Rice bran crude oil dewaxing method using cholesterol for cooling crystallization

Abstract

The invention belongs to the technical field of plant crude oil refining, and provides a rice bran crude oil dewaxing method using cholesterol for cooling crystallization. According to the rice bran crude oil dewaxing method, impurities in the rice bran crude oil are adsorbed in the process that cholesterol is cooled and crystallized to form cholesterol crystals, then the dewaxing and decolorizing effects are achieved, in the process, the turbidity of the rice bran crude oil can be effectively reduced, the transparency of the rice bran crude oil is improved, and the quality of the rice bran crude oil is improved. Moreover, the retention rate of the key nutritional ingredient oryzanol is greatly improved and reaches 85.47%, and the quality of the rice bran crude oil is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of crude plant oil refining, and particularly relates to a crude rice bran oil dewaxing method utilizing cholesterol cooling crystallization. Background Art

[0002] Crude rice bran oil naturally contains 2% to 5% bran wax, which will crystallize into particles and condense and settle due to the decrease in solubility under normal temperature. Even if there is only a small amount or trace amount of wax in the oil, it will cause its cloud point and turbidity point to increase, directly affecting the transparency of the oil, and deteriorating its smell, taste and palatability. In addition, bran wax has high chemical stability, is difficult to hydrolyze, and is not suitable for human digestion, thereby reducing the digestibility and overall nutritional value of rice bran oil. In the existing field of crude rice bran oil dewaxing technology, there are mainly two mainstream methods: freeze dewaxing and solvent dewaxing.

[0003] The specific steps of freeze dewaxing technology are: first, introduce the vacuum dehydrated rice bran oil into the crystallization tank, and then cool it under slow stirring, so that the oil temperature slowly and evenly drops from 70°C to 25°C in about 24 hours. After this stage, continue to slowly stir and keep the oil temperature unchanged to grow crystals. The crystal growth time is more than 48 hours. After the crystal growth is completed, use a leaf filter pre-coated with diatomaceous earth for filtering. However, this technology has significant disadvantages: the entire process is time-consuming and lengthy; the process relies on specific separation (filtration) and stirring equipment, and the process is complicated; the temperature control requirements are strict. If the filtration temperature is increased, the wax content in the dewaxed oil will increase, which will affect the cloud point and transparency of the oil; on the contrary, if the temperature is too low, it will significantly reduce the filtration rate and increase the oil content in the wax paste.

[0004] The technical scheme of solvent dewaxing is as follows: first preheat the deacidified and neutralized rice bran oil to 80°C, then pump it into a high-level tank, and then flow into the cooling tower from the bottom of the tank for cooling. In the mixer, add the solvent in a certain proportion (such as oil: solvent = 60:40) for mixing. After cooling to 18°C ​​to 20°C from the solvent tank through a pump and a cooler, the uniformly mixed solvent rice bran oil mixture is sent to a pre-coated vacuum filter for filtration. Although the solvent dewaxing method does not have extremely strict requirements on the solvent ratio, when the solvent content is insufficient, the improvement in fluidity is limited, which may lead to poor dewaxing effect. In addition, if toxic solvents such as butanone are used, the residue in the oil will pose a threat to human health. In addition, the large initial equipment investment and high solvent loss make this technology face challenges in promotion and application, and its process still needs to be further optimized and improved. Summary of the invention

[0005] The present invention solves the above technical problems and proposes a method for dewaxing crude rice bran oil by utilizing cholesterol cooling crystallization. The method for dewaxing crude rice bran oil provided by the present invention utilizes the process of cholesterol cooling crystallization to form cholesterol crystals to absorb impurities in the crude rice bran oil, thereby achieving the effects of dewaxing and decolorization. In this process, not only can the turbidity of the crude rice bran oil be effectively reduced and its transparency be improved, but also the retention rate of the key nutrient component oryzanol is greatly improved to 85.47%, thereby significantly improving the quality of the dewaxed rice bran oil.

[0006] The technical scheme of the present invention is: a method for dewaxing crude rice bran oil by utilizing cholesterol cooling crystallization, which mainly comprises the following steps:

[0007] Weigh 10 mL of crude rice bran oil into a stoppered conical flask, add 1.5 g of cholesterol, place in a 70°C water bath, stir at 500 r / min for 30 min, let stand at 4°C for 16 h-24 h, centrifuge at 7500 r / min for 3 min, take the supernatant after centrifugation to obtain dewaxed rice bran oil, and then calculate its decolorization rate, turbidity and oryzanol content.

