Peanut oil preparation method based on ethanol water extraction method and peanut oil

Abstract

The invention relates to a peanut oil preparation method based on an ethanol water extraction method and peanut oil, and the peanut oil preparation method comprises the following steps: soaking peanut kernels without red skins in a salt solution at a constant temperature, then carrying out microwave pretreatment, and then crushing by a dry method to obtain peanut powder; mixing the peanut powder with 0-40% ethanol water solution according to the mass volume ratio of 1: 1-1: 4, stirring in a water bath kettle to fully mix to obtain a peanut crude extracting solution, centrifuging the peanut crude extracting solution until no emulsion is generated and demulsification is not needed, and centrifuging to obtain free oil, namely the peanut oil; the extraction rate of the prepared peanut oil is as high as 94% or above, the obtained peanut oil is faint yellow, clear and transparent, the process operation is simplified, the subsequent demulsification cost is reduced, the extraction cost is greatly reduced by adopting an ethanol solution with relatively low concentration, and large-scale industrial production of a water extraction method is promoted.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, in particular to the technical field of peanut oil extraction, and specifically to a method for preparing peanut oil based on ethanol-water extraction and the peanut oil. Background Art

[0003] At present, the three main methods for extracting peanut oil are pressing, leaching and water extraction. Pressing is a traditional process that uses mechanical equipment to squeeze oil out of oil. There are no chemical additives in the whole process. It has strong adaptability and simple process, but there are bottlenecks such as high residual oil rate, high energy consumption, and serious denaturation of oil protein. The leaching method is a process that uses the difference in solubility of different components in organic solvents for extraction. The final recovery rate of peanut oil can reach about 94%, but there are solvent residues in the leached crude oil, the refining process is complicated, the operating cost is high, and the production safety environment requirements are strict. Therefore, traditional pressing and leaching methods cannot adapt to scientific and technological innovation and market development. The water extraction method for extracting peanut oil has mild production conditions, low energy consumption, good quality and safety of crude oil, and can obtain good peanut protein at the same time, truly realizing the synergistic improvement of sensory, safety and health quality, which can solve the above problems.

[0004] The water extraction method for peanut oil extraction mainly includes four steps: pretreatment, crushing, extraction and demulsification, which involves the process of uniform contact between water and oil, swelling of non-fat solids, release of oil, and floating of oil. After centrifugal separation, four phases are obtained: oil phase, emulsion phase (oil-rich components), water phase (soluble protein and sugar and a small amount of compounds) and solid phase (rich in protein and fiber components). However, compared with traditional methods, the mechanical shearing and calendering forces in the water extraction process are relatively gentle, which is not enough to dissociate the cell wall and the emulsion formed during the extraction process, resulting in oil and protein. The extraction rate is low, which limits the large-scale production application of water extraction.

[0005] There is no effective solution to the problems of low extraction rate of peanut oil by water extraction, high ethanol concentration in ethanol water extraction, need for demulsification, and limited large-scale production and application. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing peanut oil based on ethanol water extraction to address at least one of the shortcomings of the prior art, so as to solve the problems existing in the related art such as low extraction rate of peanut oil extracted by water extraction, high ethanol concentration used in ethanol water extraction, need for demulsification, and limited large-scale production and application. The peanut kernels are treated by microwave pretreatment after soaking the peeled peanut kernels in an inorganic salt solution and then using a low-concentration ethanol water extraction solution to treat the peanut kernels, which can synergistically reduce the formation of emulsions during the water extraction process, reduce the subsequent demulsification cost, improve the peanut oil extraction rate, and realize large-scale production.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] The first aspect of the present invention is to provide a method for preparing peanut oil based on ethanol water extraction, comprising the following steps:

[0009] Pre-treating peanuts to obtain pre-treated peanuts, wherein the moisture content of the peanuts is ≤10%, and the pre-treatment comprises any one of inorganic salt solution soaking pre-treatment and microwave pre-treatment or a combination of the two;

[0010] The pretreated peanuts are mixed with an ethanol aqueous solution in a mass volume ratio of 1:1 to 1:4 to obtain a crude peanut extract, wherein the concentration of the ethanol aqueous solution is ≤50%;

[0011] The crude peanut extract is subjected to oil-water separation treatment to obtain peanut oil, wherein the product obtained by the oil-water separation treatment does not contain emulsion, and the extraction rate of peanut oil is ≥80%.

