Determinación de los componentes y adulteración de la leche empleando la espectroscopia de FTIR

Abstract

En la industria láctea y alimentaría en general, por los grandes volúmenes de producción que se manejan, son de gran ayuda técnicas de monitoreo más rápidas, eficientes y que sean aplicadas en línea; para determinar la composición del producto, detectar posibles adulteraciones y como sistemas de control de calidad de las empresas. En este trabajo se presenta una metodología alternativa, basada en la espectroscopia de infrarrojo, para identificar los principales componentes de la leche así como para determinar la presencia de suero de queserías en leche (suero de queso tipo panela y Oaxaca). Inicialmente se comparó la correspondencia de los resultados obtenidos por el equipo MilkoScan con los métodos químicos de Fehling, Kjeldahl y Gerber, que marcan la norma NOM-155-SCFI- 2003 y la AOAC, para determinar las cantidades de proteínas, lactosa y grasa en la leche semidescremada. Los resultados obtenidos permitieron comprobar que la sensibilidad del equipo MilkoScan para la lactosa y proteínas fue muy buena, en tanto que para el caso de grasas el método Gerber presentó una menor variabilidad.

Abstract: In the milky industry, by the great volumes of production that are handled, techniques of monitoring faster, efficient and that could be applied at line are helpful; in order to determine the product composition, to detect possible adulterations and for quality control systems of the companies. In this work an alternative methodology is present, based in infrared spectroscopy, to identify the main components of milk as well as to determine the whey presence in milk. Initially the correspondence of the results obtained by MilkoScan equipment with the chemical methods of Fehling, Kjeldahl and Gerber was compared, as the NOM-155-SCFI-2003 and the AOAC said, to determine the amounts of proteins, lactose and fat in partially skimmed milk. The obtained results allowed verifying that the sensitivity of MilkoScan equipment for lactose and proteins was very good, whereas for the case of fats the Gerber method show a lower variability. Once determined the correspondence between the specified techniques in the actual normativity; the results obtained by two infrared spectroscopic techniques were compared, vibrational by Fourier Transformed Infrared (FTIR) and by filters by MilkoScan. The MilkoScan results, allowed us to relate of direct way the percentage variation of the components of milk, with the absorption changes in FTIR. The main components (proteins, lactose and fat) of the several analyzed samples were identified: milk, whey in dust of Oaxaca cheese, liquid whey of Oaxaca cheese and Panela cheese, milk enriched with whey in dust and milk adulterated with different amounts from 2 liquids whey. The spectra obtained by FTIR allowed to determinate the influences of the whey addition, as in liquid as in dust, in the absorption of the milk spectrum; this allowed to us obtain the calibration chart for the region that present the best correlation between both infrared techniques, proteins.