| Rice bran is the by-product of rise processing and is the superficial layer attached to the brown rice after rice hulling process. It consists of epicarp, mesocarp, crosslinking layer, seed coat and aleurone layer and accounts for5-7wt.%of rice. The yearly output of rice bran in our country is over14million tons, which is the largest amount in the world. So the rice bran is a huge, wide-spread and renewable resource. The United Nations Industrial Development Organization (UNIDO) has recognized it as a resource that hasn’t been made full use of. Rice bran is the cream of the crop. Some bioactive substances it contains, such as unsaturated fatty acid, tocopherol, tocotrienols, lipopolysaccharide, dietary fiber, squalene and γ-oryzanol have remarkable roles in human’s heart cerebrovascular disease prevention, organism immunity improvement, anticancer, constipation and obesity prevention and so on. It is an important material in the areas of functional food, medication and chemical manufacturing and is gaining a wide notice around the world.Even though the amount of the resource is huge in our country and it lies in world’s top level, rice bran hasn’t been made full use of. Comparing with American and Japan, the gap of comprehensive utilization is a bit remarkable. In our country, rice bran is mostly used for animal food, and only a small part is applied to oil expression or further prepared for phytic acid, ionsitol, oryzanol and so on. This resource hasn’t been used properly and has low additional value. Therefore, taking full advantage of this abundant resource, making further step for the research and development of rice bran product and improving economic benefit for the rice processing enterprises are extremely imperative. In this study, the rice bran was taken as raw material and the key techniques such as supercritical CO2extraction, molecular distillation and high temperature extrusion were used to extract and purify rice bran oil and active ingredients in rice bran. The whole utilization of raw material and the non-waste production would be realized and the additional value of rice bran would be greatly improved.1The main points of study(1) Studies on the extraction and refinement of rice bran oil with supercritical CO2extraction technique.(2) Studies on the extraction and purification of rice bran sterol with molecular distillation technique.(3) Studies on the extraction of rice bran phytic acid with entrainer-type supercritical CO2 extraction technique.(4) The preparation and application of the high-quality dietary fiber with low phytic acid.2The main innovations(1) The rice bran was taken as raw material and the selective supercritical CO2extraction technique was used to extract and refine the rice bran oil. The extraction and purification were completed at one time and the refined rice bran oil which is on par with national-standards was gained. Compared with traditional ones, such processes as deguming, dewaxing, decolorization and deodorizing were omitted. And the pollution was eliminated during the whole process.(2) The entrainer-type supercritical CO2extraction technique was applied to extract phytic acid. No solvent was used during the process compared with the traditional one and the processes such as acid soak, neutralization were omitted. There wasn’t any poisonous or harmful substances left in residue, which made it possible for the further process of rice bran dietary fiber.(3)The phytic acid-deprived rice bran was taken as raw material to produce low phytic acid, high-quality dietary fiber. The product was better in nutritional characteristics.3Results of studies(1) The rice bran was taken as raw material and the supercritical CO2extraction technique was used to extract the rice bran oil. Through Response surface methodology analysis, it suggested that extraction pressure showed the most noticable influence on the yield of rice bran oil. Then extraction time had relatively lower influence on the yield and lastly extraction temperature had the slightest influence. The optimized extraction temperature, extraction pressure and extraction time were52℃,24MPa and1.8h respectively. The yield of rice bran oil was95.12%under these best conditions.(2) On the basis of the optimized conditions of supercritical CO2extraction of rice bran oil, the two-step-extraction, four-step-separation and four-step-rectification type supercritical CO2extraction device was used to refine the rice bran oil. The physical and chemical properties of each rectified components under different conditions and the yield of refined rice bran oil was tested. The optimized rectification conditions were achieved when rectification pressure was lOMPa, rectification temperature was20-25-30-35-40-45℃.The yield of refined rice bran oil was61.43%.