A kind of preparation method of strong fragrant rapeseed oil

Abstract

The invention discloses a method for preparing a fragrant rapeseed oil, comprising the following steps: 1) removing impurities from raw materials; 2) frying seeds; 3) squeezing to obtain pressed oil and rapeseed meal; 4) filtering for the first time to obtain crude oil; 5) mixing crude oil and rapeseed meal; 6) filtering for the second time to obtain rapeseed cake mixed oil; 7) preparing modified silicon dioxide: a) extracting protein from rapeseed meal; b) adding glutamine aminotransferase to denature protein; c) adding calcium citrate to obtain calcium cross-linked protein gel; d) adding silicon dioxide to obtain modified silicon dioxide; 8) degumming of modified silicon dioxide: adding modified silicon dioxide to the rapeseed cake mixed oil at 0.04-0.08% of the weight of the rapeseed cake mixed oil for degumming treatment; 9) winterization to obtain fragrant rapeseed oil. The present invention adopts modified silicon dioxide for degumming treatment, improves the adsorption effect of modified silicon dioxide on moisture and peptized impurities in crude oil, shortens the degumming time, and improves the de-oiling quality.

Description

Technical Field

[0001] The invention relates to the technical field of edible oil manufacturing, in particular to a method for preparing strong-flavor rapeseed oil. Background Art

[0002] Strong aroma rapeseed oil is a kind of rapeseed oil with strong aroma obtained by frying and pressing rapeseed. It is favored by consumers for its unique flavor, and its annual consumption accounts for more than 30% of the total rapeseed oil.

[0003] Fragrance is one of the important factors that determine the quality of rapeseed oil. Maillard reaction products, heterocyclic compounds, glucosinolate degradation products and oxidized volatiles have been confirmed to be the main volatile flavor substances of rapeseed oil. These substances are mainly formed under heating conditions. Therefore, heat treatment is an effective way to prepare rapeseed oil, including heat treatment methods such as hot pressing and microwave. The rapeseed oil after heat treatment has the characteristics of strong flavor and high nutrient content, but contains a certain amount of phospholipids and other peptizing impurities, and needs to be degummed. At present, the more common degumming methods include hydration degumming method, citric acid degumming method, and saturated edible salt water degumming method. These methods are difficult to remove non-hydratable phospholipids, have high concentrations, complex operations and wastewater discharge.

[0004] Silica is a new type of environmentally friendly adsorbent material. It is a porous substance with a well-developed pore structure. It has a strong adsorption effect on phospholipids, saponification products and other impurities in oils and fats, and is widely used in the degumming process of oil processing. For example, patent application number CN202110952235.0 discloses a high-polyphenol rapeseed oil and a preparation method thereof. The preparation method comprises the following steps in sequence: cyclically heating the rapeseed raw material for 5-30 minutes to a temperature of 100-180°C to obtain the heated rapeseed raw material; squeezing the heated rapeseed raw material, and then sedimenting and filtering in sequence to obtain crude rapeseed oil; adding silica to the crude rapeseed oil, stirring for 5-30 minutes at 50-300r / min and 20-60°C, filtering or centrifuging to obtain refined rapeseed oil; mixing the refined rapeseed oil and cake, extracting for 0.5-10h at 40-100°C and 50-300r / min, filtering or centrifuging to obtain high-polyphenol rapeseed oil.

[0005] Although this method uses silica for degumming, it still has the following problems:

[0006] 1) The crude oil obtained by this method is first degummed by adding silicon dioxide, then adding rapeseed meal, and then only filtering or centrifuging to obtain polyphenol rapeseed oil. During the process of adding rapeseed meal, since the rapeseed meal still contains some peptizing impurities such as phospholipids, these peptizing impurities will be directly brought into the rapeseed oil through the addition of rapeseed meal, thereby causing instability in the quality of the edible oil and reducing the quality of the edible oil;

[0007] 2) The content of phospholipids in the rapeseed oil prepared by the method using the silica degumming process is as low as 244 mg / kg and as high as 2118 mg / kg, indicating that the method of direct silica degumming cannot effectively remove phospholipids in the degumming process, so that the content of phospholipids in the prepared rapeseed oil product is still high, which reduces the quality of the rapeseed oil;

[0008] 3) This method does not detect the content of aromatic substances in rapeseed oil, and it is impossible to know whether these aromatic substances are lost during the degumming process using silica.

[0009] Therefore, how to provide a method for preparing rapeseed oil that can effectively adsorb phospholipids and other colloidal impurities and reduce the loss of flavor substances has become a problem to be solved urgently. Summary of the invention

[0010] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for preparing fragrant rapeseed oil which has a simple process and can improve the degumming effect and oil quality.

[0011] The technical solution adopted by the present invention to solve the technical problem is: a method for preparing strong fragrant rapeseed oil, comprising the following steps: 1) removing impurities from raw materials; 2) frying seeds; 3) pressing to obtain pressed oil and rapeseed meal; 4) filtering for the first time to obtain crude oil; 5) mixing the crude oil and rapeseed meal; 6) filtering for the second time to obtain rapeseed cake mixed oil; 7) preparing modified silicon dioxide: a) extracting protein from rapeseed meal to prepare a rapeseed meal protein solution; b) adding glutamine aminotransferase to the rapeseed meal protein solution to denature the protein to obtain modified protein; c) adding calcium citrate to the modified protein to obtain calcium cross-linked protein gel; d) adding silicon dioxide to the calcium cross-linked protein gel to obtain modified silicon dioxide; 8) degumming of modified silicon dioxide: adding 0.04-0.08% of the weight of the rapeseed cake mixed oil with the modified silicon dioxide to perform degumming treatment, and then filtering for the third time to obtain degummed oil; 9) winterizing to obtain strong fragrant rapeseed oil.

