Methods for extracting protein from camellia oil cake, camellia oil cake protein wood adhesive and its preparation method

Abstract

This invention discloses a method for extracting protein from camellia oil cake. The camellia oil cake is crushed, sieved, and then subjected to low-temperature plasma treatment (30-45W power input, 12-20 seconds). The protein is extracted using an alkali-dissolution-acid-precipitation method to obtain modified camellia oil cake protein. The prepared modified camellia oil cake protein is mixed with water at a mass ratio of 1:4, and an acidic substance is added. The reaction is carried out for 20-40 minutes with continuous stirring to obtain a camellia oil cake protein wood adhesive. The advantages of this invention are: it significantly improves the extraction rate of modified camellia oil cake protein, reaching up to 14.7%. The resulting camellia oil cake protein wood adhesive has a bonding strength exceeding 1.54 MPa.

Description

Technical Field

[0001] This invention relates to the field of camellia seed cake protein extraction and adhesive preparation technology, and particularly to a method for extracting camellia seed cake protein, a camellia seed cake protein wood adhesive, and a method for preparing the same. Background Technology

[0002] Camellia oleifera Abel. is an important woody oilseed tree species in southern my country, and its oil has high nutritional value. Camellia oil cake (also known as tea meal or tea cake) is the main byproduct of oil extraction from camellia seeds, with a huge annual yield. While rich in protein, camellia oil cake has long been primarily used as fertilizer, fuel, or pond cleaning agent, resulting in low resource utilization and serious waste.

[0003] Extracting protein from camellia oil cake is a key approach to achieving its high-value utilization. Currently, the alkali dissolution and acid precipitation method is the most commonly used method for extracting plant protein, with advantages such as simple operation and low cost. However, when untreated camellia oil cake is directly subjected to the alkali dissolution and acid precipitation method, the protein extraction rate is generally low, usually only 10-11%, which is difficult to meet the needs of efficient industrial utilization. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for extracting protein from camellia oil cake with high protein extraction rate, as well as a camellia oil cake protein wood adhesive with high bonding strength and its preparation method.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is a method for extracting protein from camellia oil cake, comprising the following steps: S1. Powdering: Crush and sieve the camellia oil cake to obtain camellia oil cake powder; S2. Low-temperature plasma treatment: The camellia oil cake powder is placed in a low-temperature plasma device for low-temperature plasma treatment. The treatment conditions are: power input power 30-45W, treatment time 12-20 seconds. S3. Protein extraction: The protein in the camellia oil cake powder after low-temperature plasma treatment is extracted by alkali dissolution and acid precipitation to obtain modified camellia oil cake protein.

[0006] Furthermore, in step S2, the power input is 40-45W and the processing time is 12-15 seconds.

[0007] Furthermore, the protein extraction by alkali dissolution and acid precipitation in step S3 is as follows: the camellia oil cake powder treated with low temperature plasma is mixed with water, the pH is adjusted to 8.0, stirred at 50°C for 1 hour, centrifuged to obtain supernatant, the supernatant is adjusted to pH 3.0 for acid precipitation, centrifuged again, the precipitate is collected and dried to obtain modified camellia oil cake protein.

[0008] Furthermore, in step S1, the moisture content of the camellia oil cake is 8-12%; the particle size of the crushed camellia oil cake is sieved through a 60-mesh sieve.

[0009] The present invention also provides a method for preparing a camellia seed protein wood adhesive, wherein the modified camellia seed protein prepared according to the above method is mixed with water at a mass ratio of 1:4, an acidic substance is added and reacted for 20-40 minutes, with continuous stirring during the process.

[0010] Furthermore, the acidic substance is selected from at least one of hydrochloric acid, sulfuric acid, phosphoric acid, and citric acid.

[0011] Further, add 15% hydrochloric acid solution, which is 30-40% of the protein mass, and react for 30 minutes.

[0012] Furthermore, a crosslinking agent is added after the acid treatment, the crosslinking agent being selected from at least one of glyoxal, glutaraldehyde, or epichlorohydrin.

