3: Comparison of vacuum concentration and freeze concentration

[0084] The difference from Example 1 is that the Pueraria coffee concentrate after the secondary filtration is not concentrated by progressive freeze concentration, but by vacuum concentration. The vacuum concentration conditions are vacuum degree 0.09 MPa and temperature 50° C. The other steps and parameters are the same as those in Example 1.

[0085] Comparative Example 4: Comparison of pH Adjustment Effects

[0086] The difference from Example 1 is that the pH of the Pueraria coffee concentrate with the stabilizer added is not adjusted, and the other steps and parameters are the same as those in Example 1.

[0087] Comparative Example 5: Difference between homogenization and high-pressure microfluidization

[0088] The difference from Example 1 is that the Pueraria coffee concentrate after pH adjustment is not homogenized by superpressure microfluidization technology, but by a homogenizing device with a homogenization pressure of 15 MPa. The other steps and parameters are the same as those in Example 1.

[0089] Comparative Example 6: Comparison of Preparation of Chinese Medicine Liquid

[0090] The difference from Example 1 is that the preparation method of the traditional Chinese medicine liquid is: baking the Pueraria root in an oven for 15 minutes, taking it out and extracting it with alcohol to obtain the Pueraria root extract, then inoculating 3% yeast into the Pueraria root extract, and fermenting it at 25°C for 5 days. The other steps and parameters are the same as those in Example 1.

[0091] Comparative Example 7: Comparison between immobilized complex enzyme magnetic microspheres and magnetic gel microspheres

[0092] The difference from Example 1 is that the magnetic microspheres of the immobilized complex enzyme in Example 1 are replaced by magnetic gel microspheres. The preparation method is as follows: first, 3.0wt% sodium alginate solution is added to deionized water, and after swelling for 1h, heated and stirred until clear and transparent, then 1.0% KOH and 5.0wt% chitosan powder are added to the sodium alginate solution, stirred evenly, and placed in a -20°C refrigerator for one night. After being taken out, it is placed in room temperature and allowed to thaw slowly, and stirred continuously during the thawing period until a light yellow transparent gel is formed. 1.0wt% Fe3O4 magnetic powder is added to the gel, stirred evenly, the mixed solution is sucked with a 5mL syringe, and 20g / LZnSO4 solution is dripped dropwise at a height of about 10cm. After continuous curing for 1h, it is washed with deionized water to prepare the magnetic gel microspheres. The other steps and parameters are the same as those in Example 1.

[0093] Sensory evaluation comparison experiment

[0094] The coffee variety used in this application is the Catim variety T8667, which is the main cultivated variety of small-grain coffee in my country.

[0095] Experimental method: The Pueraria coffee concentrates obtained from Examples 1-3 and Comparative Examples 1-6 were evaluated by a sensory evaluation panel consisting of 10 coffee professionals with Arabica QGrader. The specific parameters of the sensory evaluation are shown in Table 1, and the results are shown in Table 2.

[0096] Table 1 Sensory evaluation standards

[0097]

[0098]

[0099] Table 2 Sensory evaluation

[0100] Group Color taste odor Organization Status Total score Example 1 19.0 18.5 37.5 18.5 93.5 Example 2 18.5 18.0 38.0 18.0 92.5 Example 3 18.5 18.5 37.5 18.5 93.0 Comparative Example 1 11.0 16.5 26.5 17.0 71.0 Comparative Example 2 18.5 18.0 36.5 17.5 90.5 Comparative Example 3 13.0 17.0 26.0 17.5 73.5 Comparative Example 4 17.5 14.0 27.0 17.0 75.5 Comparative Example 5 13.0 16.0 25.5 8.5 63.0 Comparative Example 6 17.0 18.0 36.5 17.5 89.0 Comparative Example 7 17.0 15.5 33.5 17.0 83.0

