Method for preparing soybean oil through cold pressing

Abstract

The invention discloses a method for preparing soybean oil through cold pressing, and belongs to the technical field of oil preparation through cold pressing, the method for preparing soybean oil through cold pressing comprises the following steps: step 1, soybean pretreatment: soybeans are dried with hot air until the moisture content is 8-11%, cooling and peeling are carried out, peeled soybeans are obtained, and cold storage is carried out; step 2, squeezing treatment: squeezing the peeled soybeans by adopting a double-helix oil press, and controlling squeezing parameters to obtain crude oil; the squeezing parameters comprise squeezing time, squeezing rotating speed and cake outlet diameter; and step 3, impurity removal: performing centrifugal impurity removal on the crude oil to obtain the soybean oil. According to the method, the cold pressing technology is improved, the yield of the soybean oil is increased, meanwhile, the quality of the oil product is improved, the production method is completely a physical process, no processing agent is added, and nutrient substances of the soybean oil are effectively kept.

Description

Technical Field

[0001] The invention belongs to the technical field of cold-pressing oil production, and particularly relates to a method for preparing soybean oil by cold-pressing. Background Art

[0002] Cold pressing is to squeeze oil out of raw materials quickly with the help of mechanical force at a temperature below 80℃. During the cold pressing process, the oil seeds mainly undergo physical changes, such as material deformation and oil separation. Compared with the leaching method, the green oil products obtained by the cold pressing process can avoid contact with harmful substances such as solvents, alkali solutions, and bleaching clay; compared with the hot pressing process, the nutrients in the oil are retained to the maximum extent, greatly improving the nutritional value of the oil.

[0003] CN101911983A discloses a method for performing microwave treatment on oil-bearing crop seeds before cold-pressing oil production, wherein the oil-bearing crop seeds include soybeans, and specifically comprises the following steps: (1) adjusting the mass water content of the oil-bearing crop seeds to 7%-30% and stirring them evenly; (2) then evenly spreading the oil-bearing crop seeds after adjusting the water content in a container, adjusting the microwave power and microwave time, and performing microwave treatment on the oil-bearing crop seeds so that the final temperature reaches 80°C-150°C; (3) spreading the microwave-treated oil-bearing crop seeds to cool them, and then cold-pressing them to produce oil or peeling and cold-pressing them to produce oil. The method is beneficial to improving the yield of cold-pressed oil and the quality of cold-pressed oil after treating soybeans.

[0004] Yan Shengkun et al. (Optimization of Low-temperature Cold-pressed Walnut Oil Process and Main Pressing Parameters [J], Agricultural Engineering, January 2010, Vol. 10, No. 1, 48-52) compared the effects of material particle size on oil yield and the main process parameters of low-temperature spiral cold press (discharge diameter and pressing shaft speed) on walnut oil cake residual oil rate and pressing efficiency, and obtained the optimal process conditions for the key technology of walnut oil cold pressing: walnut kernel particle size 10mm, pressing temperature 35℃, inlet moisture 8%, pressing shaft speed 60r / min and discharge diameter 6mm. Under this process condition, the walnut oil yield can reach 40%. Although this invention improves the oil yield, it does not examine the quality of the oil.

[0005] Existing cold-pressed soybean oil generally has problems such as low oil yield. Therefore, it is urgent to develop a cold-pressing oil production method with high oil yield and good oil stability. Summary of the invention

[0006] The invention provides a method for preparing soybean oil by cold pressing. By improving the cold pressing process, the yield of soybean oil is increased while the quality of the oil product is improved. The production method is a completely physical process without adding any processing aids, and the nutrients of the soybean oil are effectively maintained.

[0007] In order to achieve the above-mentioned purpose of the present invention, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing soybean oil by cold pressing, comprising the following steps:

[0009] Step 1: Soybean pretreatment

[0010] Drying the soybeans with hot air until the moisture content is 8-11%, cooling and peeling, and refrigerating to obtain peeled soybeans;

[0011] Step 2: Pressing

[0012] The dehulled soybeans are pressed by a double-screw oil press, and the pressing parameters are controlled to obtain crude oil;

[0013] The pressing parameters include pressing time, pressing speed and cake outlet diameter;

[0014] Step 3: Remove impurities

[0015] The crude oil is centrifuged to remove impurities to obtain soybean oil.

[0016] Preferably, the drying in step 1 is: hot air drying at 70-80°C for 2-3h; more preferably 75°C.

[0017] Preferably, the moisture content in step 1 is 9-10%; more preferably 9.7%.

[0018] Preferably, the refrigeration in step 1 is placed at 0-4°C for 2-8 hours; preferably placed at 4°C for 6 hours.

[0019] Preferably, the cooling in step 1 is: cooling to room temperature.

