Determining milk fraud with whey by analyses of CMP and Pseudo-CMP by High Performance Liquid Chromatography in reversed phase with detection by mass spectrometry / Determinação de fraude de Leite com soro de leite pela análise de CMP e Pseudo-CMP por cromatografia líquida de alta eficiência em fase reversa com detecção por espectrometria de massa

Mirella Araújo Magalhães

The main objective of this work was the development of a method of analysis by High Performance Liquid Chromatography with reversed phase and detection by mass spectrometry to determine the adulteration of milk with whey by detection caseinomacropeptídio (CMP), and determine the effect on the cultivation of milk with Pseudomonas fluorescens to verify the occurrence of pseudo-CMP or CMP produced by thermo-resistent enzymes of psychrotrophic bacteria. The milk samples were added of whey at concentrations of 0, 5, 10, 15 and 20% (v / v) and analyzed by High Performance Liquid Chromatography - Gélica Filtration (GF-HPLC) and High Performance Liquid Chromatography Reverse-phase with detection by Mass Spectrometry (HPLC- RP/MS). It was observed that there was a difference between the methods of analyses (p <0.05) and there was an effect of the whey concentration by two methods (p <0.05),that is, the increasing on the whey concentration also causes an increasing on the corresponding area of CMP by the two methods.The CMP was detected by HPLC-GF with retention time of around 5.7 minutes. When it was analyzed by HPLC- RP/MS, the CMP was detected at retention time around 19 minutes and characterized by ions of mass/charge 1697.4+4 and 2263.3+3. The samples of milk cultivated with Pseudomonas fluorescens were incubated on different days (0, 2, 4, 6 and 8) at 7 C, added in different concentrations of whey (0, 5, 10, 15 and 20% (v / v)) and analyzed by HPLC-FG and HPLC-RP/MS. On samples of milk added with Pseudomonas fluorescens and no addition of whey, analyzed by HPLC-FG, when incubated for up to 2 days, CMP was not found. Though, on samples of milk incubated for over 2 days, CMP was found; not deriving from the adulteration of milk with whey.The same samples of milk added to Pseudomonas fluorescens and no whey, analyzed by HPLC-RP/MS and incubated for up to 2 days did not present any increasing on the detection area of CMP. Though, on samples of milk incubated for over 2 days, CMP was found, characterized by ions of relation mass/charge 1697,4+4 and 2263,3+3 and other ions 1358+5, and the 1301,2+5. These latter ions derive from the hydrolysis of κ-casein by thermo-resistant enzymes of Pseudomonas fluorescens. The method of analyses by LAE- FG did not differentiate the CMP deriving from whey, from CMP and/or pseudo-CMP produced by proteasis of P. fluorescens. The analyses of CMP in the milk by CLAE-FR/EM were efficient to detect the adding of whey to the milk without proteolysis. Besides that, when the milk was proteolized by enzymes of P. fluorescens this method could indicate that there was proteolysis. Though, when the milk is proteolized by P. fluorescens, and when whey was added, there was no way of quantifying the CMP that was produced only by P. fluorescens and which was only due to the adding of whey. In such case, the result of the Index of CMP, as foreseen on IN 69/2006, is a great indicator of the intensity of proteolysis of milk protein, or then, from the fraudulent adding of milk and whey, when analyzed by CLAE-FR/EM, being then a great indicator of the quality of the milk.

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