Treatment method of coffee liquid

Abstract

The invention discloses a coffee liquid treatment method, and relates to the technical field of coffee liquid processing. The treatment method comprises the following steps: centrifugally separating coffee liquid, and collecting clear liquid and precipitates; mixing the precipitate and part of the clear liquid according to a certain proportion to obtain a mixture, and performing primary high-pressure homogenization assisted enzymolysis on the mixture to obtain an enzymolysis product; carrying out two-stage ultrahigh pressure homogenization on the enzymolysis product to obtain a homogenized solution; and uniformly mixing the homogenized liquid with the rest of the clear coffee liquid, and carrying out sterile filling to obtain the stable coffee liquid which can be stored at normal temperature. According to the invention, a solid-liquid separated treatment method is adopted, and protease is combined with a multi-stage high-pressure treatment technology, so that the use types of enzymes are reduced, the enzymolysis efficiency is improved, the time and the use amount of the enzymes are saved, the flavor loss is reduced, the astringent taste is reduced, the mellowness of coffee is retained, and the treated coffee liquid can be stored for 12 months at normal temperature, and can be stored for 12 months at normal temperature. After multiple freezing and thawing, the flavor is still stable, no obvious precipitate is observed by naked eyes, and the method is suitable for industrial continuous production.

Description

Technical Field

[0001] The present invention relates to the technical field of coffee liquid processing, and in particular to a method for processing coffee liquid. Background Art

[0002] Coffee liquid is a liquid with complex ingredients, and it exists in the states of solution and suspension. The conventional processing flow of coffee liquid is: green coffee beans - screening - roasting - grinding - extraction - separation - concentration - clarification - sterilization - metal detection - packaging - freezing - finished product. The primary clarification treatment still retains a large number of suspended particulate components, especially for coffee liquid with higher concentration. Under normal temperature storage conditions, solid-liquid stratification and precipitation will occur within 1 day at the fastest, accompanied by weakened flavor and reduced product quality. The main components of the precipitate of coffee liquid are macromolecules such as lignin, cellulose, and protein. Some small molecules are combined with macromolecules through weak molecular forces and are precipitated together. Therefore, most of the coffee liquid used in industrial raw materials is currently stored in frozen form and will be used as soon as possible after thawing. If it is not used in time, the product will change in flavor and accelerate the sinking of macromolecules after repeated freezing and thawing.

[0003] At present, the main methods for improving the stability of coffee liquid are: centrifugal separation to remove sediment, enzymatic hydrolysis, pH adjustment and adding thickening stabilizers. Centrifugal separation mainly uses centrifugal separation to separate sediment. This method will remove most of the suspended particles and greatly reduce the rate of precipitation during storage. However, some nutrients and flavors will adhere to the sediment particles, resulting in component loss, and the obtained coffee liquid has a monotonous flavor and a thin taste. Enzymatic hydrolysis is the use of biological enzymes (such as proteases, cellulases, etc.) to decompose the main macromolecular precipitation components in the coffee liquid, which reduces the molecular weight, reduces the precipitation rate of insoluble matter, and improves the solubility of some substances to a certain extent. However, enzymatic hydrolysis often takes a long time, and the material processing volume is large, and the overall efficiency is not high, which is not suitable for industrial continuous production. The method of adjusting the pH value is to use acid-base adjustment to make the pH of the coffee liquid away from the isoelectric point of protein, which can reduce the precipitation rate to a certain extent. The operation is relatively simple and does not require equipment support, but pH adjustment has almost no effect on stabilizing cellulose, and requires the addition of thickening stabilizers. In particular, if you want to achieve the ideal effect of preventing precipitation, you often need to add more stabilizers, which is not good for health for long-term consumption.

[0004] In addition, in terms of enzymatic treatment, the basic idea of ​​the existing technology is to enzymatically hydrolyze macromolecules such as proteins and cellulose in coffee liquid. However, due to the different optimal temperatures and pH of protein enzymes and cellulase, enzymes need to be added multiple times during enzymatic treatment, and the temperature and pH need to be adjusted multiple times, which makes the treatment process cumbersome, the overall efficiency is low, the enzyme dosage is large, the cost is high, and it is not suitable for industrial continuous production. Based on this, how to reduce the type and dosage of enzymes, shorten the time consumption, reduce precipitation generation, and reduce the loss of coffee flavor substances is the main research direction of the applicant. After research, it was found that protease combined with multi-stage high-pressure treatment can not only improve the efficiency of protein degradation, but also keep cellulose self-stabilized in coffee liquid, thus generating this solution. Summary of the invention