[0008] Compared with the prior art, the present invention has the following advantages and effects:

[0009] (1) The crude rice bran oil dewaxing method utilizing cholesterol cooling crystallization can dewax and decolorize the crude rice bran oil and improve the high retention rate of oryzanol;

[0010] (2) The method provided by the present invention has simple operation process, low cost, does not require complicated instruments, has short reaction time, and is suitable for industrial dewaxing of crude rice bran oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 To study the effect of adding different amounts of cholesterol on the decolorization rate of crude rice bran oil;

[0012] Figure 2 To study the effect of adding different amounts of cholesterol on the transparency of crude rice bran oil;

[0013] Figure 3 To study the effect of adding different amounts of cholesterol on the turbidity of crude rice bran oil;

[0014] Figure 4 This is the effect of adding 1.5g / 10mL of cholesterol on oryzanol in crude rice bran oil. DETAILED DESCRIPTION

[0015] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in conjunction with specific implementation methods.

[0016] Example 1

[0017] A method for dewaxing crude rice bran oil by utilizing cholesterol cooling crystallization mainly comprises the following steps:

[0018] Take 10mL of crude rice bran oil and put it in a stoppered conical flask, add 1.5g of cholesterol, stir it in a 70℃ water bath at 500r / min for 30min, let it stand at 4℃ for 20h, then centrifuge it at 7500r / min for 3min, take the supernatant and obtain dewaxed rice bran oil.

[0019] Example 2

[0020] A method for dewaxing crude rice bran oil by utilizing cholesterol cooling crystallization mainly comprises the following steps:

[0021] Take 8 mL of crude rice bran oil and put it in a stoppered conical flask, add 1.0 g of cholesterol, stir it in a 65°C water bath at 500 r / min for 30 min, let it stand at 4°C for 16 h, then centrifuge it at 7500 r / min for 2 min, take the supernatant and obtain dewaxed rice bran oil.

[0022] Example 3

[0023] A method for dewaxing crude rice bran oil by utilizing cholesterol cooling crystallization mainly comprises the following steps:

[0024] Take 12mL of crude rice bran oil and put it in a stoppered conical flask, add 2.0g of cholesterol, stir it in a 75℃ water bath at 500r / min for 30min, let it stand at 4℃ for 24h, then centrifuge it at 7500r / min for 5min, take the supernatant and obtain dewaxed rice bran oil.

[0025] Example 4

[0026] The effect of the amount of cholesterol added on the decolorization rate, transparency, turbidity and oryzanol content of the dewaxed rice bran oil was investigated. The specific experiment is as follows:

[0027] The decolorization rate, transparency, turbidity and oryzanol content of dewaxed rice bran oil were investigated according to the following methods:

[0028] (1) Calculation formula of decolorization rate

[0029] Decolorization rate (%) = (A0-A1) / A0×100%,

[0030] Where: A0—absorbance of crude rice bran oil before bleaching;

[0031] A1—absorbance of crude rice bran oil after bleaching;

[0032] (2) Transparency: Observe the color changes of the two groups of oils with the naked eye.

[0033] (3) Turbidity: Use a turbidity meter to directly output data;

[0034] Manufacturer, name and model of the above turbidity meter: Italy HANNA Portable Turbidimeter HI98703 [EPA Standard]

[0035] (4) Calculation formula for oryzanol content, refer to LS / T 6121.1-2017:

[0036]

[0037] Where:

[0038] X—oryzanol content in the sample, %;

[0039] A—absorbance of the sample to be tested;

[0040] V—volume of the liquid to be tested, in milliliters (mL);

[0041] N—the dilution multiple of the sample after it is fixed to volume. If no dilution is performed, N=1;

[0042] m—sample mass, in grams (g);

[0043] 359—Extinction coefficient (E), which indicates the absorbance measured at a wavelength of 315 nm in a 10 mm cuvette with a concentration of 1 g / 100 mL (1%).

[0044] The calculation result shall be rounded to two decimal places.

[0045] 4.1 Effect of cholesterol addition on decolorization rate of crude rice bran oil

[0046] With reference to the method in Example 1, the ratio of cholesterol to crude rice bran oil was adjusted to investigate the influence of different cholesterol additions on the decolorization rate of crude rice bran oil. The cases of different cholesterol dosages were recorded as: Examples 5, 6, 7, 8, 9; as shown in Table 1 below:

[0047] Table 1 Effect of cholesterol addition on decolorization rate of crude rice bran oil

[0048]

[0049] from Figure 1 It can be seen from the data in Table 1 that when the volume mass ratio of crude rice bran oil to cholesterol is 10 mL: 1.5 g, the decolorization rate of crude rice bran oil reaches 26.5%. This confirms that the crude rice bran oil dewaxing method using cholesterol cooling crystallization of the present invention can assist the decolorization of crude rice bran oil, and its effect is to reduce the intensity requirement of decolorization, thereby helping to reduce the amount of decolorizing agent used in the subsequent refining step.

