Method for simultaneously extracting grease and procyanidine in peanut skin

Abstract

The invention belongs to the technical field, and particularly discloses a method for simultaneously extracting grease and procyanidine in peanut skin. The method comprises the following steps: S1, filling peanut red skin dry powder into a continuous phase change extraction kettle, adding an extracting agent butane to extract grease, and recycling the extracted grease in an analysis kettle to obtain grease; and S2, adding an extracting agent ethanol into the red skin meal subjected to oil extraction, carrying out secondary extraction, adding the extracting agent dissolved with the proanthocyanidins into a desorption kettle after extraction, recovering, and carrying out freeze drying to obtain the proanthocyanidins. According to the method provided by the invention, step-by-step extraction of different polar components is realized in the same system, and the problems of component loss and cross contamination caused by multi-time meal discharge in a traditional process are effectively avoided. The method has the advantages of high selectivity and no solvent residue of supercritical extraction and the characteristics of high treatment capacity and low cost of a solvent method. The extraction can be carried out at a relatively low temperature, so that the high-temperature oxidation of the grease and the degradation of the procyanidine structure caused by high temperature are avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of crop extraction, and particularly relates to a method for simultaneously extracting oil and proanthocyanidins from peanut skins. Background Art

[0002] Peanut skins are by-products generated during peanut processing. Currently, most of them are used as feed or directly discarded, resulting in waste of resources. However, peanut skins contain rich proanthocyanidins and oil, which have extremely high economic value and development potential. Peanut skin oil is rich in unsaturated fatty acids such as oleic acid and linoleic acid, which helps regulate blood lipids and reduce the risk of cardiovascular diseases. Proanthocyanidins have strong antioxidant activity, can scavenge free radicals, delay aging, and prevent chronic diseases. Therefore, by developing efficient extraction technologies to extract these active ingredients and use them in fields such as food, medicine, and cosmetics, not only can waste be turned into treasure, but also the overall economic benefits of peanut processing can be improved.

[0003] Currently, the extraction of oil and proanthocyanidins from peanut skins mostly involves multi-stage extraction using solvents with different polarities, that is, first using non-polar solvents to extract oil, and then using polar solvents to extract proanthocyanidins. The extraction methods of oil and proanthocyanidins mainly include solvent method, microwave-assisted extraction method, supercritical fluid extraction method, and enzyme-assisted method, etc.

[0004] Different extraction methods have their own advantages and disadvantages in terms of extraction efficiency, product purity, and activity retention. For example:

[0005] 1. The solvent extraction method is simple to operate but has low efficiency, and the solvent extraction method may cause differences in the extraction efficiency and activity of substances due to different solvent types and concentrations. For example, the ethanol extraction method can usually better retain the activity of proanthocyanidins, while the methanol extraction method may cause partial degradation of proanthocyanidins.

[0006] 2. The ultrasonic and microwave-assisted extraction methods are efficient but need to optimize conditions to avoid degradation. Otherwise, long-term or high-power ultrasonic treatment may cause the oxidation of oil to produce harmful substances and damage the structure of proanthocyanidins, thus affecting their activity.

[0007] 3. The supercritical fluid extraction method has high purity and good activity retention but high cost.

[0008] 4. The enzyme-assisted extraction method has mild conditions, can effectively release the extract without damaging its structure, thus better retaining its activity, but the reaction time is longer, and the selection of enzymes and the optimization of reaction conditions are crucial for maintaining the activity of substances. Therefore, in practical applications, the appropriate extraction method should be selected according to specific requirements and conditions to maximize the retention of the activity of oil and proanthocyanidins.

[0009] Therefore, there is a need for a more efficient extraction process that can obtain both proanthocyanidins and peanut oil while ensuring the extraction efficiency and realizing continuous production. Summary of the Invention

[0010] In view of the deficiencies of the prior art, the present invention provides a method for simultaneously extracting oil and proanthocyanidins from peanut skins.

