title: Multiple reaction monitoring-based determination of bovine α-lactalbumin in infant formulas and whey protein concentrates by ultra-high performance liquid chromatography-tandem mass spectrometry using tryptic signature peptides and synthetic peptide standards.
abstract: The determination of α-lactalbumin in various dairy products attracts wide attention in multidiscipline fields because of its nutritional and biological functions. In the present study, we quantified the bovine α-lactalbumin in various infant formulas and whey protein concentrates using ultra-high performance liquid chromatography coupled to tandem mass spectrometer in multiple reaction monitoring mode. Bovine α-lactalbumin was quantified by employing the synthetic internal standard based on the molar equivalent relationship among the internal standard, bovine α-lactalbumin and their signature peptides. This study especially focused on the recovery rates of the sample preparation procedure and robust quantification of total bovine α-lactalbumin in its native and thermally denatured form with a synthetic internal standard KILDKVGINNYWLAHKALCSE. The observed recovery rates of bovine α-lactalbumin ranged from 95.8 to 100.6% and the reproducibility was excellent (RSD<6%) at different spiking levels. The limit of quantitation is 10 mg/100 g for infant formulas and whey protein concentrates. In order to validate the applicability of the method, 21 brands of infant formulas were analyzed. The acquired contents of bovine α-lactalbumin were 0.67-1.84 g/100g in these infant formulas in agreement with their label claimed values. The experiment of heat treatment time showed that the loss of native α-lactalbumin enhanced with an increasing intensity of heat treatment. Comparing with Ren's previous method by analysis of only native bovine α-lactalbumin, the present method at the peptide level proved to be highly suitable for measuring bovine α-lactalbumin in infant formulas and whey protein concentrates, avoiding forgoing the thermally induced denatured α-lactalbumin caused by the technological processing.
authors.affiliation: Department of Food Science and Nutrition, College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China.
authors.forename: Jingshun
authors.initials: J
authors.lastname: Zhang
authors.forename: Shiyun
authors.initials: S
authors.lastname: Lai
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Baifen
authors.initials: B
authors.lastname: Huang
authors.forename: Duo
authors.initials: D
authors.lastname: Li
authors.forename: Yiping
authors.initials: Y
authors.lastname: Ren
mesh_terms: D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D041943:Infant Formula / Q000737:chemistry*; D007768:Lactalbumin / Q000032:analysis*; D008894:Milk Proteins / Q000737:chemistry*; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism; D012015:Reference Standards; D053719:Tandem Mass Spectrometry; D014357:Trypsin / Q000378:metabolism*; D000067816:Whey Proteins
chemical_list: D008894:Milk Proteins; D010455:Peptides; D000067816:Whey Proteins; D007768:Lactalbumin; D014357:Trypsin