| Gelatin is a kind of important food and medical intermediate,which is mainly extracted from animal bones.With the frequent occurrence of animal epidemic and quality problem of raw materials in the world,it is of great significance to trace the geographical origin of bone raw materials to ensure gelatin safety,strengthen quality control and protect geographical indication products.However,the traceability system of bone raw material has not been well developed until now and the researches on its traceability methods are also scarce,which not only brings safety risks to gelatin products,but also greatly limits the import and export trade of bone raw materials.Inspired by the traceability research of other food,three stable isotopic compositions and the contents of 18 mineral elements as well as eight rare earth elements in bone samples from three representative areas in China were investigated.Combined with chemometrics,the composition differences of each indicator in bone samples among the three regions were analyzed,the effective methods of extracting the origin characteristic factors from stable isotopes,mineral elements and rare earth elements were discussed.Furthermore,various origin classification models of the bone samples were established and the feasibility of the above methods in traceability of bone raw materials was fully studied.The main contents are listed as follows:(1)A total of 47 samples were collected from Guangxi,Shandong and Inner Mongolia and then been pretreated.After that,the compositions of δ13C,δ15N and δ2H in all samples were analyzed by EA-IRMS.According to the results of one-way ANOVA and cluster analysis,it was found that three stable isotopic compositions in bone samples had significant regional distribution characteristics and could be basically divided into three categories in accordance with their origin.The accuracy of back substitution test and cross validation of the classification model established by linear discriminant analysis was 95.7%and 91.5%respectively,which proved that the traceability method was feasible.(2)The contents of 18 mineral elements in all samples were determined by ICP-MS and ICP-OES.Among them,16 elements with significant differences among the regions were analyzed by principal component analysis.Four principal components were extracted and then cluster analysis was carried out according to the standardized scores of these principal components.The results showed that samples could be basically distinguished.Finally,five effective variables Na,Se,Sr,Ba and Pb were screened out by a stepwise discriminant procedure,and the origin classification model was established.According to the results of back substitution,these five element characteristic factors could distinguish the origin of bone samples 100%correctly.(3)A membrane desolvation system was used to improve the ICP-MS injection system,and the effects of the flow rate of sensitizing gas and purging gas on the yield of interference ions and the sensitivity of the instrument were studied in detail.After optimizing the conditions,the signal intensity of rare earth elements was increased by about 3-7 times and the measurement accuracy was also significantly improved.Eight rare earth elements in bone samples from three regions were determined under the optimized parameters.Among them,Sc,Y and Eu showed significant differences according to ANOVA test.By analyzing the clustering results and evaluating the discriminant model,it was found that samples could be distinguished well using these three indicators and the overall accuracy of the model could reach 95.8%,which indicated that stable and effective traceability characteristic factors in animal tissues had been obtained successfully. |
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