GC-Based Analysis of Plant Stanyl Fatty Acid Esters in Enriched Foods

Abstract

Approaches for the capillary gas chromatographic (GC) based analysis of intact plant stanyl esters in enriched foods were developed. Reference compounds were synthesized by enzyme-catalyzed transesterifications. Their identities were confirmed by means of mass spectrometry. Using a medium polar trifluoropropylmethyl polysiloxane stationary phase, long-chain plant stanyl esters could be separated according to their stanol moieties and their fatty acid chains. Thermal degradation during GC analysis was compensated by determining response factors; calibrations were performed for ten individual plant stanyl esters. For the analysis of low-fat products (skimmed milk drinking yogurts), the GC separation was combined with a "fast extraction" under acidic conditions. For fat-based foods (margarines), online coupled LC-GC offered an elegant and efficient way to avoid time-consuming sample preparation steps. The robust and rapid methods allow conclusions on both, the stanol profiles and the fatty acid moieties, and thus provide a basis for the authentication of this type of functional food ingredients.

Capillary gas chromatographic analysis of complex phytosteryl/-stanyl ester mixtures in enriched skimmed milk-drinking yoghurts

“…The peak numbering is given in Table 1. (Barnsteiner et al, 2011), the steryl esters of the unsaturated fatty acid moieties could also be distinguished (Fig. 1).…”

“…The extraction of lipids from skimmed milk-drinking yoghurts was performed by the "fast extraction method" as previously described (Barnsteiner et al, 2011). The internal standard cholesteryl palmitate (750 mg), the yoghurt drink sample (100 mg), hydrochloric acid (25%; 1 mL) and bi-distilled water (400 mL) were placed into a reaction vial.…”

“…A previous study with plant stanyl fatty acid esters had demonstrated that the capillary gas chromatographic (GC) analysis of these substances is feasible (Barnsteiner et al, 2011). However, the GC-separation step involves thermal degradation processes and a quantitation was only possible because an industrial plant stanyl ester mixture was available for calibration.…”

“…Recently, a method for the quantitative analysis of individual plant stanyl fatty acid esters in enriched skimmed milk-drinking yoghurts by means of capillary gas chromatography has been described (Barnsteiner et al, 2011). The work-up was performed by a "fast extraction method" involving an acid digestion step.…”

“…The esters of unsaturated fatty acid moieties could be distinguished and quantified individually. The fact that the high boiling stanyl esters were subject to individually differing thermal degradation processes during the GC analysis was compensated by a calibration employing an industrial plant stanyl ester mixture which exhibited a profile very similar to the preparations added to the investigated commercial products (Barnsteiner et al, 2011).…”