Flaxseed microwave-assisted wall breaking and nitrogen protection cold pressing process

Abstract

The invention relates to the technical field of grain and oil processing, in particular to a flaxseed microwave-assisted wall breaking and nitrogen protection cold pressing process. The method comprises the following steps: putting flaxseeds into a microwave bin, carrying out intermittent microwave treatment, and carrying out blank rolling treatment on the flaxseeds by adopting a double-helix blank rolling mill to obtain crude oil; and after degumming, deacidifying, decolorizing and deodorizing the crude oil, filtering the crude oil to obtain refined oil. According to the method, the flaxseed cell wall rupture rate is increased through microwave pretreatment, more grease can be released, the grease flow resistance can be reduced, the released grease can be rapidly separated from a fiber network and resorption is reduced through a nitrogen-assisted pressing mode, and after first-time cold pressing, oil cakes are subjected to secondary microwave treatment, so that the flaxseed oil yield is improved. The method can further destroy residual cell structures, and can prevent oil cake hardening caused by oxidation under the protection of nitrogen, so that the oil yield during secondary repressing is increased.

Description

Technical Field

[0001] The invention relates to the technical field of grain and oil processing, in particular to a sesame seed microwave-assisted wall breaking and nitrogen-protected cold pressing process. Background Art

[0002] Sesame seeds, also known as sesame kernels, are the mature seeds of the sesame plant of the Pedulaceae family. Sesame oil is an edible oil extracted from sesame seeds. Sesame oil is rich in protein, unsaturated fatty acids, vitamin A, vitamin E, lecithin, as well as calcium, phosphorus, iron and other minerals. Moderate consumption can effectively provide the human body with essential nutrients and help maintain good health.

[0003] For example, CN106118863A relates to a process for producing rapeseed oil by direct cold rolling, which specifically includes the following steps:

[0004] (1) Rapeseed air separation; (2) Rapeseed screening; (3) Rapeseed magnetic separation; (4) Rapeseed flaking; (5) Cold pressing: Place the rapeseed flakes in step (4) into a cold press, and control the temperature in the cold press chamber to 60-70°C, and control the moisture content of the rapeseed flakes to 10-15% during cold pressing, and perform secondary re-pressing on the oil cake after cold pressing to obtain cold-pressed rapeseed oil. Secondary re-pressing can increase the oil yield of cold pressing; (6) Oil cake leaching; (7) filtration; (8) Decolorization. The rapeseed oil cold-pressed by this processing technology has bright color and is rich in various nutrients, avoiding the problem of some proteins rich in rapeseed deteriorating during the processing process.

[0005] However, compared with rapeseed, the seed coat of sesame seed is thicker and rich in lignified fiber, and its cell wall structure is denser than that of rapeseed. The mechanical force of conventional rolling is not enough to effectively destroy the cell wall, resulting in a low wall breaking rate. Insufficiently broken cells will significantly reduce the cold pressing oil yield. In addition, sesame seed oil is mainly stored in subcellular organelles and requires higher mechanical shear force to release. The rolling parameters of the above process, such as roller gap and pressure, are not optimized for sesame seeds, which easily leads to oil residue in the oil cake. Therefore, the effect of using the above processing technology for sesame seed cold pressing is not ideal. Summary of the Invention

[0006] The invention aims to solve the problem that the oil yield is low and the sesame seed cold pressing effect is unsatisfactory due to incomplete wall breaking during sesame seed cold pressing.

[0007] The purpose of the present invention is to provide a sesame seed microwave-assisted wall breaking and nitrogen-protected cold pressing process, which solves the dual problems of incomplete wall breaking and oxidation loss in sesame seed cold pressing through the synergistic effect of microwaves and nitrogen, thereby improving the cold-pressing oil yield of sesame seeds.

[0008] To achieve the above object, the present invention provides a sesame seed microwave-assisted wall breaking and nitrogen-protected cold pressing process, comprising the following steps:

[0009] Step S1: Sesame seeds are subjected to air separation, screening and magnetic separation to remove impurities, and then the empty shells in the sesame seeds are separated by flotation;

[0010] The sesame seeds are then adjusted to 12-15% moisture content and the moisture distribution is balanced using a low-temperature tempering machine.