[0101] As shown in Table 2, the Pueraria coffee concentrates of Examples 1-3 and Comparative Example 2 scored the highest, all reaching more than 90 points, indicating that the Pueraria coffee concentrate processed by the present invention performs well in color, taste, smell and tissue state. The Pueraria coffee concentrate obtained by reusing the immobilized complex enzyme in Comparative Example 2 for 6 times has a sensory evaluation of 90.5 points, which verifies that the immobilized enzyme can be reused at least 6 times, the product quality can be guaranteed, and the production cost is also saved for the enterprise. Comparative Example 1 does not use cold extraction equipment for extraction, but uses hot extraction method for extraction. The product color and smell scores are low, mainly because the extraction temperature is high, and the heat treatment causes the color of the Pueraria coffee concentrate to darken; at the same time, the hot extraction temperature is high, and the high temperature increases the kinetic energy of water molecules, and at the same time, the compounds are leached from the coffee powder, affecting the release and escape of volatile compounds in the coffee, so that the content of aromatic substances is low. Comparative Example 3 does not use progressive freeze concentration for concentration, but uses vacuum concentration for concentration. Evaporation concentration and vacuum concentration are the main methods currently used in the industry. Compared with evaporation concentration, vacuum concentration uses vacuum combined with medium and low temperature conditions for concentration, which has the advantages of low cost, easy operation and high concentration ratio. However, compared with Examples 1-3 and Comparative Example 2, the color and odor scores of the kudzu coffee concentrate are lower. The mechanism of the darkening of the concentrate color mainly includes non-enzymatic browning and enzymatic browning. The non-enzymatic browning of Maillard reaction and caramelization reaction is the fundamental reason for the deepening of color; the low odor score is mainly caused by the high thermal concentration temperature causing the volatile flavor substances to escape. Comparative Example 4 Compared with Examples 1-3 and Comparative Example 2, the taste and odor values ​​of the kudzu coffee concentrate are lower. This is because the present invention uses cold extraction equipment to extract coffee. Due to the long extraction time and low temperature, the acidity of the coffee concentrate is low, and the pH is about 4.8, so the taste and flavor are poor. The Pueraria coffee concentrate of Comparative Example 5 does not use superpressure microfluidization technology, but uses ordinary homogenization equipment for homogenization. The product color, smell, and tissue state scores are all low, among which the tissue state score is the lowest, only 8.5 points. This is because the pressure used by the high-pressure microfluidization technology is 100-150MPa, while the pressure used by ordinary homogenization is only 15MPa. The particle size of the Pueraria coffee concentrate treated with high-pressure microfluidization is significantly reduced to prevent stratification and precipitation. However, the solid particle size of the Pueraria coffee concentrate in the comparative example 5 treated with ordinary homogenization is relatively large due to the low processing pressure, resulting in the appearance of suspended particles, and the pigment distribution in the concentrated liquid is uneven, so the sensory score is low. Comparative Example 6 only ferments once, the tissue state is unstable, and a small amount of suspension occurs, so it mainly affects the score of the tissue state. The selection of the immobilized carrier of Comparative Example 7 adopts a sodium alginate-chitosan composite carrier, and the sensory score of the Pueraria coffee concentrate obtained is slightly worse than that of Examples 1-3. It can be seen that the sodium alginate-polyvinyl alcohol composite carrier used in the present invention is better for preparing the immobilized composite enzyme magnetic microspheres.

[0102] Determination of particle size and sedimentation rate of kudzu coffee concentrate

[0103] Particle size determination experimental method: The particle size distribution and polydispersity index PDI of Pueraria lobata coffee concentrate were determined by dynamic light diffraction technology of nanoparticle size analyzer.

[0104] Experimental method for determining the precipitation rate: centrifuge the coffee concentrate samples that have been frozen and thawed 0 times and 5 times at 4500r / min for 15 minutes, remove the supernatant to obtain the coffee concentrate precipitate, accurately weigh it, and calculate the precipitation rate.