[0012] Furthermore, the inorganic salt solution soaking pretreatment is to soak the peanuts in a 0.1-0.8 mol / L inorganic salt solution in a constant temperature incubator at 20-30° C. for 6-12 hours.

[0013] Preferably, the inorganic salt solution soaking pretreatment is to soak the peanuts in a 0.4 mol / L inorganic salt solution in a 25° C. constant temperature incubator for 6 to 8 hours.

[0014] Furthermore, the microwave treatment is intermittent heating for 2 to 5 minutes in a microwave oven with a power of 500 to 800 W.

[0015] Preferably, the microwave treatment is intermittent heating for 3 minutes in a microwave oven with a power of 720 W.

[0016] Furthermore, the intermittent heating is heating for 1 to 1.5 minutes, stopping for 1 minute, and then heating for 1 to 1.5 minutes.

[0017] Preferably, the intermittent heating is heating for 1.5 minutes, stopping for 1 minute, and then heating for 1.5 minutes.

[0018] Furthermore, the pretreated peanuts are mixed with a 20-40% ethanol aqueous solution in a mass volume ratio of 1:2.

[0019] Preferably, the pretreated peanuts are mixed with a 20% ethanol aqueous solution in a mass volume ratio of 1:2.

[0020] Furthermore, the mixing treatment is performed by stirring in a water bath at 50° C. to 70° C. at a rotation speed of 100 to 300 rpm for 30 to 150 minutes.

[0021] Preferably, the mixing treatment is stirring in a water bath at 60° C. at a rotation speed of 200 rpm for 90 minutes;.

[0022] Furthermore, the oil-water separation treatment is to centrifuge the peanut crude extract at a centrifugal force of 4000-6000×g for 10-18 minutes.

[0023] Preferably, the oil-water separation treatment is to centrifuge the peanut crude extract at 5000×g for 15 minutes.

[0024] Furthermore, the inorganic salt is any one or more combinations of KCl, NaCl, BaCl2, MgCl2, and CaCl2.

[0025] Preferably, the inorganic salt is CaCl2.

[0026] Furthermore, before pre-treating the peanuts, the method further comprises:

[0027] The peanuts are pre-processed to obtain pre-processed peanuts, wherein the pre-processing includes any one of a drying process and a peeling process or a combination of the two.

[0028] Furthermore, the drying process is to bake the peanuts in an oven at 50° C. to 55° C. for 6 to 8 hours.

[0029] Furthermore, the pulverizing process is dry pulverizing using a high-speed universal pulverizer.

[0030] Furthermore, after pre-treating the peanuts, the method further comprises:

[0031] The pretreated peanuts are crushed to obtain peanut powder.

[0032] Furthermore, the extraction rate of the peanut oil is 85% to 94%.

[0033] Preferably, the extraction rate of the peanut oil is 94%.

[0034] Furthermore, the method comprises the following steps:

[0035] S1. Baking the peanut raw material in an oven at 50° C. to 55° C. for 6 to 8 hours, followed by peeling to obtain peanut kernels without red skin and having a moisture content of less than 6%;

[0036] S2, placing the peanut kernels without red skin obtained in step S1 in a 0.4 mol / L CaCl2 solution in a constant temperature incubator at 25°C for 6 to 8 hours, and then intermittently heating them in a microwave oven with a power of 720 W for 3 minutes in a mode of heating for 1.5 minutes, stopping for 1 minute, and then heating for 1.5 minutes to obtain pretreated peanut kernels;

[0037] S3, dry-crushing the pretreated peanut kernels obtained in step S2 with a high-speed universal grinder to obtain peanut powder, then mixing the peanut powder with a 20% ethanol aqueous solution in a mass volume ratio of 1:2, and stirring the mixture in a water bath at 60° C. at a speed of 200 rpm for 90 minutes;

[0038] S4. Centrifuge the crude peanut extract obtained in step S3 at 5000×g for 15 minutes to obtain a system of free oil, water phase and residue phase, and separate the free oil to obtain peanut oil.