[0012] The present invention mixes rapeseed meal with crude oil before degumming, so that the peptized impurities brought by the addition of rapeseed meal and the peptized impurities contained in the crude oil itself can be degummed at the same time, so that the phospholipid content in the degummed oil after degumming is greatly reduced, and the product stability and quality of the rapeseed oil are improved;

[0013] In addition, when preparing the modified silica, the present invention uses rapeseed meal protein as a raw material, first denatures the rapeseed meal protein under the catalytic action of glutamine transaminase, so that the glutamine residues on the peptide chain in the rapeseed meal protein undergo acyl transfer with the acyl group, resulting in the formation of ε-(γ-glutamyl) lysine covalent bonds within and between protein molecules, thereby forming a cross-linked spatial network structure to obtain modified protein; then calcium citrate is used as a cross-linking agent to combine the carboxyl groups on the modified protein molecules with calcium ions to form calcium bridges, and the calcium ions are aggregated and separated to obtain a calcium cross-linked protein gel; finally, the calcium ions in the calcium cross-linked protein gel form ionic bonds with oxygen atoms inside the silica, so that the protein can be fixed on the silica to form modified silica.

[0014] The preparation of the modified silica not only makes full use of the protein in the by-product rapeseed meal and improves the comprehensive utilization rate of the rapeseed meal, but also greatly increases the specific surface area and porosity of the silica through the modification treatment, improves the adsorption effect of the modified silica on moisture and colloid-soluble impurities (mainly phospholipids) in the crude oil, and while improving the adsorption effect of moisture and phospholipids, it also greatly shortens the degumming time (the action time of the modified silica and the oil sample), improves the degumming efficiency, reduces the moisture content in the rapeseed oil, and greatly retains the flavor substances; and because there are hydrophilic and lipophilic parts in the phospholipid molecular structure, part of the free fatty acids can be removed while removing the phospholipids, which greatly reduces the acid value of the oil and improves the oxidative stability of the rapeseed oil.

[0015] Furthermore, the moisture content of the rapeseed raw material obtained after removing impurities in step 1) is 7%-15%.

[0016] Furthermore, in the step 2), the temperature for frying the seeds is 120-145° C., the frying time is 20-40 min, and the moisture content of the seeds after frying is 1%-5%.

[0017] Furthermore, the specific steps of step 5) are: after crushing the rapeseed meal, adding powdered rapeseed meal to the crude oil at a weight of 10%-30% of the crude oil, fully stirring at a temperature of 40-90° C. for 30 minutes, standing overnight to obtain a rapeseed meal mixture for standby use.

[0018] Further, the specific steps of step 7) are:

[0019] a) extracting protein from rapeseed meal to obtain rapeseed meal protein, and then dissolving the rapeseed meal protein in a 0.1 mol / L NaCl solution while stirring to prepare a rapeseed meal protein solution with a concentration of 5-20%;

[0020] b) adding 20-100 U / g of glutamine transaminase according to the weight of rapeseed meal protein, adjusting the pH value to 6-9, stirring at a temperature of 30-60° C. for 2 hours, then placing at 90° C. to inactivate the enzyme for 10 minutes, and centrifuging to obtain a modified protein;

[0021] c) adding a 200 mmol / L calcium citrate solution to the modified protein at a concentration of 2-4% of the weight of the modified protein, stirring for 30 minutes, rinsing with distilled water three times, and drying at 50° C. to obtain a calcium cross-linked protein gel;

[0022] d) dissolving the calcium cross-linked protein gel in distilled water, with the solid-liquid ratio of the calcium cross-linked protein gel to distilled water being 1:10-20, adding silicon dioxide to the calcium cross-linked protein gel at 1-5% of the weight of the calcium cross-linked protein gel, stirring for 6-12 hours, and centrifuging for 5-10 minutes to obtain modified silicon dioxide for later use.

[0023] Furthermore, the specific operation steps of extracting protein from rapeseed meal in step a) are: taking rapeseed cake meal with a mesh size of 80, adding 6 times of water and heating to 45° C., adjusting the pH to 4.3, adding cellulase at 1.25% of the weight of the rapeseed meal, and reacting for 130 minutes; then adjusting the pH to 8.0 with NaOH, adding Alcalase protease at 0.4% of the weight of the rapeseed meal, heating to 55° C. for soaking, reacting for 150 minutes, centrifuging at 3000 r / min for 20 minutes, collecting the supernatant, adjusting the pH to 5.2, and then centrifuging and vacuum drying to obtain rapeseed meal protein.

[0024] Furthermore, the specific steps of step 8) are: adding modified silicon dioxide to the rapeseed cake mixed oil at a weight of 0.04-0.08% of the rapeseed cake mixed oil, stirring at a stirring speed of 100-300 r / min and a temperature of 10-40° C. for 2-3 minutes, and then filtering for the third time to obtain degummed oil.

[0025] Since part of the aromatic substances will be lost during the degumming process, the present invention adopts modified silicon dioxide as a degumming agent. The modified silicon dioxide has a larger specific surface area and porosity. Only 0.04-0.08% of the modified silicon dioxide is added according to the weight of the rapeseed cake mixed oil and the degumming time is shortened to 2-3 minutes to achieve a good degumming effect. Not only the usage of silicon dioxide is greatly reduced, but also the degumming time is significantly shortened, so that the aromatic substances (such as glucosinolate degradation products, pyrazines and aldehydes and ketones) in the degumming process can be well retained, thereby improving the aroma and preparation efficiency of rapeseed oil.

[0026] Preferably, the amount of modified silicon dioxide added in step 8) is 0.06% by weight of the vegetable cake mixed oil, and the stirring time during degumming is 2.5 min.

[0027] Furthermore, the step 8) further includes a step of degumming the rinse liquid before the third filtration. The specific operation steps of the degumming of the rinse liquid are: adding the rinse liquid rinsed with distilled water in step c) to the oil sample obtained by degumming with modified silica, the volume ratio of the separation liquid to the oil sample is 1:50-80, and stirring for 1-1.5 minutes at a stirring speed of 100-300 r / min and a temperature of 10-40°C.

[0028] When preparing the calcium cross-linked protein gel, calcium citrate is added to the modified protein obtained by catalysis of glutamine transaminase. When the calcium cross-linked protein gel is formed, part of the citric acid is released due to the cross-linking of calcium ions and the modified protein. The distilled water is used to rinse the rinse solution. The rinse solution is further added to the oil sample treated with modified silicon dioxide in the rinse solution degumming step. The oil sample can be further degummed by using the citric acid in the rinse solution, which can not only effectively utilize the citric acid in the rinse solution, but also further utilize the citric acid to remove the gel-soluble impurities in the oil, thereby greatly reducing the content of phospholipids and improving the quality of rapeseed oil.

