A method for removing the fishy smell of legume proteins

Abstract

The application discloses a method for removing the fishy smell of legume protein, comprising the following steps: (1) dissolving the legume protein in water to prepare a solution with a concentration of 1-10%; (2) adding a pH regulator to adjust the pH value of the protein solution in the step (1) to 4-5; (3) treating the protein solution in the step (2) by using an ultrasonic physical field; (4) adding activated carbon into the solution in the step (3) and stirring and adsorbing; (5) adding a pH regulator into the solution in the step (4) to adjust the pH value of the solution to 7; and (6) spray drying the solution in the step (5) after filtration to obtain legume protein powder without fishy smell. The method for removing the fishy smell of legume protein provided by the application can adjust the acid-base degree of the solution, change the folding structure of the legume protein, expose small-molecule compounds, break the cross-linking between the protein and the small-molecule compounds by combining the ultrasonic physical field treatment, and finally adsorb the small-molecule substances by using activated carbon, so that the fishy smell can be completely removed.

Description

Technical Field

[0001] This invention relates to the field of soybean protein processing, and more particularly to a method for removing the fishy smell from soybean protein. Background Technology

[0002] In recent years, with changing consumption patterns, plant-based protein drinks have gained widespread attention due to their "natural" and "healthy" concepts. Compared to traditional animal dairy products, plant-based protein drinks have advantages such as lower prices, lower saturated fat content, and less likelihood of antibiotic and veterinary drug residues. Nowadays, more and more consumers are favoring plant-based protein drinks.

[0003] Legumes are abundant and rich in protein, making them a crucial source of plant-based protein beverages. However, legume protein has a distinctive beany odor, often resulting in unpleasant flavors in products. Masking agents are typically added during production to create flavored protein drinks like chocolate and vanilla to mask this unpleasant taste. This beany odor significantly limits the expansion of product categories. Therefore, researching techniques for removing the beany odor from legume protein is essential for broadening its application range.

[0004] The beany odor of beans is mainly composed of volatile small molecules such as aldehydes, ketones, and alcohols. These substances may originate from the beans themselves or from the enzymatic oxidation of unsaturated fats in beans during processing. Currently, more than 70 volatile compounds have been identified in beans, among which hexanal, trans-2-hexenal, acetic acid, 2-heptanone, and 4-ethylbenzaldehyde are present in relatively high amounts. These compounds respectively produce flavors reminiscent of freshly cut grass, raw, mushroom, sour, bitter almond, and spicy notes, and together they constitute the beany odor.

[0005] Currently reported de-aeration methods can be summarized as removing small molecules through physical heating or solvent treatment (CN101731441A). However, many small molecules such as aldehydes present in soybeans are bound to soybean proteins, and heating or solvent treatment cannot completely remove the beany odor. After product formation, the small molecule protein complex will release volatile substances again. Because the threshold for beany odor substances is extremely low, the beany odor will remain as long as any residue remains. Another method is to reduce enzyme activity to decrease the formation of beany odor substances through fat oxidation, but this method cannot remove existing beany odor substances. There are also methods using microbial fermentation (CN102232425A) to degrade beany odor substances, but this also produces new flavors and is not suitable for producing odorless protein products. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a method for removing the fishy smell of soybean protein. The method is simple, convenient, easy to use, and suitable for industrial mass production.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for removing the fishy smell from soybean protein includes the following steps:

[0009] (1) Dissolve the soybean protein in water to prepare a solution with a concentration of 1-10%;

[0010] (2) Add pH adjuster to adjust the pH of the protein solution in step (1) to 4-5;

[0011] (3) The protein solution from step (2) above was treated with an ultrasonic physical field;

[0012] (4) Add activated carbon to the solution from step (3) above and stir to adsorb;

[0013] (5) Add pH adjuster to the solution in step (4) to adjust the pH of the solution to 7;

[0014] (6) After filtering the solution from step (5), spray dry it to obtain odorless soy protein powder.

