A composite membrane for extracting coffee concentrate and its application

Abstract

This invention discloses a composite membrane for extracting coffee concentrate and its application. The composite membrane comprises two layers: a lower layer is a modified ceramic membrane, and an upper layer is a modified gel membrane. This invention, by preparing a bilayer composite membrane for extracting coffee concentrate, achieves excellent extraction results, removing not only coffee grounds but also harmful coffee oils, cafestol, and coffee barley. This invention utilizes the grafting modification of amino groups and succinic anhydride on the surface of the ceramic membrane. The modified membrane can adsorb cafestol and coffee barley, and enhances the membrane's ability to retain large molecules in the coffee concentrate, thereby improving the efficiency of the filtration process.

Description

Technical Field

[0001] This invention relates to the field of coffee extraction and separation technology, specifically to a composite membrane for extracting coffee concentrate and its application. Background Technology

[0002] In the extraction of coffee concentrate, the application of separation and extraction membranes has attracted widespread attention, mainly due to their superior performance in selective separation and improving extraction efficiency. However, existing extraction membranes can only simply remove coffee grounds without enhancing the flavor of the coffee. Therefore, how to improve the taste and flavor of coffee during the extraction process is a key research issue. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the purpose of this invention is to provide a composite membrane for coffee concentrate extraction and its application, so as to improve the flavor of coffee concentrate during the extraction process.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] This invention proposes a composite membrane for extracting coffee concentrate, the composite membrane comprising upper and lower layers, the lower layer being a modified ceramic membrane and the upper layer being a modified gel membrane.

[0006] Preferably, the method for preparing the modified ceramic membrane includes the following steps: treating the ceramic membrane with an ammonia atmosphere using plasma technology to ammoniaize it, then placing it in a reaction vessel containing dimethylformamide and succinic anhydride, adding phosphoric acid as a catalyst, heating and reacting, and washing and drying after the reaction is complete to obtain the modified ceramic membrane.

[0007] Preferably, the heating temperature is 40~50℃.

[0008] Preferably, the ceramic membrane includes an alumina membrane, a zirconium oxide membrane, a titanium oxide membrane, or a silicon oxide membrane.

[0009] Preferably, the pore size of the modified ceramic membrane is 0.5~20μm.

[0010] Preferably, the ratio of the ceramic membrane, dimethylformamide, succinic anhydride and phosphoric acid is (1~3g):(3~10mL):(0.2~0.4g):(0.01~0.5mL).

[0011] Preferably, the method for preparing the modified gel membrane includes the following steps:

[0012] S1. Add deionized water to the container containing sodium alginate and stir to obtain sodium alginate solution.

[0013] S2. Dissolve chitosan in acetic acid solution, then add dopamine, stir, then add glutaraldehyde and N-hydroxysuccinimide, crosslinking reaction to obtain modified chitosan, add the modified chitosan to sodium alginate solution, stir to obtain a mixture;

[0014] S3. Add sodium hydroxide solution to the mixture, stir to obtain a pregel, then inject the pregel into a mold, add calcium chloride solution to gel, then wash, freeze and dry to obtain a preliminary gel film;

[0015] S4. Immerse the preliminary gel membrane in a lipase solution, then wash and dry it to obtain a modified gel membrane.

[0016] Preferably, in step S1, the ratio of sodium alginate to deionized water is (1~5g):(100~150mL).

[0017] In step S2, the ratio of chitosan, acetic acid, dopamine, glutaraldehyde and NN-hydroxysuccinimide is (5~20g):(10~50mL):(2~5g):(2~4mL):(1~5g);

[0018] The mass ratio of sodium alginate to chitosan is (1~2):(15~25).

[0019] Preferably, in step S3, the sodium hydroxide solution has a mass fraction of 4% to 8%, and the calcium chloride solution has a mass fraction of 3% to 10%.

[0020] In step S4, the mass concentration of the lipase solution is 1~20 mg / mL.

[0021] The present invention also proposes an application of the composite membrane described above, which is used in the extraction and separation of coffee concentrate.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention prepares a double-layer composite membrane for the extraction of coffee concentrate. The extraction effect is good, not only removing coffee grounds, but also removing coffee oil, coffee alcohol and coffee white alcohol that are harmful to human health.

[0024] (2) The present invention utilizes the amino groups and succinic anhydride on the surface of the ceramic membrane for grafting modification. The modified membrane can adsorb coffee alcohol and coffee white alcohol, and improve the membrane's ability to retain large molecules in coffee liquid, thereby improving the efficiency of the filtration process.