[0020] Preferably, the pressing time in step 2 is 3-5 min, the pressing speed is 60-80 r / min, and the cake outlet diameter is 6-10 mm; further preferably, the pressing time is 3-4 min, the pressing speed is 60-70 r / min, and the cake outlet diameter is 7-10 mm; further preferably, the pressing time is 4 min, the pressing speed is 63 r / min, and the cake outlet diameter is 7.6 mm.

[0021] Preferably, the centrifugation in step 3 is 4000-8000 r / min, centrifuged at room temperature for 15-25 min; more preferably, it is 6000 r / min, centrifuged at 20°C for 20 min.

[0022] The invention also provides application of the preparation method in increasing the linoleic acid content in soybean oil.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The oil extracted by the present invention effectively retains the nutrients of soybean oil, has good quality, and meets the national edible soybean oil standards.

[0025] (2) The process of the present invention is simple. Through comprehensive adjustment of soybean pretreatment, moisture content, pressing time, pressing speed and cake outlet diameter, the soybean oil yield obtained is greater than 17%, and the quality of soybean oil is good. Among them, the content of linoleic acid in soybean oil fatty acids is greater than 53%.

[0026] (3) The production method of the present invention is a completely physical process without adding any processing aids, and is a pure natural green product with good safety. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with examples. This example is implemented based on the technology of the present invention. Detailed implementation methods and specific operating processes are now given to illustrate that the present invention is creative, but these examples do not limit the scope of the present invention.

[0028] In order to better understand the present invention but not to limit the scope of the present invention, all numerals and other numerical values ​​of expression dosage, percentage used in this application.Each numerical parameter should at least be regarded as obtained according to the reported significant digits and by conventional rounding methods.

[0029] In the present invention, the room temperature is 10-30°C, preferably 10°C, 15°C, 20°C, 25°C, 30°C or any range between the values.

[0030] The experimental methods used in the following examples are all conventional methods unless otherwise specified; the raw materials, reagents, etc. used are all raw materials and reagents that can be obtained from conventional commercial channels, etc. unless otherwise specified.

[0031] Example 1 Preparation of soybean oil by cold pressing

[0032] Step 1: Soybean pretreatment

[0033] The soybeans were placed on a tray and dried with hot air at 80°C for 2-3 hours until the moisture content was 9.7%. The soybeans were cooled to room temperature and peeled using a soybean peeling machine. The peeled soybeans were placed at 4°C for 6 hours.

[0034] Step 2: Pressing

[0035] 30 g of dehulled soybeans were put into a double-screw oil press (pressing time 4 min, pressing speed 63 r / min, cake outlet diameter 7.6 mm) to obtain crude oil;

[0036] Step 3: Remove impurities

[0037] The crude oil was centrifuged at 6000 r / min and 20° C. for 20 min to remove impurities, thereby obtaining soybean oil.

[0038] Example 2 Cold Pressing to Prepare Soybean Oil

[0039] Step 1: Soybean pretreatment

[0040] Place the soybeans on a tray and dry them with hot air at 70°C for 2-3 hours until the moisture content is 8%. Cool the soybeans to room temperature and use a soybean peeling machine to peel them. Store the peeled soybeans at 0°C for 2 hours.

[0041] Step 2: Pressing

[0042] Take 30g of dehulled soybeans and put them into a double-screw oil press (pressing time 3min, pressing speed 60r / min, cake outlet diameter 10mm) to press and obtain crude oil;

[0043] Step 3: Remove impurities

[0044] The crude oil was centrifuged at 6000 r / min and 20° C. for 20 min to remove impurities, thereby obtaining soybean oil.

[0045] Example 3 Cold Pressing to Prepare Soybean Oil

[0046] Step 1: Soybean pretreatment

[0047] The soybeans were placed on a tray and dried with hot air at 80°C for 2-3 hours until the moisture content was 11%. The soybeans were cooled to room temperature and peeled using a soybean peeling machine. The peeled soybeans were placed at 2°C for 8 hours.

[0048] Step 2: Pressing

[0049] 30 g of dehulled soybeans were put into a double-screw oil press (pressing time 5 min, pressing speed 80 r / min, cake outlet diameter 7 mm) to obtain crude oil;

[0050] Step 3: Remove impurities

[0051] The crude oil was centrifuged at 6000 r / min and 20° C. for 20 min to remove impurities, thereby obtaining soybean oil.

[0052] Comparative Example 1

[0053] The difference between this comparative example and Example 1 is that there is no refrigeration step, and the pressing process is different, including water content, pressing time, pressing speed and cake outlet diameter.

[0054] Specifically:

[0055] Step 1: Soybean pretreatment

[0056] The soybeans were placed on a tray and dried with hot air at 80°C for 4-6 hours until the moisture content was 5%. The soybeans were cooled to room temperature and peeled using a soybean peeling machine.

[0057] Step 2: Pressing

[0058] Take 30g of dehulled soybeans and put them into a double-screw oil press (pressing time 2min, pressing speed 50r / min, cake outlet diameter 5mm) to press and obtain crude oil;

[0059] Step 3: Remove impurities

[0060] The crude oil was centrifuged at 6000 r / min and 20° C. for 20 min to remove impurities, thereby obtaining soybean oil.