[0011] To overcome the drawbacks of the existing extraction technologies and realize the industrial extraction of oil from peanut skins and proanthocyanidins, the present invention is based on low-temperature continuous phase change extraction and innovatively develops a low-temperature gradient enrichment technology. That is, in the same device, first extract the oil from peanut skins with low-polarity butane, and then replace it with a polar ethanol solution to extract proanthocyanidins from the meal. Its basic principle is to use a liquid extractant to soak and extract the material in the extraction kettle, and realize the enrichment of the target components after heating and vaporization in the analytical kettle. Subsequently, the gaseous extractant is compressed back into a liquid and circulates through the extraction kettle to repeatedly extract the material. At the same time, by switching the extractant, the stepwise extraction of components with different polarities is realized in the same system, effectively avoiding the component loss and cross-contamination problems caused by multiple discharges of the meal in the traditional process. This method combines the advantages of high selectivity and solvent-free residue of supercritical extraction and the characteristics of large throughput and low cost of the solvent method. And it can be extracted at a relatively low temperature to avoid high-temperature oxidation of the oil and degradation of the proanthocyanidin structure caused by high temperature.

[0012] To achieve the above-mentioned invention object, the present invention provides the following technical solutions:

[0013] A method for simultaneously extracting oil and proanthocyanidins from peanut skins, comprising the following steps:

[0014] S1. Load the dry powder of peanut skins into a continuous phase change extraction kettle, add the extractant butane to extract the oil, and the extracted oil enters the analytical kettle for recovery to obtain the oil;

[0015] S2. Add the peanut skin meal after oil extraction to the extractant ethanol for secondary extraction. After extraction, the extractant containing proanthocyanidins is sent to the analytical kettle and recovered, and proanthocyanidins are obtained after freeze-drying.

[0016] Preferably, the flow rate of the extractant in step S1 is 60-65 L / h.

[0017] Preferably, the flow rate of the extractant in step S2 is 60-65 L / h.

[0018] Preferably, the extraction temperature in step S2 is 35-40 °C, the pressure is 0.1-0.5 MPa, and the time is 30-40 min.

[0019] Preferably, the material-liquid ratio in step S2 is 1:40-45, and the ethanol concentration is 50%.

[0020] Based on the low-temperature gradient enrichment technology, the present invention uses butane as a solvent to extract the oil from safflower seeds, and an oil yield of 6.62% can be obtained. Moreover, this oil is rich in oleic acid and linoleic acid, showing the potential for developing functional lipid products. Through single-factor and orthogonal experiments, the extraction conditions are optimized to achieve the maximum yield of proanthocyanidins. Under the optimal conditions, the yield can reach 16.18%, which is higher than that of other reported extraction methods. AB-8 macroporous resin is used for purification to obtain proanthocyanidins with a purity of 95.6 ± 1.23%. The in vitro antioxidant activity is evaluated by chemical methods, showing that the proanthocyanidins extracted from safflower seeds under this technology are superior to grape seed proanthocyanidins in scavenging DPPH free radicals and ABTS cation free radicals.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] The method provided by the present invention realizes the stepwise extraction of components with different polarities in the same system, effectively avoiding the problems of component loss and cross-contamination caused by multiple defatting processes in the traditional process. This method combines the advantages of high selectivity and solvent-free residue of supercritical extraction and the characteristics of large throughput and low cost of the solvent method. Moreover, it can be extracted at a relatively low temperature, avoiding high-temperature oxidation of the oil and degradation of the proanthocyanidin structure caused by high temperature. Description of the Drawings

[0023] Figure 1 Shows the influence of different factors on the extraction yield of proanthocyanidins.

[0024] Figure 2 Shows the DPPH free radical scavenging rate (A) and ABTS cation free radical scavenging rate (B) of safflower seed proanthocyanidins. Detailed Embodiments

[0025] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments and comparative examples of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0026] Unless otherwise specified, the test methods used in the following embodiments are all conventional methods; the materials, reagents, etc. used, unless otherwise specified, are reagents and materials that can be obtained from commercial channels.

