| Milk is rich in nutrients such as protein,lactose and minerals,which has become a very important nutritional consumer goods in people’s lives.China is a country with a large population,and the consumption of milk and dairy products(milk powder,etc.)accounts for a large proportion of the world’s milk supply.So people have stricter requirements on the quality and safety of milk.Traceability of food origin is a crucial step to ensure food safety.Traceability technology of food origin is conducive to the protection of regional specialty foods.When food quality and safety incidents occur,it can quickly trace back to the source of pollution,implement effective recalls,reduce economic losses.In this study,stable isotope technology,mineral element analysis and amino acid analysis technology were used to analyze the milk.The origin of milk in the major milk sources of China was identified by multivariate statistical analysis combined with chemometrics.The main research contents and results are as follows:(1)Determinations of stable isotope ratios,mineral element contents and amino acid contents in milk.The stable isotope ratios in milk were determined by elemental analyzer-isotope ratio mass spectrometer(EA-IRMS),the contents of mineral elements in milk were determined by inductively coupled plasma mass spectrometry(ICP-MS),and the contents of amino acids in milk were determined by high performance liquid chromatography(HPLC).(2)The origins of milk from four provinces of China were studied based on the technology of mineral element analysis.According to the analysis of variance,there were no significant difference in the concentrations of mineral elements in three lactation stages(early,middle and late),and the lactation stages had no effect on the traceability of milk samples;According to the post-hoc Duncan’s test,the concentrations of Na,Mg,K,Ca,Ti,Cr,Mn,Fe,Ni,Zn,Sr(11)in different provinces had significant difference(p<0.05);According to the results of partial least squares discriminant analysis(PLS-DA)and linear discriminant analysis(LDA),milk samples from four provinces can be distinguished very well by the mineral elements data.The accuracy of original classification was 95.8%,and the accuracy of cross-validation was 88.3%.(3)The origins of milk from small-scale regions in Inner Mongolia was studied based on the stable isotope technology,mineral element analysis and amino acid analysis.According to the post-hoc Duncan’s test,there were significant differences in δ13C,δ15N,δ18O,Na,Mg,Al,K,Ca,Sc,Ti,Mn,Fe,Zn,Se,Rb,Sr,Mo,Asp,Ser,Arg,Thr,Met,Cys,Lys and Tyr(25)among five cities in Inner Mongolia(p<0.05);The results of principal component analysis(PCA),orthogonal partial least squares discriminant analysis(OPLS-DA)and linear discriminant analysis(LDA)showed that the combination analysis of stable isotope technology,mineral element analysis and amino acid analysis was better than that of single technology for the discrimination of milk origins in Inner Mongolia;For the discrimination of milk regions in different cities,the accuracy of original classification and cross-validation by the combination of three technologies were 85.1%and 62.7%;For the discrimination of milk regions in different counties,the accuracy of original classification and cross-validation by the combination of three technologies were 100%and 71.6%;The key factors for the discrimination of milk regions were screened out according to the Variable importance values(VIP).The common elements between the five cities and eleven districts were C,O,Rb,Sr,N,Na and Ca(7),which indicated that these variables were significant indicators of milk origins. |
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