[0039] In a specific embodiment, the above method is performed as follows:

[0040] The peanut raw material is placed in an oven at 50°C to 55°C and baked for 6 to 8 hours to obtain peanut kernels with a moisture content of less than 6.0% and without red skin;

[0041] Weigh 50 g of peanut kernels without red skin, add 40 ml of CaCl2 solution (0.4 mol / L), soak in a constant temperature incubator at 25°C for 6 hours, put into a culture dish, and heat intermittently for 3 minutes (heat for 1.5 minutes, stop for 1 minute, and then heat for 1.5 minutes) in a microwave oven with a fixed power of 720 W to obtain pretreated peanut kernels;

[0042] Then, the pretreated peanut kernels are crushed by a high-speed universal grinder for 8 seconds to obtain peanut powder;

[0043] Then, the peanut powder was mixed with a 20% ethanol aqueous solution at a mass volume ratio of 1:2, and stirred at a speed of 200 rpm in a 60° C. water bath for 90 minutes to obtain a peanut crude extract;

[0044] The crude peanut extract is centrifuged at 5000×g for 15 minutes to obtain a system of free oil, water phase and residue phase. The free oil is separated to obtain peanut oil.

[0045] The second aspect of the present invention is to provide peanut oil prepared by the peanut oil preparation method described in the first aspect, wherein the peanut oil is light yellow and clear and transparent.

[0046] Furthermore, the fatty acid composition of the peanut oil includes palmitic acid (C16:0), palmitoleic acid (C16:1), stearic acid (C18:0), oleic acid (C18:1), linoleic acid (C18:3), arachidic acid (C20:0), arachidic acid (C20:1), behenic acid (C22:1), and lignoic acid (C24:0).

[0047] Furthermore, the fatty acid composition of the peanut oil includes 5.5% to 7% palmitic acid (C16:0), 0.03% to 0.05% palmitoleic acid (C16:1), 2% to 3% stearic acid (C18:0), 68% to 75% oleic acid (C18:1), 11% to 12% linoleic acid (C18:3), 1% to 2% arachidic acid (C20:0), 1% to 1.2% arachidic acid (C20:1), 3% to 4% behenic acid (C22:1), and 1 to 1.2% lignoic acid (C24:0).

[0048] Furthermore, the fatty acid composition of the peanut oil includes 6.37±0.11% palmitic acid (C16:0), 0.04% palmitoleic acid (C16:1), 2.38±0.03% stearic acid (C18:0), 70.95±0.20% oleic acid (C18:1), 11.62±0.15% linoleic acid (C18:3), 1.42±0.03% arachidic acid (C20:0), 1.90±0.05% arachidic acid (C20:1), 3.37±0.07% behenic acid (C22:1), and 1.95±0.05% lignic acid (C24:0).

[0049] The present invention adopts the above technical solution, and has the following technical effects compared with the prior art:

[0050] The peanut oil preparation method based on ethanol water extraction of the present invention adopts low-concentration ethanol water extraction to extract peanut oil, ethanol diffuses to the oil-water interface through molecules, and the strong hydrophilicity and moderate density of ethanol just make ethanol spread all over the oil-water interface, and at the same time have an adsorption effect on the hydrophilic end of the amphiphilic surfactant molecule, so that protein aggregates and oil droplets float; the extraction rate of peanut oil prepared by the method of the present application is as high as more than 94%, and the obtained peanut oil is light yellow, clear and transparent, and meets the good quality standard of peanut oil; and no emulsion is generated in the extraction process, and no demulsification step is required, and the free oil separated after centrifugation is peanut oil, and the operation method is simple and efficient; compared with the ethanol concentration of 45% in the traditional ethanol water extraction method, the ethanol concentration used in the present invention is only 20%, which is helpful to promote the large-scale industrial production of water extraction and has important application significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0052] Figure 1 is a distribution result diagram of peanut free oil and emulsion after different pretreatments in one embodiment of the present invention;

[0053] Figure 2It is a process flow chart of a method for separating peanut oil based on ethanol water extraction in one embodiment of the present invention;

[0054] Figure 3 is a result diagram showing the relationship between different concentrations of ethanol and free oil extraction rate in one embodiment of the present invention;