[0105] Sedimentation rate (%) = Sedimentation weight (g) × 100 / Coffee concentrate sample weight (g)

[0106] Table 3 Results of determination of particle size of kudzu coffee concentrate and precipitation rate at different freeze-thaw times

[0107]

[0108] Coffee concentrate has complex nutritional ingredients and contains more substances such as cellulose, polyphenols, proteins, fats and polysaccharides. The problem of product stability, especially the decrease in stability after repeated freezing and thawing, has always been a difficult problem for the industrial production of coffee concentrate, which limits the market application of coffee concentrate products. The particle size distribution of solid particles in the kudzu coffee concentrate of Examples 1-3 and Comparative Example 2 of this application is less than 220nm, and the polymer dispersion coefficient (PDI) is less than 0.40. The particle size value is combined with PDI. The smaller the particle size value and PDI, the more uniform the molecular weight distribution, and the more stable the system. The precipitation rates of 0 freeze-thaw and 5 freeze-thaw times are both lower than 0.6, indicating that the precipitation of the kudzu coffee concentrate prepared by the technology used in this application is significantly reduced, which is consistent with the smaller particle size value and PDI of the solid particles in the system. The kudzu coffee concentrate of Comparative Example 4 was not pH-adjusted, and the particle size distribution and polymer dispersion coefficient of the solid particles in its system were close to those of Examples 1-3, but the precipitation rate of the concentrate increased significantly to 1.22% after 5 freeze-thaws. The precipitation rates of the concentrates of Comparative Examples 1, 3, and 5 after 0 freeze-thaw cycles and 5 freeze-thaw cycles were both relatively large, significantly greater than those of Examples 1-3. This may be due to the instability of the system caused by the particle size values ​​in the concentrates of Comparative Examples 1, 3, and 5 being greater than 380 nm and the polymer dispersion index (PDI) being greater than 0.50. Comparative Example 7 used a different immobilized carrier to encapsulate the complex enzyme. The particle size distribution, polydispersity index, and sedimentation rates of 0 and 5 freeze-thaw cycles of the solid particles in the system were significantly greater than those of Examples 1-3, indicating that the carrier selected for Comparative Example 7 is not suitable, and the embedded complex enzyme has a poor effect in hydrolyzing insoluble substances such as proteins and polysaccharides. The coffee concentrate of Example 1 after 5 freeze-thaw cycles is as follows: Figure 1As shown, it can be seen that the texture is uniform and no precipitation is produced. The coffee concentrate of Comparative Example 6 may have a high precipitation rate due to multiple freeze-thaw cycles due to the unreasonable preparation process of the traditional Chinese medicine liquid. Figure 2 As shown, yellow precipitate can be seen at the bottom of the coffee concentrate.

[0109] The above description is a detailed description of the preferred feasible embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modified changes completed under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for preparing kudzu root coffee concentrate, characterized in that: The method comprises the following steps: (1) Grinding: roasting and grinding green coffee beans to obtain coffee powder for later use; (2) Compounding the Chinese medicine liquid: adding coffee powder to the Pueraria root Chinese medicine liquid, stirring evenly to obtain a mixed liquid for later use; (3) Extraction: The mixed liquid is subjected to steam extraction. After the extraction treatment is completed, cold extraction is then performed to lock the aroma of the coffee through low temperature and high pressure treatment. The extract is collected and set aside; (4) Enzymatic hydrolysis: adding 0.01% to 0.03% of disodium ethylenediaminetetraacetate to the extract, followed by filtration, and then enzymatic hydrolysis by immobilized complex enzyme magnetic microspheres under ultrasonic action; (5) Centrifugation: remove the immobilized complex enzyme magnetic microspheres, centrifuge the extract obtained after enzymatic hydrolysis to remove the residue, and then use a filter to perform secondary filtration to obtain the kudzu coffee concentrate; (6) Concentration: The kudzu root coffee concentrate obtained in step (5) is concentrated by a progressive freeze concentration method. First, the kudzu root coffee concentrate is pre-cooled in a 4-8° C. cold storage for 5-10 hours. The pre-cooled coffee concentrate is pumped into a cold tank and sealed for progressive freeze concentration. Refrigeration is turned on and stirred. The refrigerant temperature is -10 to -30° C., the stirring rate is 100-150 r / min, the freezing time is 1.0 to 2.0 h, and the soluble solid content of the concentrate is 30-45° Brix. Ice cubes are separated to obtain kudzu root coffee liquid. (7) Adding a stabilizer: adding 0.05-0.5% sodium carboxymethyl cellulose and 0.1%-0.5% β-cyclodextrin to the Pueraria coffee liquid, stirring thoroughly, and then adjusting the pH value of the Pueraria coffee liquid to 4.5-5.5; (8) High-pressure microfluidization and filling: The kudzu root coffee liquid treated in step (7) is subjected to high-pressure microfluidization treatment, and then filled under aseptic conditions. After filling, liquid nitrogen is added and the bottle is sealed to obtain a finished kudzu root coffee concentrate.

