| Soybean is an important cash crop,with a large area of cultivation in China.Recently,because of the complex production environments of agricultural products in the market,coupled with the adulteration and fraud of some bad vendors,it has directly affected the legitimate rights and interests of consumers.Therefore,confirming the origin of soybean and other agricultural products not only protects the geographical indications of the products but also ensures safety monitoring of soybean food “from the field to the dining table” to maintain a fair market order.In this work,we measured the contents of 25 elements and 10 fatty acids in soybean samples produced in Heilongjiang,the Inner Mongolia Autonomous Region,Jilin and Liaoning using ICP-MS and GC.The relationship between metabolic fingerprints and geographical location was analyzed by using a variety of chemometric methods.The results showed that there was a certain degree of correlation between some elements and fatty acid,and principal component analysis was used to provide a preliminary classification for all variables.Hierarchical clustering,based on heat maps,showed that all samples could be classified based on their geographical origins.Besides,the key information affecting the clustering in the four provinces were extracted,such as Mg,Al,K,Mn,Mo,P,Cu,Cr,Rb and Pb,C16:0 and C18:0,etc.Using the screened 17 elements and fatty acid indexes,a discriminant model was established for the samples in the training set by OPLS-DA,which showed a prediction ability of 91.9%,and was used for the prediction analysis of soybean samples in the test set.It turns out that the total discrimination accuracy of soybean producing areas in four provinces was 96.7%,further proving that the 17 classification indexes,comprising fatty acids and elements,could be used as molecular fingerprints to identify and distinguish soybean samples from four different production areas.Besides,pairs of soybean sample fingerprints from the four provinces were compared,and the divergence in element and fatty acid specific contents between the provinces were explained based on the climatic environment and soil distribution.In conclusion,our method of classifying and confirming soybean production areas through fatty acid and multi-element fingerprints can potentially be used for identifying soybean of similar origins.Soybean samples studied in this work were obtained from distantly located regions.Differences in geographical location,climatic environment and soil may significantly affect the elemental and the fatty acid content of soybean.In addition,when confirming the origin of agricultural products,the specific indicators that can represent the origin information are affected by many external factors.Thus,only one traceability technology does not sufficiently support the stable selection of specific indicators,and it is challenging to comprehensively detect and confirm the complex origin of samples with a single technology.Therefore,in this study,ICP-MS was used to measure various elements present in soybean obtained from the main production areas in northern China.Gas chromatography was used in measure the changes in the content of fatty acids.The production area information of all the four provinces was compared in pairs to explore the regional specificity and commonality between fatty acid and element contents in soybean samples from each province.Furthermore,this study explored the differences in geographical environment between different origins.It also classified the fingerprint characteristics of fatty acids and elements for each production area using thermography visualization. |
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