[0029] Furthermore, the specific steps of step 9) are: placing the degummed oil in a crystallization tank for stirring and crystallization, first stirring at a speed of 20-40 r / min until the oil temperature is 10°C, and then stirring at a low speed of 5-10 r / min until the oil temperature is -2--4°C, stopping stirring, and keeping the oil sample at this temperature for 24-48 hours. After the grains grow, the cooled and crystallized oil sample is filtered at 4-6°C to obtain a fragrant rapeseed oil.

[0030] Beneficial effects of the method for preparing the fragrant rapeseed oil of the present invention:

[0031] (1) The present invention mixes rapeseed meal with crude oil before degumming, so that the peptizing impurities brought by the addition of rapeseed meal and the peptizing impurities contained in the crude oil itself can be degummed at the same time, so that the phospholipid content in the degummed oil after degumming is greatly reduced, and the product stability and quality of the rapeseed oil are improved; and by mixing rapeseed meal with crude oil, aromatic substances such as pyrazine compounds, aldehydes and ketones, and nitrile substances in the rapeseed meal are dissolved, greatly enhancing the aroma of the rapeseed oil;

[0032] (2) The present invention uses modified silicon dioxide for degumming treatment, and by increasing the specific surface area and porosity of silicon dioxide, the adsorption effect of modified silicon dioxide on moisture and colloid-soluble impurities (mainly phospholipids) in crude oil is improved. While improving the adsorption effect of moisture and phospholipids, the degumming time is greatly shortened, the degumming efficiency is improved, the moisture content in rapeseed oil is reduced, and the flavor substances are greatly retained; and because there are hydrophilic and lipophilic parts in the molecular structure of phospholipids, part of the free fatty acids can be removed while removing phospholipids, which greatly reduces the acid value of oil and improves the oxidative stability of rapeseed oil;

[0033] (3) The present invention uses the rinse solution obtained by rinsing with distilled water during the preparation of calcium cross-linked protein gel to further degumming the oil sample treated with modified silica, so that the citric acid in the rinse solution can be effectively utilized. The citric acid can also be further used to remove the soluble impurities in the oil, and can synergistically enhance the degumming effect with the modified silica, thereby greatly reducing the content of phospholipids and improving the quality of rapeseed oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 — is a process flow chart of a method for preparing a strong fragrant rapeseed oil of the present invention;

[0035] Figure 2 —The effect of different degumming time on the content of phospholipid and glucosinolate degradation products;

[0036] Figure 3 —The effect of different degumming time on the content of pyrazines and aldehydes and ketones;

[0037] Figure 4 —The effect of different modified silica addition amounts on the content of phospholipid and glucosinolate degradation products;

[0038] Figure 5 —The effect of different modified silica addition amounts on the content of pyrazines and aldehydes and ketones. DETAILED DESCRIPTION

[0039] The present invention is further described below in conjunction with the accompanying drawings and examples, but these specific implementation schemes do not limit the protection scope of the present invention in any way.

[0040] Example 1

[0041] A method for preparing fragrant rapeseed oil, the process flow chart of which is as follows Figure 1 As shown, the following steps are included:

[0042] 1) Raw material impurity removal: The collected rapeseed enters the flat rotary screen through the transportation line, and after removing impurities, clean rapeseed raw materials are obtained, and the moisture content of the rapeseed raw materials is 8-10%;

[0043] 2) Seed frying: The clean rapeseed is transported to a drum seed frying machine, the temperature inside the machine is controlled at 140°C, the seed frying time is 30 minutes, and the seed surface temperature is ensured to be 120°C after the seeds are taken out, and the moisture content of the seeds is 3%;

[0044] 3) Pressing: The roasted rapeseed is conveyed to the feeding port of the single screw press through a conveyor line, and is pressed under the conditions of a seed feeding temperature of 120°C and a pressing chamber preheating temperature of 125°C to obtain rapeseed meal with a thickness of 5 mm and pressed oil, and the residual oil rate of the rapeseed meal is 5.1%;

[0045] 4) First filtration: The pressed oil is filtered through a plate and frame filter to obtain crude oil;

[0046] 5) Mixing crude oil and rapeseed meal: first, put the crude oil into a buffer tank, crush the rapeseed meal, then add powdered rapeseed meal to the crude oil at a weight of 15% of the crude oil, fully stir at a temperature of 60° C. for 30 minutes, and stand overnight to obtain a rapeseed meal mixture for standby use;

[0047] 6) Second filtration: The rapeseed meal mixture is filtered through a plate and frame filter to obtain a rapeseed cake mixed oil;

[0048] 7) Preparation of modified silicon dioxide:

[0049] a) extracting protein from rapeseed meal: taking rapeseed meal with a mesh size of 80, adding 6 times of water and heating to 45°C, adjusting the pH to 4.3, adding cellulase at 1.25% of the weight of the rapeseed meal, and reacting for 130 minutes; then adjusting the pH to 8.0 with NaOH, adding Alcalase at 0.4% of the weight of the rapeseed meal, heating to 55°C for soaking, reacting for 150 minutes, centrifuging at 3000 r / min for 20 minutes, collecting the supernatant, adjusting the pH to 5.2, centrifuging again, and vacuum drying to obtain rapeseed meal protein; dissolving the rapeseed meal protein in 0.1 mol / L NaCl solution while stirring to prepare a rapeseed meal protein solution with a concentration of 10%;

[0050] b) adding 60 U / g of glutamine transaminase according to the weight of rapeseed meal protein, stirring at 45° C. for 2 hours, then placing at 90° C. for 10 minutes to inactivate the enzyme, and after the reaction is completed, taking out and rapidly freeze-drying to obtain a modified protein;

[0051] c) adding a 200 mmol / L calcium citrate solution to the modified protein at a concentration of 2.5% of the weight of the modified protein, stirring with a magnetic force for 30 minutes, rinsing with distilled water three times, and drying at 50° C. to obtain a calcium cross-linked protein gel;

