Thermal regime and cultivar effects on squalene and sterol contents in olive fruits: Results from a field network in different Argentinian environments

Abstract

Some olive cultivars and production regions around the world, although they may provide good quality olive oils, may not comply with the current commercial regulations establishing acceptable levels of sterols in extra virgin olive oils. The present study was driven by the hypothesis that olive growing environments, differing in thermal regime conditions, affect squalene and sterol contents of olive fruits. On the basis of differences in agronomic characteristics and oil composition, two olive cultivars (Arbequina and Coratina) were selected and sampled at different fruit development stages. Various models were examined to look for relationships between environmental thermal records and chemical parameters; those including the accumulated thermal time (ATT) and minimum temperatures showed the best fit. In both cultivars, the total and individual sterol contents were positively associated with ATT over all the fruit development and ripening period considered. In all cases, the data from Arbequina fit the models better than for Coratina and differences between cultivars in individual sterol contents were greater in the warmest growing environments. Overall, findings indicated a strong impact of the growing environment on squalene and sterol contents. Such an effect was associated with specific thermal characteristics of the olive growing sites; concentrations were found to be higher in the warmer northernmost sites than in the cooler southernmost ones. There was also an effect of the cultivar, particularly on the contents of β-sitosterol, campesterol and total sterols. These latter results suggest greater sensitivity of sterol metabolism to temperature in cv. Arbequina.