[0025] (3) The modified gel membrane prepared in this invention first introduces more amino groups through chitosan modification to improve the adsorption of the gel membrane and prevent lipase oxidation. Then, sodium alginate and modified chitosan form a three-dimensional cross-linked structure. Then, the adhesion properties of sodium alginate are used to couple lipase to obtain the modified gel membrane. Under the action of lipase, the fat in the coffee liquid is degraded, which makes the gel membrane more efficient in removing impurities and maintaining a high flow rate during the filtration process. At the same time, the selective permeability of the gel membrane can selectively filter out unnecessary lipids and solid particles, making the contents purer. Furthermore, the use of lipase helps to release more aroma and flavor substances, while the gel membrane helps to remove impurities and sediments that may affect the coffee flavor, thereby improving the overall taste.

[0026] (4) The modified ceramic membrane and modified gel membrane provided by the present invention synergistically improve the extraction effect of coffee liquid, resulting in better coffee flavor, significantly shortened extraction time, and improved production efficiency. Detailed Implementation

[0027] The present invention will be further described in detail below through specific preferred embodiments, but the present invention is not limited to the following embodiments.

[0028] It should be noted that, unless otherwise specified, all chemical reagents involved in this invention were purchased through commercial channels.

[0029] Example 1

[0030] A composite membrane for extracting coffee concentrate, the composite membrane comprising upper and lower layers, the lower layer being a modified ceramic membrane and the upper layer being a modified gel membrane;

[0031] The preparation method of the modified ceramic membrane includes the following steps: 2g of aminated ceramic membrane is placed in a reaction vessel containing 5mL of dimethylformamide and 0.3g of succinic anhydride, 0.1mL of phosphoric acid is added, the reaction is heated, and after the reaction is completed, the membrane is washed and dried to obtain the modified ceramic membrane.

[0032] The method for preparing the modified gel membrane includes the following steps:

[0033] S1. Add 120mL of deionized water to a container containing 2g of sodium alginate, stir, and obtain a sodium alginate solution.

[0034] S2. Dissolve 10g of chitosan in 20mL of acetic acid solution, then add 3g of dopamine, stir, then add 3mL of glutaraldehyde and 3g of N-hydroxysuccinimide, crosslinking reaction to obtain modified chitosan, add the modified chitosan to sodium alginate solution, stir to obtain a mixture;

[0035] S3. Add 10 mL of 6% sodium hydroxide solution to the mixture, stir to obtain a pregel, then inject the pregel into a mold, add 20 mL of 8% calcium chloride solution for gelation, then wash, freeze and dry to obtain a preliminary gel film;

[0036] S4. Immerse the preliminary gel membrane in a 10 mg / mL lipase solution, then wash and dry it to obtain the modified gel membrane.

[0037] Example 2

[0038] A composite membrane for extracting coffee concentrate, the composite membrane comprising upper and lower layers, the lower layer being a modified ceramic membrane and the upper layer being a modified gel membrane;

[0039] The preparation method of the modified ceramic membrane includes the following steps: 1g of aminated ceramic membrane is placed in a reaction vessel containing 3mL of dimethylformamide and 0.2g of succinic anhydride, 0.01mL of phosphoric acid is added, the reaction is heated, and after the reaction is completed, the membrane is washed and dried to obtain the modified ceramic membrane.

[0040] The method for preparing the modified gel membrane includes the following steps:

[0041] S1. Add 100mL of deionized water to a container containing 1g of sodium alginate, stir, and obtain a sodium alginate solution.

[0042] S2. Dissolve 5g of chitosan in 10mL of acetic acid solution, then add 2g of dopamine, stir, then add 2mL of glutaraldehyde and 1g of N-hydroxysuccinimide, crosslinking reaction to obtain modified chitosan, add the modified chitosan to sodium alginate solution, stir to obtain a mixture;

[0043] S3. Add 10 mL of 4% sodium hydroxide solution to the mixture, stir to obtain a pregel, then inject the pregel into a mold, add 20 mL of 3% calcium chloride solution for gelation, then wash, freeze and dry to obtain a preliminary gel film;

[0044] S4. Immerse the preliminary gel membrane in a 1 mg / mL lipase solution, then wash and dry to obtain the modified gel membrane.

[0045] Example 3

[0046] A composite membrane for extracting coffee concentrate, the composite membrane comprising upper and lower layers, the lower layer being a modified ceramic membrane and the upper layer being a modified gel membrane;

[0047] The preparation method of the modified ceramic membrane includes the following steps: placing 3g of aminated ceramic membrane in a reaction vessel containing 10mL of dimethylformamide and 0.4g of succinic anhydride, adding 0.5mL of phosphoric acid, heating to react, and washing and drying after the reaction is complete to obtain the modified ceramic membrane;

[0048] The method for preparing the modified gel membrane includes the following steps:

[0049] S1. Add 150mL of deionized water to a container containing 5g of sodium alginate, stir, and obtain a sodium alginate solution.

