A method for extracting wheat germ oil with subcritical carbon dioxide

Abstract

The application belongs to the technical field of edible oil preparation, and particularly relates to a method for extracting wheat germ oil by using subcritical carbon dioxide. The method for extracting wheat germ oil by using subcritical carbon dioxide provided by the application adopts a process strategy of microwave coupling subcritical carbon dioxide extraction, first destroys the oil cell wall in the wheat germ through the interaction of a magnetic field and an electric field, promotes the outflow of the wheat germ oil in the oil cell, and further combines a subcritical extraction method to extract high-quality wheat germ oil by taking CO2 as a green extraction solvent. The application realizes high extraction rate of the wheat germ oil, effectively guarantees the safety and nutritional quality of the oil, and has a good application prospect in the industrial production field of the wheat germ oil.

Description

Technical Field

[0001] This invention belongs to the field of edible oil preparation technology, specifically relating to a method for extracting wheat germ oil using subcritical carbon dioxide. Background Technology

[0002] Wheat germ oil has many important physiological regulatory functions for human health. For example, vitamin E, linoleic acid, and octadecyl alcohol in wheat germ oil have effects such as maintaining cardiovascular health, anti-aging, and beauty. However, the oil content in wheat germ is low, and traditional pressing or solvent extraction methods have poor extraction efficiency, which limits the further industrial application of wheat germ oil.

[0003] Currently, common extraction methods for wheat germ oil include cold pressing, hot pressing, aqueous extraction, organic solvent extraction, and ultrasonic extraction. Cold pressing, hot pressing, and aqueous extraction generally have low oil extraction rates from wheat germ. While organic solvent extraction has high extraction efficiency, the resulting wheat germ oil contains high levels of solvent impurities, posing a significant risk of solvent residue. Although ultrasonic extraction eliminates the risk of solvent residue, improper control of ultrasonic parameters can easily cause oxidation of the wheat germ oil, thus limiting its industrial application.

[0004] my country has abundant and high-quality wheat resources. However, in the wheat processing process, wheat germ, as the essence of wheat, is mainly used for livestock feed, resulting in a large waste of wheat germ resources. Furthermore, existing conventional extraction methods are too inefficient in extracting oil from wheat germ and are prone to solvent residue or oxidation risks.

[0005] Therefore, developing a new extraction technology to prepare high-quality wheat germ oil is of profound significance for ensuring the rational utilization of wheat germ resources and high-value-added production, in response to the above problems. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for extracting wheat germ oil by subcritical carbon dioxide, which can effectively improve the extraction rate of wheat germ oil and solve the problems of low extraction rate, resource waste, solvent residue or oil oxidation.

[0007] To achieve the above objectives, the technical solution provided by the present invention is as follows: A method for extracting wheat germ oil using subcritical carbon dioxide includes the following steps: S1. Dry the wheat germ raw material, then microwave it, then crush and sieve it to obtain wheat germ powder; S2. The wheat germ powder is placed in a subcritical extraction device and subjected to subcritical extraction with carbon dioxide as the extractant to obtain crude wheat germ oil. The subcritical extraction process conditions are: extraction pressure 15~25MPa, extraction temperature 26~32℃, and extraction flow rate 30~50L / h. S3. The crude wheat germ oil is subjected to solid-liquid separation, and then the upper layer of oil is sieved and dried to obtain wheat germ oil.

[0008] More preferably, in step S1, the drying temperature is 30~50℃.

[0009] More preferably, in step S1, the moisture content of the wheat germ raw material obtained after drying is less than 5 wt%.

[0010] More preferably, in step S1, the microwave processing conditions are: microwave frequency 2000~3000MHz, microwave power 300~500W, and microwave time 2~6min.

[0011] More preferably, in step S1, the sieve used for sieving has a mesh size of 30 to 50.

[0012] More preferably, in step S2, the subcritical extraction process conditions are: extraction pressure 25 MPa, extraction temperature 26 °C, and extraction flow rate 40 L / h.

[0013] More preferably, in step S3, the solid-liquid separation is centrifugation or filtration; the centrifugation speed is 2000~4000 rpm, and the time is 10~30 min.

[0014] More preferably, in step S3, the sieve used for sieving has a mesh size of 180 to 220.

