Analysis of triacylglycerols molecular species composition, total fatty acids, and sn-2 fatty acids positional distribution in different types of milk powders

Abstract

Triacylglycerols (TAGs) are considered the main component of milk fat; possess significant functional roles from the technological, nutritional and physiological points of view. In this study, an ultra-performance liquid chromatography coupled with quadruple time-of-flight mass spectrometry was applied to identify the molecular species composition of TAGs in buffalo, camel, and ewe milk powders. The separation of TAGs was achieved by using two mobile phases; acetonitrile/isopropanol (1:9, v/v) as mobile phase A, and 40% acetonitrile as mobile phase B, the binary gradient elution allowed the separation of milk TAGs in consistent with the increase in partition number. More than 180 TAGs in buffalo milk, 90 TAGs in camel milk, and 129 TAGs in ewe milk were unambiguously identified, and the most abundant molecular species in the three types of milk powders were detected at mass to charge (m/z) values of 682.53, 822.67, and 656.53, respectively. The total acyl carbon numbers of buffalo milk TAGs ranged between 26 and 54, with double bonds from 0 to 6. While, the total acyl carbon numbers of camel milk TAGs ranged between 42 and 54, with double bonds from 0 to 3. The total acyl carbon numbers of ewe milk TAGs ranged between 26 and 52, with double bonds from 0 to 2. The major fatty acids (FAs) in the different types of milk powders were myristic, palmitic, stearic, oleic, and linoleic. The positional distribution of saturated FAs at the sn-2 position was higher in buffalo milk powder as compared to camel and ewe milk powders. This study reports a comprehensive identification of TAGs molecular species in different types of milk powders.