[0013] Beneficial effects of this invention: This invention utilizes a low-temperature plasma pretreatment followed by alkali dissolution and acid precipitation for protein extraction. This non-thermal processing technology features mild conditions and a short processing time (only a few seconds to tens of seconds), avoiding protein denaturation or structural damage caused by prolonged heating or high-intensity mechanical action, thus preserving the protein's natural activity. Low-temperature plasma pretreatment significantly improves the extraction rate of modified camellia seed cake protein. Especially under conditions of 45W power input and 12 seconds processing time, the protein extraction rate can reach 14.7%, which helps reduce raw material costs. Compared to the traditional alkali dissolution and acid precipitation method, the protein extraction rate is increased by 38.7%.

[0014] Modified protein obtained through low-temperature plasma pretreatment, combined with acid treatment process, produces camellia seed cake protein wood adhesive with a bonding strength of over 1.54 MPa, reaching as high as 1.72 MPa, which is far higher than the strength requirement of Class II plywood (≥0.70 MPa) in GB / T 17657 (2022). The entire process is free of formaldehyde and other harmful substances, making it green and environmentally friendly. Detailed Implementation

[0015] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0016] Examples 1-6 and Comparative Examples 1-4 pertain to a method for extracting protein from camellia oil cake: Example 1 Camellia oil cake (moisture content 10.7%) was crushed and passed through a 60-mesh sieve. 100g of the camellia oil cake powder was placed in a low-temperature plasma device and treated for 20 seconds at a power input of 30W. After treatment, 600mL of distilled water was added to each sample, and the pH was adjusted to 8.0 with 1mol / L NaOH. The samples were then stirred in a 50℃ constant temperature water bath for 1 hour. Subsequently, the samples were centrifuged at 3000r / min for 20 minutes. The supernatant was collected, and the pH was adjusted to 3.0 with 1mol / L HCl. The samples were then centrifuged again at 3000r / min for 20 minutes. The precipitate was collected, dried, and weighed. The protein extraction rate was calculated.

[0017] Example 2 Compared to Example 1, the processing time of 20 seconds under a power input of 30W is changed to 13 seconds under a power input of 35W. The remaining steps are the same as in Example 1.

[0018] Example 3 Compared to Example 1, the processing time of 20 seconds under a power input of 30W is changed to 12 seconds under a power input of 40W. The remaining steps are the same as in Example 1.

[0019] Example 4 Compared to Example 1, the processing time of 20 seconds under a power input of 30W is changed to 15 seconds under a power input of 43W. The remaining steps are the same as in Example 1.

[0020] Example 5 Compared to Example 1, the processing time of 20 seconds under a power input of 30W is changed to 13 seconds under a power input of 40W. The remaining steps are the same as in Example 1.

[0021] Example 6 Compared to Example 1, the processing time of 20 seconds under a power input of 30W is changed to 12 seconds under a power input of 45W. The remaining steps are the same as in Example 1.

[0022] Comparative Example 1 Camellia oil cake (moisture content 10.7%) was crushed and passed through a 60-mesh sieve. 100g of camellia oil cake powder was accurately weighed, added to 600mL of distilled water, and the pH was adjusted to 8.0 with 1mol / L NaOH. The mixture was then placed in a 50℃ constant temperature water bath and stirred for 1 hour. Subsequently, it was centrifuged at 3000r / min for 20 minutes. The supernatant was collected, and the pH was adjusted to 3.0 with 1mol / L HCl. The mixture was then centrifuged again at 3000r / min for 20 minutes. The precipitate was collected, dried, and weighed. The protein extraction rate was calculated.

[0023] Comparative Example 2 Compared to Example 1, the processing time of 20 seconds under a power input of 30W is changed to 12 seconds under a power input of 50W. The remaining steps are the same as in Example 1.

[0024] Comparative Example 3 Compared to Example 1, the processing time of 20 seconds under a power input of 30W is changed to 15 seconds under a power input of 45W. The remaining steps are the same as in Example 1.

[0025] Comparative Example 4 Compared to Example 1, the processing time of 20 seconds under a power input of 30W is changed to 10 seconds under a power input of 60W. The remaining steps are the same as in Example 1.