[0005] In view of the above shortcomings, the present invention provides a method for treating coffee liquid, which solves the problem that coffee liquid needs to be treated with multiple enzymes, resulting in cumbersome procedures, long time consumption, high cost, and unsuitability for industrial continuous production. The treated coffee liquid can be stored at room temperature for 12 months, and after multiple freeze-thaw cycles, the flavor remains stable and there is no obvious precipitation observed by naked eye. The specific technical scheme is as follows:

[0006] A method for processing coffee liquid, the processing of the coffee liquid comprising: centrifuging the coffee liquid to collect a clear liquid and a precipitate; mixing the precipitate with part of the clear liquid in a certain proportion to obtain a mixture, first subjecting the mixture to primary high-pressure homogenization-assisted enzymolysis to obtain an enzymolysis product; then subjecting the enzymolysis product to secondary ultra-high pressure homogenization to obtain a homogenized liquid; and finally uniformly mixing the homogenized liquid with the remaining coffee clear liquid and aseptically filling the mixture to obtain a stable coffee liquid that can be stored at room temperature.

[0007] Furthermore, the concentration of the coffee liquid is 1 to 30° Bx.

[0008] Furthermore, the centrifugation is carried out using a horizontal centrifuge or a butterfly centrifuge of a continuous slag discharge type.

[0009] Furthermore, the rotation speed of the horizontal centrifuge is 3000-4000 r / min, and the rotation speed of the butterfly centrifuge is 7000-9000 r / min.

[0010] Furthermore, the mixing volume ratio of the precipitate to the clear liquid is 1:2 to 4. The precipitate is mixed with part of the coffee clear liquid, and through appropriate proportioning, the fluidity of the precipitate can be increased, so that it can better adapt to the working conditions of the homogenization equipment, and at the same time, the substrate concentration of the enzymatic hydrolysis can be adjusted to improve the utilization rate of the enzyme.

[0011] Furthermore, the first-stage high-pressure homogenization conditions are: pressure of 50-70 MPa, temperature of 40-45° C., and homogenization cycle of 3 times.

[0012] Furthermore, the enzyme is a neutral protease. During enzymolysis, the neutral protease is first added in an amount of 0.3-0.5%wt of the mixture, and then the pH of the mixture is adjusted to 6-7.

[0013] Furthermore, the secondary ultra-high pressure homogenization conditions are: pressure of 120-150 MPa, temperature of 60-80° C., and homogenization cycle of 2 times.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. The present invention adopts a method of separate solid-liquid treatment, and does not perform high-temperature and high-pressure homogenization on most of the clear liquid, thereby better retaining the mellow flavor of coffee, and also reducing the amount of enzymatic hydrolysis treatment of the liquid, indirectly improving the utilization rate of the enzyme, saving the amount of enzyme used, and improving the enzymatic hydrolysis efficiency.

[0016] 2. The present invention adopts high-pressure assisted enzymolysis, and sets the pressure of high-pressure assisted enzymolysis to 50-70Mpa, which not only does not inhibit the enzymatic activity of the protease, but also changes the secondary structure of the protein, allowing more molecular structures to be exposed, thereby improving the enzymolysis efficiency, saving time, and saving enzyme usage, and is suitable for industrial production.

[0017] 3. The present invention does not use cellulase to enzymolyze the cellulose in the precipitate, but uses a multi-stage high-pressure treatment technology, with the pressure first low and then high, which changes the molecular spatial structure of cellulose, improves its water holding capacity and oil holding capacity, increases its emulsification performance, and uses its own spatial structure to play a self-stabilizing role in the solution, so that cellulose can exist in the coffee liquid without generating precipitation. The multi-stage high-pressure treatment technology can reduce the number of enzymes, and only protease treatment can achieve the desired effect.

[0018] 4. The two-stage ultra-high pressure homogenization of the present invention also plays the role of inactivating enzymes and sterilizing bacteria. The ultra-high pressure exceeding 100MPa has the following effects on microorganisms: ① causing protein denaturation ② destroying the cell morphology of microorganisms ③ causing changes in the genetic mechanism of microorganisms ④ rupture of cell membranes and leakage of substances in the body ⑤ inactivation of microbial enzymes; the above results in the inability of most microorganisms to survive.

