The oil campaign 2018/2019 can now be considered concluded for this year and, as performed for the other years, we are able to comment on the results of the analyses carried out on a few dozen samples from various areas of Tuscany.
The climatic conditions
Undoubtedly it was a very varied season considering the entire national territory, with areas where the summer drought was probably excessive and with others, especially in the south, where instead the rains of August and September favoured proliferation of the olive fly.
In Tuscany in particular the first case occurred, that is a prolonged drought that created various problems both in the field and in the mill.
The first doubt raised by producers was relative to the time of harvest because the olives started to ripen as early as September, but was it already an indication of maturation or water stress due to the lack of rain?
The question is not easy to answer even in retrospect. Some decided to collect immediately while others waited for the canonical calendar times Undoubtedly those who harvested early enjoyed good yields which then partially decreased in November.
Instead, in the oil mill the first olives that arrived were not easy to process because the lack of water inside the drupes generated very dry pastes that required the expert intervention of the miller.
The quality of the olive oil
From a qualitative point of view, there were no major problems but on average more “flat” oils were produced, with an average lower polyphenol content and therefore with clean but not particularly strong aromas and flavours. Bitter and spicy aromas were not particularly accentuated despite the absence of organoleptic defects.
The results of the analysis for oil quality control
Regarding the results of the analyses carried out with the CDR OxiTester system to assess the quality of the oils produced, the acidity was generally very low with an average value of 0.18% while the number of peroxides was in line with previous years. The value that underwent a major variation is that of polyphenols with an average of just 439 mg/kg compared to 560 mg/Kg in 2017.
Below is the analysis table sorted according to the production date. As can be seen, the oils with the highest quantity of polyphenols are not concentrated solely in the first harvesting period but there were also a few oils at the end of November:
Control of the maturation and quality of the olives
To understand more about determining the appropriate harvesting period, a “snapshot” was taken of the situation of the main quality parameters, extracting a minimum quantity of oil from the olives in the field at the end of October to analyse how these change according to the cultivar.
A small study on the quality parameters determined on the olives
We carried out this small study to understand if, in a heterogeneous olive grove, at the same time of harvest, the quality parameters concerning the various cultivars, therefore also their maturation, are similar or present significant differences.
The analysed olive sample was collected from nearby trees, in the same area of the olive grove, taking the drupes as a sample on all sides of the plant and with the most variable veraison possible.
The cultivars analysed were: Leccino, Frantoiano, Moraiolo and Pendolino.
Through the use of the CDR cold extraction system and a centrifuge it is possible to obtain from a sample of olives a small quantity of oil that is sufficient to perform analyses with the CDR OxiTester system.
As can be seen in the photographs below, the pastes obtained have quite different colours, even the oil extracted through centrifugation appears to have distinctly different colours between one cultivar and another.
The analytical values obtained on the 4 samples are the following:
|Acidity (FFA) (% Oleic Acid)||0.08||0.04||0.12||0.07|
|Peroxide Value (meqO2/Kg)||0.88||1.51||1.9||2.32|
|Total Polyphenols (mg/Kg tyrosol)||1300||946||505||829|
As can be seen from the table, the 4 types of olives and the extracted oil have a noticeable difference on all the parameters. The acidity, albeit low for all the samples, varies between 0.04 for the Moraiolo and 0.12 for the Frantoiano and there are also significant variations for peroxides and polyphenols.
This latter figure was the most surprising given that from the colour of the pastes we would have expected a high polyphenol value for the Frantoiano and a lower one for the Pendolino and the Leccino and instead precisely the opposite was obtained.
Given the unexpected result of this analysis, we repeated the sampling and the test after a week, with the same sampling methods, obtaining the following values:
|Total Polyphenols (mg/Kg tyrosol)||576||889||463||807|
A decrease in the quantity of polyphenols on all the cultivars can be seen, undoubtedly due to a progress of maturation and probably to a few days of rain that may have increased the percentage of water inside the olive and that favoured a passage of the phenolic compounds into the aqueous phase.
However the value of the minor polyphenols also found in this analysis session is that of the Frantoiano.
The quality of the oil obtained
Other interesting considerations can be made on the basis of the results obtained on the oil, obtained from the olive grove examined after milling of the entire batch of olives in the mill, 2 days after the harvest and sampling.
The oil obtained produced the following values:
|Acidity (FFA) (% Oleic Acid)||0.13|
|Peroxide Value (meqO2/Kg)||3.37|
|Total Polyphenols (mg/Kg tyrosol)||485|
Here there are no big surprises, the acidity and peroxides are in line with what we found on the olives, while the quantity of polyphenols is on average much lower because the mixing phase inevitably favours the passage of polyphenols from the apolar phase (oil) to the polar phase (water).
Our small study confirmed how complex it is to understand the correct period for harvest which is however linked to different productive aspects.
We can state without a doubt that working on monocultivar could have advantages from the point of view of control and also in identifying the right harvest time, while in a heterogeneous olive grove it is more difficult to “manage” the qualitative parameters.
The study also confirms the loss of polyphenols in the mill, a phenomenon that is certainly inevitable but one which can probably be improved.