[0055] Figure 4 is a result diagram showing the relationship between different concentrations of ethanol and emulsion content in one embodiment of the present invention;

[0056] Figure 5 is a result diagram showing the relationship between the solid-liquid ratio and the free oil extraction rate in one embodiment of the present invention;

[0057] Figure 6 is a result diagram showing the relationship between extraction time and free oil extraction rate in one embodiment of the present invention;

[0058] Figure 7 This is a result diagram of the relationship between different inorganic salt solution immersion treatments and free oil extraction rates in one embodiment of the present invention. DETAILED DESCRIPTION

[0059] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without creative work belong to the scope of protection of the present invention. The experimental methods without specific conditions in the following embodiments are usually measured according to national standards. The experimental materials without the source indicated in the following embodiments are all commercially available raw materials. The equipment used in each step in the following embodiments is conventional equipment. If there is no corresponding national standard, it is carried out according to the general international standards, conventional conditions, or according to the conditions recommended by the manufacturer. Unless otherwise specified, all parts are weight parts and all percentages are mass percentages. Unless otherwise defined or specified, all professional and scientific terms used in the present invention have the same meaning as those familiar to those skilled in the art. In addition, any method and material similar or equal to the recorded content can be applied to the method of the present invention.

[0060] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention is further described below in conjunction with the drawings and specific embodiments, but is not intended to be a limitation of the present invention.

[0061] Other materials not specifically marked with manufacturers in the examples can be obtained through conventional commercial purchases.

[0062] The present invention is described below by way of example.

[0063] Example 1 - Optimizing the pretreatment method

[0064] This embodiment relates to the optimization of the peanut pretreatment method in the peanut oil preparation method based on ethanol water extraction.

[0065] In this example, the peanut raw material is subjected to the following pretreatments, and the free oil yield, oil emulsion yield and stability obtained by different pretreatments are compared to select a better pretreatment method for the peanut sample.

[0066] Step 1: bake the peanut raw material in a 50° C. oven for 8 hours, then remove the peanut skin to obtain the peanut kernel without the red skin (the moisture content of the peanut is below 6.0%).

[0067] Step 2, soaking the peanuts without red skin in salt and then pre-treating them with microwave, specifically comprising the following steps:

[0068] 1) Microwave method:

[0069] Weigh 50 grams of peanut kernels without red skin and put them into a culture dish, and heat them intermittently in a microwave oven with a fixed power of 720 W for 3 minutes (heat for 1.5 minutes, stop for 1 minute, and then heat for 1.5 minutes).

[0070] 2) Soak in CaCl2 solution and then bake at low temperature:

[0071] Weigh 50 g of peeled peanuts, add 40 ml of CaCl2 solution (0.4 mol / L), soak in a 25°C constant temperature incubator for 6 hours, and then bake in a 60°C oven for 2 hours.

[0072] 3) Microwave pretreatment after soaking in CaCl2 solution:

[0073] Weigh 50 g of peanut kernels without red skin, add 40 ml of CaCl2 solution (0.4 mol / L), soak in a constant temperature incubator at 25°C for 6 hours, and then heat intermittently in a microwave oven with a fixed power of 720 W for 3 minutes.

[0074] Step 3: Use a high-speed universal grinder to grind the peanut kernels after the above different pretreatments for 8 seconds to obtain peanut powder.

[0075] Step 4: Mix the obtained peanut powder with deionized water in a mass volume ratio of 1:2.

[0076] Step 5: Stirring at 200 rpm in a 60° C. water bath for 90 minutes to obtain a crude peanut extract.

[0077] Step 6: Centrifuge the thoroughly mixed solution at 5000×g for 15 minutes to obtain a system of free oil, emulsion, water phase and residue phase, and separate the free oil.

[0078] The results of the above different pretreatments are shown in Tables 1-2 and Figure 1 shown.

[0079] Table 1 Free oil and emulsion obtained by different pretreatments

[0080]

[0081] In the above Table 1, the peanut free oil extraction rate (%) is the mass percentage of the free oil obtained after different pretreatments in the oil contained in the raw material; the emulsion content (%) is the mass percentage of the emulsion obtained after different pretreatments in the entire extraction system.

