The Studies On The Effects Of Refining Conditions On The Trans Fatty Acids In (n-3/n-6) Polyunsaturated Oils

In this thesis, the effects of different refining technologies and conditions on the contentand kind of trans fatty acids in the (n-3/n-6) polyunsaturated oils (grape oil, wheat germ oiland linseed oil), which were refined by chemical and physical and enzymatic deacidification,were main investigated. Variations of the trans fatty acids, acid value, peroxide value,p-anisidine value and content of tocopherol in different refined oils were discussed to furtheranalyze the suitable refining technology and condition.When the grape oil and wheat germ oil and linseed oil were chemical refined, the acidvalues all reduced to0.20mgKOH/g; the peroxide values and p-anisidine values of the wheatgerm oil and linseed oil increased at different degree while those of the grape oil decreased;the loss of the tocopherol content were37%-43%while the adding fo the trans fatty acidswere0.07%-0.09%.The effects of conditions of deacidification on the kinds and contents of trans fatty acidsin physical refined the grape oil and wheat germ oil and linseed oil of high acid values weremainly researched, then the effects of distilling temperatures and times on the degree ofdeacidification and oxidation also studied. With the same deacidification conditions, the orderof the formation rare of trans fatty acids was as follow: linseed oil＞wheat germ oil＞grapeoil. The best condition of physical deacidifications of the grape oil was as follow:deacidification temperature220℃, time4h. Under these conditions, the quality of the grapeoil was as follow: the acid value0.36mgKOH/g, the peroxide value1.68mmol/kg, thep-anisidine value30.97, the tocopherol content15.70mg/100g, the trans fatty acids content0.41%. The best condition of physical deacidifications of the linseed oil was as follow:deacidification temperature200℃, time4h. Under these conditions, the quality of the linseedoil was as follow: the acid value0.98mgKOH/g, the peroxide value5.52mmol/kg, thep-anisidine value55.48, the tocopherol content32.79mg/100g, the trans fatty acids content0.91%. The best condition of physical deacidification of the wheat germ oil was as follow:deacidification temperature200℃, time6h. Under these conditions, the quality of the wheatgerm oil was as follow: the acid value0.92mgKOH/g, the peroxide value0.61mmol/kg, thep-anisidine value8.90, the tocopherol content289.43mg/100g, the trans fatty acids content0.13%.High acid value of the grape oil and wheat germ oil and linseed oil as raw material, thebest condition of esterify deacidification and the content of trans fatty acids in different temperature and time was studied, which was caused by the immobilized lipase Novozym435catalyzing esterification of glycerol and free fatty acids. The best condition of esterifydeacidification of the grape oil was as follow: temperature90℃, addition of glycerol300%,addition of enzyme3%, time8h. Under these conditions, the acid value declined from22.07mgKOH/g (bleached oil) to2.36mgKOH/g, while the content of trans fatty acids increasedfrom0.022%to0.035%-0.041%. The best condition of esterify deacidification of the wheatgerm oil was as follow: temperature60℃, time11h, addition of glycerol300%, addition ofenzyme2%. Under these conditions, the acid value declined from30.50mgKOH/g (crude oil)to3.99mgKOH/g, while the content of trans fatty acids increased from0.047%to0.059%-0.079%.During the course of preservation (35temperature evades under light), the effects ofoxygenation on the functional ingredients and the trans fatty acids of grape seed oil andlinseed oil were investigated. The results showed that the growth rare of the p-anisidine valueof the linseed oil was4.36times that of the grape oil and the average rares of the peroxidevalue were similar. The contents of tocopherol in the grape oil and linseed oil decreasedsignificantly while the content of tans fatty acid did not change basically. At the same time,the unsaturated fatty acids decreased by0.35%and0.41%, respectively.