[0052] d) dissolving the calcium cross-linked protein gel in distilled water, wherein the solid-liquid ratio of the calcium cross-linked protein gel to the distilled water is 1:15, adding food-grade silicon dioxide to the calcium cross-linked protein gel at 2.5% of the weight of the calcium cross-linked protein gel, stirring at a speed of 300 rpm for 6 hours to prepare a modified silicon dioxide solution; placing the solution in a refrigerated centrifuge at 4000 r / min for 10 minutes, and the lower layer of the separated product obtained by centrifugation is the modified silicon dioxide, which is set aside;

[0053] 8) Degumming with modified silica: adding modified silica to the rapeseed cake mixed oil at a weight of 0.06%, stirring at a stirring speed of 200 r / min and a temperature of 25° C. for 2.5 min, and then sending it to a plate and frame filter for a third filtration to obtain degummed oil;

[0054] 9) Winterization: The degummed oil is placed in a crystallization tank for stirring and crystallization. First, it is stirred at a speed of 30 r / min until the oil temperature reaches 10°C, and then stirred at a low speed of 8 r / min until the oil temperature reaches -3°C. Stirring is stopped and the oil sample is kept at this temperature for 36 hours. After the grains grow, the cooled and crystallized oil sample is filtered at 5°C to obtain a fragrant rapeseed oil.

[0055] Example 2

[0056] A method for preparing fragrant rapeseed oil comprises the following steps:

[0057] 1) Raw material impurity removal: The collected rapeseed enters the flat rotary screen through the transportation line, and after removing impurities, clean rapeseed raw materials are obtained, and the moisture content of the rapeseed raw materials is 8-10%;

[0058] 2) Seed frying: The clean rapeseed is transported to a drum-type seed frying machine, the temperature inside the machine is controlled at 120°C, the seed frying time is 20 minutes, and the seed surface temperature is ensured to be 100°C after the seeds are taken out, and the moisture content of the seeds is 5%;

[0059] 3) Pressing: The roasted rapeseed is conveyed to the feeding port of the single screw press through a conveyor line, and is pressed under the conditions of a seed feeding temperature of 100°C and a preheating temperature of the pressing chamber of 110°C to obtain rapeseed meal with a thickness of 8 mm and pressed oil, and the residual oil rate of the rapeseed meal is 6%;

[0060] 4) First filtration: The pressed oil is filtered through a plate and frame filter to obtain crude oil;

[0061] 5) Mixing crude oil and rapeseed meal: first, put the crude oil into a buffer tank, crush the rapeseed meal, then add powdered rapeseed meal to the crude oil at 10% of the weight of the crude oil, fully stir at 40° C. for 30 minutes, and stand overnight to obtain a rapeseed meal mixture for standby use;

[0062] 6) Second filtration: The rapeseed meal mixture is filtered through a plate and frame filter to obtain a rapeseed cake mixed oil;

[0063] 7) Preparation of modified silicon dioxide:

[0064] a) extracting protein from rapeseed meal: taking rapeseed meal with a mesh size of 80, adding 6 times of water and heating to 45°C, adjusting the pH to 4.3, adding cellulase at 1.25% of the weight of the rapeseed meal, and reacting for 130 minutes; then adjusting the pH to 8.0 with NaOH, adding Alcalase at 0.4% of the weight of the rapeseed meal, heating to 55°C for soaking, reacting for 150 minutes, centrifuging at 3000 r / min for 20 minutes, collecting the supernatant, adjusting the pH to 5.2, centrifuging again, and vacuum drying to obtain rapeseed meal protein; dissolving the rapeseed meal protein in 0.1 mol / L NaCl solution while stirring to prepare a rapeseed meal protein solution with a concentration of 5%;

[0065] b) adding 60 U / g of glutamine transaminase according to the weight of rapeseed meal protein, stirring at 45° C. for 2 hours, then placing at 90° C. for 10 minutes to inactivate the enzyme, and after the reaction is completed, taking out and rapidly freeze-drying to obtain a modified protein;

[0066] c) adding a 200 mmol / L calcium citrate solution to the modified protein at a concentration of 2% of the weight of the modified protein, stirring with a magnetic force for 30 minutes, rinsing with distilled water three times, and drying at 50° C. to obtain a calcium cross-linked protein gel;

[0067] d) dissolving the calcium cross-linked protein gel in distilled water, with the solid-liquid ratio of the calcium cross-linked protein gel to the distilled water being 1:10, adding food-grade silicon dioxide to the calcium cross-linked protein gel at 1% of the weight of the calcium cross-linked protein gel, stirring at a speed of 200 rpm for 6 hours to prepare a modified silicon dioxide solution; placing the solution in a refrigerated centrifuge at 3000 r / min for 5 minutes, and the lower layer of the separated product obtained by centrifugation is the modified silicon dioxide, which is set aside;

[0068] 8) Degumming with modified silica: adding modified silica to the rapeseed cake mixed oil at a weight of 0.04%, stirring at a stirring speed of 100 r / min and a temperature of 10° C. for 2 min, and then sending it to a plate and frame filter for a third filtration to obtain degummed oil;

[0069] 9) Winterization: The degummed oil is placed in a crystallization tank for stirring and crystallization. First, it is stirred at a speed of 20 r / min until the oil temperature reaches 10°C, and then stirred at a low speed of 5 r / min until the oil temperature reaches -2°C. Stirring is stopped and the oil sample is kept at this temperature for 24 hours. After the grains grow, the cooled and crystallized oil sample is filtered at 4°C to obtain a fragrant rapeseed oil.

