Abstract:
Mastitis is one of the most common diseases in dairy cows, causing a mild (subclinical infection) and serious infection (clinical symptoms) in the mammary glands. This pathogenicity results in a significant decrease in milk yield and provides negative influences on physical, chemical and microbiological properties of raw milk. Metabolomics is an emerging field of ~omics approaches that focuses on comprehensive characterization of the overall small molecular weight metabolites (<1.5 kDa) present in a biological system. Recently, this analytical approach has been well acknowledged in food and dairy research. Still, the application of metabolomics for molecular investigation of Thai dairy products is rather limited. Therefore, the aims of this study were to characterize and compare non-volatile metabolite profiles of raw milk collected from healthy, subclinical and clinical mastitis cows from selected farms in the central part of Thailand. After fat and proteins removal, milk serum was analyzed using a high resolution proton nuclear magnetic resonance spectroscopy (1H-NMR at 500 MHz). 1H-NMR derived data were analyzed and compared by means of multivariate statistics. Results demonstrated that a total of 46 metabolites were presumptively identified in this study. Principal component analysis and hierarchical clustering allowed discriminating raw milk from healthy cows and cows associated with different mastitis status according to their 1H-NMR metabolite profiles. Changes in the concentration of acetoacetate, phenylalanine, threonine, isoleucine, leucine, hippurate, lactate, fumarate and N-acetylglucosamine were identified as potential biomarkers accountable for discrimination. This study demonstrates a very promising application of 1H-NMR combined with chemometrics to provide new insights on the molecular authentication of Thai dairy product.