Preparation method of quick cold extraction coffee

Abstract

The invention belongs to the technical field of food processing, and particularly relates to a rapid cold extraction coffee preparation method which comprises the steps of coffee bean baking, grinding, enzymolysis, ultrasonic treatment, heat treatment for terminating enzymolysis, antioxidant and protection system adding, homogenizing treatment, freeze concentration, freeze drying and the like, and specifically comprises the steps that coffee beans are baked and then ground to 250-300 microns, the coffee beans are mixed with water according to the ratio of 1: 8, and the mixture is put into a freeze-drying machine to be subjected to freeze-drying; performing enzymolysis for 60 + / -10 minutes at the temperature of 10 + / -2 DEG C, performing ultrasonic treatment for 20 + / -5 minutes with the frequency of 20 + / -2kHz during enzymolysis, performing heat treatment for 5 + / -1 minutes at the temperature of 75 + / -5 DEG C, stopping enzymolysis, adding antioxidants such as ascorbic acid, tocopherol and rosemary extract and protection systems such as Arabic gum and maltodextrin, performing homogenization, performing freeze concentration at the temperature of-5 + / -1 DEG C until Brix is 18-22 degrees, and finally performing freeze-drying to obtain coffee powder. The extraction time of 6-24 hours of traditional cold extraction of coffee is shortened to only 60 + / -10 minutes, so that the production efficiency is improved by 6-10 times.

Description

Technical Field

[0001] The present invention belongs to the technical field of food processing, and specifically relates to a method for preparing rapid cold-brewed coffee, and more particularly to a method for preparing cold-brewed coffee with high efficiency, low energy consumption and high quality by using enzymatic hydrolysis-assisted and ultrasonic synergistic technology combined with a plant colloid protection system. Background Art

[0002] With the popularization of coffee culture and the growing demand for high-quality coffee, cold brew coffee is favored by more and more consumers due to its low acidity, smooth taste and unique flavor. The traditional method of preparing cold brew coffee is to mix coffee powder with cold water, soak it at room temperature or low temperature for a long time (usually 8-24 hours), and then filter it to obtain cold brew coffee liquid. Although this method can extract coffee with a soft flavor, it has problems such as long preparation cycle, low production efficiency, and high energy consumption, which is not conducive to large-scale production.

[0003] In recent years, freeze-dried coffee has attracted widespread attention as a form of instant coffee that can better retain the flavor of coffee. For example, Chinese patent CN 116473146 B discloses a method for preparing freeze-dried coffee, which comprises mixing cold-brewed concentrated coffee liquid with coffee ground slurry at a mass ratio of 5 to 10:1 and then freeze-drying the mixture, wherein the concentration of the cold-brewed concentrated coffee liquid is 10.0 to 20.0° Brix, the solid content of the coffee ground slurry is 8% to 15%, and the solid particle size is 10 to 100 μm. Although this method improves the quality and processing efficiency of freeze-dried coffee to a certain extent, the following technical problems still exist: 1. Low extraction efficiency: The traditional cold extraction process takes 6-10 hours or even longer, with low extraction efficiency and long production cycle; 2. Insufficient extraction of flavor substances: Conventional cold brewing methods are difficult to efficiently extract some flavor substances in coffee beans, limiting the full expression of coffee flavor; 3. Coffee flavor is easily lost: During the extraction, concentration and drying process, the volatile aromatic substances in coffee are easily lost, affecting the quality of the final product; 4. Insufficient product stability: Freeze-dried coffee easily absorbs moisture and clumps, has unstable solubility, and its flavor easily decays during storage.

[0004] Therefore, there is an urgent need to develop a method for preparing rapid cold brew coffee that can improve extraction efficiency, enhance flavor extraction, protect aromatic substances and improve product stability. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing fast cold-brewed coffee, aiming to solve the technical problems existing in the preparation process of existing cold-brewed coffee, such as long extraction time, insufficient extraction of flavor substances, easy loss of aromatic substances, and poor product stability, so as to achieve high-efficiency, low-energy-consumption, and high-quality production of cold-brewed coffee.

[0006] To achieve the above object, the present invention provides a method for preparing fast cold-brewed coffee, including the following steps: S1. Roast coffee beans to obtain roasted coffee beans; S2. Grind the roasted coffee beans to a particle size of 250 - 300 μm to obtain coffee ground powder; S3. Mix the coffee ground powder and water at a weight ratio of 1:8, and add a composite enzyme preparation for enzymatic hydrolysis at 10 ± 2°C. The composite enzyme preparation includes pectinase, hemicellulase, and cellulase; S4. During the enzymatic hydrolysis process, perform ultrasonic treatment at a frequency of 20 ± 2 kHz for 20 ± 5 minutes; S5. After the total enzymatic hydrolysis time reaches 60 ± 10 minutes, terminate the enzymatic hydrolysis by heat treatment at 75 ± 5°C for 5 ± 1 minute to obtain coffee extract; S6. Add a natural antioxidant protection system to the coffee extract. The natural antioxidant protection system includes ascorbic acid, natural mixed tocopherols, and rosemary extract; S7. Add a plant colloid protection system to the coffee extract. The plant colloid protection system includes gum arabic, maltodextrin, modified starch, and β-cyclodextrin, and perform high-speed homogenization treatment to obtain a coffee extract protected by colloids; S8. Freeze-concentrate the coffee extract protected by colloids at -5 ± 1°C to 18 - 22°Brix; S9. Perform freeze-drying treatment on the concentrated coffee extract, including pre-freezing, primary drying, and secondary drying, to obtain freeze-dried coffee powder.

