Waxy fraction containing long-chain aliphatic aldehydes in virgin olive oils

Long-chain aliphatic aldehydes are natural minor components occurring in the cuticle of numerous plant species and also evidenced in virgin olive oils. The fraction containing these compounds can be isolated from the oil samples by using a solid-phase extraction silica-gel cartridge and then directly analysed by GC on a 5% diphenyl-95% dimethylsiloxane capillary column, using an on column-injection system. The proposed methodology showed that extra virgin olive oils contain long-chain aliphatic aldehydes, with even carbon-atom numbers from C₂₂ to C₃₀. Quantitative results, using the synthesised aldehyde C₂₁ as internal standard, give concentrations of total long-chain aliphatic aldehydes in a variable range below 116 mg kg⁻¹, being hexacosanal (C₂₆-al) the most abundant aldehyde. The different experimental conditions utilised during olive oil extraction processes influence the total aldehydes concentration. Besides contribution to the knowledge of the minor-component composition present in olive oil, their interest and relationship with wax esters, aliphatic alcohols and n-alkanes are discussed.