Identification of plant proteins in adulterated skimmed milk powder by high-performance liquid chromatography—mass spectrometry

• Published in: Journal of Chromatography A 2007-09, Vol.1164 (1), p.189-197
• Main Authors: Luykx, Dion M.A.M., Cordewener, Jan H.G., Ferranti, Pasquale, Frankhuizen, Rob, Bremer, Maria G.E.G., Hooijerink, Hendricus, America, Antoine H.P.
• Format: Article
• Language: English
• Subjects: adulterated products; Adulteration; Animals; beta-conglycinin; Biological and medical sciences; Borate buffer; Borates - chemistry; Chromatography, High Pressure Liquid - methods; Dairy Products - analysis; dried skim milk; Enrichment; feeds; Food Analysis - methods; Food industries; Fundamental and applied biological sciences. Psychology; glycinin; high performance liquid chromatography; HPLC; legumin; Mass spectrometry; Mass Spectrometry - methods; Milk and cheese industries. Ice creams; Milk powder; Milk Proteins - analysis; Milk Proteins - chemistry; peas; Plant proteins; Plant Proteins - analysis; Plant Proteins - chemistry; Plant Proteins - isolation & purification; Protein identification; Reproducibility of Results; soy protein; soybeans; Tandem Mass Spectrometry; vicilin
• ISSN: 0021-9673
• DOI: 10.1016/j.chroma.2007.07.017

The EU subsidises the use of skimmed-milk powder (SMP) in compound feeding stuffs. There are indications of falsified SMP content due to the addition of plant proteins. These proteins are not allowed in SMP and cannot be identified by the official reference method. Since soy and pea proteins are most likely to be added to SMP, manufactured SMP containing 1 and 5% of these plant proteins was used to develop a sensitive protein identification method based on mass spectrometry (MS). The method included a pre-fractionation step to enrich for plant proteins by using a borate buffer. A very fast perfusion liquid chromatography method including sensitive and selective intrinsic fluorescence detection was developed for monitoring and quantifying the efficiency of the pre-fractionation and screening for plant proteins. After tryptic digestion of the enriched fraction from manufactured adulterated SMP, numerous peptides originating from the major seed proteins of soy (glycinin, β-conglycin) and pea (legumin, vicilin) could be identified by MS/MS analysis on a quadrupole time-of-flight MS instrument.