[0007] Preferably, the coffee beans in S1 include the following components in parts by weight: 30 - 40 parts by weight of Ethiopian Yirgacheffe G1 coffee beans; 30 - 40 parts by weight of Colombian supremo coffee beans; 20 - 30 parts by weight of Guatemalan Antigua SHB coffee beans.

[0008] Preferably, the roasting treatment in S1 includes: medium roasting: roasting temperature 205 ± 5°C, time 13 - 15 minutes, Colorate value 95 - 105, 40 - 50 parts by weight; deep roasting: roasting temperature 220 ± 5°C, time 14 - 16 minutes, Colorate value 75 - 85, 50 - 60 parts by weight; after roasting, let it stand for degassing for 24 ± 2 hours.

[0009] Preferably, the composition of the complex enzyme preparation in S3 is: pectinase 0.03 - 0.05 parts by weight; hemicellulase 0.02 - 0.04 parts by weight; cellulase 0.01 - 0.03 parts by weight; enzyme stabilizer maltodextrin 0.1 - 0.2 parts by weight.

[0010] Preferably, the enzymatic hydrolysis conditions in S3 are: enzymatic hydrolysis temperature is 12 ± 2°C; enzymatic hydrolysis pH value is 5.5 ± 0.3, adjusted by citric acid / sodium citrate buffer system; stirring speed is 60 ± 10 rpm.

[0011] Preferably, the composition of the natural antioxidant protection system in S6 is: ascorbic acid 0.05 - 0.1 parts by weight; natural mixed tocopherols 0.01 - 0.03 parts by weight; rosemary extract 0.02 - 0.05 parts by weight; citric acid 0.05 - 0.1 parts by weight; sodium citrate 0.03 - 0.06 parts by weight.

[0012] Preferably, the composition of the plant colloid protection system in S7 is: gum arabic 0.8 - 1.2 parts by weight; maltodextrin 0.3 - 0.7 parts by weight; modified starch 0.1 - 0.3 parts by weight; β - cyclodextrin 0.1 - 0.2 parts by weight.

[0013] Preferably, the high - speed homogenization treatment conditions in S7 are: homogenization speed is 10000 ± 1000 rpm; homogenization temperature is 10 ± 2°C; homogenization time is 5 ± 1 minute; colloid particle size is 10 - 20 μm.

[0014] Preferably, the freeze - drying treatment conditions in S9 are: pre - freezing: cooling rate is 1 ± 0.2°C / minute, from 5°C to - 30°C, keep the temperature at - 30 ± 2°C, keep the time for 120 ± 20 minutes; primary drying: shelf temperature slowly rises from - 30°C to 20°C, vacuum degree is 100 ± 20 Pa, drying time is 8 ± 1 hour; secondary drying: shelf temperature is 30 ± 2°C, vacuum degree is 50 ± 10 Pa, drying time is 3 ± 0.5 hour, and the final moisture content ≤ 2.5%.

[0015] Preferably, it further includes a product stability treatment step: adding a food - grade anti - caking agent to the freeze - dried coffee powder, the food - grade anti - caking agent includes silicon dioxide 0.1 - 0.3 parts by weight and tricalcium phosphate 0.1 - 0.2 parts by weight; using a multi - layer composite material packaging bag for nitrogen filling packaging, residual oxygen content ≤ 1.0%; adding 1 - 2 parts by weight of food - grade silica desiccant.

[0016] Compared with the prior art, the rapid cold - extraction coffee preparation method provided by the present invention has the following remarkable technical effects: 1. Greatly improve the extraction efficiency: Through the synergistic treatment of complex enzymatic hydrolysis and ultrasonic waves, the extraction time of traditional cold-brew coffee, which is 6 - 24 hours, is shortened to only 60 ± 10 minutes, increasing the production efficiency by 6 - 10 times. The complex enzyme system can effectively decompose the coffee cell wall structure and promote the release of inclusions; ultrasonic treatment further enhances the mass transfer process through cavitation effect. The synergistic effect of the two significantly improves the extraction efficiency.

[0017] 2. More comprehensive extraction of flavor substances: Enzymatic hydrolysis treatment enables better release and transformation of macromolecular substances such as polyphenols, proteins, and polysaccharides in coffee, while ultrasonic treatment promotes the release of fat-soluble flavor substances. Experiments show that compared with traditional cold-brew coffee, the total polyphenol content of coffee prepared by the method of the present invention increases by 25 - 35%, the soluble solid content increases by 15 - 20%, and the flavor substance spectrum is more abundant.

[0018] 3. More complete retention of aromatic substances: The natural antioxidant protection system inhibits the oxidative degradation of aromatic substances in coffee, and the plant colloid protection system fixes and protects volatile aromatic substances through microencapsulation. Flavor chemical analysis shows that the retention rate of aromatic substances in the freeze-dried coffee prepared by the method of the present invention is 40 - 50% higher than that of the traditional process, especially the retention of key flavor substances such as aldehydes, ketones, and furans increases significantly.

