Differences in n-alkane profiles between olives and olive leaves as potential indicators for the assessment of olive leaf presence in virgin olive oils

The olive (Olea europaea) is one of the most important crops in the Mediterranean region for economic and culinary reasons. Cuticular waxes coat olives and olive leaves and play a significant role in plant physiology and resistance against environmental stresses. The present study describes n-alkane profiles in cuticular waxes of olives and leaves of three Italian varieties (Frantoio, Leccino and Maraiolo) during different stages of olive development. Additionally, the study investigates the differences between n-alkane profiles of extra virgin olive oils with low and high leaf content. Olive leaves are characterised by the predominance of n-alkanes with longer carbon chains (n-C-29-C-33) compared with olives (n-C-25-C-29). During all stages of olive ripening period, n-alkane average chain length (ACL) values of olive leaves are significantly higher compared with those of olives. Extra virgin olive oils with admixture of leaves have significantly different n-alkane profiles than those free from leaf material. Practical applications: The results of this study will contribute significantly to the currently very limited information on n-alkane data from olive tree varieties used for oil production. The presence of leaves increases the concentrations of long chain n-alkanes (n-C-31-C-35) in extra virgin olive oils, therefore studying the differences between n-alkane profiles of olives and olive leaves could help establishing the presence of leaf material in produced extra virgin olive oils. Information about the relative and absolute concentrations of n-alkanes in olives, olive leaves and olive oil will also be useful for biochemical and metabolic studies of the olive tree. Significant differences in n-alkane profiles of olives and olive leaves can be used for detecting the presence of leaf material in virgin olive oils.