Influence of the nocturnal harvesting of olives from Salento (Italy) on the quality of the extra virgin olive oil

Abstract

SUMMARY:In southern Italy, some olive cultivars such as 'Ogliarola Salentina' ripen when the day temperature is still high, at up to 28 to 30 °C. This can affect both the oil quality and the expression of its valuable characteristics. In addition, it increases the risk of undesirable fermentation that can generate off-flavors. In the present study, nocturnal olive harvesting was carried out to determine the influence that temperature can have on the characteristics of the extra virgin olive oil, and particularly on the volatile and oxidative compounds. The data obtained are encouraging: the lower temperatures that occur during the night appear to have a particular and positive impact on the organoleptic characteristics of the extra virgin olive oil produced, with enhanced formation of the volatile compounds that contribute to the 'green' notes of the flavor. In areas where daytime temperatures are very high, the nocturnal harvesting of olives at the correct stage of maturity therefore represents a good agronomic practice for the production of oils with high organoleptic and nutritional merit. KEYWORDS: Extra virgin olive oil; Nocturnal harvesting; Quality; Volatile substancesRESUMEN: Influencia de un cosechado nocturno de aceitunas en "Salento" sobre la calidad del aceite de oliva virgen extra. En el sur de Italia, algunas variedades de olivo maduran cuando la temperatura del día sigue siendo alta, hasta 28 °C a 30 °C. Esto puede perjudicar la calidad del aceite y a la expresión de sus valiosas caracterís-ticas, y aumenta el riesgo de fermentación indeseable que puede generar malos sabores. En el presente estudio, la cosecha nocturna de aceitunas se llevó a cabo para determinar la influencia que la temperatura puede tener sobre las características del aceite de oliva virgen extra, y en particular sobre los compuestos volátiles y los compuestos relacionados con la oxidación. Los datos obtenidos son alentadores: las temperaturas más bajas que se producen durante la noche parecen tener un impacto positivo en las características organolépticas del aceite de oliva virgen extra producido, con una mejora de la formación de los compuestos volátiles que contribuyen a las notas "verdes" del sabor. En las zonas donde las temperaturas diurnas son muy altas, la cosecha nocturna de aceitunas, representa, por tanto, una buena práctica agronómica para la producción de aceites con grandes ventajas organoléptica y nutritivas.

Quality of olives: A focus on agricultural preharvest factors

“…Early harvesting can also reduce the negative effects of irrigation on oil quality and prevent damages from frost (Gracia et al, 2012), olive fly adult activity (Rojnic´et al, 2015) and Anthracnose (Moral et al, 2014) and may contribute to preventing negative global warming because cultivation under extreme climatic conditions (i.e., higher temperature and lower rainfall) causes fruits to ripen faster (Dag et al, 2014). Moreover, harvesting at night to avoid the effects of high temperature at harvest seems to improve the oil's sensory qualities (Di Serio et al, 2014).…”

Effect of Halyomorpha halys Infestation on the Physicochemical Composition and Sensory Characteristics of Olive Fruits and Olive Oils

“…Ethyl esters are considered to be a reliable indicator of olive quality and their increase is due to hydrolytic modifications of triglycerides (the release of fatty acids) and fermentation of sugars by microorganisms (the production of ethanol), while the presence of methyl esters indicates a loss of structural integrity, causing the release of methanol from the pectins by the action of specific enzymes. 24 The amount of methyl esters in EVOOs (extra virgin olive oils) is usually connected to the drupes' degree of ripeness. However, in this experiment, the ripeness of the drupes was close to the optimal value (IM 3.5).…”