[0027] Example 1:

[0028] 1. Design of single-factor experiments for proanthocyanidin extraction

[0029] On the premise that defatted red-skin rapeseed meal does not leave the kettle, explore the effects of extraction temperature (30°C, 40°C, 50°C, 60°C, 70°C), extraction time (20 min, 30 min, 40 min, 50 min, 60 min), extraction pressure (0.4 Mpa, 0.45 Mpa, 0.5 Mpa, 0.55 Mpa, 0.6 Mpa), solid-liquid ratio (1:15, 1:25, 1:35, 1:45, 1:55), and extractant concentration (30%, 40%, 50%, 60%, 70%) on the yield of proanthocyanidins.

[0030] 2. Orthogonal experimental design for the extraction of proanthocyanidins

[0031] On the basis of single-factor experiments, a four-factor and three-level orthogonal experiment was conducted on the solid-liquid ratio, extraction temperature, extraction time, and extraction pressure to select the optimal process. The factor level table is shown in Table 1.

[0032] Table 1 Orthogonal factor level table

[0033]

[0034] 3. Purification of proanthocyanidins from red-skin rapeseed meal by AB-8 macroporous resin

[0035] The crude extract powder was prepared into a loading solution of 1.0 mg / mL and passed through an AB-8 macroporous resin column. After static adsorption, it was first eluted with distilled water for 5 column volumes to remove impurities, and then eluted with an ethanol solution with a volume fraction of 40%. The eluate part collected with the ethanol solution was filtered and concentrated, and freeze-dried to obtain PSPC.

[0036] 4. Evaluation of the in vitro antioxidant activity of proanthocyanidins from red-skin rapeseed meal

[0037] The scavenging rates of 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation free radicals were measured. PSPC and GSPC with concentrations of 0.2, 0.5, 1, 2 mg / mL, and 5 mg / mL were prepared respectively, and VC was used as a positive control. There were 3 parallels for each sample.

[0038] Experimental results and conclusions

[0039] 1. Extraction of red-skin rapeseed oil

[0040] By using the low-temperature gradient enrichment technology, butane was used as the solvent to extract the oil from red-skin peanuts, and the oil yield was 6.62%. GC-MS analysis showed that oleic acid (C18:1) and linoleic acid (C18:2) in the fatty acid composition accounted for 54.6% of the total fatty acid content. It has been reported that vegetable oils rich in oleic acid and linoleic acid have potential functions such as reducing blood pressure and cholesterol and protecting the cardiovascular and cerebrovascular system. Therefore, this oil has the potential to develop functional lipid products.

[0041] Table 2 Fatty acid composition of red-skin peanut oil

[0042]

[0043]

[0044] 2. Results of single-factor experiments on optimizing the extraction conditions of proanthocyanidins

[0045] The effects of extraction temperature, time, and pressure on the yield of proanthocyanidins all showed a trend of increasing first and then decreasing. The increase in temperature and the extension of extraction time were beneficial to the dissolution of proanthocyanidins, resulting in an increase in yield. However, when the time was too long and the temperature was too high, excessive heat accumulation in the extraction system would easily cause the degradation of proanthocyanidins and reduce the yield. The increase in extraction pressure was beneficial to increasing the contact frequency between the extractant and the material and accelerating the dissolution of proanthocyanidins. However, too high pressure would increase the packing density of the material in the extraction kettle and thus reduce the yield. Therefore, it was more appropriate to choose an extraction temperature of 40 °C, a pressure of 0.5 MPa, and a time of 40 min.

[0046] The effects of the solid-liquid ratio and extractant concentration on the yield also showed a trend of increasing first and then decreasing. An increase in the solid-liquid ratio could accelerate the precipitation of solutes from the raw materials. However, when the precipitation of solutes reached the highest level, continued addition of the solvent would cause the precipitation of impurities in the raw materials and reduce the yield. Too high an ethanol concentration would affect the yield. This might be because the increase in ethanol concentration increased the polarity, increased the dissolution rate of alcohol-soluble and fat-soluble components in the raw materials, and reduced the binding rate of proanthocyanidins with ethanol-water molecules, thus reducing the yield. Considering comprehensively, it was more suitable to choose a solid-liquid ratio of 1:45 and an ethanol concentration of 50%.