[0026] The protein weights and protein extraction rates obtained from Examples 1-6 and Comparative Examples 1-4 are shown in the table below:

[0027] Protein extraction rate = (Weight of protein obtained from the example or comparative treatment / Weight of camellia oil cake powder) * 100% The examples and comparative studies clearly demonstrate that pretreatment of camellia oil cake powder with low-temperature plasma for 12-20 seconds at a power input of 30-45W before alkali dissolution and acid precipitation effectively improves protein extraction rate. Compared to no low-temperature plasma treatment, the protein extraction rate can be increased from 10.6% to 14.7%. Only one low-temperature plasma treatment unit needs to be added before the traditional alkali dissolution and acid precipitation production line, making the investment cost controllable, the processing efficiency high, and the project a promising prospect for industrial application.

[0028] The following Examples 7-9 and Comparative Examples 5-10 pertain to the preparation method of camellia seed cake protein wood adhesive. Example 7 Take 20g of the modified camellia seed protein obtained in Example 6, add 80g of distilled water, stir and mix well, add 7.5g of 15% HCl solution, and react for 30 minutes while stirring continuously.

[0029] Example 8 Take 20g of the modified camellia seed protein obtained in Example 4, add 80g of distilled water, stir and mix well, add 7.5g of 15% HCl solution, and react for 30 minutes while stirring continuously.

[0030] Example 9 Based on Example 7, after acid treatment, 0.5g of glyoxal was added, and stirring was continued for 10 minutes.

[0031] Comparative Example 5 Take 20g of the ordinary camellia seed protein prepared in Comparative Example 1, add 80g of distilled water, stir and mix well, add 7.5g of 15% HCl solution, and react for 30 minutes while stirring continuously.

[0032] Comparative Example 6 Take 20g of the ordinary camellia seed protein prepared in Comparative Example 1, add 80g of distilled water, stir and mix well, add 7.5g of 15% HCl solution, react for 30 minutes while stirring continuously, then add 0.5g of glyoxal and continue stirring for 10 minutes.

[0033] Comparative Example 7 Take 20g of the modified camellia seed protein obtained in Example 6, add 80g of distilled water, stir and mix well, heat to 80℃ and react for 30 minutes, stirring continuously during the process.

[0034] Comparative Example 8 Take 20g of the modified camellia seed protein obtained in Example 6, add 80g of distilled water, stir and mix well, add 7.5g of 15% NaOH solution, and react for 30 minutes while continuously stirring.

[0035] Comparative Example 9 Take 20g of the ordinary camellia seed protein prepared in Comparative Example 1, add 80g of distilled water, stir and mix well, heat to 80℃ and react for 30 minutes, stirring continuously during the process.

[0036] Comparative Example 10 Take 20g of the ordinary camellia seed protein prepared in Comparative Example 1, add 80g of distilled water, stir and mix well, add 7.5g of 15% NaOH solution, and react for 30 minutes while stirring continuously.

[0037] The adhesives prepared in Examples 7-9 and Comparative Examples 5-10 were subjected to bonding strength tests: Three-layer poplar plywood (veneer size 400×400mm, thickness 1.5mm) was prepared according to the method of GB / T17657-2022, with an adhesive application rate of 180g / m². 2 (Single-sided), hot pressing temperature 140℃, pressure 1.5MPa, time 3min.

[0038] The adhesives prepared in Examples 7-9 and Comparative Examples 5-10 were used to evenly coat the surface of poplar veneer (170 mm × 110 mm) with a flat brush, ensuring that the coating amount on one side was 100 mm. The veneers with adhesive were then stacked into three layers, left to stand for 15 minutes, and then hot-pressed at 140°C and 1.5 MPa for 3 minutes to produce plywood. The plywood was placed at room temperature (25°C, 50% relative humidity) for 24 hours and then cut into standard test specimens of 100 mm × 25 mm. The dry bond strength of the plywood was tested according to the national standard GB / T 17657 (2022). Three specimens were taken from each group, and the final strength value was the average of the three specimens. The obtained bond strength data are shown in the table below:

[0039] It is evident that the adhesive strength of the modified camellia seed protein prepared by low-temperature plasma combined with acid treatment is significantly improved compared to ordinary camellia seed protein wood adhesive, reaching 1.58 MPa. After adding a crosslinking agent, it can be further improved to 1.72 MPa, which is far higher than the strength requirement of Class II plywood (≥0.70 MPa) in GB / T 17657 (2022).