[0015] More preferably, in step S3, the drying is vacuum drying; the temperature of the vacuum drying is 40~60℃, and the time is 0.5~2h.

[0016] More preferably, in step S3, the moisture content of the wheat germ oil obtained after drying is less than 0.2 wt%.

[0017] Compared with the prior art, the beneficial effects and advantages of the present invention are as follows: This invention provides a method for extracting wheat germ oil using subcritical carbon dioxide, employing a microwave-coupled subcritical carbon dioxide extraction process. First, the interaction of a magnetic field and an electric field disrupts the cell walls of the oil-producing cells, promoting the outflow of wheat germ oil. Then, subcritical extraction is combined with CO2 as a green extraction solvent to obtain high-quality wheat germ oil. Furthermore, the use of CO2 as the extraction solvent is a green medium, and the extraction process is mild, effectively ensuring the product's antioxidant capacity while eliminating the risk of solvent residue.

[0018] Therefore, the extraction method provided by this invention can achieve a high extraction rate of wheat germ oil while effectively ensuring the safety and nutritional quality of the oil, and has good application prospects in the industrial production of wheat germ oil. Detailed Implementation

[0019] The technical solution of the present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are merely further clarifications of the present invention and not limitations thereof. Unless otherwise specified, the experimental methods mentioned in the following embodiments are conventional methods. Unless otherwise specified, the experimental materials used in the following embodiments are all purchased from conventional commercial channels.

[0020] The fresh wheat germ used in this invention is high-quality wheat germ from the Yellow River Delta, with an initial moisture content of 10±0.5wt%. Example

[0021] This embodiment provides a method for extracting wheat germ oil using subcritical carbon dioxide, including the following steps: Step S1, Moisture control: Take fresh wheat germ and spread it flat on a stainless steel plate with a thickness of 0.5±0.1cm. Dry it at a low temperature of 40℃, turning it over once every 1 hour to reduce the moisture content of the wheat germ to below 5wt%. Step S2, Microwave Treatment: Place 300g of low-temperature dried wheat germ into a microwave-safe ceramic bowl (15cm diameter) and spread it evenly. Place the bowl in a microwave oven and microwave at 2450MHz and 400W for 0min, 2min, 4min, 6min, 8min, and 10min. After treatment, pour the wheat germ onto a stainless steel plate (1±0.1cm thick) and allow it to cool to room temperature. During microwave treatment, remove the wheat germ from the microwave oven every 2 minutes, gently turn it over, and continue microwave to prevent overheating and scorching. Step S3, Grinding and Sieving: Grind the microwave-treated wheat germ and pass it through a 40-mesh sieve to obtain wheat germ powder. Step S4, Extraction: The sieved wheat germ powder is placed in a subcritical extraction device and extracted with CO2 as the extractant. The extraction pressure is set to 15 MPa, the extraction temperature is 26℃, and the extraction flow rate is 40 L / h. After extraction, the solvent is removed under reduced pressure to obtain crude wheat germ oil. Step S5, centrifugation, filtration and drying: Centrifuge the crude wheat germ oil at 3000 rpm for 15 minutes. After centrifugation, remove the sediment and retain the upper layer of oil. Then filter the upper layer of oil through a 200-mesh sieve and vacuum dry it at 50°C for 1 hour to ensure that the moisture content in the wheat germ oil is below 0.2 wt%, thus obtaining the finished wheat germ oil product. Example

[0022] This embodiment provides a method for extracting wheat germ oil using subcritical carbon dioxide. The preparation process is basically the same as that in Example 1, except that the microwave treatment time in step S2 is 6 min and the extraction pressure in step S4 is set to 10 MPa, 15 MPa, 20 MPa and 25 MPa respectively. The other process conditions are the same as in Example 1. Example

[0023] This embodiment provides a method for extracting wheat germ oil using subcritical carbon dioxide. The preparation process is basically the same as that in Example 1, except that the microwave treatment time in step S2 is 6 min; the extraction temperature in step S4 is set to 20℃, 23℃, 26℃, 29℃, and 32℃ respectively, and the other process conditions are the same as in Example 1. Example

[0024] This embodiment provides a method for extracting wheat germ oil using subcritical carbon dioxide. The preparation process is basically the same as that in Example 1, except that the microwave treatment time in step S2 is 6 min; the extraction flow rate in step S4 is set to 20 L / h, 30 L / h, 40 L / h, 50 L / h, and 60 L / h, respectively, and the other process conditions are the same as in Example 1.