[0019] 4. Better product stability: The microcapsule structure formed by the plant colloid protection system not only protects the coffee flavor but also significantly improves the solubility of the freeze-dried product; the anti-caking system and nitrogen filling packaging technology effectively solve the problem of easy moisture absorption and caking of freeze-dried coffee. After the freeze-dried coffee prepared by the present invention is placed in an environment with a relative humidity of 75% for 30 days, the moisture absorption rate is only 40 - 50% of that of traditional freeze-dried coffee, and the dissolution time is shortened by about 50%.

[0020] 5. Energy-saving and environmental protection: Compared with the traditional process, the method of the present invention can save about 40 - 50% of energy consumption, reduce production water by about 60%, shorten the production cycle by 70 - 80%, and avoid using toxic reagents, meeting the concept of green production. Detailed implementation mode

[0021] The following further elaborates on the present invention in detail with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0022] In the embodiments of the present invention, unless otherwise specified, the technical terms or scientific terms used should have the ordinary meaning understood by those with ordinary skills in the field to which the present invention belongs.

[0023] Example 1: A method for preparing fast cold-brew coffee based on the synergistic treatment of complex enzymatic hydrolysis and ultrasonic waves This embodiment provides a method for preparing fast cold-brewed coffee based on the synergistic treatment of compound enzymatic hydrolysis and ultrasonic waves, comprising the following steps: (1) Selection and roasting of coffee beans: Select 35 parts by weight of Ethiopian Yirgacheffe G1 coffee beans (origin: Ethiopia), 35 parts by weight of Colombian supremo coffee beans (origin: Colombia), and 25 parts by weight of Guatemalan Antigua SHB coffee beans (origin: Guatemala). After mixing according to the ratio of the present invention, they are roasted in batches. Among them, 45 parts by weight of coffee beans are medium-roasted: in a professional coffee roaster (model: Probat P12, Germany), the roasting temperature is controlled at 205 °C, the roasting time is 14 minutes, and the final Colorate value (measured using an Agtron coffee colorimeter) is 100; 55 parts by weight of coffee beans are deeply roasted: in the same roaster, the roasting temperature is 220 °C, the roasting time is 15 minutes, and the final Colorate value is 80. The roasted coffee beans are left to degas for 24 hours in an environment at room temperature (about 22 °C) and a relative humidity of 50%.

[0024] (2) Grinding of coffee beans: Grind the above-mentioned roasted coffee beans in a ceramic cutter head grinder (model: Mahlkönig EK43, Germany) to a particle size of 275 ± 25 μm (measured using a standard sieve) to obtain coffee ground powder.

[0025] (3) Enzymatic hydrolysis-ultrasonic synergistic extraction: Weigh 100 parts by weight of coffee ground powder, add 800 parts by weight of low-temperature pure water (conductivity < 5 μS / cm), and mix evenly. Adjust the temperature of the mixture to 10 °C and the pH value to 5.5 (using a citric acid / sodium citrate buffer system, where citric acid is 0.08 parts by weight and sodium citrate is 0.05 parts by weight).

[0026] Add a food-grade complex enzyme preparation to the mixed solution, including: pectinase (EC 3.2.1.15, derived from Aspergillus niger, activity ≥ 3000 U / g, manufacturer: Novozymes, product name: Pectinex Ultra SP-L) 0.04 parts by weight, hemicellulase (EC 3.2.1.8, derived from Bacillus amyloliquefaciens, activity ≥ 2500 U / g, manufacturer: DuPont, product name: Hemicellulase TCAE) 0.03 parts by weight, cellulase (EC 3.2.1.4, derived from Trichoderma, activity ≥ 1500 U / g, manufacturer: Novozymes, product name: Celluclast 1.5L) 0.02 parts by weight, and the enzyme stabilizer maltodextrin (DE value 10 - 12, manufacturer: Roquette, product name: MDX 10) 0.15 parts by weight.

[0027] Perform enzymatic hydrolysis at a stirring speed of 60 rpm. After 20 minutes from the start of enzymatic hydrolysis, transfer the mixture to an ultrasonic treatment device (model: Hielscher UP400St, Germany), and perform ultrasonic treatment for 20 minutes under the conditions of a frequency of 20 kHz and a power density of 180 W / L, while maintaining the system temperature at 12 °C (using an external cooling system). After the ultrasonic treatment is completed, continue enzymatic hydrolysis until the total time reaches 60 minutes, then raise the system temperature to 75 °C and maintain it for 5 minutes to terminate the enzyme activity. Subsequently, filter through a 100-mesh sieve to obtain the coffee extract.

[0028] (4) Antioxidant protection treatment: After the coffee extract is cooled to 15 °C, add a natural antioxidant protection system, including: ascorbic acid (vitamin C, E300, purity ≥ 99%, manufacturer: DSM) 0.08 parts by weight, natural mixed tocopherols (vitamin E, E306, purity ≥ 95%, manufacturer: DSM) 0.02 parts by weight, rosemary extract (E392, standardized extract, containing rosmarinic acid ≥ 30%, manufacturer: Kemin, product name: Fortium R20) 0.04 parts by weight, citric acid (E330, purity ≥ 99.5%, manufacturer: Jungbunzlauer) 0.08 parts by weight, and sodium citrate (E331, purity ≥ 99%, manufacturer: Jungbunzlauer) 0.05 parts by weight. Stir gently at 8 °C and 30 rpm for 10 minutes to fully dissolve the additives and disperse them evenly.