[0070] Example 3

[0071] A method for preparing fragrant rapeseed oil comprises the following steps:

[0072] 1) Raw material impurity removal: The collected rapeseed enters the flat rotary screen through the transportation line, and after removing impurities, clean rapeseed raw materials are obtained, and the moisture content of the rapeseed raw materials is 8-10%;

[0073] 2) Seed frying: The clean rapeseed is transported to a drum seed frying machine, the temperature inside the machine is controlled at 145°C, the seed frying time is 40 minutes, and the seed surface temperature after the seed is taken out is ensured to be 130°C and the moisture content of the seed is 1%;

[0074] 3) Pressing: The roasted rapeseed is conveyed to the feeding port of the single screw press through a conveyor line, and is pressed under the conditions of a seed feeding temperature of 125°C and a pressing chamber preheating temperature of 130°C to obtain rapeseed meal with a thickness of 4 mm and pressed oil, and the residual oil rate of the rapeseed meal is 4%;

[0075] 4) First filtration: The pressed oil is filtered through a plate and frame filter to obtain crude oil;

[0076] 5) Mixing crude oil and rapeseed meal: first, put the crude oil into a buffer tank, crush the rapeseed meal, then add powdered rapeseed meal to the crude oil at 30% of the weight of the crude oil, fully stir at 90° C. for 30 minutes, and stand overnight to obtain a rapeseed meal mixture for standby use;

[0077] 6) Second filtration: The rapeseed meal mixture is filtered through a plate and frame filter to obtain a rapeseed cake mixed oil;

[0078] 7) Preparation of modified silicon dioxide:

[0079] a) extracting protein from rapeseed meal: taking rapeseed meal with a mesh size of 80, adding 6 times of water and heating to 45°C, adjusting the pH to 4.3, adding cellulase at 1.25% of the weight of the rapeseed meal, and reacting for 130 minutes; then adjusting the pH to 8.0 with NaOH, adding Alcalase at 0.4% of the weight of the rapeseed meal, heating to 55°C for soaking, reacting for 150 minutes, centrifuging at 3000 r / min for 20 minutes, collecting the supernatant, adjusting the pH to 5.2, centrifuging again, and vacuum drying to obtain rapeseed meal protein; dissolving the rapeseed meal protein in 0.1 mol / L NaCl solution while stirring to prepare a rapeseed meal protein solution with a concentration of 20%;

[0080] b) adding 60 U / g of glutamine transaminase according to the weight of rapeseed meal protein, stirring at 45° C. for 2 hours, then placing at 90° C. for 10 minutes to inactivate the enzyme, and after the reaction is completed, taking out and rapidly freeze-drying to obtain a modified protein;

[0081] c) adding a 200 mmol / L calcium citrate solution to the modified protein at a concentration of 4% of the weight of the modified protein, stirring with a magnetic force for 30 minutes, rinsing with distilled water three times, and drying at 50° C. to obtain a calcium cross-linked protein gel;

[0082] d) dissolving the calcium cross-linked protein gel in distilled water, wherein the solid-liquid ratio of the calcium cross-linked protein gel to the distilled water is 1:20, adding food-grade silicon dioxide to the calcium cross-linked protein gel at a weight of 5% of the calcium cross-linked protein gel, stirring at a speed of 400 rpm for 12 hours to prepare a modified silicon dioxide solution; placing the solution in a refrigerated centrifuge and centrifuging it at 6000 r / min for 10 minutes, and the lower layer of the separated product obtained by centrifugation is the modified silicon dioxide, which is set aside;

[0083] 8) Degumming with modified silica: adding modified silica to the rapeseed cake mixed oil at a weight of 0.08% by weight, stirring for 3 min at a stirring speed of 300 r / min and a temperature of 40° C., and then sending the mixture into a plate and frame filter for a third filtration to obtain degummed oil;

[0084] 9) Winterization: The degummed oil is placed in a crystallization tank for stirring and crystallization. First, it is stirred at a speed of 40 r / min until the oil temperature reaches 10°C, and then stirred at a low speed of 10 r / min until the oil temperature reaches -4°C. Stirring is stopped and the oil sample is kept at this temperature for 48 hours. After the grains grow, the cooled and crystallized oil sample is filtered at 6°C to obtain a fragrant rapeseed oil.

[0085] Example 4

[0086] The difference between this embodiment and embodiment 1 is that: before the third filtration in step 8), a step of degumming with a rinse solution is also included. The specific operation steps of the degumming with a rinse solution are as follows: the rinse solution rinsed with distilled water in step c) is added to the oil sample obtained by degumming with modified silica, the volume ratio of the rinse solution to the oil sample is 1:75, and after stirring at a stirring speed of 200 r / min and a temperature of 25°C for 1 minute, a third filtration is performed to obtain degummed oil.

[0087] Comparative Example 1

[0088] The difference between this comparative example and Example 1 is that step 7) and step 8) are deleted.

[0089] Comparative Example 2

[0090] The difference between this comparative example and Example 1 is that step 7) is deleted, and step 8) adopts hydration degumming, and its specific operation steps are: adding a citric acid solution with a temperature of 45°C and a concentration of 50% to the vegetable cake mixed oil at a rate of 4% by weight of the vegetable cake mixed oil, and at the same time adding deionized water with a temperature of 45°C at a rate of 4% by weight of the vegetable cake mixed oil, stirring at a stirring speed of 300 r / min and a temperature of 40°C for 2.5 minutes, and then sending it into a plate and frame filter for a third filtration to obtain hydrated degummed oil.

[0091] Comparative Example 3

[0092] The difference between this comparative example and Example 1 is that step 7) is deleted and step 8) is degummed with citric acid. The specific operation steps are: 0.08% of the weight of the rapeseed cake mixed oil is added to the rapeseed cake mixed oil, and after stirring for 2.5 minutes at a stirring speed of 300 r / min and a temperature of 40°C, the oil is sent into a plate and frame filter for a third filtration to obtain degummed oil.

[0093] Comparative Example 4

[0094] The difference between this comparative example and Example 1 is that step 7) is deleted and step 8) is degummed by silica. The specific operation steps are: food-grade silica is added to the vegetable cake mixed oil at a weight of 0.08% by weight of the vegetable cake mixed oil, and the mixture is stirred at a stirring speed of 300 r / min and a temperature of 40°C for 2.5 minutes, and then sent to a plate and frame filter for a third filtration to obtain degummed oil.

[0095] Comparative Example 5

[0096] The difference between this comparative example and Example 1 is that step 7) is deleted and step 8) is degummed by silica. The specific operation steps are: food-grade silica is added to the vegetable cake mixed oil at 5% by weight of the vegetable cake mixed oil, and the mixture is stirred at a stirring speed of 300 r / min and a temperature of 40°C for 2.5 minutes, and then sent to a plate and frame filter for a third filtration to obtain degummed oil.

