Study On Determination Of Whey Protein In Infant Formula

Formulated milk powder is considered as the supplementary foods for newborn babies because of its comprehensive nutrition and similar protein components.As a mandatory index,the content of whey proteins in infant formulas must account for 60% near to the level in breast milk.In the present,there is few corresponding quantitative methods.As a result,the production enterprises of whey can't directly control quality of whey products and the regulatory authorities can not supervise the quality of final products containing whey proteins to ensure the food safety of infants and young children.Therefore,the development of quantitative methods for whey proteins is an urgent requirement of infant formula industry,national regulation and the guarantee of infant health.This paper studied the determination method for whey proteins from three aspects.First of all,the classical enzymatic digestion technology in proteomics was employed to digest the ?-lactalbumin protein into peptides.The digested peptides from ?-lactalbumin protein were separated by ultra performance liquid chromatorgraphy.The signature peptide of ?-lactalbumin protein was selected according to theoretical digestion fragments and practical digests,then determination by tandem mass spectrometry with isotope dilution.The final contents of ?-lactalbumin protein were calculated on the basis of equimolar relationship between the signature peptide and ?-lactalbumin protein.By the same way,the signature peptide of ?-lactoglobulin protein was selected and the corresponding detection conditions were optimized.After that,the isotope-labeled signature peptide and internal standard for ?-lactoglobulin were designed and employed to acquired the accurate contents of ?-lactoglobulin protein in samples.The mathematical model of a total of whey proteins was established based on the previous research data and conclusions.In addition,the contents of total whey proteins in raw materials for producing formulated milk powder were measured using the established methods for determination of ?-lactalbumin and ?-lactoglobulin proteins to further evaluate the mathematical model.The calculation formula was finally confirmed by the acquired data and results.In this work,the classical enzymatic digestion technology was combined with the most accurate MS-based multiple reaction monitoring mode.The quantitative methods for determination of ?-lactalbumin and ?-lactoglobulin proteins were developed by the aid of their isotopelabeled signature peptides and internal standards,respectively.On this basis,the total whey proteins in samples were calculated according to the evaluated mathematical model.