[0029] (5) Plant colloid protection treatment: Add a plant colloid protection system to the above coffee extract, including: 1.0 part by weight of gum arabic (E414, purity ≥ 99%, manufacturer: Nexira, product name: Fibregum B), 0.5 part by weight of maltodextrin (DE value 9 - 11, manufacturer: Roquette, product name: MDX 10), 0.2 part by weight of modified starch (E1450, acetylated starch, DS value 0.05 - 0.08, manufacturer: Ingredion, product name: N-Tack), and 0.15 part by weight of β-cyclodextrin (E459, purity ≥ 98%, manufacturer: Wacker, product name: CAVAMAX W7).

[0030] Perform high-speed homogenization treatment for 5 minutes at 10000 rpm and 10 °C using a high-speed homogenizer (model: IKA Ultra-Turrax T25, Germany). Measured by a laser particle size analyzer (model: Malvern Mastersizer 3000, UK), the average particle size of the finally formed protective colloid is 15 μm.

[0031] (6) Freeze concentration: Perform freeze concentration on the colloid-protected coffee extract in a low-temperature condensation concentration device (model: GEA FC-500, Germany). The concentration temperature is controlled at -5 °C, the initial concentration is about 6 °Brix, and it is slowly concentrated at a rate of 1.8 °Brix / hour until the final concentration reaches 20 °Brix. Recover aromatic substances using a low-temperature condensation recovery system (temperature -12 °C) during the concentration process, and control the reflux ratio above 85%.

[0032] (7) Lyophilization treatment: Transfer the concentrated coffee extract to a lyophilization device (model: Telstar Lyobeta 25, Spain) for lyophilization treatment. The lyophilization process includes the following stages: Pre-freezing stage: Cool from 5 °C to -30 °C at a cooling rate of 1.0 °C / minute and maintain this temperature for 120 minutes to ensure complete freezing; Main drying stage: Under a vacuum of 100 Pa, raise the shelf temperature from -30 °C to 20 °C at a heating rate of 0.75 °C / hour, and the drying time is 8 hours; Secondary drying stage: Under a vacuum of 50 Pa, raise the shelf temperature to 30 °C and dry for 3 hours.

[0033] The moisture content of the final product is 2.0% (measured using a Karl Fischer moisture meter).

[0034] (8) Product stability treatment: The freeze-dried coffee powder is crushed to a uniform state, and 0.2 parts by weight of a food-grade anti-caking agent: silica (E551, specific surface area 300 m² / g, manufacturer: Evonik Corporation, product name: AEROSIL 200) and 0.15 parts by weight of tricalcium phosphate (E341, purity ≥ 98%, manufacturer: Innophos Inc.) are added and mixed evenly.

[0035] The product is packed into a multi-layer composite packaging bag (PET / AL / PE, thickness 12 μm / 9 μm / 70 μm), filled with nitrogen and sealed (nitrogen purity ≥ 99.999%, residual oxygen content 0.8%), and at the same time, 1.5 parts by weight of a food-grade silica gel desiccant (moisture absorption capacity ≥ 30%, manufacturer: Grace Company, product name: Syloid FP) is placed in the package.

[0036] The freeze-dried coffee product prepared in this example has a rich coffee aroma, a rich flavor profile, including obvious chocolate, nut, and berry aromas, a moderate acidity, a smooth taste, and a dissolution time ≤ 10 seconds (in 85 °C hot water) after brewing. The stability test shows that after storage for 12 months at 25 °C / relative humidity 60%, the flavor retention rate of the product is ≥ 85% and there is no obvious caking phenomenon.

[0037] Example 2: Preparation method of fast cold-brewed coffee using different coffee bean ratios The difference between this example and Example 1 lies in the coffee bean ratio and roasting parameters, which are as follows: (1) Selection and roasting of coffee beans: 30 parts by weight of Ethiopian Yirgacheffe G1 grade coffee beans, 40 parts by weight of Colombian supremo grade coffee beans, and 30 parts by weight of Guatemalan Antigua SHB grade coffee beans are selected, mixed according to the ratio of the present invention, and then roasted in batches. Among them, 40 parts by weight of coffee beans are medium-roasted: the roasting temperature is controlled at 200 °C, the roasting time is 13 minutes, and the final Colorate value is 105; 60 parts by weight of coffee beans are dark-roasted: the roasting temperature is 225 °C, the roasting time is 16 minutes, and the final Colorate value is 75. The roasted coffee beans are left to degas in an environment at room temperature (about 22 °C) and relative humidity 50% for 24 hours.

[0038] The remaining steps are the same as those in Example 1.

[0039] The freeze-dried coffee product prepared in this example has a relatively rich aroma, more obvious chocolate and roasting flavors, a lower acidity, and a more mellow taste, and is suitable for consumers who like strong-style coffee.