[0097] Comparative Example 6

[0098] The difference between this comparative example and Example 1 is that: in step 7), no glutamine aminotransferase is added to modify the protein, and the specific operation steps are as follows:

[0099] a) extracting protein from rapeseed meal: taking rapeseed meal with a mesh size of 80, adding 6 times of water and heating to 45°C, adjusting the pH to 4.3, adding cellulase at 1.25% of the weight of the rapeseed meal, and reacting for 130 minutes; then adjusting the pH to 8.0 with NaOH, adding Alcalase at 0.4% of the weight of the rapeseed meal, heating to 55°C for soaking, reacting for 150 minutes, centrifuging at 3000 r / min for 20 minutes, collecting the supernatant, adjusting the pH to 5.2, centrifuging again, and vacuum drying to obtain rapeseed meal protein; dissolving the rapeseed meal protein in 0.1 mol / L NaCl solution while stirring to prepare a rapeseed meal protein solution with a concentration of 20%;

[0100] b) adding a 200 mmol / L calcium citrate solution to rapeseed meal protein at a concentration of 2.5% of the rapeseed meal protein weight, stirring magnetically for 30 min, rinsing with distilled water three times, and drying at 50° C. to obtain a calcium cross-linked protein gel;

[0101] d) dissolving the calcium cross-linked protein gel in distilled water, with the solid-liquid ratio of the calcium cross-linked protein gel to distilled water being 1:15, adding food-grade silicon dioxide to the calcium cross-linked protein gel at 2.5% of the weight of the calcium cross-linked protein gel, stirring at a speed of 300 rpm for 6 hours to prepare a modified silicon dioxide solution; placing the solution in a refrigerated centrifuge and centrifuging it at 4000 r / min for 10 minutes, and the lower layer of the separated product obtained by centrifugation is the modified silicon dioxide, which is set aside.

[0102] Comparative Example 7

[0103] The difference between this comparative example and Example 1 is that the crude oil is directly degummed with modified silicon dioxide, and then rapeseed meal is added to the degummed oil obtained by the degumming treatment. The following steps are included: 1) removing impurities from the raw materials; 2) frying the seeds; 3) pressing to obtain pressed oil and rapeseed meal; 4) filtering for the first time to obtain crude oil; 5) preparing modified silicon dioxide: a) extracting protein from rapeseed meal to prepare a rapeseed meal protein solution; b) adding glutamine aminotransferase to the rapeseed meal protein solution to denature the protein to obtain modified protein; c) adding calcium citrate to the modified protein to obtain calcium cross-linked protein gel; d) adding silicon dioxide to the calcium cross-linked protein gel to obtain modified silicon dioxide; 6) adding modified silicon dioxide to the crude oil at 0.04-0.08% of the weight of the crude oil to perform degumming treatment, and then filtering for the second time to obtain degummed oil; 7) mixing the degummed oil and rapeseed meal; 8) filtering for the third time to obtain rapeseed cake mixed oil; 9) winterizing to obtain fragrant rapeseed oil. Each specific operation step is the same as the corresponding step in Example 1.

[0104] The differences between the methods for preparing the fragrant rapeseed oil in the above comparative examples 1-7 and Example 1 are shown in Table 1:

[0105] Table 1 Differences between the methods for preparing fragrant rapeseed oil in comparative examples 1-7 and example 1

[0106]

[0107] In the present invention, the phosphorus content, moisture, acid value and peroxide value and the content of aromatic substances (glucosinolate degradation products, pyrazines, aldehydes and ketones) in the aromatic rapeseed oil prepared in Examples 1-4 and Comparative Examples 1-7 were measured, and the results are shown in Tables 2 and 3:

[0108] Table 2 Phosphorus content, moisture, acid value, peroxide value of the fragrant rapeseed oil prepared in Examples 1-4 and Comparative Examples 1-7

[0109]

[0110] As can be seen from Table 2, the phosphorus content, moisture, acid value and peroxide value of the rapeseed oil prepared by the method of Examples 1-4 are lower than those of Comparative Examples 1-5, and compared with Example 1, the three degumming effects in Comparative Examples 1-5 are significantly lower than those in Example 1. It can be seen that the order of degumming effects of Example 1 and Comparative Examples 1-5 is: modified silica method > citric acid method > hydration method > silica method. The reason is that in Examples 1-4, silica is treated by protein modification and cross-linking, which increases the size of the prepared silica. The specific surface area and porosity of the modified silica thus improve the adsorption effect of the modified silica on water and colloid-soluble impurities (mainly phospholipids) in crude oil, and while improving the adsorption effect of water and phospholipids, the degumming time is greatly shortened, the degumming efficiency is improved, the water content in rapeseed oil is reduced, and the flavor substances are greatly retained; and because there are hydrophilic and lipophilic parts in the molecular structure of phospholipids, part of the free fatty acids can be removed while removing phospholipids, which greatly reduces the oil acid value and improves the oxidation stability of rapeseed oil;

[0111] At the same time, compared with Comparative Examples 2 and 3, the phosphorus content, moisture, acid value and peroxide value of the rapeseed oil prepared in Comparative Example 6 are lower than those in Comparative Example 2, but higher than those in Comparative Example 3, indicating that the modified protein obtained by cross-linking treatment without modifying the protein can improve the degumming effect to a certain extent, so that the corresponding degumming effect is higher than that of hydration degumming, but still weaker than that of citric acid degumming;

[0112] Moreover, the phosphorus content, moisture content, acid value and peroxide value in the rapeseed oil prepared in Comparative Example 6 are significantly higher than those in Example 1, indicating that omitting the protein modification step will greatly reduce the degumming effect of the modified silica, and it is impossible to obtain modified silica with a larger specific surface area and porosity. The modification of protein is an indispensable step to improve the degumming effect of the modified silica, and it is coordinated with the cross-linking step to jointly play a role in the degumming effect of the modified silica. The method of preparing modified silica by modifying the protein and then cross-linking can greatly improve the degumming effect, thereby reducing the content of phospholipids, moisture, acid value and peroxide value.

[0113] In the method of Comparative Example 7, the crude oil is first degummed with modified silica and then rapeseed meal is added. During this process, due to the addition of rapeseed meal, some phospholipids, soaps and other substances in the oil are dissolved in the oil, making its phospholipid content, moisture, acid value and peroxide value higher than those in Example 1.

