Lipoxygenase and hydroperoxide lyase activities in two olive varieties from Northern Italy

Abstract

AbstractLipoxygenase (LOX) and hydroperoxide lyase (HPL) activities were characterised in olive pulp microsomes from two cultivars (Ghiacciolo and Nostrana di Brisighella) from Northern Italy. LOX activity exhibited a maximum at pH 5.5 in both cultivars, and the highest value was found in cv Ghiacciolo. This was correlated with the higher total antioxidant capacity detected in cv Nostrana, rather than by a different LOX expression, as demonstrated by immunoblotting assay. Furthermore, isomer characterisation showed the predominance of 13‐hydroperoxides of linoleic acid (HPOD) in both cultivars, suggesting the occurrence of a 13‐LOX. HPL activity exhibited an optimum at pH 7.5 in the two cultivars, but was higher in cv Nostrana, as confirmed by the increased amount of hexanal production after 13‐HPOD addition. In addition, the constitutive aldehyde profile in cv Nostrana fruits were shown to be enriched in aldehydes too when compared to cv Ghiacciolo. These results suggest that the different features in the two olive cultivars are mainly due to genetic rather than environmental factors.Practical applications: In this paper we studied the lipoxygenase (LOX) and hydroperoxide lyase (HPL) activities, and the formation of their products (hydroperoxides and aldehydes) in microsomes extracted from olive pulp of two Italian cultivars. The study of LOX and HPL, belonging to the so‐called ‘oxylipin pathway’, has important implications on the aroma development in both fruit and oil. Thus, a better knowledge of the properties of these enzymes can be useful to improve the organoleptic features of the oil. In fact, ‘LOX pathway’ may play a positive role in the formation of pleasant flavours during the technological processes. The preliminary study of the activity of the LOX/HPL enzymes could represent an important tool to facilitate the varietal choice in order to improve oil quality.