[0040] Example 3: Preparation method of fast cold-brewed coffee using different enzymatic hydrolysis conditions The differences between this example and Example 1 lie in the enzymatic hydrolysis conditions and the amount of enzyme used, which are as follows: (3) Enzymatic hydrolysis - ultrasonic assisted extraction: Weigh 100 parts by weight of coffee ground powder, add 800 parts by weight of low-temperature purified water, and mix evenly. Adjust the temperature of the mixture to 12°C and the pH value to 5.8. Add a food-grade composite enzyme preparation to the mixed solution, including: 0.03 parts by weight of pectinase, 0.02 parts by weight of hemicellulase, 0.01 parts by weight of cellulase, and 0.1 parts by weight of the enzyme stabilizer maltodextrin.

[0041] Perform enzymatic hydrolysis at a stirring speed of 50 rpm. After 15 minutes from the start of enzymatic hydrolysis, subject the mixture to ultrasonic treatment, and treat it for 25 minutes under the conditions of a frequency of 22 kHz and a power density of 200 W / L, while maintaining the system temperature at 14°C. After the ultrasonic treatment ends, continue enzymatic hydrolysis until the total time reaches 70 minutes, then raise the system temperature to 80°C and maintain it for 4 minutes to terminate the enzyme activity, and then filter to obtain the coffee extract.

[0042] The remaining steps are the same as those in Example 1.

[0043] In this example, the enzymatic hydrolysis time is extended, but the amount of enzyme used is reduced. The final product has a more balanced flavor, slightly higher acidity, a more obvious flavor layer, and more obvious floral and fruity characteristics.

[0044] Example 4: Method for preparing fast cold-brewed coffee using different antioxidant protection systems The differences between this example and Example 1 lie in the composition of the antioxidant protection system, which are as follows: (4) Antioxidant protection treatment: After the coffee extract is cooled to 15°C, add a natural antioxidant protection system, including: 0.05 parts by weight of ascorbic acid, 0.01 parts by weight of natural mixed tocopherols, 0.02 parts by weight of rosemary extract, 0.05 parts by weight of citric acid, and 0.03 parts by weight of sodium citrate. Stir gently at 10°C and 25 rpm for 8 minutes to fully dissolve the additives and disperse them evenly.

[0045] The remaining steps are the same as those in Example 1.

[0046] In this example, the amount of antioxidant used is reduced. The flavor retention rate of the product after long-term storage is slightly lower than that in Example 1, but it is still significantly higher than that of the traditional process. The flavor of the freshly prepared product is more refreshing and suitable for consumers who pursue the original flavor.

[0047] Example 5: Method for preparing fast cold-brewed coffee using different plant colloid protection systems The differences between this example and Example 1 lie in the composition of the plant colloid protection system, which are as follows: (5) Plant colloid protection treatment: Add a plant colloid protection system to the coffee extract, including: 1.2 parts by weight of gum arabic, 0.7 parts by weight of maltodextrin, 0.3 parts by weight of modified starch, and 0.2 parts by weight of β-cyclodextrin.

[0048] Use a high-speed homogenizer to perform high-speed homogenization treatment at 12,000 rpm and 8 °C for 6 minutes. The average particle size of the finally formed protective colloid is 12 μm.

[0049] The remaining steps are the same as those in Example 1.

[0050] In this example, the dosage of the colloid protectant is increased and the homogenization conditions are stronger. The product has better flavor stability and dissolution performance, the dissolution time in 85 °C hot water is ≤8 seconds, and the flavor retention rate after long-term storage reaches over 90%.

[0051] Example 6: Preparation method of fast cold-brew coffee using different freeze-concentration conditions The difference between this example and Example 1 lies in the parameters of freeze concentration, specifically as follows: (6) Freeze concentration: Perform freeze concentration on the colloid-protected coffee extract. The concentration temperature is controlled at -4 °C, the initial concentration is about 6.5 °Brix, and it is slowly concentrated at a rate of 1.5 °Brix / hour until the final concentration reaches 18 °Brix. During the concentration process, a low-temperature condensation recovery system (temperature -10 °C) is used to recover aromatic substances, and the reflux ratio is controlled above 90%.

[0052] The remaining steps are the same as those in Example 1.

[0053] In this example, the concentration temperature is slightly higher, the concentration rate is slightly slower, and the final concentration is lower. The product has a brighter aroma characteristic, but the concentration feeling after dissolution is slightly lower than that in Example 1.

[0054] Example 7: Preparation method of fast cold-brew coffee using different freeze-drying parameters The difference between this example and Example 1 lies in the parameters of freeze-drying treatment, specifically as follows: (7) Freeze-drying treatment: Perform freeze-drying treatment on the concentrated coffee extract. The freeze-drying process includes the following stages: Pre-freezing stage: Cool from 5 °C to -28 °C at a cooling rate of 0.8 °C / minute and maintain this temperature for 140 minutes; Main drying stage: Under a vacuum of 120 Pa, raise the shelf temperature from -28 °C to 18 °C at a heating rate of 0.5 °C / hour, and the drying time is 9 hours; Secondary drying stage: Raise the shelf temperature to 32 °C under a vacuum of 40 Pa and dry for 3.5 hours.

[0055] The moisture content of the final product is 1.8%.