[0114] Table 3 Proportions of glucosinolate degradation products, pyrazines, aldehydes and ketones in the fragrant rapeseed oil prepared in Examples 1-4 and Comparative Examples 1-7

[0115]

[0116]

[0117] As can be seen from Table 3, the aromatic rapeseed oils prepared in Examples 1-3 have no significant difference in the proportions of glucosinolate degradation products, pyrazines, and aldehydes and ketones, and the contents of aromatic substances in Examples 1-3 are also not significantly different from those in Comparative Example 1. Compared with Example 1, the contents of aromatic substances (glucosinolate degradation products, pyrazines, aldehydes and ketones) in the aromatic rapeseed oils prepared in Comparative Examples 1-5 are significantly lower than those in Example 1, which indicates that the method for degumming using the modified silica prepared by the present invention has a better effect of reducing the loss of aromatic substances compared with the hydration method, the citric acid method and the silica degumming method, and can greatly retain the aromatic substances in the oil during the degumming process, thereby improving the aroma of the rapeseed oil.

[0118] The content of aromatic substances in the aromatic rapeseed oil prepared in Comparative Example 6 is higher than that in Comparative Examples 1-5, but lower than that in Example 1, indicating that the modified protein obtained by cross-linking without modifying the protein can reduce the loss of aromatic substances to a certain extent, so that its retention effect on aromatic substances is still lower than the retention effect of modified silica obtained by modifying and cross-linking the protein;

[0119] Compared with Comparative Example 7, Example 1 shows that the crude oil is first degummed by modified silica and then rapeseed meal is added. This method produces more aromatic substances, indicating that some substances in the rapeseed meal (aromatic substances, soaps, phospholipids, etc.) are dissolved in the oil, resulting in instability in product quality.

[0120] Therefore, it can be seen from the data in Table 2 and Table 3 that the modified silicon dioxide prepared by the method of the present invention is used for degumming treatment, which not only improves the adsorption effect of the modified silicon dioxide on moisture and colloid-soluble impurities (mainly phospholipids) in crude oil, greatly improves its degumming effect, but also the method can greatly retain the aromatic substances in the rapeseed oil during the degumming process, reduces the loss of aromatic substances during the degumming process, and improves the aroma of the rapeseed oil.

[0121] In addition, the present invention also measured the specific surface area and porosity of the modified silica and food-grade silica prepared in Examples 1-3 and Comparative Example 6, and the results are shown in Table 4:

[0122] Table 4 Specific surface area and porosity of Examples 1-3, Comparative Example 6 and food grade silicon dioxide

[0123]

[0124]

[0125] As can be seen from the above table, the specific surface area of ​​the modified silica prepared in Examples 1-3 is more than 2 times larger than that of the food-grade silica, and its porosity is also larger than that of the food-grade silica, up to more than 95%, indicating that the modified silica prepared by the method of the present invention has a larger specific surface area and porosity than food-grade silica, so that it has a better adsorption effect on the colloidal impurities in the oil sample, and can greatly reduce the content of phospholipids in the crude oil; and its specific surface area and porosity are also significantly greater than those of Comparative Example 6, indicating that in the preparation of the modified silica When denaturing the modified silica by glutaminase, the specific surface area of ​​the modified silica can be significantly increased, and the pores on the surface of the modified silica can be increased, which greatly improves the adsorption and degumming effect of the modified silica. In addition, the colloidal particles formed in the process of adsorbing degumming soluble impurities by the modified silica will adsorb a certain amount of free fatty acids and water, so that the phospholipid content, moisture, peroxide value and acid value in the rapeseed oil corresponding to Examples 1-3 are significantly lower than those in Comparative Example 6, which effectively improves the degumming effect and the quality of the rapeseed oil.

[0126] Experimental Example 1

[0127] This experimental example investigates the degumming time required for preparing degummed oil using the methods of Example 1 and Comparative Examples 2-7 when the content of phospholipids in the degummed oil reaches 2.2±0.3 mg / kg, specifically:

[0128] During the degumming step, the corresponding degumming agent (modified silicon dioxide, water, citric acid, food-grade silicon dioxide) is added to the vegetable cake mixed oil and the timing is started, and stirring is performed. The corresponding stirring time is the degumming time. After sampling and preservation every 0.5 minutes, the content of phospholipids in the degummed oil is measured, and the degumming time and the change of the content of aromatic substances corresponding to the phospholipid content in the degummed oil of each treatment group reaching 2.2±0.3 mg / kg are recorded. The results are shown in Table 5:

[0129] It can be seen from the experimental results in Table 5 that when different degumming processes are used, the phospholipid content reaches 2.2±0.3 mg / kg, and the degumming time of Example 1 is the shortest, indicating that the modified silica degumming method can not only shorten the degumming time, but also has no effect on the aroma substances.

[0130] Table 5 Degumming time and changes in the percentage of aromatic substances when the phospholipid content in the degummed oil prepared in Example 1 and Comparative Examples 2-7 reaches 2.2±0.3 mg / kg

[0131]

[0132]

[0133] Experimental Example 2 Optimization experiment of degumming time

[0134] This experimental example refers to the method of Example 1, and studies the effects of different degumming times (i.e., stirring times) in step 8) of 0 min, 0.5 min, 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 3.5 min, and 4 min on the content of phospholipids and aromatic substances in rapeseed oil. The results are as follows Figure 2-3 shown.

[0135] from Figure 2-3 It can be seen from the experimental results that with the extension of degumming time, the phospholipid content shows a trend of decreasing and then gradually flattening. When the degumming time reaches 2.5 minutes, the phosphorus content reaches 2.2 mg / kg, and there is no obvious change in the phospholipid content as time goes by. This may be because the modified silica adsorption sites fully exert their adsorption effect as time goes by, and then when the saturation point is reached, the adsorption effect is not obvious; and with the extension of degumming time, the percentage of aromatic substances shows a slow downward trend. In order to ensure the degumming effect and efficiency and retain more aromatic substances, the present invention selects a degumming time of 2-3 minutes, which can achieve a good degumming effect and retention of aromatic substances.