[0082] As can be seen from Table 1, the peanut free oil extraction rate obtained by soaking the peeled peanut kernels in 0.4 mol / L CaCl2 and then performing microwave pretreatment was significantly higher than that obtained by simple microwave pretreatment and CaCl2 solution soaking followed by low-temperature baking pretreatment, and the content of the emulsion obtained by CaCl2 soaking followed by microwave pretreatment was significantly lower than that by microwave pretreatment and CaCl2 solution soaking followed by low-temperature baking pretreatment.

[0083] Table 2 Comparison of the stability of emulsions obtained by different pretreatments

[0084]

[0085] As shown in Table 2, the emulsion stability obtained by soaking the peanut kernels with 0.4 mol / L CaCl2 and then pre-treating them with microwaves is the worst, which is beneficial to reduce the formation of emulsions in the later stage and is critical to the optimization of subsequent processes.

[0086] From the above, it can be seen that when separating peanut oil based on ethanol water extraction method, by comparing the free oil yield, oil emulsion yield and stability obtained, it is found that the method of microwave pretreatment after CaCl2 immersion is better than microwave pretreatment and low-temperature baking pretreatment after CaCl2 solution immersion.

[0087] Example 2- Preparation method of peanut oil based on ethanol water extraction

[0088] This embodiment relates to a preferred method for preparing peanut oil based on ethanol-water extraction, and its process flow is as follows: Figure 2 As shown, the following steps are included:

[0089] Step 1, baking the peanut raw material in an oven at 50°C to 55°C for 6 to 8 hours, then removing the red skin to obtain peanut kernels without the red skin, wherein the moisture content of the peanut kernels without the red skin is below 6.0%.

[0090] Step 2, soaking the peanut kernels without red skin in a constant temperature incubator at 20-30°C for 6-12 hours with a 0.1-0.8 mol / L salt solution, and then intermittently heating the peanut kernels in a microwave oven at a power of 500-800 W for 2-5 minutes to obtain pretreated peanut kernels. The salt solution is one of KCl, NaCl, BaCl2, MgCl2, and CaCl2 solutions, preferably CaCl2 solution; and the intermittent heating is intermittent heating in a mode where the microwave oven runs for 1-1.5 minutes and pauses for 1 minute.

[0091] Step 3: using a high-speed universal grinder (FW-100) to dry-grind the pretreated peanut kernels to obtain peanut powder.

[0092] Step 4: Mix the obtained peanut powder with a 0-40% ethanol aqueous solution in a mass volume ratio of 1:1-1:4, and stir in a 50°C-70°C water bath at a speed of 100-300 rpm for 30-150 minutes to obtain a crude peanut extract.

[0093] Step 5: Centrifuge the fully mixed peanut crude extract at 4000-6000×g for 10-18 minutes to obtain a system consisting of only free oil, water phase and residue phase and separate the free oil.

[0094] The free oil obtained by the peanut oil preparation method of the present application does not contain emulsion and does not need to be demulsified. Therefore, the separated free oil is peanut oil.

[0095] Example 3 - Effect of different concentrations of ethanol on free oil extraction rate

[0096] This example adopts the peanut oil preparation method based on ethanol water extraction of Example 2 to explore the effect of different concentrations of ethanol on the free oil extraction rate, comprising the following steps:

[0097] Step 1, baking the peanut raw material in an oven at 50° C. for 7 hours, then removing the peanut skin to obtain the peanut kernel without the red skin;

[0098] Step 2: Soak the peanut kernels without red skin in a 0.4 mol / L CaCl2 solution for 6 hours, and then heat them intermittently in a microwave oven with a power of 720 W for 3 minutes in a mode of 1.5 minutes of operation and 1 minute of pause to obtain pretreated peanut kernels.

[0099] Step 3: dry-crush the pretreated peanut kernels using a high-speed universal grinder (FW-100) to obtain peanut powder.

[0100] Step 4: The obtained peanut powder was mixed with ethanol aqueous solutions with concentrations of 0%, 20%, 30% and 40% in a mass volume ratio of 1:2, and stirred in a 60°C water bath at a speed of 180 rpm for 90 minutes to obtain a crude peanut extract.