[0050] 4.2 Effect of cholesterol addition on the transparency of crude rice bran oil

[0051] Figure 2 It represents the effect of adding different amounts of cholesterol on the transparency of crude rice bran oil. From left to right in the figure, the transparency of dewaxed rice bran oil obtained when the volume mass ratio of crude rice bran oil to cholesterol is 10mL:0g, 10mL:1.5g, and 10mL:1.0g. It can be observed very intuitively that the addition of cholesterol can effectively improve the transparency of dewaxed rice bran oil, and the effect is best when the volume mass ratio of crude rice bran oil to cholesterol is 10mL:1.5g.

[0052] 4.3 Effect of cholesterol addition on turbidity of crude rice bran oil

[0053] Table 2 Effect of different cholesterol addition amounts on the turbidity of crude rice bran oil

[0054]

[0055] Combined with Table 2 Figure 3 It can be seen from the data that the turbidity of the control group was 35.38NTU. When the volume mass ratio of crude rice bran oil to cholesterol was 10mL:1.5g, the turbidity of crude rice bran oil was 13.12NTU, which significantly reduced the turbidity of crude rice bran oil.

[0056] 4.4 Effect of cholesterol addition on oryzanol content in crude rice bran oil

[0057] Table 3 Effect of different cholesterol addition amounts on oryzanol content in crude rice bran oil

[0058]

[0059] Table 3 Figure 4 The data show that when the amount of cholesterol added is 0, the oryzanol content of crude rice bran oil is 1.79, when the volume mass ratio of crude rice bran oil to cholesterol is 10mL:1.5g, the oryzanol content of dewaxed rice bran oil is 1.53, and the oryzanol retention rate of the dewaxed rice bran oil obtained by the method of the present invention is as high as 85.47%.

[0060] In summary, the crude rice bran oil dewaxing method proposed in the present invention not only achieves a significant dewaxing effect by utilizing the cooling crystallization mechanism of cholesterol, but also has a decolorization function and ensures a high retention rate of oryzanol.

[0061] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent changes and modifications made within the scope of the present invention should still fall within the scope of the present invention.

[0062] Comparative Example 1

[0063] Referring to the method in the article "Study on esterification and deacidification of high-acid rice oil and enzymatic preparation of diglyceride-rich rice oil", crude rice bran oil was treated with enzyme method. The oryzanol retention rate was 92.44% after testing, and the oryzanol retention rate of crude rice bran oil obtained by chemical esterification treatment was 40.23%.

[0064] In contrast, the method in the present application is used to treat crude rice bran oil, and the oryzanol retention rate is as high as 85.47%, which is much higher than the chemical method disclosed in the above document. Although the enzymatic treatment in the document makes the oryzanol retention rate at a relatively high level, the enzymatic treatment has the following significant drawbacks: first, the high cost of the enzyme and its special requirements for storage and transportation greatly increase the production cost; second, the stability of the enzyme cannot be ignored, and a slight change in the reaction conditions may lead to a decrease in enzyme activity or inactivation, thereby affecting the treatment effect; furthermore, the enzyme is often difficult to recycle and reuse in the process of treating crude rice bran oil, which not only causes a waste of resources, but also further increases the cost; finally, improper enzyme usage or reaction conditions may have a negative impact on product quality, such as residual enzyme affecting the purity of rice bran oil, or causing changes in other components in rice bran oil.

Claims

1. A method for dewaxing crude rice bran oil utilizing cholesterol cooling crystallization, characterized in that, The following steps are involved: Put crude rice bran oil in a stoppered conical flask, add cholesterol, the volume mass ratio of crude rice bran oil to cholesterol is: (8-12) mL: (1.0-2.0) g; heat the material in the stoppered conical flask to 65-75°C, stir at 500 r / min for 30 min, let stand at 4°C for 16-24 h, then centrifuge at 7500 r / min for 2-5 min, take the supernatant and obtain dewaxed rice bran oil.

2. a kind of rice bran crude oil dewaxing method utilizing cholesterol crystallization by cooling as claimed in claim 1, is characterized in that, The volume mass ratio of crude rice bran oil: cholesterol is 10 mL: (1~2) g.

3. a kind of rice bran crude oil dewaxing method utilizing cholesterol crystallisation by cooling as claimed in claim 1, is characterized in that, Heating method: water bath heating.

4. a kind of rice bran crude oil dewaxing method utilizing cholesterol crystallisation by cooling as claimed in claim 3, is characterized in that, The volume mass ratio of crude rice bran oil: cholesterol is 10 mL:1.5 g; the water bath temperature is 70°C.

5. a kind of rice bran crude oil dewaxing method utilizing cholesterol crystallization by cooling as claimed in claim 1, is characterized in that, The following steps are involved: Take 10mL of crude rice bran oil and put it in a stoppered conical flask, add 1.5g of cholesterol, stir it in a 70℃ water bath at 500r / min for 30min, let it stand at 4℃ for 20h, then centrifuge it at 7500r / min for 3min, take the supernatant and obtain dewaxed rice bran oil.

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