[0019] 5. The present invention has little loss of flavor in the process of treating coffee liquid. Compared with the method of removing sediment by centrifugation, the mellowness of coffee is retained to the greatest extent. At the same time, the inventors unexpectedly found that the astringency of coffee treated by the present method is significantly reduced. It may be that the astringent substances are combined with other substances under high pressure, and the free state is changed into a combined state, which is not easy to be tasted by people.

[0020] 6. After the coffee liquid treated by the present invention is stored at room temperature for 12 months, the amount of precipitation is reduced by more than 70% compared with the untreated coffee liquid, which is better than the conventional enzymatic hydrolysis method (the amount of precipitation is only reduced by 25.9% compared with the untreated coffee liquid). At the same time, the flavor remains almost unchanged, and the amount of precipitation does not increase significantly after repeated freezing and thawing. DETAILED DESCRIPTION

[0021] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0022] The coffee liquids in the following examples and comparative examples were provided by food raw material supplier Olam Food Ingredients (OFI for short). It should be noted that the protein content in the coffee liquid is higher than the cellulose content.

[0023] Example 1

[0024] A method for treating coffee liquid with a concentration of 15°Bx, the treatment comprising: using a horizontal centrifuge with continuous slag discharge to centrifuge the coffee liquid at a speed of 3500r / min, collecting a clear liquid and a precipitate; mixing the precipitate and the clear liquid evenly at a volume ratio of 1:3 to obtain a mixture, adding 0.4%wt of a neutral protease based on the weight of the mixed liquid, adjusting the pH to 6.5 to obtain a solution to be hydrolyzed, preheating to 42°C, adding a first-level high-pressure homogenizer to keep warm and homogenize under the condition of 60Mpa, homogenizing for 3 times, and obtaining a hydrolyzed liquid; heating again to 70°C, keeping warm and homogenizing under the condition of 130Mpa in a second-level ultra-high-pressure homogenizer, homogenizing for 2 times, and obtaining a homogenized liquid; mixing the homogenized liquid evenly with the remaining coffee clear liquid, and aseptically filling to obtain a stable coffee liquid that can be stored at room temperature.

[0025] Example 2

[0026] A method for treating coffee liquid with a concentration of 1°Bx, the treatment comprising: using a horizontal centrifuge of a continuous slag discharge type to centrifuge the coffee liquid at a speed of 3000r / min, collecting a clear liquid and a precipitate; mixing the precipitate and the clear liquid evenly at a volume ratio of 1:2 to obtain a mixture, adding 0.3%wt of a neutral protease based on the weight of the mixed liquid, adjusting the pH to 6 to obtain a solution to be hydrolyzed, preheating to 40°C, adding a first-level high-pressure homogenizer to keep warm and homogenize under the condition of 50Mpa, homogenizing for 3 times, and obtaining a hydrolyzed liquid; heating again to 60°C, keeping warm and homogenizing under the condition of 120Mpa in a second-level ultra-high-pressure homogenizer, homogenizing for 2 times, and obtaining a homogenized liquid; mixing the homogenized liquid evenly with the remaining coffee clear liquid, and aseptically filling to obtain a stable coffee liquid that can be stored at room temperature.

[0027] Example 3

[0028] A method for treating coffee liquid with a concentration of 30°Bx, the treatment comprising: centrifuging the coffee liquid at a speed of 8000r / min using a butterfly centrifuge to collect a clear liquid and a precipitate; uniformly mixing the precipitate and the clear liquid at a volume ratio of 1:4 to obtain a mixture, adding 0.5%wt of a neutral protease based on the weight of the mixed liquid, adjusting the pH to 7 to obtain a solution to be hydrolyzed, preheating to 45°C, adding a first-level high-pressure homogenizer to keep warm and homogenize under the condition of 70Mpa, homogenizing for 3 times to obtain a hydrolyzed liquid; heating again to 80°C, keeping warm and homogenizing under the condition of 150Mpa using a second-level ultra-high-pressure homogenizer, homogenizing for 2 times to obtain a homogenized liquid; uniformly mixing the homogenized liquid with the remaining coffee clear liquid, and aseptically filling to obtain a stable coffee liquid that can be stored at room temperature.

