light and temperature influence the quantity and quality of the oil

light and temperature influence the quantity and quality of the oil
light and temperature influence the quantity and quality of the oil
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We are now in the most delicate phase of olive development, at least for the olive grower.

It is the period in which the oil is accumulated but also the minor compounds, the balances between the graddi acids are formed and more generally the quality is formed which will then be extracted in the mill.

It is therefore important to be well aware of how much some environmental and meteorological factors, partly controllable and partly uncontrollable, can influence the development of the fruit.

The influence of light on the development of the olive

The influence of different irradiation conditions was evaluated in conditions of natural solar radiation, comparing well exposed (in) and shaded (out) fruits in olive trees (Olea europaea L).

For a period of two years, from 50 days after full flowering to the moment of harvest, samples of “in” and “out” olives of two genotypes (“Frantoio Millennio” and “Coratina 5/19”) were periodically collected. .

Morphological, histochemical and biochemical analyzes were performed to study the changes in the morphometric traits of the fruit, in the accumulation of oil bodies and in the activity of the β-glucosidase enzyme.

Some parameters were modified by the shading inside the canopy, in which the percentage of photosynthetically active radiation intercepted by the crop was 47%.

The shaded fruits developed at a slow pace and were characterized by a late browning time, small size and a basically oblong shape.

The proposed rapid histochemical procedure to estimate the accumulation of oil bodies during fruit ripening showed that reduced irradiation caused a decrease in the density of the oil bodies.

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These results indicate that adequate and uniform lighting of the olive canopy, thanks to a careful choice of orchard management practices, can be a key factor for different components of the yield.

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The influence of temperature on the development of the olive

The effect of a high temperature on the vegetative growth and on the oil concentration in the fruits of two olive cultivars (Olea europaea) was studied by directly manipulating the temperature. The experiment was conducted in an experimental station in the province of La Rioja, in northwestern Argentina. Two temperature levels were applied (a control treatment and a heated 3 ° C above the control) from fruit set to final harvest, using open chambers (OTC) with electronically controlled heating systems on Coratina and Arbequina varieties.

The leaf area of ​​the whole tree was significantly greater in the open chambers (OTC) with electronically controlled heating systems compared to the control OTC for both cultivars. Shoot elongation showed a similar trend, but the apparent difference was not statistically significant.

Conversely, the elevated temperature had a negative effect on the dry weight of the fruit and the oil concentration in both cultivars. The elevated temperature reduced the dry weight of the fruits by 0.34 and 0.22 g in Coratina and Arbequina, respectively. Furthermore, the oil concentration (%) of the fruits was found to be 4.6 and 6.2% lower on a dry weight basis in the fruits exposed to high temperatures.

The results indicate that high temperatures favor vegetative growth and negatively affect the oil concentration in olive trees in our climatic conditions.

Biogenesis of fatty acids, tocopherols and phenols in relation to temperature

The biogenesis of fatty acids, tocopherols and phenolic compounds of two important Spanish olive cultivars was analyzed as a function of the thermal regime during fruit development.

Regressions between accumulated thermal time (TT) and oleic and linoleic acid levels showed different responses to temperature for each olive cultivar. After reaching similar TT-like absolute maximum oleic acid contents, the levels of this fatty acid decreased significantly in the CV. Arbequina and its final concentration was 10% lower than that found in the CV. Manzanilla. In both cultivars, the concentrations of all tocopherol isoforms were negatively associated with the accumulated TT during the entire period of oil storage. The dynamics of phenolic compound biogenesis did not show clear trends with TT. However, regardless of the stage of development of the fruit, secoiridoids were the main phenolic components. The results suggest an increased sensitivity of fatty acid metabolism to temperature in the CV. Arbequina.

The article is in Italian

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