Study On Moderate Processing Technology Of Rapeseed Oil

Over refinement of edible oil has become a more and more serious problem that has puzzled almost the whole oil processing industries.The excessive dosage of acid and alkali,the large amount of clay consumption,too high deodorization temperature and too long deodorization time are the common problems during the over refinement process.These problems can not only cause huge waste of natural resources(decoloration agent dosage,acid and alkali consumption,etc.)and energy(power and steam consumption,etc.),intensify environmental pollution and increase the loss of neutral oil,but also remove large amounts of the benefit micronutrients in oil,including vitamin E,phytosterol,squalene and oryzanol.Besides,it can inevitably produce new harmful substances,such as trans-fatty acids and glyceride polymeride,which can decrease the edible safety and nutritional quality of oil and cause a series of new food safety problems.Hence,the disadvantages of edible oil over refinement bring on to the health of consumers and the harmonious of the society should not be ignored.In present study,the degumming process and decoloration process of rapeseed oil were studied,respectively.Both of the degumming and decoloration process were improved by experiment optimization,and then,analysis and comparison were also made between the effects of the conventional and the present optimized process,so as to explore the oil moderate processing technology.The main conclusions were as follows:1.Taking crude rapeseed oil as raw material,the optimization experiments of PLC degumming and hydration degumming were conducted by quadratic regression orthogonal methods.The optimization conditions of PLC degumming were as follows:pH was 5.4,the PLC amount was 10 ?L/kg,enzymolysis temperature was 43 ?,the confirmatory experiment of the optimization process showed that the phospholipids residual content of rapeseed oil was 7.45 mg/kg.The optimization of hydrated degumming were as follows:the degumming time was 5h,the degumming temperature was 85 ?,the water addition was 3.25 times of phospholipids content in crude rapeseed oil,confirmatory experiment of hydrated degumming showed that the phospholipid content of rapeseed oil after hydrated degumming was 76.32 mg/kg.Then the basic quality indexes such as phosphorus content,moisture content and peroxide value,were tested according to the national standard methods,respectively,so as to make a comparison of the two degumming processes,the results showed that apart from the indexes of saponification value,iodine value,taste,odor and transparency,all other indexes of the former oil are better than the latter,and after the full refining process,the quality of the two oils were almost the same.However,the soft water used and the waste water produced in PLC degumming process were both lower than water degumming,and less bleaching clay and alkali were consumed in latter bleaching and neutralization process,whereas,more vitamin E was gathered in the deodorizer distillate.2.The detection wavelength of rapeseed oil decolorization ratio was confirmed by means of full wave scanning which was conducted by ultraviolet-visible spectrophotometer(Model Evolution 220).Decolorization ratios under 537nm and 612nm were selected as the experiment indicators,and the effects of the 5 single-factors(decolorant amount,proportion of activated clay and attapulgite,decolorization temperature,decolorization time and agitation rate)on the decolorization rate were studied,respectively.On the basis of single-factor experiments,three factors(the decolorant amount,decolorization temperature and decolorization time)were chosen to conduct 3-variable 3-level response surface methodology(RSM)to optimize the decoloration process,analysis of variance(ANOVA)and regression model fitting were also made.The highest composite decoloring rate(97.02%)was obtained when the decolorant amount was 3.4%,the decolorization temperature was 100 ? and decolorization time was 27 min.The phytosterol and vitamin E content of the oils bleached by compound decolorant and bleaching clay were tested by gas chromatographic method(GC)and high performance liquid chromatography(HPLC),respectively.As well as the basic physical and chemical indexes,the results showed that acid value(AV)and phosphorus content of the rapeseed oil bleached by compound decolorant were much lower than the oil bleached by activated clay,while the content of Vitamin E,sterols and the decolorization ratio of the former oil were higher,and it could reach the national standards for first grade rapeseed oil.3.Attapulgite was adopted to conduct decolorization test of crude rapeseed oil,influences of attapulgite on the peroxide value,phosphorus content,soap content and anisidine value were discussed.Then the surface micro structure of fresh activated bleaching earth and two kinds of spent bleaching earth was observed by scanning electron microscope(SEM),so as to explore the feasibility of the reutilization of spent bleaching earth on rapeseed oil decolorization.The detection wavelength of rapeseed oil decolorization ratio was confirmed(537rmn and 612nm)by full-wavelength scanning which was conducted by ultraviolet-visible spectrophotometer.On the basis of single factor experiments,comprehensive decolorization ratio of the two wavelengths was selected as the experiment indicator,and the processing of spent bleaching earth pre-bleaching and attapulgite re-bleaching for rapeseed oil was optimized by orthogonal experiment,optimal conditions were achieved when the decolorization time of pre-bleaching and re-bleaching were both 15min,the decolorising agents were 1.0%and 2.0%,respectively and the activated carbon dosage was 0.1%,under these conditions,the comprehensive decolorization ratio could reach as high as 95.97%and the decolorizing effect was best.The comparison results of different oil quality showed the quality of pre-bleaching and attapulgite re-bleaching oil was much better,meanwhile,the contend of vitamin E and phytosterol was equal to the oil which only bleached by activated clay.However,in this new decolorizing technology,the decolorization time was shorter and temperature was lower,which was more suitable for the requirement oil moderately processing technology,and more eco-friendly.