[0101] Step 5: Centrifuge the fully mixed peanut crude extract at 5000×g for 20 minutes to obtain a system consisting of only free oil, water phase and residue phase, and separate the free oil, which is peanut oil.

[0102] The results of the effects of different ethanol concentrations on the free oil extraction rate are shown in Figure 3 and Figure 4 As shown in the figure, it can be seen that the free oil obtained by extracting peanut oil with 20%, 30% and 40% ethanol aqueous solution is the largest, and no emulsion is formed.

[0103] Example 4 - Effect of different solid-liquid ratios on free oil extraction rate

[0104] This example is based on the peanut oil preparation method based on ethanol water extraction in Example 2, and uses 20% ethanol aqueous solution to separate peanut oil to explore the effect of different material-liquid ratios on the free oil extraction rate, comprising the following steps:

[0105] Step 1, baking the peanut raw material in an oven at 50° C. for 8 hours, then removing the peanut skin to obtain the peanut kernel without the red skin;

[0106] Step 2: Soak the peanut kernels without red skin in a 0.4 mol / L CaCl2 solution for 8 hours, and then heat them intermittently in a microwave oven with a power of 720 W for 3 minutes in a mode of 1.5 minutes of operation and 1 minute of pause to obtain pretreated peanut kernels.

[0107] Step 3: dry-crush the pretreated peanut kernels using a high-speed universal grinder (FW-100) to obtain peanut powder.

[0108] Step 4: Mix the obtained peanut powder with a 20% ethanol aqueous solution in a mass volume ratio of 1:1 to 1:4, and stir at a speed of 200 rpm in a 60°C water bath for 90 minutes to obtain a peanut crude extract. The specific material-liquid ratio is set to 1:1, 1:1.5, 1:2, 1:3 and 1:4.

[0109] Step 5: Centrifuge the fully mixed peanut crude extract at 5000×g for 15 minutes to obtain a system consisting of only free oil, water phase and residue phase, and separate the free oil, which is peanut oil.

[0110] The results are as follows Figure 5As shown in the figure, it can be seen that no emulsion is generated under the extraction conditions of solid-liquid ratios of 1:1, 1:1.5, 1:2, 1:3 and 1:4, and the peanut oil extraction rate when the solid-liquid ratio is above 1:2 is about 94%.

[0111] Example 5 - Effect of different extraction times on free oil extraction yield

[0112] This example is based on the method for preparing peanut oil based on ethanol water extraction in Example 2, wherein peanut powder is mixed with a 20% ethanol aqueous solution in a mass volume ratio of 1:2 to explore the effect of different extraction times on the free oil extraction rate, and comprises the following steps:

[0113] Step 1, baking the peanut raw material in an oven at 55° C. for 6 hours, then removing the peanut skin to obtain the peanut kernel without the red skin;

[0114] Step 2: Soak the peanut kernels without red skin in a 0.4 mol / L CaCl2 solution for 6 hours, and then heat them intermittently in a microwave oven with a power of 720 W for 3 minutes in a mode of 1.5 minutes of operation and 1 minute of pause to obtain pretreated peanut kernels.

[0115] Step 3: dry-crush the pretreated peanut kernels using a high-speed universal grinder (FW-100).

[0116] Step 4: Mix the obtained peanut powder with a 20% ethanol aqueous solution in a mass volume ratio of 1:2, and stir at a speed of 200 rpm in a 60°C water bath for 30 to 150 minutes (the specific stirring time is set to 30, 60, 90, 120, and 150 minutes, respectively) to obtain a crude peanut extract.

[0117] Step 5: Centrifuge the fully mixed peanut crude extract at 5000×g for 15 minutes to obtain a system consisting of only free oil, water phase and residue phase, and separate the free oil, which is peanut oil.

