title: Fast and selective determination of total protein in milk powder via titration of moving reaction boundary electrophoresis.
abstract: In this paper, moving reaction boundary titration (MRBT) was developed for rapid and accurate quantification of total protein in infant milk powder, from the concept of moving reaction boundary (MRB) electrophoresis. In the method, the MRB was formed by the hydroxide ions and the acidic residues of milk proteins immobilized via cross-linked polyacrylamide gel (PAG), an acid-base indicator was used to denote the boundary motion. As a proof of concept, we chose five brands of infant milk powders to study the feasibility of MRBT method. The calibration curve of MRB velocity versus logarithmic total protein content of infant milk powder sample was established based on the visual signal of MRB motion as a function of logarithmic milk protein content. Weak influence of nonprotein nitrogen (NPN) reagents (e.g., melamine and urea) on MRBT method was observed, due to the fact that MRB was formed with hydroxide ions and the acidic residues of captured milk proteins, rather than the alkaline residues or the NPN reagents added. The total protein contents in infant milk powder samples detected via the MRBT method were in good agreement with those achieved by the classic Kjeldahl method. In addition, the developed method had much faster measuring speed compared with the Kjeldahl method.
authors.affiliation: Laboratory of Bioseparation and Analytical Biochemistry, State Key Laboratory of Microbial Metabolism, School of Life Science and Biotechnology, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Cheng-ye
authors.initials: CY
authors.lastname: Guo
authors.forename: Hou-yu
authors.initials: HY
authors.lastname: Wang
authors.forename: Xiao-ping
authors.initials: XP
authors.lastname: Liu
authors.forename: Liu-yin
authors.initials: LY
authors.lastname: Fan
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Cheng-xi
authors.initials: CX
authors.lastname: Cao
mesh_terms: D019075:Electrophoresis, Capillary / Q000191:economics / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D006801:Humans; D041943:Infant Formula / Q000737:chemistry*; D007231:Infant, Newborn; D008894:Milk Proteins / Q000032:analysis*; D012680:Sensitivity and Specificity; D013997:Time Factors; D017186:Titrimetry / Q000191:economics / Q000295:instrumentation / Q000379:methods
chemical_list: D008894:Milk Proteins