2. The method according to claim 1, characterized in that The coffee beans in step (1) are roasted in a medium-dark roast and ground to a particle size of 10-30 mesh.

3. The method according to claim 1, characterized in that: The Pueraria root Chinese medicine liquid in the step (2) is obtained by the following method: baking the Pueraria root in an oven for 10-20 minutes, taking it out and performing alcohol extraction to obtain a Pueraria root extract, then adding a fermentation agent to the Pueraria root extract, performing a first fermentation at 24-27° C. for 1-2 days, and then performing a secondary fermentation at 20-23° C. for 3-5 days.

4. The method according to claim 1, characterized in that: In the step (2), the mass ratio of the Pueraria root Chinese medicinal liquid to the coffee powder is 15-18:

1.

5. The method according to claim 1, characterized in that The temperature of the cold extraction in step (3) is 4-10° C., the pressure is 100-200 MPa, and the extraction time is 30-100 min.

6. The method according to claim 1, characterized in that The preparation method of the immobilized complex enzyme magnetic microspheres in step (4) is as follows: (1) A sodium alginate solution with a concentration of 1.0 to 4.0 wt% and a polyvinyl alcohol solution with a concentration of 8.0 to 12.0 wt% are mixed in equal weight ratios to obtain a mixed solution, 0.4 to 1.3 wt% of Fe3O4 magnetic powder is added based on the weight of the mixed solution, and the mixture is stirred evenly, and then the mixture is injected into a boric acid-calcium chloride solution with a concentration of 0.5 to 1.0 wt% by using a syringe to obtain sodium alginate-polyvinyl alcohol composite microspheres with uniform particles and regular shapes, and then washed with water until neutral, and then washed with acetone, and then vacuum dried at a temperature of 40 to 50° C. to prepare a magnetic gel microsphere carrier; (2) adding the dried magnetic gel microspheres to an immobilized complex enzyme solution, wherein the immobilized complex enzyme solution includes: 0.05-0.3 wt% of papain, 0.5-1.0 wt% of glutamine aminotransferase and 0.2-0.6 wt% of cellulase, and then further dissolving them with a phosphate buffer solution, and then adding 1.5-3.0 wt% of glutaraldehyde as a cross-linking agent, incubating and shaking at 25±2° C. and 100-200 rpm / min for 1-2 hours; and then washing the magnetic gel microspheres with a phosphate buffer solution to remove free enzymes, thereby obtaining immobilized complex enzyme magnetic microspheres.

7. The method according to claim 1, characterized in that The ultrasonic intensity in step (4) is 3.0 to 6.0 W / cm 2 , the ultrasonic frequency is 10-30KHz, the ultrasonic temperature is 20-40℃, and the ultrasonic time is 10-20min.

8. The method according to claim 1, characterized in that The concentration endpoint in step (6) is that the soluble solid content of the concentrated liquid is 30-45° Brix.

9. The method according to claim 1, characterized in that: In the step (8), the pressure used during the treatment by the high-pressure microfluidic device is 100-150 MPa.

10. The method according to claim 3, characterized in that: The fermentation agent is yeast, and the inoculation amount is 2%-5%. During the second fermentation process, oxygen is added to the fermentation tank every day, and the daily oxygen addition amount is 0.5-0.8 ml / L.

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