Regio- and Stereospecific Analysis of Triacylglycerols—A Brief Overview of the Challenges and the Achievements

Progress in triacylglycerol isomer detection in milk lipids

In triacylglycerols (TAGs), position differences of fatty acids on the glycerol skeleton produce various TAG isomers. These TAG isomers have different pathways of digestion, absorption, and utilization in infants, thereby affecting TAG nutritional properties of TAGs. Here, we review the progress of research on methods for detecting TAG isomers, and identify direction and thought for improving these methods, including novel chromatographic combinations, perfect algorithm, and improved equipment. The ensuing optimization of these methods is expected to provide robust guarantee for the gradual improvement of milk-derived TAG isomer detection, and is an important prerequisite for infant formula to mimic the structured lipids of human milk.

Impact of column temperature on triacylglycerol regioisomers separation in silver ion liquid chromatography using heptane-based mobile phases

This work presents the investigation of the use of heptane as an alternative and less toxic mobile phase to the most used hexane for triacylglycerols (TAGs) analysis in silver ion high-performance liquid chromatography (Ag⁺-HPLC). The impact of column temperature (in the 5 °C-35 °C range) on the retention and resolution of five pairs of regioisomers relevant for the confectionery industry was investigated using a heptane-based mobile phase modified with acetonitrile (ACN). The retention behaviour was compared for a standard TAG mixture and an interesterified cocoa butter. The temperature effect previously observed with hexane-based mobile phases was confirmed for this new system, and it was also observed that the ACN concentration had an important impact on the strength of the temperature effect, with a higher ACN concentration leading to a lesser impact of temperature on the TAGs' elution behaviour. In general, the study allowed to conclude on the equivalence of hexane and heptane for TAGs regioisomers separation in Ag⁺-HPLC, independently of the used temperature or the ACN concentration. In addition, the applicability of heptane-based mobile phases for the separation of TAGs regioisomers was demonstrated on three other confectionary fat samples, namely palm olein, interesterified palm olein, and interesterified shea olein.

LC-Orbitrap-HRMS method for analysis of traces of triacylglycerols featuring furan fatty acids

Furan fatty acids (FuFAs) are valuable antioxidants that are highly relevant for the protection of polyunsaturated fatty acids (PUFAs) in biological systems and food. Despite their low contributions to the total fatty acids, their widespread occurrence has been documented in food and biological samples. Like other fatty acids, FuFAs are also stored esterified, e.g., in triacylglycerols. However, FuFA-containing triacylglycerols had not been detected in lipidomics analyses. Here, we present a screening method that allows for the identification of traces of FuFA-containing triacylglycerols (TAGs) utilizing LC-Orbitrap-HRMS. Initially developed with the help of purposefully synthesized FuFA-containing TAGs, the screening method was successfully applied to the analysis of two fish oil samples and one mushroom extract sample. Several FuFA-containing TAGs could be identified by direct analysis using the method and database developed in this study.