[0011] Step S2: placing sesame seeds into a microwave chamber, and introducing nitrogen into the microwave chamber to replace oxygen until the oxygen concentration in the microwave chamber is less than 1%;

[0012] After subjecting the sesame seeds in the microwave chamber to intermittent microwave treatment for 3-5 minutes, the sesame seeds are taken out;

[0013] Step S3: In a nitrogen-protected environment, the sesame seeds are subjected to a flaking process using a double-screw flaking mill to obtain crude oil;

[0014] The oil residue after the first cold pressing is treated with microwave for the second time and then re-pressed to obtain residual crude oil;

[0015] Step S4: transferring the cold-pressed crude oil into a nitrogen-filled storage tank, and then subjecting the crude oil to degumming, deacidification, decolorization, and deodorization processes;

[0016] Finally, the crude oil is filtered to obtain refined oil and sealed in a light-proof ceramic bottle or aluminum foil bag filled with nitrogen.

[0017] As a further improvement of the present technical solution, in step S1, clean water is sprayed on the sesame seeds, and then brine is prepared in a double-layer inclined flotation tank. The sesame seeds are put into the double-layer inclined flotation tank. After standing and stratification, the upper overflow port collects the empty shells, and the lower discharge port collects the full sesame seeds.

[0018] As a further improvement of this technical solution, the density of the brine is 1.05-1.10 g / cm 3 .

[0019] As a further improvement of the present technical solution, in step S1, the moisture adjustment method is to dehydrate the sesame seeds through a centrifugal dehydrator, and the rotation speed of the centrifugal dehydrator is 1000-1200 rpm, and the processing time is 3-5 minutes.

[0020] As a further improvement of the present technical solution, in step S2, the power during the intermittent microwave treatment is set to 800-1000W.

[0021] As a further improvement of the present technical solution, in step S3, the roller pressing gap of the twin-screw slab rolling mill is 0.1-0.2 mm.

[0022] As a further improvement of the present technical solution, in step S3, during the slab rolling process, the pressing chamber temperature of the twin-screw slab rolling mill is ≤60°C, and nitrogen is continuously injected into the pressing chamber to maintain an oxygen concentration of <2%.

[0023] As a further improvement of the present technical solution, in step S4, the nitrogen-filled storage tank is equipped with a nitrogen blanket, a pressure balancing valve is installed on the top, and the temperature inside the nitrogen-filled storage tank is 25-30°C.

[0024] As a further improvement of the present technical solution, in step S4, the degumming is performed by adding 70-75°C hot water to the crude oil and stirring for 20 minutes to allow the phospholipids to absorb water and condense to form colloid, and nitrogen is continuously introduced during the degumming process, and the colloid is separated by a disc centrifuge under a nitrogen environment;

[0025] As a further improvement of the present technical solution, in step S4, the filtration temperature during the crude oil filtration is 8-15°C.

[0026] In the present invention, a microwave-nitrogen synergistic wall breaking mechanism is utilized. The thermal effect and non-thermal effects such as electromagnetic field oscillation generated by microwaves directionally destroy the lignin-cellulose composite structure, while nitrogen protection reduces oxidation side reactions, thereby improving the wall breaking efficiency and thus increasing the oil yield.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] In the sesame seed microwave-assisted wall breaking and nitrogen-protected cold pressing process, the sesame seed cell wall rupture rate is increased through microwave pretreatment, which can release more oil, and the nitrogen-assisted pressing method can reduce the oil flow resistance, so that the released oil can quickly break away from the fiber network and reduce back-absorption. After the first cold pressing, the oil cake is subjected to a secondary microwave treatment, which can further destroy the residual cell structure, and under nitrogen protection, it can prevent the oil cake from hardening due to oxidation, thereby increasing the oil yield during the secondary pressing. The synergistic effect of microwave-assisted wall breaking and nitrogen protection forms a "wall breaking-release-protection" closed loop, which improves the cold-pressed oil yield of sesame seeds. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Flowchart of the present invention. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0031] See also Figure 1 As shown, the present invention aims to provide a sesame seed microwave-assisted wall breaking and nitrogen-protected cold pressing process, comprising the following steps:

[0032] Step S1: Sesame seeds are subjected to air separation, screening and magnetic separation to remove impurities, and then the empty shells in the sesame seeds are separated by flotation. Specifically, the density difference between the full sesame seeds and the empty shells is used to adjust the density of the liquid medium so that the light empty shells float up and the heavy full seeds sink, thereby achieving efficient separation. A small amount of clean water is sprayed on the sesame seeds (humidity is increased by 3-5%) to increase the surface tension difference between the empty shells and the full seeds, thereby improving the flotation sensitivity. Then, a double-layer inclined flotation tank (made of stainless steel or corrosion-resistant PVC) is configured with a density of 1.05-1.10 g / cm 3 The sesame seeds are put into a double-layer inclined flotation tank with salt water. After standing and stratification, the light shriveled shells overflow with the liquid surface to the collection tank, and the plump seeds settle to the bottom. The upper overflow port collects the shriveled shells, and the lower discharge port collects the plump sesame seeds.

[0033] The sesame seeds are then dehydrated by a centrifugal dehydrator to adjust the moisture content to 12-15%. The speed of the centrifugal dehydrator is 1000-1200 rpm, and the processing time is 3-5 minutes. A low-temperature tempering machine (≤40°C) is then used to balance the moisture distribution and enhance the penetration of subsequent microwave treatment.

[0034] Step S2: putting sesame seeds into a microwave chamber, and introducing nitrogen (purity ≥ 99.9%) into the microwave chamber to replace oxygen until the oxygen concentration in the microwave chamber is less than 1%, so as to prevent high-temperature local oxidation reaction.

[0035] After the sesame seeds in the microwave chamber are subjected to intermittent microwave treatment (frequency 2450MHz) for 3-5 minutes, the sesame seeds are taken out. The power during the intermittent microwave treatment is set to 800-1000W. Under this condition, the lignified seed coat of the sesame seeds can be effectively softened, the cell wall structure can be destroyed, and the oxidation of heat-sensitive components such as α-linolenic acid can be avoided.

[0036] Step S3: In a nitrogen-protected environment, a twin-screw flaking mill is used to flak the sesame seeds to obtain crude oil, thereby reducing the exposure of the oil to oxygen during the flaking process. The roller gap of the twin-screw flaking mill is 0.1-0.2 mm, and during the flaking process, the pressing chamber temperature of the twin-screw flaking mill is ≤60°C, the pressure gradient is controlled in stages (initial pressure 10 MPa, final pressure 25 MPa), and nitrogen is continuously injected into the pressing chamber to maintain an oxygen concentration of less than 2%, thereby reducing the risk of oil oxidation.

[0037] The oil residue after the first cold pressing was subjected to a second microwave treatment (power 500W, time 2min) to further destroy the residual cell structure, and then re-pressed to obtain the residual crude oil.

[0038] Step S4: Immediately transfer the cold-pressed crude oil to a nitrogen-filled storage tank (oxygen concentration <1%), wherein the nitrogen-filled storage tank is equipped with a nitrogen blanket and a pressure-balancing valve on the top. The temperature in the nitrogen-filled storage tank is maintained at 25-30° C. to prevent the oil from coming into contact with oxygen and causing rancidity. The crude oil is then subjected to degumming, deacidification, decolorization, and deodorization processes. The degumming process comprises adding 70-75° C. hot water (2-3% by weight of the oil) to the crude oil and stirring at a low speed (30-40 rpm) for 20 minutes to allow the phospholipids to absorb water and condense to form a colloid. During the degumming process, nitrogen is continuously introduced (at a flow rate of 5-8 L / min) to prevent the phospholipids from oxidizing and turning black. The colloid is separated by a disc centrifuge (at a speed of 6000-8000 rpm) under a nitrogen atmosphere.

[0039] Finally, the crude oil is filtered to obtain refined oil and sealed in a light-proof ceramic bottle or an aluminum foil bag filled with nitrogen. The filtration temperature during crude oil filtration is 8-15°C.

[0040] The following specific examples are used to further illustrate the sesame seed microwave-assisted wall breaking and nitrogen-protected cold pressing process provided by the present invention.

[0041] Example 1

[0042] This example proposes a sesame seed microwave-assisted wall breaking and nitrogen-protected cold pressing process, and the specific steps are as follows:

[0043] Step S1: Sesame seeds are subjected to air separation, screening and magnetic separation to remove impurities, and then the shrunken shells in the sesame seeds are separated by flotation. Specifically, a small amount of clean water is sprayed on the sesame seeds, and then a double-layer inclined flotation tank with a density of 1.05g / cm is placed. 3 The sesame seeds are put into a double-layer inclined flotation tank with salt water. After standing and stratification, the upper overflow port collects the empty shells and the lower discharge port collects the full sesame seeds.