[0118] The results are as follows Figure 6 As shown in the figure, it can be seen that the free oil obtained by extracting peanut oil at an extraction time of 90 minutes or more is the largest, and no emulsion is generated at this time, and the separated free oil is peanut oil. The fatty acid composition results of the peanut oil extracted at the extraction time of 90 minutes are shown in Table 3:

[0119] Table 3 Fatty acid composition when the extraction time is 90 minutes

[0120]

[0121] Example 6 - Effect of different inorganic salt solutions on free oil extraction rate

[0122] This example is based on the peanut oil preparation method based on ethanol water extraction in Example 2, and peanut powder is mixed with a 20% ethanol aqueous solution in a mass volume ratio of 1:2 to explore the effect of different inorganic salt solutions on the free oil extraction rate.

[0123] In this application, a peanut oil preparation method using the present application is also preliminarily explored. When the inorganic salt solution is used for immersion pretreatment, the cations of the inorganic salt have a greater influence on the extraction of peanut oil. In order to keep the cation charge consistent, in this embodiment, the inorganic salt solutions are set to 0.4 mol / L CaCl2 solution, 0.8 mol / L LiCl solution, 0.8 mol / L KCl solution, 0.8 mol / L NaCl solution, 0.4 mol / L BaCl2 solution, 0.4 mol / L MgC12 solution, and 0.4 mol / L Na2CO3.

[0124] The specific steps include:

[0125] Step 1, soak the peanut kernels with red skin removed in 0.4 mol / L CaCl2 solution, 0.8 mol / L LiCl solution, 0.8 mol / L KCl solution, 0.8 mol / L NaCl solution, 0.4 mol / L BaCl2 solution, 0.4 mol / L MgCl2 solution, and 0.4 mol / L Na2CO3 solution for 6 hours, and then heat them intermittently in a microwave oven with a power of 720 W for 3 minutes in a mode of running for 1.5 minutes and pausing for 1 minute to obtain pretreated peanut kernels.

[0126] Step 2: Use a high-speed universal grinder (FW-100) to dry grind the pretreated peanut kernels.

[0127] Step 3: Mix the obtained peanut powder with a 20% ethanol aqueous solution in a mass volume ratio of 1:2, and stir in a 60° C. water bath at a speed of 200 rpm for 90 minutes to obtain a crude peanut extract.

[0128] Step 4: Centrifuge the fully mixed peanut crude extract at 5000×g for 15 minutes to obtain a system consisting of only free oil, water phase and residue phase, and separate the free oil.

[0129] The results are as follows Figure 7As shown in the figure, it can be seen that the free oil obtained by extracting peanut oil treated with BaCl2, MgC12, and CaCl2 solutions is relatively large, among which the free oil obtained by extracting peanut oil treated with 0.4 mol / L CaCl2 solution inorganic salt solution is the largest, and no emulsion is generated at this time, and the separated free oil is peanut oil.

[0130] In summary, the present invention soaks the peeled peanut kernels in a 0.4 mol / L CaCl2 solution in a constant temperature incubator at 25°C for 6 to 12 hours, then heats the kernels intermittently in a microwave oven at a power of 720 W for 3 minutes to obtain pretreated peanut kernels, then grinds the pretreated peanut kernels into powder by dry grinding, mixes the powder with a 20% ethanol aqueous solution at a mass volume ratio of 1:2, and extracts the powder in a 60°C water bath at a speed of 200 rpm for 90 minutes to obtain a crude peanut extract, and then centrifuges the crude peanut extract at a centrifugal force of 5000×g for 15 minutes to separate the peanut oil. The present application reduces the generation of emulsions during the peanut oil extraction process through the above-mentioned pretreatment, and the extraction rate of peanut oil is as high as more than 94%. The obtained peanut oil is light yellow, clear and transparent, and meets the good quality standards of peanut oil. In addition, the method for preparing peanut oil disclosed by the present invention does not generate emulsions and does not require demulsification. The separated free oil is peanut oil, which simplifies the process operation and reduces the subsequent demulsification cost. In addition, a relatively low concentration of ethanol solution is used, which greatly reduces the extraction cost and helps promote large-scale industrial production of water extraction.