[0025] Experimental Example 1: Effects of Different Factors on Wheat Germ Oil Extraction Rate This experimental example tested the extraction rate of wheat germ oil prepared in Examples 1-4 to investigate the effects of different factors (microwave treatment time, extraction pressure, extraction temperature, and extraction flow rate) on the extraction rate of wheat germ oil. The extraction rate of wheat germ oil was calculated using the formula: "Extraction rate (%) = ((wheat germ oil mass / g) / (oil content in wheat germ / g)) × 100%". The oil content in wheat germ was determined using the Soxhlet extraction method (GB 5009.6-2025).

[0026] (1) Effect of microwave treatment time on wheat germ oil extraction rate Using wheat germ oil extraction rate as the evaluation index, and with fixed extraction conditions of 15 MPa extraction pressure, 26 ℃ extraction temperature, and 40 L / h extraction flow rate, the effects of different microwave treatment times (0 min, 2 min, 4 min, 6 min, 8 min, 10 min) on wheat germ oil extraction rate in Example 1 were investigated.

[0027] Test results showed that the wheat germ oil extraction rate gradually increased with the extension of microwave treatment time, reaching its highest level (83.5%) at a treatment time of 4 minutes. Further extension of microwave treatment time to 6 minutes or more resulted in a decrease in the wheat germ oil extraction rate. Therefore, a microwave treatment time of 4 minutes was selected for subsequent wheat germ oil extraction process optimization.

[0028] (2) Effect of extraction pressure on wheat germ oil extraction rate Using wheat germ oil extraction rate as the evaluation index, and with fixed extraction conditions including microwave treatment time of 6 min, extraction temperature of 26℃, and extraction flow rate of 40 L / h, the effect of different extraction pressures (10 MPa, 15 MPa, 20 MPa, 25 MPa) on wheat germ oil extraction rate was investigated in Example 2.

[0029] Test results showed that the extraction rate of wheat germ oil gradually increased when the extraction pressure was between 10 MPa and 20 MPa, reaching its highest level (82.1%) at 20 MPa. As the extraction pressure continued to increase, the extraction rate gradually decreased. Taking all factors into consideration, an extraction pressure of 20 MPa was selected for subsequent optimization of the wheat germ oil extraction process.

[0030] (3) Effect of extraction temperature on wheat germ oil extraction rate Using wheat germ oil extraction rate as the evaluation index, and with fixed extraction conditions including microwave treatment time of 6 min, extraction pressure of 15 MPa, and extraction flow rate of 40 L / h, the effects of different extraction temperatures (20℃, 23℃, 26℃, 29℃, and 32℃) on wheat germ oil extraction rate were investigated in Example 3.

[0031] Test results show that the extraction rate of wheat germ oil increases almost linearly with increasing extraction temperature, reaching its highest level (86.1%) at 29℃. Further increases in extraction temperature lead to a gradual decrease in the extraction rate. Therefore, considering all factors, an extraction temperature of 29℃ was chosen for subsequent optimization of the wheat germ oil extraction process.

[0032] (4) Effect of extraction flow rate on wheat germ oil extraction rate Using wheat germ oil extraction rate as the evaluation index, and with fixed extraction conditions including microwave treatment time of 6 min, extraction pressure of 15 MPa, and extraction temperature of 26 °C, the effects of different extraction flow rates (20 L / h, 30 L / h, 40 L / h, 50 L / h, 60 L / h) on wheat germ oil extraction rate were investigated in Example 4.

[0033] Test results showed that within the range of 20 L / h to 40 L / h, the extraction rate of wheat germ oil gradually increased with increasing extraction flow rate, reaching its highest level (85.6%) at an extraction flow rate of 40 L / h. Further increases in the extraction flow rate led to a gradual decrease in the extraction rate. Therefore, considering all factors, an extraction flow rate of 40 L / h was selected for subsequent optimization of the wheat germ oil extraction process.

