Study of enriched olive oil with high nutritional and biological value: olives and hazelnuts co-pressing

Olive oil is the main source of fat in the Mediterranean diet and its consumption has been related to a low incidence of coronary heart disease and certain cancers. These protective effects are attributed mainly to two fundamental components of oilve oil: monounsaturated fatty acids (MUFA) and antioxidant substances. Also nuts are included in healthy diets and, among them, hazelnuts (Corylus avellana L.) are very interesting as a source of nutritious food with a high content of functional lipids. Hazelnut’s benefits are mainly related to its fatty acid composition, rich in MUFA, tryacylglycerol profile, tocopherols and other bioactive compounds like phytorterol and polyphenols. On the basis of these considerations the aim of this work was to investigate the quality of an olive oil obtained by a co-pressing of olives and hazelnuts. In particular, three different samples were studied: olive oil obtained crushing 0% (O), 5% (O5N) and 10% (O10N) of hazelnuts. Classical methods based on gas-chromatography (GC) and high-performance liquid chromatography (HPLC) have been used for fatty acid, tryacylglycerol, phytosterol and tocopherol characterization. No significant differences were noticed among the three olive oils, except for phytosterols. The small components 7-stigmastenol and 7-avenasterol, charatcteristic of the hazelnut sterol profile, were found to be present in higher amount in samples O5N and O10N than the simple olive oil Besides, the samples were also analysed by FT-MIR spectroscopy in the frequency range 1500 -900 cm-1. The FT-MIR spectra were processed by using principal component analysis (PCA) and partial least squares regression (PLS). The first one was used to discriminate the sample oils with different content ofhazelnut, instead the second one was employed to predict tocopherol and tryacylglycerol content (R2 up to 0.87 in cross verification)