[0044] The sesame seeds were then dehydrated by a centrifugal dehydrator to adjust the moisture content of the sesame seeds to 15%, and the speed of the centrifugal dehydrator was 1000 rpm, the processing time was 5 minutes, and then a low-temperature tempering machine (≤40° C.) was used to balance the moisture distribution.

[0045] Step S2: putting sesame seeds into a microwave chamber, and introducing nitrogen (purity ≥ 99.9%) into the microwave chamber to replace oxygen until the oxygen concentration in the microwave chamber is less than 1%.

[0046] The sesame seeds in the microwave chamber were subjected to intermittent microwave treatment (frequency 2450 MHz) for 3 minutes, and then the sesame seeds were taken out. The power of the intermittent microwave treatment was set to 1000 W.

[0047] Step S3: In a nitrogen-protected environment, sesame seeds are subjected to flaking treatment using a twin-screw flaking mill to obtain crude oil. The roller gap of the twin-screw flaking mill is 0.1 mm. During the flaking treatment, the pressing chamber temperature of the twin-screw flaking mill is ≤60°C, the pressure gradient is controlled in stages (initial pressure 10 MPa, final pressure 25 MPa), and nitrogen is continuously injected into the pressing chamber to maintain an oxygen concentration of <2%.

[0048] The oil residue after the first cold pressing was subjected to a second microwave treatment (power 500 W, time 2 min) and then re-pressed to obtain the residual crude oil.

[0049] Step S4: The crude oil obtained after the cold pressing is immediately transferred to a nitrogen-filled storage tank (oxygen concentration <1%), the nitrogen-filled storage tank is equipped with a nitrogen blanket, a pressure balance valve is installed on the top, and the temperature in the nitrogen-filled storage tank is 30° C., and then the crude oil is subjected to degumming, deacidification, decolorization, and deodorization processes. The degumming process is performed by adding 70° C. hot water to the crude oil and stirring at a low speed for 20 minutes to allow the phospholipids to absorb water and condense to form colloid, and nitrogen is continuously introduced during the degumming process, and the colloid is separated by a disc centrifuge under a nitrogen environment.

[0050] Finally, the crude oil is filtered to obtain refined oil and sealed in a light-proof ceramic bottle or an aluminum foil bag filled with nitrogen. The filtration temperature during crude oil filtration is 15°C.

[0051] Example 2

[0052] This example proposes a sesame seed microwave-assisted wall breaking and nitrogen-protected cold pressing process, and the specific steps are as follows:

[0053] Step S1: Sesame seeds are subjected to air separation, screening and magnetic separation to remove impurities, and then the shrunken shells in the sesame seeds are separated by flotation. Specifically, a small amount of clean water is sprayed on the sesame seeds, and then a double-layer inclined flotation tank with a density of 1.05g / cm is placed. 3 The sesame seeds are put into a double-layer inclined flotation tank with salt water. After standing and stratification, the upper overflow port collects the empty shells and the lower discharge port collects the full sesame seeds.

[0054] The sesame seeds were then dehydrated by a centrifugal dehydrator to adjust the moisture content to 15%, with the speed of the centrifugal dehydrator being 1100 rpm and the processing time being 4 minutes. The moisture distribution was then balanced by a low-temperature tempering machine (≤40° C.).

[0055] Step S2: putting sesame seeds into a microwave chamber, and introducing nitrogen (purity ≥ 99.9%) into the microwave chamber to replace oxygen until the oxygen concentration in the microwave chamber is less than 1%.

[0056] The sesame seeds in the microwave chamber were subjected to intermittent microwave treatment (frequency 2450 MHz) for 4 minutes, and then the sesame seeds were taken out. The power of the intermittent microwave treatment was set to 9000 W.

[0057] Step S3: In a nitrogen-protected environment, sesame seeds are subjected to flaking treatment using a twin-screw flaking mill to obtain crude oil. The roller gap of the twin-screw flaking mill is 0.1 mm. During the flaking treatment, the pressing chamber temperature of the twin-screw flaking mill is ≤60°C, the pressure gradient is controlled in stages (initial pressure 10 MPa, final pressure 25 MPa), and nitrogen is continuously injected into the pressing chamber to maintain an oxygen concentration of <2%.

