Detection and confirmation of milk adulteration with cheese whey using proteomic-like sample preparation and liquid chromatography-electrospray-tandem mass spectrometry analysis.
Caseinomacropeptide (CMP) is a peptide released by chymosin in cheese production, remaining in whey. Thus, CMP can be used as a biomarker to fluid milk adulteration through whey addition. Commonly, CMP is analyzed by reversed phase (RP-HPLC) or size-exclusion chromatography (SEC). However, some psychrotropic microorganisms - specially Pseudomonas fluorescens - when present in storaged milk, can produce, by enzymatic pathway, a CMP-like peptide generally called pseudo-CMP. These two peptides differ from each other only by one amino acid. RP-HPLC and SEC methods are unable to distinguish these two peptides, which demand development of a confirmatory method with high selectivity. Considering the several degrees of glycosilation and phosphorylation sites in CMP, allied with possible genetic variation (CMP A and CMP B), analytical methods able to differentiate these peptides are extremely complex. In the present work, we developed a proteomic-like technique for separation and characterization of these peptides, using liquid chromatography coupled to mass spectrometry with electrospray ionization able to differentiate and subsequently quantify CMP and pseudo-CMP in milk samples in order to identify adulteration or contamination of these products. The method shows satisfactory precision (<11%) with a detection limit of 1.0 µg mL(-1) and quantification limit of 5.0 µg mL(-1). Specificity, matrix effects and applicability to real samples analysis were also performed and discussed.
Instituto de Química, Universidade Federal do Rio Grande do Sul - UFRGS, Porto Alegre, RS, Brazil; Laboratorio Nacional Agropecuário - LANAGRO/RS, Ministerio da Agricultura, Pecuária e Abastecimento, Brazil. Electronic address: tanara.mc@gmail.com.
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Campos Motta
Instituto de Química, Universidade Federal do Rio Grande do Sul - UFRGS, Porto Alegre, RS, Brazil; Laboratorio Nacional Agropecuário - LANAGRO/RS, Ministerio da Agricultura, Pecuária e Abastecimento, Brazil.
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Hoff
Laboratorio Nacional Agropecuário - LANAGRO/RS, Ministerio da Agricultura, Pecuária e Abastecimento, Brazil; Faculdade de Farmacia, Universidade Federal do Rio Grande do Sul - UFRGS, Porto Alegre, RS, Brazil.
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Barreto
Laboratorio Nacional Agropecuário - LANAGRO/RS, Ministerio da Agricultura, Pecuária e Abastecimento, Brazil.
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Andrade
Laboratorio Nacional Agropecuário - LANAGRO/RS, Ministerio da Agricultura, Pecuária e Abastecimento, Brazil.
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Lorenzini
Laboratorio Nacional Agropecuário - LANAGRO/RS, Ministerio da Agricultura, Pecuária e Abastecimento, Brazil.
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Meneghini
Instituto de Química, Universidade Federal do Rio Grande do Sul - UFRGS, Porto Alegre, RS, Brazil.
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Pizzolato
D000818:Animals; D002364:Caseins / Q000032:analysis*; D002611:Cheese / Q000032:analysis; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D005504:Food Analysis / Q000379:methods*; D063427:Food Quality; D057230:Limit of Detection; D008892:Milk / Q000737:chemistry*; D010446:Peptide Fragments / Q000032:analysis*; D040901:Proteomics; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods
D002364:Caseins; D010446:Peptide Fragments; C065989:caseinomacropeptide
Caseinomacropeptide; Food adulteration; Mass spectrometry; Milk proteins; Pepsin digestion