The extent and conditions of storage may affect the stability and quality of extra virgin olive oil (EVOO). This study aimed at evaluating the effects of different storage conditions (ambient, 4 °C and −18 °C temperatures, and argon headspace) on three EVOOs (low, medium, and high phenols) over 18 and 36 months, analyzing the main metabolites at six time points. The results showed that low temperatures are able to maintain all three EVOOs within the legal limits established by the current EU regulations for most compounds up to 36 months. Oleocanthal, squalene, and total phenols were affected by storage temperatures more than other compounds and degradation of squalene and α-tocopherol was inhibited only by low temperatures. The best temperature for 3-year conservation was 4 °C, but −18 °C represented the optimum temperature to preserve the organoleptic properties. The present study provided new insights that should guide EVOO manufacturers and traders to apply the most efficient storage methods to maintain the characteristics of the freshly extracted oils for a long conservation time.

A comprehensive effort was devoted to exploring, collecting and characterizing the local Maltese olive germplasm, often represented by ancient, monumental trees and by plants of uncertain origin. SSR and cp-SSR analysis of all samples enabled the identification of 46 genotypes and establishment of the correspondence between ancient trees, main local varieties and other Mediterranean cultivars. The application of plastid markers enabled identification of two lineages among Maltese genotypes, with more than 50% represented by lineage E2. Twenty-nine cases of grafting were identified among the various genotypes and lineages. In most cases, E1 canopies were grafted on E2 rootstocks, but reverse cases were also observed. The phylogenetic study of Maltese genotypes, together with hundreds of cultivars from the Mediterranean Basin and beyond, highlights the richness of Maltese olive diversity and drawing attention to the genetic similarity of some Maltese olive genotypes with neighboring Italian and Algerian varieties. These results underline the long-lasting presence of the olive in the country, contributing to the reconstruction of its phylogeny and demonstrating a possible autochthonous origin of many samples. Some still-living ancient trees are at serious risk of extinction due to abandonment, urban expansion and environmental threats. This study supports the preservation of the Maltese olive germplasm and highlights its importance as a rich genetic source to face new agronomical challenges and future climatic constraints.

The phenotypic and genetic variability of local olives in a perspective of diversity conservation should be maintained and preserved. Fourteen unknown olive genotypes were selected from abandoned and isolated plants in Umbria region and characterized by ten SSR markers. The molecular analysis led to identify ten previously unknown genotypes within the patrimony of the region, made up by about 10 main cultivars and more than 100 minor ones. Fruit samples were randomly collected from the selected plants during two growing seasons and oil was extracted from each sample. Analyses of fatty acid composition, phenolic profile (flavonoids, phenolic acids, phenolic alcohols and lignans), tocopherols, squalene and sterols were performed on these oils. Significant differences were observed in terms of main fatty acids (e.g. oleic acid from 71.83 to 76.73%), but not for the minor ones. The important differences were instead obtained on the amount of α-tocopherol, ranging from 149 to 583 mg kg⁻¹, and on squalene, spanning from 1059 to 5447 mg kg⁻¹. Evaluation of major and minor compounds with the principal component analysis of the main oil quality parameters revealed differentiation according to the genotypes. The analysis of neglected olive genotypes from a small area of cultivation has led to the identification of a promising source of variability for most sought-after traits, which could be exploited for new olive plantations and to magnify the spectrum of local olive oils.

The health, therapeutic, and organoleptic characteristics of olive oil depend on functional bioactive compounds, such as phenols, tocopherols, squalene, and sterols. Genotype plays a key role in the diversity and concentration of secondary compounds peculiar to olive. In this study, the most important bioactive compounds of olive fruit were studied in numerous international olive cultivars during two consecutive seasons. A large variability was measured for each studied metabolite in all 61 olive cultivars. Total phenol content varied on a scale of 1–10 (3831–39,252 mg kg⁻¹) in the studied cultivars. Squalene values fluctuated over an even wider range (1–15), with values of 274 to 4351 mg kg⁻¹. Total sterols ranged from 119 to 969 mg kg⁻¹, and total tocopherols varied from 135 to 579 mg kg⁻¹ in fruit pulp. In the present study, the linkage among the most important quality traits highlighted the scarcity of cultivars with high content of at least three traits together. This work provided sound information on the fruit metabolite profile of a wide range of cultivars, which will facilitate the studies on the genomic regulation of plant metabolites and development of new olive genotypes through genomics-assisted breeding.