[0058] The oil residue after the first cold pressing was subjected to a second microwave treatment (power 500 W, time 2 min) and then re-pressed to obtain the residual crude oil.

[0059] Step S4: The crude oil obtained after the cold pressing is immediately transferred to a nitrogen-filled storage tank (oxygen concentration <1%), the nitrogen-filled storage tank is equipped with a nitrogen blanket, a pressure balance valve is installed on the top, and the temperature in the nitrogen-filled storage tank is 25° C., and then the crude oil is subjected to degumming, deacidification, decolorization, and deodorization processes. The degumming process is to add 75° C. hot water to the crude oil and stir at a low speed for 20 minutes to allow the phospholipids to absorb water and condense to form colloid, and nitrogen is continuously introduced during the degumming process, and the colloid is separated by a disc centrifuge under a nitrogen environment.

[0060] Finally, the crude oil is filtered to obtain refined oil and sealed in a light-proof ceramic bottle or an aluminum foil bag filled with nitrogen. The filtration temperature during crude oil filtration is 10°C.

[0061] Example 3

[0062] This example proposes a sesame seed microwave-assisted wall breaking and nitrogen-protected cold pressing process, and the specific steps are as follows:

[0063] Step S1: Sesame seeds are subjected to air separation, screening and magnetic separation to remove impurities, and then the shrunken shells in the sesame seeds are separated by flotation. Specifically, a small amount of clean water is sprayed on the sesame seeds, and then a double-layer inclined flotation tank with a density of 1.10 g / cm is placed. 3 The sesame seeds are put into a double-layer inclined flotation tank with salt water. After standing and stratification, the upper overflow port collects the empty shells and the lower discharge port collects the full sesame seeds.

[0064] The sesame seeds were then dehydrated by a centrifugal dehydrator to adjust the moisture content of the sesame seeds to 12%, and the speed of the centrifugal dehydrator was 1200 rpm, the processing time was 3 minutes, and then a low-temperature tempering machine (≤40° C.) was used to balance the moisture distribution.

[0065] Step S2: putting sesame seeds into a microwave chamber, and introducing nitrogen (purity ≥ 99.9%) into the microwave chamber to replace oxygen until the oxygen concentration in the microwave chamber is less than 1%.

[0066] The sesame seeds in the microwave chamber were subjected to intermittent microwave treatment (frequency 2450 MHz) for 5 minutes, and then the sesame seeds were taken out. The power of the intermittent microwave treatment was set to 800 W.

[0067] Step S3: In a nitrogen-protected environment, sesame seeds are subjected to flaking treatment using a twin-screw flaking mill to obtain crude oil. The roller gap of the twin-screw flaking mill is 0.2 mm. During the flaking treatment, the pressing chamber temperature of the twin-screw flaking mill is ≤60°C, the pressure gradient is controlled in stages (initial pressure 10 MPa, final pressure 25 MPa), and nitrogen is continuously injected into the pressing chamber to maintain an oxygen concentration of <2%.

[0068] The oil residue after the first cold pressing was subjected to a second microwave treatment (power 500 W, time 2 min) and then re-pressed to obtain the residual crude oil.

[0069] Step S4: The crude oil obtained after the cold pressing is immediately transferred to a nitrogen-filled storage tank (oxygen concentration <1%), the nitrogen-filled storage tank is equipped with a nitrogen blanket, a pressure balance valve is installed on the top, and the temperature in the nitrogen-filled storage tank is 25° C., and then the crude oil is subjected to degumming, deacidification, decolorization, and deodorization processes. The degumming process is to add 75° C. hot water to the crude oil and stir at a low speed for 20 minutes to allow the phospholipids to absorb water and condense to form colloid, and nitrogen is continuously introduced during the degumming process, and the colloid is separated by a disc centrifuge under a nitrogen environment.

[0070] Finally, the crude oil is filtered to obtain refined oil and sealed in a light-proof ceramic bottle or an aluminum foil bag filled with nitrogen. The filtration temperature during the crude oil filtration is 8°C.

[0071] The original oil content (dry basis) of sesame seeds was determined by Soxhlet extraction. The sesame seeds were accurately weighed before cold pressing and converted to dry basis. The sesame seeds were then processed according to the cold pressing process provided in Examples 1-3. The refined oil was weighed and the oil yield was calculated (oil yield = refined oil weight / (total sesame seed weight × original sesame seed oil content) × 100%). The results are recorded in Table 1.