[0015] Further, the beans in step (1) are one of soybeans, peas, chickpeas, mung beans, red beans, broad beans, lentils, or kidney beans.

[0016] Furthermore, the pH adjuster in step (2) is a hydrochloric acid solution, and the pH adjuster in step (5) is a sodium hydroxide solution.

[0017] Furthermore, in step (3) above, the ultrasonic physical field is 20-25 kHz and the processing time is 10-20 min.

[0018] Furthermore, in step (3) above, the ultrasonic physical field is 20 kHz and the processing time is 15 min.

[0019] Furthermore, in step (4) above, the amount of activated carbon used is 2-8%, and the adsorption is carried out by stirring for 5-30 minutes.

[0020] Furthermore, in step (4) above, the amount of activated carbon used is 5%, and the adsorption is carried out by stirring for 10 minutes.

[0021] Furthermore, the filtration in step (6) above is performed using plate and frame filtration or microfiltration.

[0022] Furthermore, in step (2), the pH of the adjusted protein solution is 4.5.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a method for removing the fishy smell of soybean protein. By adjusting the pH of the solution, the folding structure of soybean protein is changed, allowing small molecule compounds to be fully exposed. At the same time, ultrasonic physical field treatment is combined to break the cross-linking between protein and small molecules. Finally, activated carbon is used to adsorb small molecule substances, thereby completely removing the fishy smell. Detailed Implementation

[0024] The present invention will now be further described in conjunction with specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0025] Example 1

[0026] (1) Dissolve soybean protein in water to prepare a 2% solution;

[0027] (2) Add hydrochloric acid solution to adjust the pH of the protein solution from step (1) to 4.5;

[0028] (3) Treat the protein solution from step (2) above with a 20kHz ultrasonic physical field for 15 minutes;

[0029] (4) Add 5% activated carbon to the solution in step (3) above and stir to adsorb for 10 min;

[0030] (5) Add sodium hydroxide solution to the solution from step (4) to adjust the pH of the solution to 7;

[0031] (6) The solution from step (5) was filtered by plate and frame filter and then spray-dried to obtain odorless soybean protein powder.

[0032] Example 2

[0033] (1) Dissolve pea protein in water to prepare a 5% solution;

[0034] (2) Add hydrochloric acid solution to adjust the pH of the protein solution in step (1) to 4;

[0035] (3) Treat the protein solution from step (2) above with a 22kHz ultrasonic physical field for 20 minutes;

[0036] (4) Add 2% activated carbon to the solution in step (3) above and stir to adsorb for 20 min;

[0037] (5) Add sodium hydroxide solution to the solution from step (4) to adjust the pH of the solution to 7;

[0038] (6) After microfiltration of the solution from step (5), spray drying is performed to obtain odorless pea protein powder.

[0039] Example 3

[0040] (1) Dissolve broad bean protein in water to prepare a 10% solution;

[0041] (2) Add hydrochloric acid solution to adjust the pH of the protein solution in step (1) to 5;

[0042] (3) Treat the protein solution from step (2) above with a 25kHz ultrasonic physical field for 10 minutes;

[0043] (4) Add 8% activated carbon to the solution from step (3) above and stir for 5 minutes to adsorb.

[0044] (5) Add sodium hydroxide solution to the solution from step (4) to adjust the pH of the solution to 7;

[0045] (6) The solution from step (5) was filtered by plate and frame filter and then spray-dried to obtain odorless soybean protein powder.

[0046] Comparative Example 1

[0047] Comparative Example 1 provides a method for removing the fishy smell of soybean protein. The difference between Comparative Example 1 and Example 1 is that step (3) is omitted, while the rest is the same as Example 1.

[0048] Comparative Example 2

[0049] Comparative Example 2 provides a method for removing the fishy smell of soybean protein. The difference between Comparative Example 2 and Example 1 is that steps (2) and (5) are omitted, while the rest are the same as Example 1.

[0050] Comparative Example 3

[0051] Comparative Example 3 provides a method for removing the fishy smell of soybean protein. The difference between Comparative Example 3 and Example 1 is that the pH value is adjusted to 3 in step (2), while the rest is the same as Example 1.

