PROTEOMIC PROFILE OF CASEINS AND MINOR PROTEINS IN BOVINE MILK

Bovine milk contains a high number of proteins and peptides displaying important biological activity.[1] Proteomic studies have usually focused on the analysis and characterization of caseins [2] and of the predominant whey fraction proteins (α-lactalbumin, β-lactoglobulin and lactoferrin). However, a full protein profile of bovine milk is highly desirable to fully understand its nutritional and biological properties and use them for the preparation of subject-oriented dairy products. Recent studies performed on human milk stress the lack of information on minor water-soluble proteins, often trapped in caseine micelles. [3,4] The aim of the present work is to identify both major and minor proteins and peptides present in bovine milk. Injection of skim milk into a capillary monolithic column (based on lauryl methacrylate and 1,6-hexanediol dimethacrylate) yielded a complex chromatographic profile. Further studies have been performed on the casein fraction obtained from bovine milk present in the market: UHPLC-MS and micro-(nano)-UHPLC-MS have been exploited to obtain an optimum of separation and detection of the casein fraction and related bioactive peptides, both before and after digestion with proteolytic enzymes. The data provide new insight into the proteomic profile and can be used to better understand and utilize their physiological properties.