[0072] Table 1 Oil yield of cold pressing process of Examples 1-3

[0073] Example 1 Example 2 Example 3 Oil yield / % 39 40 38

[0074] According to Table 1, the oil yield of the sesame seeds cold-pressed according to Examples 1-3 is not less than 38%, indicating that the sesame seed microwave-assisted wall breaking and nitrogen-protected cold pressing process provided by the present invention has a high oil yield.

[0075] In the present invention, microwave pretreatment is used to increase the rupture rate of sesame seed cell walls, thereby releasing more oil. Nitrogen-assisted pressing is used to reduce oil flow resistance, allowing the released oil to quickly detach from the fiber network and reduce back-absorption. After the first cold pressing, the oil cake is subjected to a secondary microwave treatment, which can further destroy the residual cell structure. Under nitrogen protection, the oil cake can be prevented from hardening due to oxidation, thereby increasing the oil yield during the secondary re-pressing. That is, microwave-assisted cell wall breaking directionally destroys the sesame seed cell walls through a physical-thermodynamic mechanism to release the encapsulated oil; nitrogen protection inhibits oxidation from a chemical level and improves oil fluidity. The two work synergistically to form a "wall breaking-release-protection" closed loop, thereby increasing the cold-pressed oil yield of sesame seeds.

[0076] Example 4

[0077] In the present invention, microwave pretreatment causes polar molecules such as water and oil inside sesame seeds to vibrate at high frequencies, generating frictional heat, causing the local temperature of the cell wall to instantly rise to 80-100°C. Furthermore, when microwaves act on the substance, a high-frequency alternating electromagnetic field is formed inside the substance. This electromagnetic field can cause the molecular chains of the cellulose-lignin complex to break, further reducing the mechanical strength of the cell wall. The dense seed coat and cell wall of the sesame seeds are directionally destroyed, opening the oil channels and making it easier for the oil encapsulated in subcellular organelles such as oil bodies to be released.

[0078] Microwave heating evenly distributes moisture inside the sesame seeds, softens the material, and makes it easier to form thin and uniform sheets (thickness ≤ 0.2mm) during billet rolling, increasing the contact area for pressing. Microwave treatment also reduces oil viscosity by 20-30% (due to intensified molecular thermal motion), making it easier for oil to flow out of the intercellular spaces during cold pressing, reducing residue and increasing the oil yield of sesame seeds during cold pressing.

[0079] In order to determine that the intermittent microwave treatment step is one of the important steps in the sesame seed cold pressing process provided by the present invention to achieve a higher oil yield, this example is based on the above Example 1, but lacks the intermittent microwave treatment step or replaces the intermittent microwave treatment step with a heating treatment at 40°C or 50°C for 5 minutes, and then the sesame seeds are cold pressed. The cold pressing oil yield of the sesame seeds is calculated according to the test method provided in the above example, and the results are shown in Table 2.

[0080] Table 2 Comparison of sesame seed cold pressing oil yield

[0081]

[0082] According to Table 2, compared with Example 1, when the intermittent microwave treatment is missing or the intermittent microwave treatment is replaced by heating treatment at 40°C or 50°C for 5 min, the cold-pressing oil yield of sesame seeds is significantly reduced. Therefore, it can be seen that the intermittent microwave treatment step is one of the important steps for the sesame seed cold-pressing process provided by the present invention to have a high oil yield.

[0083] Secondly, in order to determine that the 3-5 min treatment time of the intermittent microwave treatment is one of the important factors for the sesame seed cold pressing process provided by the present invention to have a higher oil yield, on the basis of the above Example 1, only the treatment time was changed, and the treatment time of the intermittent microwave treatment was set to 1 min, 2 min, 3 min, 4 min, 5 min or 6 min, and then the sesame seeds were cold pressed. The cold pressing oil yield of the sesame seeds was calculated according to the test method provided in the above embodiment, and the results are shown in Table 3.

