Are virgin olive oils obtained below 27 °C better than those produced at higher temperatures?

Within the European Union, indications of 'first cold pressing' and 'cold extraction' can only be used for virgin olive oil (VOO) obtained below 27 degrees C from mechanical processing. Three different malaxing temperatures (25, 35 and 45 degrees C) are here evaluated for the quality of the VOO obtained in a continuous industrial plant. The oils were stored at room temperature in the dark for 12 months. Initially, oil obtained from a blend of Frantoio/Leccino cultivars (F/L) had higher acidity and peroxide levels and lower phenolic content than a Coratina cultivar (Cor). The oxidative stability of the oils positively correlated with malaxation temperature (F/L, R-2 = 0.818; Cor, R-2 = 0.987) as the phenolic content was directly proportional to the temperature (F/L, R-2= 0.887; Cor, R-2 = 0.992). Only oils obtained at 45 degrees C were rejected because of 'heated or burnt' off-flavour. Decarboxymethylation of secoiridoids and further hydrolysis of phenolic esters occurred during storage. The oxidation products of derivatives of tyrosol and hydroxytyrosol were detected after nine months in both the F/L and Cor samples. Thus, VOO obtained at a processing temperature lower than 27 degrees C does not show higher chemical and sensory qualities than VOO obtained at 35 degrees C. (c) 2008 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.