| 3-monochloropropane-1,2-diol esters(3-MCPDEs)and glycidyl esters(GEs)are the two harmful substance which are formed in the process of oil processing.Its hydrolysate can stimulate and trigger the canceration of human organs.The safety of edible oil on 3-MCPDEs and GEs is a hotspot of recent attention in the field of oil at home and abroad.Previous research shows:corn oil is one of the edible oils which were seriously polluted by 3-MCPDEs and GEs.The formation of 3-MCPDEs and GEs in edible oils is mainly influenced by monoglyceride,diglyceride,chlorine ion,and oil refining process.In this article,the influence of the content of monoglyceride and diglyceride in the process of degumming,alkali refining,bleaching,dewaxing and deodorization on the contents of 3-MCPDEs and GEs in corn oil was discussed.The changes of 3-MCPDEs and GEs in corn oil in the process of degumming,alkali refining,bleaching,dewaxing and deodorization were analyzed.Based on the control of3-MCPDEs and GEs,the refining process of corn oil was optimized.Firstly,different amounts of monoglyceride and diglyceride were added to the crude oil,degumming oil,alkali refining oil,bleaching oil and dewaxing oil,then the oils were refined under the same conditions.Results showed:during the degumming process,the contents of3-MCPDEs and GEs in the degumming oil increased with the increase of the content of monoglyceride and diglyceride in the crude oil,and the diglyceride had a stronger effect on3-MCPDEs and GEs than the monoglyceride in the process.The content of 3-MCPDEs increased with the increase of the content of monoglyceride and diglyceride,and the monoglyceride had a stronger effect on the 3-MCPDEs than the diglyceride during alkali deacidification process.The content of GEs increased with the increase of monoglyceride and decreased with the increase of the content of diglyceride in the process of alkali refining and deacidification.During the decolorization process,the contents of 3-MCPDEs and GEs increased with the increase of the content of monoglyceride and diglyceride.And the diglyceride had a stronger effect on the 3-MCPDEs and GEs than the monoglyceride in the process.The contents of 3-MCPDEs and GEs increased with the increase of the content of monoglyceride and diglyceride,but the increment of 3-MCPDEs was much larger than GEs during the dewaxing process.During the deodorization process of steam distillation,the contents of 3-MCPDEs and GEs increased with the increase of the content of monoglyceride and diglyceride.The increment of GEs was much larger than 3-MCPDEs.The diglyceride had a stronger effect on the GEs than the monoglyceride in the process.Secondly,the changes of the content of 3-MCPDEs and GEs in the process of degumming of corn oil,alkali refining and deacidification,adsorption decolorization,winter dewaxing and steam distillation deodorization were studied.The contents of 3-MCPDEs and GEs in 7 kinds of degumming oil,alkali oil refining,dewaxing oil and deodorizing oil were detected and analyzed.The results showed that the content of 3-MCPDEs decreased,and the reduction range was 5.67%~32.82%after hydrated degumming.The change of the content of GEs was not regular.After the alkali refining,the changes of the contents of 3-MCPDEs and GEs were not regular.The content of 3-MCPDEs in alkaline refining oil 2 increased by 0.531mg/kg to 0.685 mg/kg,which increased by 29.01%.The content of 3-MCPDEs in alkaline refining oil 4 decreased by 0.611 mg/kg to 0.423 mg/kg,which decreased by 30.76%.GEs content in degummed oil 7 increased from 0.312 mg/kg to 0.554 mg/kg,an increase of77.56%,and the GEs content in alkaline refining oil 4 decreased from 0.585 mg/kg to 0.233mg/kg,a decrease of 60.17%.The maximum increment of 3-MCPDEs and GEs was 29.01%and 77.56%,respectively.The maximum reduction of 3-MCPDEs and GEs was 30.76%and61.88%respectively.The content of 3-MCPDEs increased,the range of increase was22.91%~52.95%,and the content of GEs decreased,the reduction range was 4.04%~64.55%after the process of adsorption and decolorization.In corn oil dewaxing process,the content of 3-MCPDEs were lower,the reduction range was 10.54%~34.93%,and the scope of reduction was-25.19%~31.84%;the content of 3-MCPDEs and GEs increased significantly.The fold increase in 3-MCPDEs content ranged from 3.62 to 7.52,and the fold increase in GEs content ranged from 12.42 to 25.41.Finally,based on the content control of 3-MCPDEs and GEs,the refining process was optimized in corn oil.Hydrated degumming:phosphoric acid was 0.05%,the temperature was65°C,and the time was 35 min.Under these conditions,the content of 3-MCPDEs decreased from 0.662 mg/kg to 0.597 mg/kg,and the reduction range was 9.81%.The content of GEs decreased from 0.338 mg/kg to 0.205 mg/kg,and the reduction was 39.34%.The content of monoglyceride decreased from 1.41%to 0.38%,and the content of diglyceride decreased from 6.02%to 2.10%.The reduction of monoglyceride and diglyceride was 74.04%and65.11%,respectively.The content of phospholipid in the oil was 0.03 mg/g.The concentration of sodium hydroxide solution was 16 ~oBe,the excess alkali amount was 0.3%,the temperature was 15°C,and the reaction time was 35 min.At these conditions,the maximum reductions of3-MCPDEs and GEs were 30.56%and 41.70%,respectively.The acid value in alkaline refining was 0.44 mgKOH/g.The optimum conditions for adsorption and decolorization:the dosage of active clay was 2%,decolorization temperature was 110°C,and decolorization time was 20 min.Although this condition could not decrease the content of 3-MCPDEs,it could minimize the content of GEs.The Color of the decolorization oil was Y:30 R:3.0.The best conditions for dewaxing:dewaxing temperature was 22°C,the dosage of diatomaceous earth was 3%,and the dewaxing time was 13 h,which could reduce the content of 3-MCPDEs and GEs to some extent.The content of 3-MCPDEs reduced by 25.74%.The content of GEs reduced by 10.74%.The result of the freezing test was qualified.Deodorization process,when the deodorization time was constant,the contents of 3-MCPDEs and GEs increased as the deodorization temperature increased.The contents of 3-MCPDEs and GEs slowly increased from 210°C to 230°C.When the temperature reached 230°C,the contents of 3-MCPDEs and GEs increased rapidly.when the deodorization temperature was constant,the contents of3-MCPDEs and GEs increased gradually with the increase of deodorization time.Before 100min,the contents of 3-MCPDEs and GEs in the deodorized oil slowly increased,100 min after,the contents of 3-MCPDEs and GEs increased rapidly.Therefore,the best deodorization process was determined:temperature 230°C,time 120 min,and residual pressure 80 Pa.At this time,the acid value of oil was 0.05 mgKOH/g.These conditions could not only achieve the ideal deodorization effect,but also prevent the content of 3-MCPDEs and GEs increasing dramatically. |
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