| Because the data and system of single molecule milk fatty acid hydrocarbon isotope evaluation was rarely reported,this research focuses on 15 milk products from different areas and classes as the research object,using a variety of test methods(GC,GC/C/IRMS,GC/TC/IRMS)for qualitative and quantitative analysis of fatty acids,and determination of its stable composition and change trend of stable isotope hydrocarbon as the origin,to establish a new method for discrimination of milk powder,and provide the basic data for the establishment of reference data table of the milk base,the main research results are as follows:(1)the tests were 32 kinds of fatty acid found such recognition,the trend of the overall content of milk fatty acids: C18: 1 >C16: 0>C18: 2>C14:0 ?C12: 0>C18:0,and in infant milk powder,single unsaturated fatty acid is dominant;in adult milk,saturated fatty acids accounted for the major advantage.(2)lauric acid,myristic acid and SFA:MUFA: PUFA ratio of trans fatty acids and total milk are in line with the provisions of the state and nutrition,but polyunsaturated and saturated fatty acid ratio and nutritionist recommended value is larger,and the addition of linoleic acid,linolenic acid,DHA,ARA,EPA and DPA the outer packing is not serious.(3)establish the following discriminant indicator: when the C18:1/C18:2 value is less than 5,or the UFA/SFA ratio is greater than 1,we can think of this infant formula is milk powder;when the C18:1/C18:2 value is greater than 10,or the UFA/SFA ratio is less than 0.5,we can think this is adult milk powder milk powder.(4)on the whole,the carbon isotope of the fatty acid is depleted,the hydrogen isotope is enriched with the extension of the carbon chain,and the change trend of the two isotopes is opposite.The average ?13C changes of fatty acids: C14:0 > C16:0 =C18:0 > C20:0 > C22:0 > C24:0,C14:0 > C12:0 > C10:0 > C8:0,the average ?2H changes of fatty acids: C12:0 < C14:0 < C16:0 < C18:0.(5)synthesis is an important precursor of other fatty acids in animal C16:0,i.e.C18:0,C20:0,C22:0,C24:0 and other fatty acids by carbon chain extension formation,while C8:0,C10:0,C12:0,C14:0 are formed by the carbon chain cleavage of C16:0,and the C18:0 of the fatty acids in addition to the extension of the carbon chain,may also in part by C18:1,C18:2 hydrogenation to hydrogenation,after 2H values willbecome more depleted,may be the result of hydrogenation of rumen microorganisms.(6)?13C of OCN fatty acids even is lower than ?13C of ECN fatty acids.The value of the relative enrichment of odd carbon,and has a certain relationship with the content,when the content is high enough,to a certain extent exacerbated the 13 C values were enriched or depleted,will also slow change of delta 13 C carbon chain extended or shortened to the value in a certain extent.(7)in the extension of the carbon chain,the hydrogen isotope fractionation is very little or zero,and the 2H value becomes more depleted in the hydrogenation process.Hydrogen isotope fractionation process,can make the unsaturated fatty acid of the delta 2H value is more increased,which indicates that 2H depends on the relative metabolic flux,different fatty acid 2H values could be a useful tool for quantitative flux and direction in the biosynthesis.(8)the ?13C difference of C3 or C4 plants was reflected in the regional differences of milk powder,and the ?2H value of long chain fatty acids was also recorded with the regional characteristics. |
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