Introduction
About two decades ago, food labeling regulations requiring the declaration of the trans-fat content on food packaging were introduced in several countries [1]. Available gas chromatographic (GC) methods for the quantification of fatty acids (FA) (as methyl esters, FAME) were redesigned to privilege the accurate quantification of the transFA (TFA) contained in partially hydrogenated oils (PHO). All revised methods adopted 100% poly(biscyanopropyl siloxane) (BCS) capillary columns in the format 100 x 0.25 mm, the commercial columns providing the highest resolving capabilities for unsaturated fatty acids based on the number and geometry of double bonds (DB). More polar columns coated with ionic liquids, which provide even stronger selectivity, were introduced only a decade later [2,3]. The isothermal elution at 180°C emerged as the preferred compromise for the resolution of 18:1, 18:2 and 18:3 TFA from the other FA present in PHO [4] and was selected by the American Oil Chemists’ Society (AOCS) for its Official Method Ce 1H-05 [5]. AOCS later introduced the sibling Official Method Ce 1J-07 [6], adding a temperature ramp after the elution of 18:3n-3 to shorten the retention time of remaining FAME.
Ruminant fats and dairy products, rich in short chain FA (SCFA), are generally analyzed applying a temperature gradient. Golay et al.developed a method capable of simultaneously measuring the SCFA,trans -18:1 and trans -18:2 present in ruminant fats by applying a rapid temperature ramp [7]. This method was validated for the quantification of TFA in milk products, infant formula, and adult/pediatric nutritional formula [8]. The application of the temperature program, however, resulted in the coelution oftrans -18:3 with 20:1 FA, which affects the measurement of TFA when applying this method to the analysis of refined vegetable oils (RVO) and PHO.
Although each method proved very effective for the analysis of the lipid extracts it was developed for, no single method may be applied to all extracts. To address this gap, this short communication proposes a modification of the method of Golay et al. [7,8]. This modified approach can be used to measure the SCFA, trans -18:1 andtrans -18:2 present in ruminant fats while simultaneously achieving more accurate quantification of trans -18:3 present fat in PHO and RVO.