[0136] Experimental Example 3 Optimization experiment of modified silica addition amount

[0137] This experimental example refers to the method of Example 1 to study the effects of different modified silicon dioxide addition amounts of 0, 0.02%, 0.04%, 0.06%, 0.08%, 0.1%, and 0.2% in step 8) on the contents of phospholipids and aromatic substances in rapeseed oil. The results are as follows: Figure 4-5 shown.

[0138] from Figure 4-5 It can be seen that with the increase of the amount of modified silica added, the phospholipid content shows a trend of first decreasing and then leveling off. When the amount of silica added is 0.04-0.08%, the phospholipid content is within 3 mg / kg, and when the amount of modified silica added continues to increase, the modified silica has reached saturation and will agglomerate to form silica scale, causing the degummed oil to become turbid and the agglomerated modified silica to lose its adsorption capacity, so that even if its addition amount is increased, the phospholipid content no longer changes significantly; in addition, with the increase of the amount of modified silica added, various aroma substances show a downward trend without any difference, and the degumming of surface modified silica will not cause a great loss in the content of aroma substances. Considering its adsorption effect and the loss of aroma substances, the preferred addition amount is 0.04%-0.08%.

[0139] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing fragrant rapeseed oil, characterized in that: The following steps are involved: 1) Remove impurities from raw materials; 2) Roast the seeds; 3) Press to obtain pressed oil and rapeseed meal; 4) Filter for the first time to obtain crude oil; 5) Mix the crude oil and rapeseed meal; 6) Filter for the second time to obtain rapeseed cake mixed oil; 7) Preparation of modified silica: a) extracting protein from rapeseed meal to prepare a rapeseed meal protein solution; b) adding glutamine transaminase to the rapeseed meal protein solution to denature the protein to obtain a modified protein; c) adding calcium citrate to the modified protein to obtain calcium cross-linked protein gel; d) adding silicon dioxide to the calcium cross-linked protein gel to obtain modified silicon dioxide; 8) degumming with modified silicon dioxide: adding modified silicon dioxide to the rapeseed mixed oil at a weight of 0.04-0.08% of the rapeseed mixed oil, stirring at a stirring speed of 100-300 r / min and a temperature of 10-40° C. for 2-3 minutes, and then filtering for the third time to obtain degummed oil; 9) winterizing to obtain fragrant rapeseed oil; The specific steps of step 7) are: a) extracting protein from rapeseed meal to obtain rapeseed meal protein, and then dissolving the rapeseed meal protein in a 0.1 mol / L NaCl solution while stirring to prepare a rapeseed meal protein solution with a concentration of 5-20%; b) adding 20-100 U / g of glutamine transaminase according to the weight of rapeseed meal protein, adjusting the pH value to 6-9, stirring at a temperature of 30-60°C for 2 hours, then placing at 90°C for 10 minutes to inactivate the enzyme, and after the reaction is completed, taking out and quickly freeze-drying to obtain modified protein; c) adding a 200 mmol / L calcium citrate solution to the modified protein at a concentration of 2-4% of the weight of the modified protein, stirring for 30 minutes, rinsing with distilled water three times, and drying at 50° C. to obtain a calcium cross-linked protein gel; d) dissolving the calcium cross-linked protein gel in distilled water, wherein the solid-liquid ratio of the calcium cross-linked protein gel to the distilled water is 1:10-20, adding silicon dioxide to the calcium cross-linked protein gel at a rate of 1-5% of the weight of the calcium cross-linked protein gel, stirring for 6-12 hours, and centrifuging for 5-10 minutes to obtain modified silicon dioxide for later use; The specific operation steps of extracting protein from rapeseed meal in step a) are as follows: taking rapeseed meal with a mesh size of 80, adding 6 times of water and heating to 45°C, adjusting the pH to 4.3, adding cellulase at 1.25% of the weight of the rapeseed meal, and reacting for 130 minutes; then adjusting the pH to 8.0 with NaOH, adding Alcalase at 0.4% of the weight of the rapeseed meal, heating to 55°C for soaking, reacting for 150 minutes, centrifuging at 3000 r / min for 20 minutes, collecting the supernatant, adjusting the pH to 5.2, centrifuging again, and vacuum drying to obtain rapeseed meal protein.

2. The method for preparing a fragrant rapeseed oil as claimed in claim 1, wherein: After removing impurities in the step 1), the moisture content of the rapeseed raw material is 7%-15%.

3. A method for preparing a fragrant rapeseed oil as claimed in claim 1, characterized in that: In the step 2), the temperature for frying the seeds is 120-145° C., the frying time is 20-40 min, and the moisture content of the seeds after frying is 1%-5%.

4. A method for preparing a fragrant rapeseed oil as claimed in claim 1, characterized in that: The specific steps of step 5) are: after crushing rapeseed meal, add powdered rapeseed meal into the crude oil at 10%-30% of the weight of crude oil, fully stir at a temperature of 40-90° C. for 30 minutes, and stand overnight to obtain a rapeseed meal mixture for standby use.

5. The method for preparing a fragrant rapeseed oil as claimed in claim 1, wherein: In the step 8), the amount of modified silicon dioxide added is 0.06% of the weight of the vegetable cake mixed oil, and the stirring time during degumming is 2.5 minutes.

6. A method for preparing a fragrant rapeseed oil as claimed in claim 1, characterized in that: The step 8) also includes a step of degumming the rinse solution before the third filtration. The specific operation steps of the degumming of the rinse solution are: adding the rinse solution rinsed with distilled water in step c) to the oil sample degummed by the modified silica, the volume ratio of the rinse solution to the oil sample is 1:50-80, and stirring for 1-1.5 minutes at a stirring speed of 100-300 r / min and a temperature of 10-40°C.

7. A method for preparing a fragrant rapeseed oil as claimed in claim 1, characterized in that: The specific steps of step 9) are: placing the degummed oil in a crystallization tank for stirring and crystallization, first stirring at a speed of 20-40 r / min until the oil temperature reaches 10°C, then stirring at a low speed of 5-10 r / min until the oil temperature reaches -2--4°C, stopping stirring, and keeping the oil sample at this temperature for 24-48 hours. After the grains grow, the cooled and crystallized oil sample is filtered at 4-6°C to obtain the fragrant rapeseed oil.

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