TW201713219A - A processing method for rice bran oil extraction - Google Patents

Abstract

This is an extraction processing for rice bran oil. First, rice ban is quickly heated by radio frequency to inactivate lipase and to enhance stability and utilization of rice bran. Then ethanol is the extraction solvent, and rice bran oil and oil-soluble substances can be rapidly extracted by a focused ultrasound and microwave extraction system to obtain higher extraction yield. Finally, the ethanol extract is obtain by a solid-liquid separation; and ethanol can be rapidly vacuum evaporated, condensate and recovery by a microwave vacuum system, The rice bran oil can be concentrated and purified in this extraction processing to avoid high-temperature oxidation. Overall, this rice bran oil extraction process is quick, energy saving and higher extraction yield and stability.

Description

Method for preparing extracted rice bran oil

The invention of the process for extracting rice bran oil first uses radio frequency rapid heating to inactivate the lipolytic enzyme in the rice bran, because the frequency of the radio frequency electromagnetic wave is smaller than that of the microwave, greatly increasing the penetration depth and increasing the temperature distribution uniformity of the rice bran heating, and overcoming the heat transfer obstacle. It can be used to enhance the stability of the production of rice bran. Replacing traditional n-hexane with ethanol as an extraction solvent not only enhances the safety of the extract, but also is a friendly and ecological extraction solvent. It uses continuous focused ultrasound and microwave to quickly extract the oil and oil-soluble substances in rice bran. The focused ultrasonic effect is better than the traditional washing ultrasonic method and the time is shorter, but it is easy to generate heat, so it is not suitable for the solvent to be heated and extracted first. This will cause the focus ultrasonic device to malfunction, so it is changed to follow the microwave again. Heating equipment can quickly heat the extract to increase the extraction rate of rice bran oil, which can save energy and save time. Finally, the solid-liquid separation extract is concentrated by microwave vacuum to dilute the rice bran oil, the evaporation temperature of the ethanol solvent can be lowered under the vacuum system, and the solvent can be rapidly heated by the microwave, and the evaporated ethanol can be condensed and recovered, and the rice bran oil can be avoided as much as possible. Oxidized because of high temperature for a long time Overall, this rice bran oil extraction process is fast, energy efficient and enhances the quality of rice bran oil.

Rice bran is a by-product of the rice milling industry, accounting for 5-8% of the grain. Because rice bran is rich in protein, lipids, dietary fiber and antioxidant compounds such as tocopherol, tocotrienol and oryzanol, it is a natural nutritious food worthy of development and utilization. Overall, rice bran nutrition The composition accounts for 60% of the nutritional value of rice, and the oil content of rice bran is about 15-20%, and rice bran oil (black rice oil) is a nutrient-rich vegetable oil, in which the main fatty acid is oleic acid (C16:1) accounted for 40~ 50%, linoleic acid (C18:2) accounted for 30-40% and palmitic acid (C16:0) accounted for 12-18% (Hu et al., 2013). However, because rice bran contains lipolytic enzymes, it can easily hydrolyze rice bran lipids, causing rapid decomposition of oils and oxidative rancidity, and increasing the acid value of rice bran (oil). Therefore, before extracting rice bran oil, firstly, lipolytic enzymes need to be inactivated to increase rice bran utilization. And the stability of storage.

Rice bran can be destroyed by lipothermal heating for 3 min, and then combined with vacuum packaging and low temperature storage to stabilize rice bran to prolong storage time (Ramzanzadeh et al., 1999 &2000; Tao et al, 1993). Lakkakula et al. (2004) also studied heating with ohms to increase the stability of rice bran and increase the extraction rate of rice bran oil. Thanonkaew et al. (2012) used hot air, microwave, baking and steam heating to increase the stability of rice bran, and then cold pressed rice bran oil. The brightness, acid value, free fatty acid, peroxide price and antioxidant of rice bran oil Substances such as polyphenols, flavonoids and oryzanol are mostly heated by microwaves and hot air, which are superior to baking and steam. They are better than unheated rice bran oil, but because the author cannot heat the rice bran by microwave heating, Hot air preheated rice bran is recommended. This further demonstrates that this patent replaces microwave dielectric heating and hot air by means of RF heating, and must be the mainstream process for preheating rice bran to increase stability.