[0050] S2. Dissolve 20g of chitosan in 50mL of acetic acid solution, then add 5g of dopamine, stir, then add 4mL of glutaraldehyde and 5g of N-N-hydroxysuccinimide, crosslinking reaction to obtain modified chitosan, add the modified chitosan to sodium alginate solution, stir to obtain a mixture;

[0051] S3. Add 10 mL of 8% sodium hydroxide solution to the mixture, stir to obtain a pregel, then inject the pregel into a mold, add 20 mL of 10% calcium chloride solution for gelation, then wash, freeze and dry to obtain a preliminary gel film.

[0052] S4. Immerse the preliminary gel membrane in a 20 mg / mL lipase solution, then wash and dry it to obtain the modified gel membrane.

[0053] Comparative Example 1

[0054] A composite membrane for extracting coffee concentrate, the composite membrane comprising upper and lower layers, the lower layer being a ceramic membrane and the upper layer being a modified gel membrane;

[0055] The method for preparing the modified gel membrane includes the following steps:

[0056] S1. Add 120mL of deionized water to a container containing 2g of sodium alginate, stir, and obtain a sodium alginate solution.

[0057] S2. Dissolve 10g of chitosan in 20mL of acetic acid solution, then add 3g of dopamine, stir, then add 3mL of glutaraldehyde and 3g of N-hydroxysuccinimide, crosslinking reaction to obtain modified chitosan, add the modified chitosan to sodium alginate solution, stir to obtain a mixture;

[0058] S3. Add 10 mL of 6% sodium hydroxide solution to the mixture, stir to obtain a pregel, then inject the pregel into a mold, add 20 mL of 8% calcium chloride solution for gelation, then wash, freeze and dry to obtain a preliminary gel film;

[0059] S4. Immerse the preliminary gel membrane in a 10 mg / mL lipase solution, then wash and dry it to obtain the modified gel membrane.

[0060] Compared with Example 1, the ceramic membrane in Comparative Example 1 was not modified.

[0061] Comparative Example 2

[0062] A composite membrane for extracting coffee concentrate, the composite membrane comprising upper and lower layers, the lower layer being a modified ceramic membrane and the upper layer being a modified gel membrane;

[0063] The preparation method of the modified ceramic membrane includes the following steps: 2g of aminated ceramic membrane is placed in a reaction vessel containing 5mL of dimethylformamide and 0.3g of succinic anhydride, 0.1mL of phosphoric acid is added, the reaction is heated, and after the reaction is completed, the membrane is washed and dried to obtain the modified ceramic membrane.

[0064] The method for preparing the modified gel membrane includes the following steps:

[0065] S1. Add 120mL of deionized water to a container containing 2g of sodium alginate, stir, and obtain a sodium alginate solution.

[0066] S2. Add chitosan to sodium alginate solution and stir to obtain a mixture;

[0067] S3. Add 10 mL of 6% sodium hydroxide solution to the mixture, stir to obtain a pregel, then inject the pregel into a mold, add 20 mL of 8% calcium chloride solution for gelation, then wash, freeze and dry to obtain a preliminary gel film;

[0068] S4. Immerse the preliminary gel membrane in a 10 mg / mL lipase solution, then wash and dry it to obtain the modified gel membrane.

[0069] Compared with Example 1, the chitosan in Comparative Example 2 was not modified.

[0070] Comparative Example 3

[0071] A composite membrane for extracting coffee concentrate, the composite membrane comprising upper and lower layers, the lower layer being a modified ceramic membrane and the upper layer being a gel membrane;

[0072] The preparation method of the modified ceramic membrane includes the following steps: 2g of aminated ceramic membrane is placed in a reaction vessel containing 5mL of dimethylformamide and 0.3g of succinic anhydride, 0.1mL of phosphoric acid is added, the reaction is heated, and after the reaction is completed, the membrane is washed and dried to obtain the modified ceramic membrane.

[0073] The method for preparing the gel membrane includes the following steps:

[0074] S1. Add 120mL of deionized water to a container containing 2g of sodium alginate, stir, and obtain a sodium alginate solution.

