| After a long fermentation process in the production process, the crude corn oil extractedfrom DDGS had a high acid value and a strong odor; At the same time, after the heating anddrying process, the color of crude corn oil was much deeper than the general crude corn oildirectly extracted from corn germ. Impact of different refining factors on the refining yield,acid value, color and phospholipid content in the crude corn oil refining process was studied.Through the process, the optimum refining conditions of the crude corn oil were obtained.The main factors and reasons for color reversion of the refined corn oil were studied forproviding some theoretical reference for delaying color reversion of refined corn oil.The process of alkali refining of the corn oil with a high acid value extracted from cornalcohol stillage was studied. The results showed that: no matter how much the content ofsolvent was in the miscella, the acid values of corn oil could be reduced below0.50mg/g byalkali refining, the phospholipid contents could be reduced to56.4mg/kg (phosphorus contentof2.1mg/kg). Comparing with the alkali refining in the solvent-free system, content ofdiacylglycerol could reach to4.61%(the remaining ratio of diacylglycerol was3.70%), andthe refining rate was also higher. However, there was a great difference in the content ofdiacylglycerols among the different deacidified corn oil. When the acid value of corn oil wasin the2.0-5.0mg/g range, phospholipid contents could decreased to a level lower than150.0mg/kg (phosphorus content was5.7mg/kg), refining rate reached to78.0%, and the colour andlustre of oil could be improved obviously. In addition, the remaining ratio of diacylglycerolunder alkali refining was still in the range of73.0%~89.4%.The chemocatalysis esterification deacidification of high acid corn oil was studied usingsingle factor-response surface methodology. Results showed that under the optimum conditions ofzinc chloride charge0.18wt%, glycerol charge150wt%, a reaction temperature of189℃anda reaction time of30min, the acid value of the esterified oil could be reduced to1.2mg/g andthe diacylglycerol content reached6.38%.The optimum conditions of single factor experiment of corn oil bleaching process were asfollows: the addition of activated clay was10wt%, bleaching temperature was100℃,bleaching time was30min. Under the conditions of that, the refining rate of decolorization was91.4%, the Lovibond color were reduced to Y30.0, R3.2from the original Y30.0, R20.0,and the removal rate of color was91.5%.The factors affecting color reversion of refresh corn oil was exploratory discussed.Comparing with the fresh corn oil, the color reversion corn oil’s acid value and anisidinevalue changed little, but the peroxide value was about40times higher than that of the freshcorn oil, the total tocopherol content was only half of the fresh corn oil. Color reversion of thecorn oil was closely related to the storage temperature and time, lower temperature caneffectively delay color reversion of the oil. Color reversion of corn oil occurred in the earlystage of oil oxidation, peroxide value was under0.55mmol/kg during that time, and thetocopherol content and anisidine value barely changed. But the color of corn oil maintained ata deeper level in the later oxidation stage(peroxide value was more than2.2mmol/kg), but inthe meanwhile，the tocopherol content was significantly reduced with the deepening of theoil’s oxidation. Exogenous antioxidant TBHQ could effectively inhibit the oxidation of cornoil and tocopherol, but there was no significant improvement for the color reversion of cornoil. |
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