Rice bran oil can also be pretreated first, mainly including steaming (roasting), granulation and extrusion, and then reacting with enzyme to accelerate the decomposition of rice bran and help extract rice bran oil. For example, the extrusion-expansion assisted aqueous enzymatic method can be utilized, which firstly decomposes the starch in the rice bran by extrusion to increase the degree of gelatinization, and after the rice bran protein is deactivated by heat, the ratio of liquid to material is 1:7. 2% protease was added and reacted at 56 ° C for 2 hours, the extraction rate of rice bran oil reached 85% (week, 2014). In addition, the ultrasonic assisted aqueous enzymatic method utilizes cellulase, protease and amylase to decompose rice bran first. The cavitation effect of the supersonics is used to break the cell wall of rice bran and promote the release of oil. At present, 100 g of rice bran can be batch-treated, 1.5% enzyme reaction is added for 3 hours, and the liquid-to-liquid ratio is 1:6. After extraction for 15 min, the extraction rate of rice bran oil reached 88%, and it was more able to preserve oryzanol (Wei et al., 2014).

Rice bran oil can be prepared by different methods after the stabilized rice bran. If the rice bran oil is obtained by pressing, but the oil content in the rice bran is only 15-20%, the oil yield of the pressing is lower, and the oil yield of the leaching method is lower. High, but the antioxidant components in the oil, such as: tocopherol, oryzanol loss, and often used hexane leaching temperature of 50 ~ 60 ° C, hexane is a flammable, explosive solvent, harmful to the human body and the environment Or isopropanol as the leachate, at 60, the ratio of material to liquid is 1:5, the leaching time is 2 hours, and the extraction rate of rice bran oil can reach 89% (Zhang Hexu, 2007). Using ethanol as a solvent, the ratio of rice bran to ethanol is 1:6 (g/mL), and the ultrasonic extraction at 20 kHz and 35 °C can obtain 10.8% of rice bran oil, which is different from the traditional rice or n-hexane soaked rice bran oil. It is high at 6% and 8% (Krishnan et al., 2015).

The use of supercritical carbon dioxide to extract rice bran oil is a non-toxic extraction method, but due to the high cost of equipment, long extraction time and high cost of quantification (Wei et al., 2014). The supercritical carbon dioxide extraction method can increase the extraction rate of rice bran oil and oryzanol by controlling the flow rate of CO2 ((1-9mL/min), temperature (40-80°C) and pressure (20-40MPa) for 3 hours. An extraction amount of 0.223 g of oil/g rice bran sample (Tomita et al., 2014) was extracted with n-hexane solvent for 7 hours.

The solvent extraction of rice bran oil is necessary to carry out heating and vacuum evaporation to remove or recover the solvent to enhance the purity of the rice bran oil. This step is also quite time-consuming and energy-consuming. It is necessary to improve this step to meet safety, energy saving and carbon reduction. The principle.

The invention consists of three parts. The first part is RF heating to promote the stability of rice bran. The second part uses ethanol as the extraction solvent to extract the oil and oil-soluble substances in rice bran by focused ultrasound and microwave, such as: vitamin E and oryzanol. Etc., the third part is to use microwave vacuum to concentrate the solid-liquid separation extract to purify rice bran oil to evaporate and recover ethanol to achieve the goal of safe process, time saving, energy saving and environmental friendliness.

Figure 1 is a flow chart of the method of the present invention.

Firstly, the rice bran is placed in a high temperature resistant polypropylene (PP) plastic box and placed in an RF heating system. Generally, the weight increase of the rice bran will increase the RF output, so it is necessary to adjust the appropriate RF electrode plate spacing operation (Fig. 1), in order to obtain a larger heating rate. The temperature rise of 1kg rice bran placed under the heating of different RF electrode plates (Fig. 2), because the temperature rise of rice bran is mainly caused by the polar moisture in the RF electrode rapidly changing the positive and negative electrodes to cause rapid rotation and friction heating, at the RF electrode It is required to be 1, 5, 2, 3 and 3.5 cm at a distance of 5, 6, 8, 10 and 12 cm to reach about 100 °C. If we consider the temperature uniformity of the RF heating rice bran, 1kg rice bran is preferably heated at a distance of 6cm from the RF electrode plate for 2min, and the rice radix heating curve and the lipolytic enzyme inactivation effect of Figure 3 indicate lipolysis. Enzymes can indeed lose activity due to RF heating. The rice bran storage stability test was carried out at 25 ° C in the RF inhibitory group and the untreated (control group). The results of Table 1 show that the acid value and peroxide price of the rice bran in the control group were both at 1 week of storage. Compared with the RF treatment group, the acid value of the RF treatment group did not change significantly after 4 weeks of storage. However, the acid value of the rice bran in the control group was more than 2.5 times that of the RF treatment group, indicating that the RF heating inhibitor could indeed be used. Increase the stability of rice bran to facilitate the extraction of subsequent rice bran oil.

