Changes in squalene and sterols associated with olive maturation

Squalene and sterols are biologically active compounds of great relevance for olive oil quality. The objective of this research was to study the dynamics of squalene and sterols accumulation during olive maturation. Fruits of cultivars 'Picual' and 'Arbequina' and two breeding selections derived from crosses between them were harvested monthly from September to December in Córdoba, Spain. Squalene and sterols contents were measured directly in olive flesh by gas chromatography. The fresh fruit weight, oil content, and ripening index were also determined. Oil content reached a maximum in November (19.4%) and maintained similar levels in December (19.8%). Squalene content in the fruit flesh increased significantly from September (4102 mg kg− 1) to November (4673 mg kg− 1), showing no significant difference between November and December. Sterol content increased significantly every harvest date, from 723 mg kg− 1 in September to 1188 mg kg− 1 in December, though no significant differences were observed between November and December in three out of four genotypes. The concentration of β-sitosterol was reduced from 87.3% in September to 75.9% in November, whereas Δ5-avenasterol concentration concomitantly increased from 7.2% in September to 18.6% in November, remaining unaltered in December. As only very small differences were found for oil, squalene and sterols contents between samples collected in November and December, it can be concluded that early harvest in November will not affect the fruit and oil composition for squalene and sterols.