[0056] The remaining steps are the same as those in Example 1.

[0057] In this example, the freeze-drying process is slower, the moisture content of the final product is lower, and it has better storage stability, but the energy consumption is higher and the production cycle is extended.

[0058] Example 8: Preparation method of fast cold-brewed coffee using different product stability treatments The difference between this example and Example 1 lies in the parameters of product stability treatment, which are specifically as follows: (8) Product stability treatment: Crush the freeze-dried coffee powder to a uniform state, and add 0.3 parts by weight of food-grade anti-caking agent: silica and 0.2 parts by weight of tricalcium phosphate, and mix evenly.

[0059] Pack the product into a multi-layer composite material packaging bag, fill it with nitrogen and seal it (residual oxygen content 0.5%), and at the same time put 2.0 parts by weight of food-grade silica gel desiccant in the package.

[0060] The remaining steps are the same as those in Example 1.

[0061] In this example, the dosage of the anti-caking agent increases, the dosage of the desiccant increases, the residual oxygen content decreases, the product has better storage stability, and it is not easy to cake in a high-humidity environment, but the cost is slightly higher than that in Example 1.

[0062] Example 9: Preparation method of fast cold-brewed coffee under boundary conditions (lower limit parameter combination) This example uses the lower limit values of the parameter ranges in the claims to verify the feasibility of the present invention under the lower limit conditions of the parameters, which are specifically as follows: (1) Selection and roasting of coffee beans: Select 30 parts by weight of Ethiopian Yirgacheffe G1 grade coffee beans, 30 parts by weight of Colombian supremo grade coffee beans, and 20 parts by weight of Guatemalan Antigua SHB grade coffee beans. Among them, 40 parts by weight of coffee beans are medium-roasted: roasting temperature 200 °C, roasting time 13 minutes, Colorate value 105; 50 parts by weight of coffee beans are deeply roasted: roasting temperature 215 °C, roasting time 14 minutes, Colorate value 85.

[0063] (2) Grinding of coffee beans: Grind to a particle size of 250 μm.

[0064] (3) Enzymatic-ultrasonic synergistic extraction: Dosage of complex enzyme preparation: 0.03 parts by weight of pectinase, 0.02 parts by weight of hemicellulase, 0.01 parts by weight of cellulase, and 0.1 parts by weight of enzyme stabilizer maltodextrin.

[0065] Enzymolysis temperature: 10°C, pH value: 5.2, stirring speed: 50 rpm.

[0066] Ultrasonic treatment: frequency 18 kHz, treatment time 15 minutes.

[0067] Total enzymolysis time: 50 minutes, termination temperature: 70°C, holding time: 4 minutes.

[0068] (4) Antioxidant protection treatment: 0.05 parts by weight of ascorbic acid, 0.01 parts by weight of natural mixed tocopherols, 0.02 parts by weight of rosemary extract, 0.05 parts by weight of citric acid, 0.03 parts by weight of sodium citrate.

[0069] (5) Plant colloid protection treatment: 0.8 parts by weight of gum arabic, 0.3 parts by weight of maltodextrin, 0.1 parts by weight of modified starch, 0.1 parts by weight of β-cyclodextrin.

[0070] Homogenization conditions: rotation speed 9000 rpm, temperature 8°C, time 4 minutes.

[0071] (6) Freezing concentration: concentration temperature -6°C, final concentration 18°Brix.

[0072] (7) Freeze-drying treatment: Pre-freezing: cooling rate 0.8°C / minute, final temperature -28°C, holding time 100 minutes.

[0073] Primary drying: vacuum degree 120 Pa, drying time 7 hours.

[0074] Secondary drying: shelf temperature 28°C, vacuum degree 60 Pa, drying time 2.5 hours.

[0075] Final moisture content: 2.5%.

[0076] (8) Product stability treatment: 0.1 parts by weight of silicon dioxide, 0.1 parts by weight of tricalcium phosphate, 1.0 parts by weight of silica gel desiccant, residual oxygen content 1.0%.

[0077] The product prepared in this example is still significantly superior to traditional cold-brewed coffee in terms of sensory quality and stability, but compared with the optimal parameter combination, the flavor retention rate and storage stability are slightly reduced. Example 10: Preparation method of fast cold-brewed coffee under boundary conditions (high-limit parameter combination) In this embodiment, the upper limit values of the parameter ranges in the claims are adopted to verify the feasibility of the present invention under the upper limit conditions of the parameters, as follows: (1) Selection and roasting of coffee beans: Select 40 parts by weight of Ethiopian Yirgacheffe G1 coffee beans, 40 parts by weight of Colombian supremo coffee beans, and 30 parts by weight of Guatemalan Antigua SHB coffee beans. Among them, 50 parts by weight of coffee beans are medium-roasted: roasting temperature 210°C, roasting time 15 minutes, Colorate value 95; 60 parts by weight of coffee beans are dark-roasted: roasting temperature 225°C, roasting time 16 minutes, Colorate value 75.

[0078] (2) Grinding of coffee beans: Grind to a particle size of 300 μm.

[0079] (3) Enzymatic hydrolysis-ultrasonic synergistic extraction: Dosage of compound enzyme preparation: 0.05 parts by weight of pectinase, 0.04 parts by weight of hemicellulase, 0.03 parts by weight of cellulase, and 0.2 parts by weight of enzyme stabilizer maltodextrin.