Weigh 20g of RF-treated rice bran and add 20 times of 95% ethanol to 400mL. The ratio of material to liquid is 1:20 in the focused ultrasonic ear extraction and microwave extraction equipment. The extraction time is controlled at 1, 3, 5 and At 7 min, the extraction rate of rice bran oil reached a maximum of 0.2125 and 0.239 g oil/g rice bran at 5 min (Table 2). However, with the extraction of rice bran oil by washing ultrasonic waves for 20, 40, 60, 80 and 100 min, the yield of extracted rice bran oil will gradually increase with the extraction time, and it will be extracted to 0.2025 g oil/g rice bran after 100 min. (Table 3), so the extraction efficiency of the focused ultrasonic wave is significantly higher than that of the washed ultrasonic wave. On the other hand, the extraction of rice bran oil with supercritical carbon dioxide for 120min and 180min can obtain 0.06 and 0.18g oil/g rice bran, so the supercritical carbon dioxide extraction time is much longer than that of ultrasonic and microwave extraction, not only expensive equipment, but also excellent extraction effect. . Finally, combined with focused ultrasound and microwave extraction, the treatment is 1.5min, the total extraction time is 3min, then the extraction amount of rice bran oil is 0.2275g oil / g rice bran, so combined with focused ultrasound and microwave extraction can significantly shorten the extraction time.

The above-mentioned rice bran ethanol extract 400mL is firstly centrifuged to obtain an ethanol extract. If a 50°C water bath is used for rotary decompression and concentration, it takes 30 to 40 minutes to complete the ethanol recovery. Rice bran oil. However, using microwave vacuum to concentrate 400mL ethanol extract, it takes only 10 minutes to complete the evaporation and condensation operation of ethanol, and the rice bran oil is collected. Therefore, the microwave vacuum concentration technology can accelerate the recovery of ethanol extraction solvent.

Claims (4)

The invention relates to a method for preparing rice bran oil, which comprises radiofrequency heating and enzyme inhibition treatment of rice bran to increase the safety, and then using ethanol as an extraction solvent, using a focused ultrasonic wave and microwave to rapidly extract the oil in the rice bran, and performing solid-liquid separation by centrifugation. Finally, the microwave is quickly evaporated, the ethanol is recovered by condensation, and the rice bran oil product is collected. The method for extracting rice bran oil according to claim 1, wherein the radio frequency heating and enzyme inhibiting the rice bran, the quantitative rice bran is first loaded in the high temperature resistant polypropylene plastic box, due to the load of the rice bran and the spacing of the radio frequency electrode plate. Will affect the output power of the radio frequency, so first determine the appropriate RF electrode plate spacing, then RF heating rice bran, and measure the surface temperature of the rice bran to more than 90 °C by infrared temperature, then the rice bran that completes the RF inhibition treatment, immediately cold air After cooling, seal the rice bran package for use. The method for extracting rice bran oil according to claim 1, wherein the focused ultrasonic wave and the microwave rapidly extract the oil in the rice bran, and the ethanol is used as the extraction solvent, and the ratio of the material to the liquid is controlled at 1:5-20, and the mixture is fully stirred. Extracted by focused ultrasonic and microwave extraction equipment for about 5~10min or continuous extraction with focused ultrasonic wave for 1~3min, then adjust the microwave power heating solution for 1~3min to obtain rice bran oil ethanol extract. The extract and the rice bran residue were subjected to solid-liquid separation using a centrifuge, and the rice bran oil extract was collected. The method for extracting rice bran oil according to claim 1, wherein the rice vacuum oil is concentrated by microwave vacuum, and the rice bran oil ethanol extract is placed in a microwave vacuum concentrator, and the vacuum degree can be controlled below 60 mmHg to reduce ethanol evaporation. The temperature and the microwave power can be adjusted to determine the temperature of the solution and the rate of heating the ethanol to evaporate, and the ethanol can be recovered by condensation to obtain the rice bran oil product quickly.