Integrated Mass Spectrometry And Chemometrics For Related System Process And Marker Identification

Mass spectrometry(MS)has the advantages of abundant data,high selectivity and sensitivity.In particular,high resolution mass spectrometry(HRMS)have the advantages of high mass accuracy and resolution.It can be used for screening of trace components and have great advantages in the analysis of complex systems.For the extraction and analysis of massive data generated by mass spectrometry,chemometrics provides a powerful means to solve problems such as multidimensional and complex data.Mass spectrometry combined with chemometrics to establish a relevant statistical model that can discover the key markers in the process of the relevant system.It is possible to discover the internal relationship between the marker and the related process system quickly and accurately.This study takes the frozen-thawed process and the mining of related markers as the research object.In reality,due to the imperfection of cold chain technology,it is inevitable that fresh meat will frozen-thawed during storage,transportation,and sales.In the market,the price of fresh meat is higher than frozen meat,which makes some illegal traders use frozen-thawed meat as fresh meat to obtain illegal benefits.It is particularly important to develop methods to identify fresh and frozen-thawed meats and to discover key markers in the frozen-thawed process.The main research is as follows:(1)In this study,ultra high liquid chromatography-quadrupole orbitrap mass spectrometry(UHPLC/Q-Orbitrap-MS)combined with chemometric methods were used to identify fresh and frozen-thawed beef.The top 10 main components were selected using PCA model,which explained 70.9%of the total variance(R²),and 52.1%of predictive power(Q²).The results showed that PCA could effectively distinguish fresh and frozen-thawed beef.R²and Q²in the two orthogonal partial least squares discriminant analysis(OPLS-DA)are both close to 1,indicating that the model have good predictive ability and accuracy.P<0.05 combined with variable projection importance analysis value(VIP)were used to discover biomarkers for discrimination of fresh and frozen-thawed beef,including lactic acid,nicotinic acid and tyramine.It is concluded that UHPLC/Q-Orbitrap-MS and chemometric methods has great potential for the rapid detection of fresh and frozen-thawed beef.(2)An intelligent surgical knife(i Knife)coupled with rapid evaporative ionization mass spectrometry(REIMS)was employed for the lipidomic profiling of fresh and frozen-thawed beef muscle.The characteristic lipid ions were selected to optimize the working conditions of REIMS.The results showed that the best working conditions were cutting speed 8 mm/s,power output 20 W,and flow rate 110?L min^-1.A total of18 fatty acids and 60 phospholipid molecules were detected under optimal working conditions.The PCA-LDA model was used to distinguish fresh beef from different frozen-thawed times and the real-time identification of blind test samples.The results show that the fresh group and the frozen-thawed one-time group partially overlap,and they are well distinguished from other frozen-thawed times groups.It could be seen from the PCA-LDA model that there were some overlaps between the fresh group and the F-T1 group,but there was significant separation between fresh and other frozen-thawed groups.The discrimination of fresh and frozen-thawed beef has been achieved and the real-time identification accuracy was 92-100%.Changes in the composition and content of fatty acids and phospholipids were statistically analyzed by OPLS-DA,and the ions of m/z 279.2317(FA 18:2),m/z 681.4830(PA O-16:0/20:4)and m/z697.4882(PA 18:1/18:2)were selected as differential compounds/metabolites.The results showed that REIMS as a high-throughput,rapid,and real-time mass spectrometry detection technology can be used for the identification of fresh and frozen-thawed beef muscle.