A Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS) Method for the Determination of Free Hydroxy Fatty Acids in Cow and Goat Milk.

Maroula G Kokotou,George Kokotos,Olga G Mountanea,Asimina Bourboula,Christiana Mantzourani

doi:10.3390/molecules25173947

Maroula G Kokotou, George Kokotos + Show 3 more

Open Access

https://doi.org/10.3390/molecules25173947

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Abstract

A liquid chromatography–high resolution mass spectrometry (LC-HRMS) method for the direct determination of various saturated hydroxy fatty acids (HFAs) in milk was developed for the first time. The method involves mild sample preparation conditions, avoids time-consuming derivatization procedures, and permits the simultaneous determination of 19 free HFAs in a single 10-min run. This method was validated and applied in 17 cow milk and 12 goat milk samples. This work revealed the existence of various previously unrecognized hydroxylated positional isomers of palmitic acid and stearic acid in both cow and goat milk, expanding our knowledge on the lipidome of milk. The most abundant free HFAs in cow milk were proven to be 7-hydroxystearic acid (7HSA) and 10-hydroxystearic acid (10HSA) (mean content values of 175.1 ± 3.4 µg/mL and 72.4 ± 6.1 µg/mL in fresh milk, respectively). The contents of 7HSA in cow milk seem to be substantially higher than those in goat milk.

Highlights

Lipids are one of the most important classes of milk components [1,2]
Such a method may unravel the existence of potential bioactive ingredients in milk that may play a role in human health
The high-resolution mass spectra of these hydroxy fatty acids (HFAs) were recorded in electrospray ionization (ESI) negative mode

Summary

Introduction

Lipids are one of the most important classes of milk components [1,2]. Apart from their role as a source of energy, they contribute to the sensory and physical properties of milk. The majority of lipids in dairy fat are triacylglycerols [3], while small amounts of free fatty acids (FFAs) are present as a result of the enzymatic hydrolysis of triacylglycerols by lipoprotein lipase and other lipolytic enzymes [4]. Among the numerous fatty acids (FAs) found in milk, long-chain saturated fatty acids (SFAs) are the predominant class [5,6]. Various FAs present in milk fat are linked either in a positive or a negative way with human health [9]. Nutritional guidelines have suggested a reduction in the intake of milk

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