[0034] Example 2: Determination of the optimal processing technology for wheat germ oil Based on the optimal parameters of the four factors—microwave treatment time, extraction pressure, extraction temperature, and extraction flow rate—determined in Experiment Example 1, this invention conducts an orthogonal experiment on wheat germ oil extraction and measures the extraction rate of wheat germ oil, thereby determining the optimal conditions for microwave-coupled subcritical carbon dioxide extraction of wheat germ oil. The orthogonal factor level table is shown in Table 1, and the orthogonal experiment table is shown in Table 2.

[0035] Table 1. Orthogonal Factor Level Table

[0036] Table 2. Orthogonal Experiment Table

[0037] As shown in Tables 1 and 2, this invention uses L9(34) orthogonal optimization to optimize the wheat germ oil production process. The orthogonal optimization results show that the order of influence of each factor on the extraction rate is: extraction flow rate > microwave treatment time > extraction temperature > extraction pressure. The optimal combination obtained is A2B3C1D2, which is: microwave treatment time 4 min, extraction pressure 25 MPa, extraction temperature 26 °C, and extraction flow rate 40 L / h. The optimal combination obtained in the orthogonal optimization shows that the wheat germ oil extraction rate is the highest (88.6%) among all orthogonal groups. Therefore, this invention determines A2B3C1D2 as the optimal process parameters.

[0038] In summary, the subcritical carbon dioxide extraction method for wheat germ oil provided by this invention employs a microwave-coupled subcritical carbon dioxide extraction process strategy. This method achieves a high extraction rate of wheat germ oil while effectively ensuring the safety and nutritional quality of the oil, and has promising application prospects in the industrial production of wheat germ oil.

[0039] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. It should be noted that, for those skilled in the art, modifications and improvements can be made within the technical scope disclosed in the present invention, which will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. Therefore, these modifications and improvements should also be considered within the scope of protection of the present invention.

Claims

1. A method for extracting wheat germ oil using subcritical carbon dioxide, characterized in that, Includes the following steps: S1. Dry the wheat germ raw material, then microwave it, then crush and sieve it to obtain wheat germ powder; S2. The wheat germ powder is placed in a subcritical extraction device and subjected to subcritical extraction with carbon dioxide as the extractant to obtain crude wheat germ oil. The subcritical extraction process conditions are: extraction pressure 15~25MPa, extraction temperature 26~32℃, and extraction flow rate 30~50L / h. S3. The crude wheat germ oil is subjected to solid-liquid separation, and then the upper layer of oil is sieved and dried to obtain wheat germ oil.

2. The method for extracting wheat germ oil using subcritical carbon dioxide according to claim 1, characterized in that, In step S1, the drying temperature is 30~50℃.

3. The method for extracting wheat germ oil using subcritical carbon dioxide according to claim 1, characterized in that, In step S1, the moisture content of the wheat germ raw material obtained after drying is less than 5 wt%.

4. The method for extracting wheat germ oil using subcritical carbon dioxide according to claim 1, characterized in that, In step S1, the microwave processing conditions are: microwave frequency 2000~3000MHz, microwave power 300~500W, and microwave time 2~6min.

5. The method for extracting wheat germ oil using subcritical carbon dioxide according to claim 1, characterized in that, In step S1, the sieve used for sieving has a mesh size of 30 to 50.

6. The method for extracting wheat germ oil using subcritical carbon dioxide according to any one of claims 1 to 5, characterized in that, In step S2, the subcritical extraction process conditions are: extraction pressure 25 MPa, extraction temperature 26 °C, and extraction flow rate 40 L / h.

7. The method for extracting wheat germ oil using subcritical carbon dioxide according to any one of claims 1 to 5, characterized in that, In step S3, the solid-liquid separation is performed by centrifugation or filtration; the centrifugation speed is 2000~4000 rpm and the time is 10~30 min.

8. The method for extracting wheat germ oil using subcritical carbon dioxide according to any one of claims 1 to 5, characterized in that, In step S3, the sieve used for sieving has a mesh size of 180 to 220.

9. The method for extracting wheat germ oil using subcritical carbon dioxide according to any one of claims 1 to 5, characterized in that, In step S3, the drying is vacuum drying; the temperature of the vacuum drying is 40~60℃ and the time is 0.5~2h.

10. The method for extracting wheat germ oil using subcritical carbon dioxide according to any one of claims 1 to 5, characterized in that, In step S3, the moisture content of the wheat germ oil obtained after drying is less than 0.2 wt%.

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