[0040] The bonding strength of Examples 7 and 8 was significantly higher than that of Comparative Example 5, indicating that low-temperature plasma pretreatment and acid treatment synergistically improved the bonding strength. This synergistic effect is due to the following: plasma bombards the camellia seed cake protein particles with high-energy particles, etching the surface (increasing specific surface area and reagent penetration channels), introducing polar functional groups such as carboxyl groups, and relaxing the molecular structure, thus creating a better reaction interface for subsequent acid treatment; acid treatment utilizes the structural changes brought about by plasma to achieve efficient and controllable hydrolysis of peptide bonds, while simultaneously protonating carboxyl groups, significantly enhancing the hydrogen bonding ability with wood hydroxyl groups. The synergy of both ultimately resulted in a bonding strength significantly higher than that of acid treatment alone.

[0041] The comparison between Comparative Examples 7 and 9 shows that the bonding strength of the method of pretreatment with low-temperature plasma followed by heat treatment is similar to that of the method of heat treatment without pretreatment with low-temperature plasma, indicating that the pretreatment with low-temperature plasma and heat treatment do not produce a synergistic effect.

[0042] The comparison between Comparative Examples 8 and 10 shows that the bonding strength of the method that pre-treats with low-temperature plasma and then treats with alkali is significantly lower than that of the method that treats directly with alkali without pre-treating with low-temperature plasma. This indicates that the low-temperature plasma pre-treatment and alkali treatment not only do not produce a synergistic effect, but also produce an antagonistic effect.

[0043] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A method for extracting protein from camellia oil cake, characterized in that: Includes the following steps: S1. Powdering: Crush and sieve the camellia oil cake to obtain camellia oil cake powder; S2. Low-temperature plasma treatment: The camellia oil cake powder is placed in a low-temperature plasma device for low-temperature plasma treatment. The treatment conditions are: power input power 30-45W, treatment time 12-20 seconds. S3. Protein extraction: The protein in the camellia oil cake powder after low-temperature plasma treatment is extracted by alkali dissolution and acid precipitation to obtain modified camellia oil cake protein.

2. The method for extracting protein from camellia oil cake according to claim 1, characterized in that: In step S2, the power input is 40-45W and the processing time is 12-15 seconds.

3. The method for extracting protein from camellia oil cake according to claim 1, characterized in that: The protein extraction method of alkali dissolution and acid precipitation in step S3 is as follows: the camellia oil cake powder treated with low temperature plasma is mixed with water, the pH is adjusted to 8.0, stirred at 50°C for 1 hour, and centrifuged to obtain the supernatant. The supernatant is adjusted to pH 3.0 for acid precipitation, centrifuged again, the precipitate is collected and dried to obtain modified camellia oil cake protein.

4. The method for extracting protein from camellia oil cake according to claim 1, characterized in that: The moisture content of the camellia oil cake in step S1 is 8-12%; the particle size of the crushed camellia oil cake is sieved through a 60-mesh sieve.

5. Modified camellia seed protein, characterized in that: It is prepared by the protein extraction method of camellia seed cake according to any one of claims 1-4.

6. A method for preparing camellia oil cake protein wood adhesive, characterized in that: The modified camellia seed protein of claim 5 is mixed with water at a mass ratio of 1:4, and an acidic substance is added and reacted for 20-40 minutes with continuous stirring.

7. The preparation method according to claim 6, characterized in that: The acidic substance is selected from at least one of hydrochloric acid, sulfuric acid, phosphoric acid, and citric acid.

8. The preparation method according to claim 6, characterized in that: Add 15% hydrochloric acid solution, which is 30-40% of the protein mass, and react for 30 minutes.

9. The preparation method according to claim 6, characterized in that: After the acid treatment, a crosslinking agent is added, which is selected from at least one of glyoxal, glutaraldehyde, or epichlorohydrin.

10. A camellia oil cake protein wood adhesive, characterized in that: It is prepared by the preparation method according to any one of claims 6-9.

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