[0061] Comparative Example 2

[0062] The difference between this comparative example and Example 1 is that the vacuum drying is carried out at a drying temperature of 50° C., and the pressing process is different, including the water content, pressing time, pressing speed and cake outlet diameter.

[0063] Specifically:

[0064] Step 1: Soybean pretreatment

[0065] The soybeans were placed on a tray and vacuum dried at 50°C for 1-2 hours until the moisture content was 12%. The soybeans were cooled to room temperature and peeled using a soybean peeling machine. The peeled soybeans were placed at 4°C for 6 hours.

[0066] Step 2: Pressing

[0067] 30 g of dehulled soybeans were put into a double-screw oil press (pressing time 6 min, pressing speed 85 r / min, cake outlet diameter 12 mm) to obtain crude oil;

[0068] Step 3: Remove impurities

[0069] The crude oil was centrifuged at 6000 r / min and 20° C. for 20 min to remove impurities, thereby obtaining soybean oil.

[0070] The results of measuring the oil yield of the prepared soybeans and the content of linoleic acid in the soybean oil fatty acids (gas chromatography-mass spectrometry, model QP2020 ULTRA) are shown in Table 1.

[0071] The calculation method of soybean oil yield is:

[0072] Oil yield = crude oil mass / (soybean mass - impurity-removed mass) × 100%.

[0073] Table 1

[0074] Soybean oil yield% Linoleic acid content% Example 1 18.05±0.33 54.72±0.72 Example 2 17.97±0.35 53.05±0.61 Example 3 17.35±0.31 53.54±0.67 Comparative Example 1 11.69±0.23* 52.18±0.58 Comparative Example 2 17.21±0.28 40.75±0.44*

[0075] Note: Compared with Example 1, *P<0.05.

[0076] The results show that the oil yield of the cold-pressed soybean oil prepared in Examples 1-3 is greater than 17%, and the content of linseed oil in soybean oil fatty acids exceeds 53%, indicating that the cold-pressing method of the present invention can increase the oil yield of soybean oil and increase the content of linseed oil in soybean oil fatty acids.

[0077] At the same time, by comparing Comparative Example 1 and Example 1, it can be seen that compared with Example 1, the oil yield of soybean oil in Comparative Example 1 is significantly reduced (P < 0.05), indicating that the refrigeration step of defoamed soybeans and the overall pressing process have an important influence on the oil yield of cold-pressed soybean oil.

[0078] Comparing Comparative Example 2 and Example 1, it can be seen that the content of linseed oil in soybean oil fatty acids in Comparative Example 2 is significantly reduced (P < 0.05) compared with Example 1, indicating that the drying temperature and the overall pressing process have an important influence on the linseed oil content in cold-pressed soybean oil fatty acids.

[0079] The invention takes into account both the export rate and the linoleic acid content in soybean oil fatty acids by comprehensively adjusting soybean pretreatment, moisture content, pressing time, pressing speed and cake outlet diameter. The invention has a simple preparation process, is a completely physical process, does not add any processing aids, is a pure natural green product, has good safety, and meets market demand.

[0080] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing soybean oil by cold pressing, characterized in that: The steps include: Step 1: Soybean pretreatment Drying the soybeans with hot air until the moisture content is 8-11%, cooling and peeling to obtain peeled soybeans, and refrigerating; Step 2: Pressing The dehulled soybeans are pressed by a double-screw oil press, and the pressing parameters are controlled to obtain crude oil; The pressing parameters include pressing time, pressing speed and cake outlet diameter; Step 3: Remove impurities The crude oil is centrifuged to remove impurities to obtain soybean oil.

2. The method according to claim 1, characterized in that The drying in step 1 is: hot air drying at 70-80° C. for 2-3 hours.

3. The method according to claim 1, characterized in that The refrigeration in step 1 is placed at 0-4°C for 2-8 hours.

4. The method according to claim 3, characterized in that The refrigeration in step 1 is placed at 4° C. for 6 hours.

5. The method according to claim 1, characterized in that The moisture content in step 1 is 9.7%.

6. The method according to claim 1, characterized in that The pressing time in step 2 is 3-5 minutes; the pressing speed is 60-80r / min, and the cake outlet diameter is 6-10mm.

7. The method according to claim 6, characterized in that The pressing time is 3-4 minutes; the pressing speed is 60-70 r / min, and the cake outlet diameter is 7-10 mm.

8. The method according to claim 7, characterized in that The pressing time is 4 minutes; the pressing speed is 63 r / min, and the cake outlet diameter is 7.6 mm.

9. The method according to claim 1, characterized in that: The centrifugation in step 3 is 4000-8000 r / min, and the centrifugation is carried out at room temperature for 15-25 min.

10. Use of the method according to any one of claims 1 to 9 in increasing the linoleic acid content in soybean oil.