[0075] S2. Dissolve 10g of chitosan in 20mL of acetic acid solution, then add 3g of dopamine, stir, then add 3mL of glutaraldehyde and 3g of N-hydroxysuccinimide, crosslinking reaction to obtain modified chitosan, add the modified chitosan to sodium alginate solution, stir to obtain a mixture;

[0076] S3. Add 10 mL of 6% sodium hydroxide solution to the mixture, stir to obtain a pregel, then inject the pregel into a mold, add 20 mL of 8% calcium chloride solution for gelation, then wash, freeze and dry to obtain a gel membrane.

[0077] Compared with Example 1, the gel membrane in Comparative Example 3 did not contain chelating lipase.

[0078] Test methods and results

[0079] Fresh coffee beans were ground into a medium to coarse sand-like consistency. The coffee beans were ground with gauze. The composite membranes prepared in Examples 1-3 and Comparative Examples 1-3 were placed on coffee filter baskets, and boiling water was allowed to flow through the coffee beans. After waiting for 10 minutes, coffee concentrate was obtained.

[0080] A sensory evaluation panel of 20 professional perfumers and experts conducted a sensory evaluation of the aroma and flavor of the coffee concentrate. The coffee concentrates with the best aroma and flavor were selected based on their sensory scores. Specific sensory evaluation criteria are detailed in Table 1.

[0081] Table 1 Sensory Evaluation Criteria

[0082]

[0083] The sensory evaluation results and extraction rate results are detailed in Table 2.

[0084] Table 2 Sensory evaluation results and extraction rate

[0085]

[0086] As shown in Table 2, compared with Comparative Examples 1-3, the composite membrane extracts prepared using Examples 1-3 of this invention have higher extraction rates, higher sensory scores, and better flavor.

[0087] Finally, it should be noted that the above embodiments do not limit the present invention in any way. Those skilled in the art can make modifications and improvements based on the present invention. Therefore, any modifications or improvements made without departing from the spirit of the present invention are within the scope of protection claimed by the present invention.

Claims

1. A composite membrane for extracting coffee concentrate, characterized in that, The composite membrane comprises two layers, the lower layer being a modified ceramic membrane and the upper layer being a modified gel membrane; The ceramic membrane was treated with an ammonia atmosphere using plasma technology to ammonia-induced amination, and then placed in a reaction vessel containing dimethylformamide and succinic anhydride. Phosphoric acid catalyst was added, and the reaction was heated. After the reaction was completed, the membrane was washed and dried to obtain the modified ceramic membrane. The method for preparing the modified gel membrane includes the following steps: S1. Add deionized water to the container containing sodium alginate and stir to obtain sodium alginate solution. S2. Dissolve chitosan in acetic acid solution, then add dopamine, stir, then add glutaraldehyde and N-hydroxysuccinimide, crosslinking reaction to obtain modified chitosan, add the modified chitosan to sodium alginate solution, stir to obtain a mixture; S3. Add sodium hydroxide solution to the mixture, stir to obtain a pregel, then inject the pregel into a mold, add calcium chloride solution to gel, then wash, freeze, and dry to obtain a preliminary gel film. S4. Immerse the preliminary gel membrane in a lipase solution, then wash and dry it to obtain a modified gel membrane.

2. The composite membrane for extracting coffee concentrate according to claim 1, characterized in that, The heating temperature is 40~50℃.

3. The composite membrane for extracting coffee concentrate according to claim 1, characterized in that, The ceramic membrane includes an alumina membrane, a zirconia membrane, a titanium oxide membrane, or a silicon oxide membrane.

4. The composite membrane for extracting coffee concentrate according to claim 1, characterized in that, The modified ceramic membrane has a pore size of 0.5~20μm.

5. The composite membrane for extracting coffee concentrate according to claim 1, characterized in that, The ratio of the amount of ceramic membrane, dimethylformamide, succinic anhydride and phosphoric acid is (1~3g): (3~10mL): (0.2~0.4g): (0.01~0.5mL).

6. The composite membrane for extracting coffee concentrate according to claim 1, characterized in that, In step S1, the ratio of sodium alginate to deionized water is (1~5g):(100~150mL). In step S2, the ratio of chitosan, acetic acid, dopamine, glutaraldehyde and N-hydroxysuccinimide is (5~20g):(10~50mL):(2~5g):(2~4mL):(1~5g); The mass ratio of sodium alginate to chitosan is (1~2):(15~25).

7. The composite membrane for extracting coffee concentrate according to claim 1, characterized in that, In step S3, the sodium hydroxide solution has a mass fraction of 4% to 8%, and the calcium chloride solution has a mass fraction of 3% to 10%. In step S4, the mass concentration of the lipase solution is 1~20 mg / mL.

8. An application of the composite membrane as described in any one of claims 1 to 7, characterized in that, It is used in the extraction of coffee concentrate.

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