Identification Of Different Processing Technologies Of Milk Based On Peptidomics And Metabolomics

Milk is called "white blood" because of its high yield,rich nutritional value and good taste.Even in milk samples from healthy dairy cows,there are many microorganisms and bacterial flora,among which pathogenic bacteria will seriously threaten human health.Therefore,in order to prevent the occurrence of diseases,the harm of pathogenic bacteria and the deterioration of milk caused by microorganisms,raw milk usually needs heat treatment before consumption,and the sterilized and aseptic packaged milk is easy to store and transport..At present,homogenized milk is usually pasteurized(Pa),extended shelf life(ESL)or ultra-high temperature(UHT)for heat treatment.Different processing temperature has different effects on milk storage time,nutritional value and functional activity.In this study,the milk samples with different processing technologies were used as the research object,and the peptidomics and metabolomics techniques were used to detect the different substances,which could be used as the markers of milk products with different processing technologies.In order to provide monitoring methods and evaluation indexes for the identification of milk at different processing technologies.The research contents are as follows.(1)In this study,the peptide spectrum of milk samples based on HLB and Stage Tip was studied by the quadrupole orbit trap high-resolution mass spectrometry.The types and response intensity of peptides obtained by the two extraction methods were analyzed,and the superiority of HLB method for extracting peptides from milk were determined.Furthermore,high performance liquid chromatography-mass spectrometry(LC-MS/MS)was used to detect additional reference peptides in milk.Three methods of extracting peptides from milk were compared,including organic solvent precipitation method,solid phase extraction-Me OH method and solid phase extraction-ACN method.The results showed that the recovery of added reference peptides detected by solid phase extraction-Me OH method was between 52.99% and 175.87%,The results were stable.In conclusion,the advantages of solid phase extraction-Me OH method were determined to provide technical support for the study of milk peptidomics.(2)Based on UPLC-QTOF-MS and multivariable data analysis,26 differential marker peptides were selected from pasteurized milk,ESL milk and UHT milk samples and verified by supermarket random samples.Meanwhile,the formation mechanism of candidate markers related to milk processing temperature was elaborated.The results showed that the peptide content of pasteurized milk was generally lower than that of ESL milk and UHT milk,especially the peptide content of m/z 804.8813 was the highest in UHT milk.The results showed that the peptidomics method based on UPLC-QTOF-MS and chemometrics analysis was an effective method to identify different processed milk.(3)The non-target metabolomics technology based on UPLC-QTOF-MS was used to analyze three kinds of milk samples with different processing technologies.Unsupervised PCA analysis and supervised OPLS-DA analysis were used to distinguish the three kinds of milk,indicating that non-target metabolomics could be used as an effective method to distinguish pasteurized milk,extended shelf life milk and UHT milk.Under the positive and negative ion collection mode,a total of 22 different metabolites were screened in three types of milk,of which 11 were identified as peptide,nicotinamide,nicotinamide riboside,N6-methyladenosine and 2-hydroxydecanoic acid,and the results were verified by the test set.Nicotinamide and methyladenosine,and the results were verified by the test set.The results showed that the non-targeted metabolomics technology was used to analyze the metabolic components of different processed milk,and the selected differential metabolites could successfully distinguish the heating degree of milk,which provided technical support for the identification of different processed milk in the future.