[0080] Enzymatic hydrolysis temperature 12°C, pH value 5.8, stirring speed 70 rpm.

[0081] Ultrasonic treatment: frequency 22 kHz, treatment time 25 minutes.

[0082] Total enzymatic hydrolysis time 70 minutes, termination temperature 80°C, holding time 6 minutes.

[0083] (4) Antioxidant protection treatment: 0.1 parts by weight of ascorbic acid, 0.03 parts by weight of natural mixed tocopherols, 0.05 parts by weight of rosemary extract, 0.1 parts by weight of citric acid, 0.06 parts by weight of sodium citrate.

[0084] (5) Plant colloid protection treatment: 1.2 parts by weight of gum arabic, 0.7 parts by weight of maltodextrin, 0.3 parts by weight of modified starch, 0.2 parts by weight of β-cyclodextrin.

[0085] Homogenization conditions: rotation speed 11000 rpm, temperature 12°C, time 6 minutes.

[0086] (6) Freeze concentration: concentration temperature -4°C, final concentration 22°Brix.

[0087] (7) Freeze-drying treatment: Pre-freezing: cooling rate 1.2°C / minute, final temperature -32°C, holding time 140 minutes.

[0088] Primary drying: Vacuum degree 80 Pa, drying time 9 hours.

[0089] Secondary drying: Shelf temperature 32 °C, vacuum degree 40 Pa, drying time 3.5 hours.

[0090] Final moisture content 1.5%.

[0091] (8) Product stability treatment: Silica 0.3 parts by weight, tricalcium phosphate 0.2 parts by weight, silica gel desiccant 2.0 parts by weight, residual oxygen content 0.5%.

[0092] The product prepared in this example has excellent flavor retention rate and storage stability, but the production cost and energy consumption are relatively high.

[0093] In order to verify the effectiveness of the technical solution of the present invention, the following comparative tests were carried out: Comparative Example 1: Adopt the traditional cold extraction process After roasting and grinding the coffee beans with the same ratio in Example 1 in the same manner, they were mixed with cold water at a ratio of 1:8, soaked at 10 °C for 12 hours, and then filtered to obtain cold brew coffee liquid. The coffee liquid was concentrated to 20 °Brix and then freeze-dried under the same conditions.

[0094] Comparative Example 2: Adopt the method of Patent CN 116473146 B According to the method of Patent CN 116473146 B, the cold brew concentrated coffee liquid and the coffee grinding slurry were mixed in a mass ratio of 9:1 and then freeze-dried.

[0095] The product of Example 1 of the present invention was compared with the products of Comparative Example 1 and Comparative Example 2, and the test results are as follows (Table 1): Table 1 Comparison between Example 1 of the present invention and Comparative Example 1 and Comparative Example 2 Test items Example 1 Comparative Example 1 Comparative Example 2 Extraction time (h) 1 12 10 Total polyphenol content (mg GAE / g) 42.5 32.6 35.8 Soluble solid content (%) 28.3 23.5 25.2 Retention rate of aromatic substances (%) 85.2 51.3 62.5 Dissolution time (s, 85°C water) 10 25 18 Moisture absorption rate (%, RH75%, 30 days) 3.2 7.5 5.8 Flavor score (out of 10) 8.7 6.5 7.3 Note: The flavor score was evaluated by 10 professional coffee tasters according to the SCAA coffee cupping scoring standard.

[0096] As can be seen from Table 1, compared with the comparative examples, Example 1 of the present invention has obvious technical advantages: the extraction time is greatly shortened, the total polyphenol and soluble solids content are significantly increased, the retention rate of aromatic substances is significantly increased, the dissolution performance and anti-humidity absorption performance are greatly improved, and the flavor score is also significantly higher than that of the comparative examples.

[0097] The rapid cold extraction coffee preparation method described in the present invention can be applied to coffee production enterprises of various scales. The raw materials and equipment used are all standard raw materials and equipment commonly used in the food industry. The process flow is simple and clear, easy to operate and control, and has strong industrial applicability. Compared with the traditional process, the present invention significantly shortens the production cycle, improves production efficiency, reduces energy consumption and costs, and at the same time improves the product quality and stability, with remarkable economic and social benefits.

[0098] The freeze-dried coffee product prepared by the method of the present invention has rich flavor, smooth taste, rapid dissolution and good stability, and can be widely applied to fields such as home drinking, coffee shops, hotel catering, and the processing and production of ready-to-drink coffee beverages. The product conforms to the consumption concept of green health and meets the needs of modern consumers for high-quality and convenient coffee products.

[0099] In short, the present invention provides a rapid cold extraction coffee preparation method with high efficiency, low energy consumption and high quality, solves the technical problems existing in the preparation of traditional cold extraction coffee, and has remarkable innovation and practical value.