[0029] Comparative Example 1

[0030] The first step of centrifugal separation of solid and liquid components in Example 1 was omitted, and the subsequent ultrahigh pressure homogenization-assisted enzymatic hydrolysis and ultrahigh pressure homogenization treatment were performed on the whole coffee liquid, with specific parameters as in Example 1. The total amount of enzyme added was the same as in Example 1.

[0031] Comparative Example 2

[0032] The amount of enzyme added in Comparative Example 1 was replaced by the original amount of added mass, that is, 0.4%wt of the whole coffee liquid was added. The remaining steps were the same as those in Comparative Example 1.

[0033] Comparative Example 3

[0034] The first-stage high-pressure homogenization-assisted enzymatic hydrolysis in Example 1 was replaced with conventional enzymatic hydrolysis (without the first-stage high-pressure homogenization assistance) for 12 hours, and the enzyme addition amount, enzymatic hydrolysis temperature and pH value remained unchanged. The remaining operations were the same as in Example 1 (retaining the step of the second-stage ultra-high pressure homogenization).

[0035] Comparative Example 4

[0036] The amount of enzyme added in Comparative Example 3 was increased by 1 time, and the remaining operations were the same as those in Comparative Example 3.

[0037] Comparative Example 5

[0038] The neutral protease in Comparative Example 3 was replaced by cellulase, and the other operations remained unchanged.

[0039] Comparative Example 6

[0040] The neutral protease in Comparative Example 4 was replaced with a mixed enzyme preparation (neutral protease: cellulase mass ratio was 1:1), and the other operations remained unchanged.

[0041] Comparative Example 7

[0042] A mixed enzyme preparation (neutral protease and cellulase in a mass ratio of 1:1) was added for conventional enzymolysis for 12 hours. The total amount of enzyme added, the enzymolysis temperature and the pH value were the same as those in Comparative Example 2.

[0043] The inventor designed experiments for comparative examples 1 and 2, and verified the effects of full liquid treatment and single treatment of precipitate on the mellowness and overall flavor of coffee through experiments. The coffee obtained in Example 1 and comparative examples 1 and 2 was prepared with normal temperature drinking water to a ready-to-drink concentration, and 5 baristas holding Q certificates were invited to identify the mellowness and comprehensive flavor scores of the coffee flavors of Example 1 and comparative examples 1 and 2, with scores set to 1 to 10 points, with higher scores representing more mellow and better flavors. The scores for each item are shown in Table 1:

[0044] project Coffee thickness Coffee liquid flavor comprehensive score Example 1 7.6 7.8 Comparative Example 1 6.5 7.4 Comparative Example 2 6.7 7.5

[0045] As can be seen from Table 1, the full liquid processing will reduce the body and flavor of the coffee liquid to a certain extent. The reason is presumably that the full liquid processing will lose more flavor components. Therefore, it can be seen that the flavor components of the coffee liquid can be better preserved by processing the sediment separately after solid-liquid separation.

[0046] The inventor unexpectedly discovered that the coffee liquids in the examples all had a different degree of reduced astringency. Therefore, experiments for comparative examples 3, 4, 5, 6, and 7 were designed to verify whether the reduced astringency of the coffee liquid was related to high-pressure assisted enzymatic hydrolysis and ultra-high pressure homogenization. The untreated coffee liquid, the coffee obtained in Example 1, and comparative examples 3, 4, 5, 6, and 7 were brewed with normal temperature drinking water to a ready-to-drink concentration, and 5 baristas holding Q certificates were invited to identify the astringency intensity and comprehensive taste scores of the untreated coffee liquid, Example 1, and the above comparative examples. The scores were set to 1 to 5 points. The higher the astringency intensity score, the more obvious the astringency, and the higher the comprehensive taste score, the smoother the taste. The scores for each item are shown in Table 2:

[0047] project Astringency intensity Coffee liquid flavor comprehensive score Unprocessed coffee liquid 6.2 7.0 Example 1 5.5 7.9 Comparative Example 3 5.8 7.3 Comparative Example 4 5.7 7.3 Comparative Example 5 5.8 7.3 Comparative Example 6 5.7 7.4 Comparative Example 7 6.1 7.0

[0048] As shown in Table 2, the astringency intensity of Example 1 and Comparative Examples 3-6 after two-stage ultra-high pressure treatment is significantly reduced; the degree of astringency reduction of Example 1 after high-pressure assisted enzymatic hydrolysis is more obvious; while the change in astringency intensity of Comparative Example 7 without high-pressure treatment is almost imperceptible, that is, the astringency intensity is equivalent to that of untreated coffee liquid. It can be seen that high-pressure treatment has the effect of reducing the astringency of coffee liquid.

