Quantitative TLC and Gas Chromatography Determination of the Lipid Composition of Raw and Microwaved Roasted Walnuts, Hazelnuts, and Almonds

Abstract

Analytical and preparative thin‐layer chromatography (TLC) on intact silica gel and silica gel layers modified with either silver nitrate (Ag‐TLC) or dimethyldichlorosilane (RP‐TLC), combined with densitometric quantification and gas chromatography (GC), have been used to elucidate the lipid classes, their fatty acid profiles, the triacylglycerol, and sterol compositions of raw and microwaved roasted walnuts, hazelnuts and almond kernels harvested in Bulgaria. The results on fatty acid and triacylglycerol compositions are in good agreement with those reported for other geographical regions. Microwave roasting on full power for 3 min produced ready‐to‐consume kernels and no changes in lipids were detected. The combination of TLC techniques used for identification and quantification of triacylglycerols gave results comparable with those obtained using reversed phase liquid chromatography‐mass spectrometry (LC‐MS).

Keywords:

• Thin‐layer chromatography
• Gas chromatography
• Lipid composition
• Walnut
• Hazelnut
• Almond

Acknowledgments

The partial financial support from the Bulgarian National Science Fund, contract #X‐1513, is gratefully acknowledged.