Evaluation of the caseinomacropeptide (CMP) content in raw and uht milk during storage time.

Resumo

Coolers are used in raw milk storage in order to inhibit the growth of lactic acid producer mesophilic microorganisms. However, refrigerated milk is a favorable environment to psychrotrophic aerobic bacteria growth. These psychrotrophic bacteria promote proteolysis which is of concern to the dairy industry since it may indicate a false positive of fraudulent addition of whey to raw milk. This study evaluated the influence of storage time on the presence of caseinmacropeptide (CMP) in raw milk during storage as well as in ultra-high temperature milk (UHT) throughout its shelf life. Three different determination methods were compared each other, namely the standard chromatographic method and two spectroscopy methods for the quantitative determination of sialic acid. One is based on the determination of ninhydrin acid and the other one is an adapted method using the Ehrlich reagent. An increase of CMP content throughout the storage period for the cooled raw milk and UHT milk was detected despite the fact that none had cheese whey. The spectrophotometric methods showed correlation coefficients greater than 0.97 with the chromatographic method established by Brazilian legislation. The results indicate that the spectrophotometric method using the ninhydrin acid can be used as an alternative method for the determination of CMP in milk samples.

DOI: http://dx.doi.org/10.14685/rebrapa.v2i2.54