Claims

1. A method for preparing instant cold brew coffee, characterized in that, It includes the following steps: S1. Roast coffee beans to obtain roasted coffee beans; S2. Grind the roasted coffee beans to a particle size of 250 - 300 μm to obtain coffee ground powder; S3. Mix the coffee ground powder and water at a weight ratio of 1:8, and add a composite enzyme preparation for enzymatic hydrolysis at 10 ± 2°C. The composite enzyme preparation includes pectinase, hemicellulase, and cellulase; S4. During the enzymatic hydrolysis process, perform ultrasonic treatment at a frequency of 20 ± 2 kHz for 20 ± 5 minutes; S5. After the total enzymatic hydrolysis time reaches 60 ± 10 minutes, terminate the enzymatic hydrolysis by heat treatment at 75 ± 5°C for 5 ± 1 minute to obtain coffee extract; S6. Add a natural antioxidant protection system to the coffee extract. The natural antioxidant protection system includes ascorbic acid, natural mixed tocopherols, and rosemary extract; S7. Add a plant colloid protection system to the coffee extract. The plant colloid protection system includes gum arabic, maltodextrin, modified starch, and β - cyclodextrin, and perform high - speed homogenization treatment to obtain colloid - protected coffee extract; S8. Freeze - concentrate the colloid - protected coffee extract at - 5 ± 1°C to 18 - 22°Brix; S9. Perform freeze - drying treatment on the concentrated coffee extract, including pre - freezing, primary drying, and secondary drying, to obtain freeze - dried coffee powder.

2. The method for preparing instant cold brew coffee according to claim 1, characterized in that, The coffee beans in S1 include the following components in parts by weight: 30 - 40 parts by weight of Ethiopian Yirgacheffe G1 - grade coffee beans; 30 - 40 parts by weight of Colombian supremo - grade coffee beans; 20 - 30 parts by weight of Guatemalan Antigua SHB - grade coffee beans.

3. The method for preparing instant cold brew coffee according to claim 1, characterized in that, The roasting treatment in S1 includes: Medium roasting: roasting temperature 205 ± 5°C, time 13 - 15 minutes, Colorate value 95 - 105, 40 - 50 parts by weight; Deep roasting: roasting temperature 220 ± 5°C, time 14 - 16 minutes, Colorate value 75 - 85, 50 - 60 parts by weight; After roasting, let it stand for degassing for 24 ± 2 hours.

4. The method for preparing instant cold brew coffee according to claim 1, characterized in that, The composition of the composite enzyme preparation in S3 is: 0.03 - 0.05 parts by weight of pectinase; 0.02 - 0.04 parts by weight of hemicellulase; 0.01 - 0.03 parts by weight of cellulase; 0.1 - 0.2 parts by weight of enzyme stabilizer maltodextrin.

5. The method for preparing instant cold brew coffee according to claim 1, characterized in that, The enzymatic hydrolysis conditions in S3 are: The enzymatic hydrolysis temperature is 12 ± 2°C; The enzymatic hydrolysis pH value is 5.5 ± 0.3, adjusted using a citric acid / sodium citrate buffer system; The stirring speed is 60 ± 10 rpm.

6. The method for preparing instant cold brew coffee according to claim 1, characterized in that, The composition of the natural antioxidant protection system in S6 is: 0.05 - 0.1 parts by weight of ascorbic acid; 0.01 - 0.03 parts by weight of natural mixed tocopherols; 0.02 - 0.05 parts by weight of rosemary extract; 0.05 - 0.1 parts by weight of citric acid; 0.03 - 0.06 parts by weight of sodium citrate.

7. The preparation method of the instant cold-brewed coffee according to claim 1, wherein, The composition of the plant colloid protection system in S7 is: 0.8 - 1.2 parts by weight of gum arabic; 0.3 - 0.7 parts by weight of maltodextrin; 0.1 - 0.3 parts by weight of modified starch; 0.1 - 0.2 parts by weight of β - cyclodextrin.

8. The preparation method of the instant cold-brewed coffee according to claim 1, wherein, The high-speed homogenization treatment conditions in S7 are as follows: The homogenization rotation speed is 10000 ± 1000 rpm; The homogenization temperature is 10 ± 2 °C; The homogenization time is 5 ± 1 minute; The colloid particle size is 10 - 20 μm.

9. The preparation method of the instant cold-brewed coffee according to claim 1, wherein, The freeze-drying treatment conditions in S9 are as follows: Pre-freezing: The cooling rate is 1 ± 0.2 °C / minute, from 5 °C to -30 °C, maintaining the temperature at -30 ± 2 °C, and the holding time is 120 ± 20 minutes; Primary drying: The shelf temperature slowly rises from -30 °C to 20 °C, the vacuum degree is 100 ± 20 Pa, and the drying time is 8 ± 1 hour; Secondary drying: The shelf temperature is 30 ± 2 °C, the vacuum degree is 50 ± 10 Pa, the drying time is 3 ± 0.5 hour, and the final moisture content ≤ 2.5%.

10. The preparation method of the instant cold-brewed coffee according to claim 1, wherein, It also includes the product stability treatment step: Adding a food-grade anti-caking agent to the freeze-dried coffee powder, and the food-grade anti-caking agent includes 0.1 - 0.3 parts by weight of silicon dioxide and 0.1 - 0.2 parts by weight of tricalcium phosphate; Using a multi-layer composite packaging bag for nitrogen filling packaging, and the residual oxygen content ≤ 1.0%; Adding 1 - 2 parts by weight of food-grade silica gel desiccant.