Study On Rapid Detection Method Of Adulterated Milk And Freshness Of Milk Based On Low Field Nuclear Magnetic Resonance Technology

Fresh milk has high nutritional value, and is well welcomed by consumers.Its sales also rise gradually, but with sales growth, quality and safety problems of fresh milk appear constantly, mainly performed as adulteration and freshness problems, these have a serious impacts on the milk safety problems. So it is urgent to set up a method for rapid detection of adulterated milk and freshness. The low field nuclear magnetic resonance (NMR) technique combined with chemometric methods, study of adulterated milk, cold storage days and freshness, realized the adulterated milk, cold storage days and freshness of the online detection provided a new way. The main results are as follows:(1) Adulterated milk with different adulterant proportion showed a certain regularity distribution in the PCA score plot. It was easy to identify adulterated milk. PLS-DA and LDA were used to establish the models of all adulterated milk, and the accuracy discrimination rates of milk adulterated with water, urea, salt and sucrose were 100% and 100%,100% and 100%,83.33% and 100%, 73.33% and 76.67%, respectively.(2) The building function model of the LDA in Mahalanobis was better than the function model of Linear and Quadratic, the model of C-SVM in SVM was better than that model of Nu-SVM, the function model of the radial basis and linear was better than the function of S-shaped and polynomial. The total recognition accuracy of SIMCA model was 95.83%, the total recognition accuracy of the LDA Mahalanobis building function model was 100%, the total recognition accuracy was 87.50%, which was based on the radial basis function of C-SVM in SVM Mahalanobis model.(3) With an increase in cold days,the freshness index pH decreased, the total number of microorganisms increased, the bound water decreased first and increased later,and the free water became less gradually.quantitative analysis model of PH and quantitative analysis model of total number of microorganisms for fresh milk were Established by PCR and PLSR, it was found that PLSR performed better than PCR both for models of pH and total microbial counts. Its Rc2 and Rp2 were 0.915 and 0.913,0.904 and 0.910 respectively, RMSEC and RMSEP were 0.046 and 0.055,0.044 and 0.053 respectively.