[0049] The mass percentage of the enzyme dosage of the untreated coffee liquid, each embodiment, and each comparative example in the total liquid was recorded, and the finished product was sealed in a 1cm*30cm cylindrical test tube with a lid, and the height of the precipitation was observed after standing at room temperature for 6 months, 9 months, and 12 months. After 12 months, 5 freeze-thaw tests were performed, and the precipitation was continued to stand for 24 hours, and the height of the precipitation was recorded again. The results are shown in Table 3:

[0050] Table 3

[0051]

[0052]

[0053] From the data of Example 1 and Comparative Examples 1 and 2 in Table 3, it can be seen that treating the precipitate separately after centrifugal separation can save the amount of enzyme used, reduce the amount of liquid to be treated, improve efficiency and thus reduce energy consumption.

[0054] From the comparison data of Example 1 and Comparative Examples 3, 4, 5, and 6, it can be seen that the best combination of the enzymatic hydrolysis step is high pressure assisted enzymatic hydrolysis + neutral protease. In the absence of high pressure assisted enzymatic hydrolysis, increasing the amount of neutral protease added or adding additional cellulase can make up for the lack of efficiency to a certain extent, but the effect is not as good as that of high pressure assisted enzymatic hydrolysis. In addition, the enzymatic hydrolysis effect of using cellulase alone is not good.

[0055] In Example 1 and Comparative Example 7 (conventional enzymatic hydrolysis), after standing at room temperature for 12 months, the amount of coffee liquid sedimentation was 70.1% and 25.9% less than that of the untreated coffee liquid, respectively.

[0056] In summary, the present invention adopts a method of separate solid-liquid treatment and uses protease combined with multi-stage high-pressure treatment technology, which not only reduces the types of enzymes used, improves enzymatic hydrolysis efficiency, saves time, saves enzyme dosage, but also reduces flavor loss, reduces astringency, and retains the mellowness of coffee. The processed coffee liquid can be stored at room temperature for 12 months, and after multiple freeze-thaw cycles, the flavor remains stable and there is no obvious precipitation observed by the naked eye, which is suitable for industrial continuous production.

[0057] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A method for processing coffee liquid, characterized in that: The treatment of the coffee liquid includes: centrifuging the coffee liquid to collect the clear liquid and the precipitate; mixing the precipitate with part of the clear liquid in a certain proportion to obtain a mixture, first subjecting the mixture to a first-level high-pressure homogenization-assisted enzymatic hydrolysis to obtain an enzymatic hydrolysis product; then subjecting the enzymatic hydrolysis product to a second-level ultra-high-pressure homogenization to obtain a homogenous liquid; finally, uniformly mixing the homogenous liquid with the remaining coffee clear liquid, and aseptically filling the mixture to obtain a stable coffee liquid that can be stored at room temperature.

2. The method for processing coffee liquid according to claim 1, characterized in that: The concentration of the coffee liquid is 1-30° Bx.

3. The method for processing coffee liquid according to claim 1, characterized in that: The centrifugation is carried out by using a horizontal centrifuge or a butterfly centrifuge of a continuous slag discharge type.

4. The method for processing coffee liquid according to claim 3, characterized in that: The rotation speed of the horizontal centrifuge is 3000-4000 r / min, and the rotation speed of the butterfly centrifuge is 7000-9000 r / min.

5. The method for processing coffee liquid according to claim 1, characterized in that: The mixing volume ratio of the precipitate to the clear liquid is 1:2-4.

6. The method for processing coffee liquid according to claim 1, characterized in that: The first-stage high-pressure homogenization conditions are: pressure of 50-70 MPa, temperature of 40-45° C., and homogenization cycle of 3 times.

7. The method for processing coffee liquid according to claim 1, characterized in that: The enzyme is a neutral protease. During enzymolysis, the neutral protease is first added in an amount of 0.3-0.5%wt of the weight of the mixture, and then the pH of the mixture is adjusted to 6-7.

8. The method for processing coffee liquid according to claim 1, characterized in that: The secondary ultra-high pressure homogenization conditions are: pressure of 120-150 MPa, temperature of 60-80° C., and homogenization cycle of 2 times.

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