[0131] The above description is only a preferred embodiment of the present invention, and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing peanut oil based on ethanol water extraction, characterized in that: The following steps are involved: Pre-treating peanuts to obtain pre-treated peanuts, wherein the moisture content of the peanuts is ≤10%, and the pre-treatment comprises any one of inorganic salt solution soaking pre-treatment and microwave pre-treatment or a combination of the two; The pretreated peanuts are mixed with an ethanol aqueous solution in a mass volume ratio of 1:1 to 1:4 to obtain a crude peanut extract, wherein the concentration of the ethanol aqueous solution is ≤50%; The crude peanut extract is subjected to oil-water separation treatment to obtain peanut oil, wherein the product obtained by the oil-water separation treatment does not contain emulsion, and the extraction rate of peanut oil is ≥80%.

2. The method for preparing peanut oil according to claim 1, wherein The inorganic salt solution soaking pretreatment is to soak the peanuts in a 0.1-0.8 mol / L inorganic salt solution in a constant temperature incubator at 20-30° C. for 6-12 hours; and / or The microwave treatment is intermittent heating for 2 to 5 minutes in a microwave oven with a power of 500 to 800 W; and / or Mixing the pretreated peanuts with a 20-40% ethanol aqueous solution in a mass volume ratio of 1:2; and / or The mixing treatment is stirring in a water bath at 50°C to 70°C at a speed of 100 to 300 rpm for 30 to 150 minutes; and / or The oil-water separation process is to centrifuge the peanut crude extract at a centrifugal force of 4000-6000×g for 10-18 minutes.

3. The method for preparing peanut oil according to claim 2, wherein The inorganic salt is any one or more of KCl, NaCl, BaCl2, MgCl2, and CaCl2; and / or The intermittent heating is heating for 1 to 1.5 minutes, stopping for 1 minute, and then heating for 1 to 1.5 minutes.

4. The method for preparing peanut oil according to claim 1, wherein Before the peanuts are pre-processed, they also include: Pre-processing the peanuts to obtain pre-processed peanuts, wherein the pre-processing includes any one of drying treatment and peeling treatment or a combination of both; and / or After the peanuts are pre-processed, it also includes: The pretreated peanuts are crushed to obtain peanut powder.

5. The method for preparing peanut oil according to claim 4, wherein The drying treatment is to bake the peanuts in an oven at 50°C to 55°C for 6 to 8 hours; and / or The pulverizing process is dry pulverizing using a high-speed universal pulverizer.

6. The method for preparing peanut oil according to claim 1, wherein The extraction rate of the peanut oil prepared by the peanut oil preparation method is 85% to 94%.

7. The method for preparing peanut oil according to claim 1, wherein The following steps are involved: S1. Baking the peanut raw material in an oven at 50° C. to 55° C. for 6 to 8 hours, followed by peeling to obtain peanut kernels without red skin and having a moisture content of less than 6%; S2, placing the peanut kernels without red skin obtained in step S1 in a 0.4 mol / L CaCl2 solution in a constant temperature incubator at 25°C for 6 to 8 hours, and then intermittently heating them in a microwave oven with a power of 720 W for 3 minutes in a mode of heating for 1.5 minutes, stopping for 1 minute, and then heating for 1.5 minutes to obtain pretreated peanut kernels; S3, dry-crushing the pretreated peanut kernels obtained in step S2 with a high-speed universal grinder to obtain peanut powder, then mixing the peanut powder with a 20% ethanol aqueous solution in a mass volume ratio of 1:2, and stirring the mixture in a water bath at 60° C. at a speed of 200 rpm for 90 minutes; S4. Centrifuge the crude peanut extract obtained in step S3 at 5000×g for 15 minutes to obtain a system of free oil, water phase and residue phase. The separated free oil is peanut oil.

8. Peanut oil prepared by the method for preparing peanut oil according to any one of claims 1 to 7, characterized in that: The peanut oil is light yellow and clear and transparent.

9. Peanut oil according to claim 8, characterized in that The fatty acid composition of the peanut oil includes palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, arachidic acid, arachidic acid, behenic acid and lignoic acid.

10. Peanut oil according to claim 9, characterized in that The fatty acid composition of the peanut oil comprises 5.5% to 7% palmitic acid, 0.03% to 0.05% palmitoleic acid, 2% to 3% stearic acid, 68% to 75% oleic acid, 11% to 12% linoleic acid, 1% to 2% arachidic acid, 1% to 1.2% arachidic acid, 3% to 4% behenic acid and 1% to 1.2% lignoic acid.

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