[0047] 3. Results of orthogonal experiments on optimizing the extraction conditions of proanthocyanidins

[0048] According to the result analysis of the following table, the influence order of each test factor is: A (material-liquid ratio) > B (temperature) > C (time) > D (pressure). Through the result analysis of the orthogonal experiment, the optimal process for the extraction of procyanidins is A3B2C3D2, that is, the material-liquid ratio is 1:50, the extraction temperature is 45 °C, the time is 40 min, and the pressure is 0.5 MPa. Extracting procyanidins according to this process, the yield is 16.18%, which is higher than that of other reported procyanidin extraction methods. Research reports show that the procyanidin content in peanut skins can reach 17%, indicating that the gradient enrichment technology developed based on the low-temperature type phase change extraction equipment can achieve the maximum enrichment of procyanidins in peanut skins, reaching a separation of 95%.

[0049] Table 2 Results of the orthogonal experiment

[0050]

[0051]

[0052] 4. Purification of procyanidins from peanut skins by AB-8 resin

[0053] The procyanidin content in the purified extract is 95.6 ± 1.23%.

[0054] 5. In vitro antioxidant evaluation of procyanidins from peanut skins

[0055] Within the experimental concentration range, the ability of procyanidins from peanut skins to scavenge DPPH free radicals increases with the increase of mass concentration. At a concentration of 2.0 mg / ml, its scavenging rate is equivalent to that of the positive control and is better than that of grape seed procyanidins at the same concentration. This shows that procyanidins from peanut skins can exhibit stronger DPPH free radical scavenging ability than grape seed procyanidins. At the same time, procyanidins from peanut skins also perform better than grape seed procyanidins in scavenging ABTS cation free radicals and show a concentration-dose relationship within the concentration range. Procyanidins from peanut skins exhibit stronger in vitro antioxidant activity than grape seed procyanidins, which may be because the low-temperature gradient enrichment technology can keep the extraction process at a lower temperature, protecting the structure and activity of procyanidins to the greatest extent.

[0056] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solutions of the present invention, rather than limitations on the specific implementation manners of the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the claims of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A method for simultaneously extracting oil and proanthocyanidins from peanut red skin, characterized in that: The steps include: S1. Put the peanut red skin powder into a continuous phase change extraction kettle, add the extractant butane to extract the oil, and the extracted oil enters the analytical kettle to recover the oil; S2, adding ethanol as an extractant to the red rice cake after oil extraction for secondary extraction, and after extraction, placing the extractant containing proanthocyanidins in a decomposition kettle, recovering the proanthocyanidins, and freeze-drying them to obtain proanthocyanidins.

2. The method for simultaneously extracting oil and proanthocyanidins from peanut red skin according to claim 1, characterized in that: The flow rate of the extractant in step S1 is 60-65 L / h.

3. The method for simultaneously extracting oil and proanthocyanidins from peanut red skin according to claim 1, characterized in that: The flow rate of the extractant in step S2 is 60-65 L / h.

4. The method for simultaneously extracting oil and proanthocyanidins from peanut red skin according to claim 1, characterized in that: The extraction temperature in step S2 is 35-40°C, the pressure is 0.1-0.5 MPa, and the time is 30-40 min.

5. The method for simultaneously extracting oil and proanthocyanidins from peanut red skin according to claim 1, characterized in that: The material-liquid ratio in step S2 is 1:40-45, and the ethanol concentration is 50%.

6. The method for simultaneously extracting oil and proanthocyanidins from peanut red skin according to claim 1, characterized in that: After crude extraction, the product was purified by AB-8 macroporous resin.

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