[0052] Comparative Example 4

[0053] Comparative Example 4 provides a method for removing the fishy smell of soybean protein. The difference between this method and Example 1 is that the pH value is adjusted to 6 in step (2), while the rest is the same as in Example 1.

[0054] Sensory evaluations were performed on the soybean protein powders of Examples 1 to 3 and Comparative Examples 1 to 4, and the results are shown in Table 1.

[0055] Table 1

[0056] sample Beany smell Acceptance Example 1 Tasteless accept Example 2 Tasteless accept Example 3 It has a slight beany smell accept Comparative Example 1 Strong beany smell Not accepted Comparative Example 2 Strong beany smell Not accepted Comparative Example 3 Strong beany smell Not accepted Comparative Example 4 Strong beany smell Not accepted

[0057] The composition of the odor-producing substances in the soybean protein powders of Examples 1 to 3 and Comparative Examples 1 to 4 was analyzed by gas chromatography-mass spectrometry to determine the changes in their content (expressed as peak area). The results are shown in Table 2.

[0058] Table 2

[0059]

[0060]

[0061] As shown in Table 1, the soybean protein powder treated using the method of this invention has almost no fishy odor, which is acceptable to the sensory evaluators, while all four comparative examples showed a strong beany odor. Gas chromatography-mass spectrometry analysis revealed that 2-heptanone, trans-2-hexenal, 3-octanone, 2-ethylhexanol, and 4-ethylbenzaldehyde were not found in any of the three examples, indicating complete removal. The content of hexanal was also reduced to about one-tenth of that in the comparative examples. Comparative Examples 1 to 4 show that when ultrasonic treatment (Comparative Examples 1, 3, and 4) is omitted, or pH adjustment is omitted (Comparative Example 2), or the pH value of the solution is changed (Comparative Examples 3 and 4), the results of odor removal are inferior to those of this invention. This demonstrates that the method for removing the fishy odor from soybean protein provided by this invention, by adjusting the solution pH and combining it with ultrasonic physical field treatment, breaks the cross-linking between protein and small molecules, and finally utilizes activated carbon to adsorb small molecule substances, thereby completely removing the fishy odor.

[0062] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for removing the fishy odor from soybean protein, characterized in that, Includes the following steps: (1) Dissolve the soybean protein in water to prepare a solution with a concentration of 1-10%; (2) Add a pH adjuster to adjust the pH value of the protein solution in step (1) to 4-5, wherein the pH adjuster is a hydrochloric acid solution; (3) The protein solution from step (2) above is treated with an ultrasonic physical field, wherein the ultrasonic physical field is 20-25 kHz and the treatment time is 10-20 min; (4) Add activated carbon to the solution in step (3) above, stir and adsorb, the amount of activated carbon is 2-8%, and stir and adsorb for 5-30 minutes. (5) Add a pH adjuster to the solution in step (4) to adjust the pH of the solution to 7, wherein the pH adjuster is a sodium hydroxide solution; (6) After filtering the solution from step (5), spray dry it to obtain odorless soy protein powder.

2. The method for removing the fishy odor from soybean protein according to claim 1, characterized in that, The beans in step (1) are one of the following: soybeans, peas, chickpeas, mung beans, red beans, broad beans, lentils, or kidney beans.

3. The method for removing the fishy odor from soybean protein according to claim 1, characterized in that, In step (3) above, the ultrasonic physical field is 20 kHz and the processing time is 15 min.

4. The method for removing the fishy odor from soybean protein according to claim 1, characterized in that, In step (4) above, the amount of activated carbon used is 5%, and the adsorption is stirred for 10 minutes.

5. The method for removing the fishy odor from soybean protein according to claim 1, characterized in that, The filtration in step (6) above is performed using plate and frame filtration or microfiltration.

6. The method for removing the fishy odor from soybean protein according to claim 1, characterized in that, In step (2), the pH of the protein solution is adjusted to 4.5.

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