[0084] Table 3 Comparison of cold-pressed oil yield of sesame seeds at different processing times

[0085] Intermittent microwave treatment time / min 1 2 3 4 5 6 Oil yield / % 31 33 39 40 39 32

[0086] According to Table 3, when the intermittent microwave treatment time is 1 min, 2 min or 6 min, the cold-pressing oil yield of sesame seeds is significantly lower than the cold-pressing oil yield of sesame seeds when the intermittent microwave treatment time is 3 min, 4 min or 5 min. Therefore, it can be seen that the intermittent microwave treatment time of 3-5 min is one of the important factors for the sesame seed cold-pressing process provided by the present invention to have a higher oil yield.

[0087] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and improvements fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. The sesame seed microwave-assisted wall breaking and nitrogen-protected cold pressing process is characterized by: The following steps are involved: Step S1: Sesame seeds are subjected to air separation, screening and magnetic separation to remove impurities, and then the empty shells in the sesame seeds are separated by flotation; The sesame seeds are then adjusted to 12-15% moisture content and the moisture distribution is balanced using a low-temperature conditioning machine. Step S2: placing sesame seeds into a microwave chamber, and introducing nitrogen into the microwave chamber to replace oxygen until the oxygen concentration in the microwave chamber is less than 1%; After subjecting the sesame seeds in the microwave chamber to intermittent microwave treatment for 3-5 minutes, the sesame seeds are taken out; Step S3: In a nitrogen-protected environment, the sesame seeds are subjected to a flaking process using a double-screw flaking mill to obtain crude oil; The oil residue after the first cold pressing is treated with microwave for the second time and then re-pressed to obtain the residual crude oil; Step S4: transferring the cold-pressed crude oil into a nitrogen-filled storage tank, and then subjecting the crude oil to degumming, deacidification, decolorization, and deodorization processes; Finally, the crude oil is filtered to obtain refined oil and sealed in a light-proof ceramic bottle or aluminum foil bag filled with nitrogen.

2. The sesame seed microwave-assisted wall breaking and nitrogen-protected cold pressing process according to claim 1, characterized in that: In step S1, clean water is sprayed on the sesame seeds, and then salt water is prepared in a double-layer inclined flotation tank. The sesame seeds are put into the double-layer inclined flotation tank, and after standing and stratification, the upper overflow port collects the empty shells, and the lower discharge port collects the full sesame seeds.

3. The sesame seed microwave-assisted wall breaking and nitrogen-protected cold pressing process according to claim 2, characterized in that: The density of the brine is 1.05-1.10 g / cm 3 .

4. The sesame seed microwave-assisted wall breaking and nitrogen-protected cold pressing process according to claim 1, characterized in that: In step S1, the moisture content is adjusted by dehydrating the sesame seeds using a centrifugal dehydrator, with the rotation speed of the centrifugal dehydrator being 1000-1200 rpm and the processing time being 3-5 minutes.

5. The sesame seed microwave-assisted wall breaking and nitrogen-protected cold pressing process according to claim 1, characterized in that: In step S2, the power of the intermittent microwave treatment is set to 800-1000W.

6. The sesame seed microwave-assisted wall breaking and nitrogen-protected cold pressing process according to claim 1, characterized in that: In step S3, the roller gap of the twin-screw rolling mill is 0.1-0.2 mm.

7. The sesame seed microwave-assisted wall breaking and nitrogen-protected cold pressing process according to claim 1, characterized in that: In step S3, during the rolling process, the temperature of the pressing chamber of the twin-screw rolling mill is ≤60° C., and nitrogen is continuously injected into the pressing chamber to maintain the oxygen concentration less than 2%.

8. The sesame seed microwave-assisted wall breaking and nitrogen-protected cold pressing process according to claim 1, characterized in that: In step S4, the nitrogen-filled storage tank is equipped with a nitrogen blanket, a pressure balancing valve is installed on the top, and the temperature in the nitrogen-filled storage tank is 25-30°C.

9. The sesame seed microwave-assisted wall breaking and nitrogen-protected cold pressing process according to claim 1, characterized in that: In step S4, degumming is performed by adding 70-75° C. hot water to the crude oil and stirring for 20 minutes to allow the phospholipids to absorb water and condense to form colloids, and nitrogen is continuously introduced during the degumming process, and the colloids are separated by a disc centrifuge under a nitrogen environment.

10. The sesame seed microwave-assisted wall breaking and nitrogen-protected cold pressing process according to claim 1, characterized in that: In step S4, the crude oil is filtered at a temperature of 8-15°C.

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