(3) GC-MC was performed to determine the components of fatty acids in rice bran oil. Through the search of NIST search2.0standard-spectrogram library, eight fatty acids were identified, in which there were four unsaturated fatty acids. The relative content of unsaturated fatty acids was80.30%and the main components were oleic acid and linoleic acid, which were 39.51%and38.03%respectively. There are four saturated fatty acids, and their relative content was19.70%.(4) The distillate from rectification I was used as raw material and molecular distillation technique was applied to extract and purify rice bran sterol. Through Response surface methodology analysis, it suggested that evaporating temperature showed the most noticable influence on the phytosterol content. Then feed rate had relatively lower influence on the phytosterol content and the wiper rolling speed had the slightest influence. The optimal conditions of molecular distillation were achieved when evaporating temperature was180℃, wiper rolling speed was420r/min and feed rate was2.7mL/min. The content of phytosterol was63.85%.(5) Anhydrous ethanol was used as the recrystallization solvent for further refined phytosterol. The final sterol product had purely colour, with90.17%of purification and65.54%of yield.(6) GC-MC was performed to determine the phytosterol components of refined sterol product. Three phytosterols was identified, which are campesterol, stigmasterol and sitosterol. The contents of campesterol, stigmasterol and sitosterol were25.57%,21.18%and53.25%respectively.(7) The defatted rice bran was used as raw material and the entrainer type supercritical CO2extraction technique was applied to extract phytic acid. Through Response surface methodology analysis, it suggested that extraction temperature showed the most noticable influence on the yield of phytic acid. Then extraction time had relatively lower influence on the yield and at last extraction temperature had the slightest influence. The optimal extraction conditions were achieved when extraction time was3h, extraction temperature was54℃and extraction pressure was26MPa. The yield of phytic acid was93.14%.(8) Four anion exchange resins D315,717#, Amberlite IRA-68and DEAE Sephadex A-25were applied for the static absorption experience. The717#anion exchange resin showed more absorption capacity and was suitable for industrial production. So it was selected in this study to purify phytic acid. The concentration of NaCl eluant was determined as1.0mol/L, and flow rate was2mL/min.(9) The quality of phytic acid product was detected and results showed that the purity was58%and the contents of all impured ions met the standard.(10) The rice bran contained low phytic acid was used as raw material to produce high-quality dietary fiber. The twin-screw extrusion technique was applied to modified LPA-DF and to improve the SDF content. Through Response surface methodology analysis, it suggested that extrusion temperature showed the most noticable influence on the yield of SDF. Then the particle size of material had relatively lower influence on the yield and moisture had the slightest influence. The optimal extrusion conditions were achieved when extrusion temperature175℃, moisture was90%and partical size was60mesh. The yield of SDF was11.38%.(11) The physical characteristics of LPA-DF and LPA-HQDF were studied. The swelling capacity, water-holding capacity and oil-holding capacity of LPA-DF were3.55mL/g,5.74g/g, and4.52g/g respectively, while the ones of LPA-HQDF were5.38mL/g,7.06g/g and5.45g/g respectively. The physical property of extrusion-modified LPA-HQDF is much better than that of non-modified LPA-DF.(12) LPA-HQODF was observed from micro structure level. The structure was loose and there were rose-like wrinkles and many big cavities. There are many holes on the surface, which were benefit to water permeation and bound. However, the structure of LPA-DF was relatively tight and flaky and the surface was smooth and flat. X-ray diffraction curves showed that extrusion modification did not destroy or had little destructive effect on the crystalline region of LPA-HQDF. The extrusion treatment make it possible for the release of water-soluble substances of amorphous region.(13) The application of LPA-HQDF into bread was studied. Through sensory evaluation and bread texture analysis with different amounts of LPA-HQDF, the maximum addition of LPA-HQDF into bread was determined as9%. Under this condition, the bread had good flavor. It was soft and resilient and had slight fragrance of rice bran. |
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