Master Miller at “Cortijo la Torre” José Luis Burgos explains how to know when and how to harvest. Objective: obtaining the highest quality in the extraction of your extra virgin olive oil (EVOO).
José Luis Burgos has a proven track record in the development of quality EVOOs. He participates as speaker in some of the specialised Master Miller Courses of the Olive Oil School of Spain.
When is the ideal moment to start harvesting the olives?
The ideal moment to start planning the harvesting of the olives that we are going to devote to the production of a maximum quality Extra Virgin Olive Oil starts by the end of September in my region – Jaen -.
We should start by selecting those plots that have a medium / high quantity of olive and a larger fruit size.
Once we have selected the plots that we want to collect, take about 2 kg of olives from each plot located at the height of the view and in the 4 orientations of the tree.
We homogenize the sample, we separate about 100 fruits and classify them in the following categories:
- Intense green skin
- Yellow-green skin
- Green skin with some reddish stain.
Another factor to take into account when deciding the optimum moment for harvesting is the color that the olive is taking.
That is to say, at the moment in which the olive passes from the intense green color to the yellowish green, we return to sample the plots and send the samples to the laboratory.
It will be necessary to be attentive to the following parameters:
- Fat Content on Dry matter: this parameter must be between 36 and 40%;
- Humidity. Between 58 and 64%;
- Fatty performance. It has to be between 15 and 18% but this parameter is not relevant since what we are looking for is quality and not quantity.
When we already have our olive meeting these parameters, then it is the key moment to submit it to the abencor test, which simulates the oil extraction process that we would do in the mill but this time it is done in a laboratory.
Once we have extracted the oil from the olive samples, it is filtered, tasted and, if the oil has enough characteristics (fruity, balanced, etc.), we will proceed to harvest, but always starting with the plots that indicate a highest maturity index.
Why should we start harvesting the most ripe olives?
If we start harvesting the less ripe olives, as the collection lasts about 10 days, when we get to collect the ripest, possibly it will be already too mature to develop top quality EVOO.
Why is fat performance so variable even over dry matter?
The fat yield, even on dry matter varies from year to year, by varieties and by zones.
In view of the knowledge of the entire process described above, I explain the factors that influence and make it so complicated to determine for each variety, on each farm, in each location and in each campaign the Optimum Moment of Collection of the Olives.
During the whole process of lipogenesis, the climatic conditions greatly affects the total or final amount of oil to accumulate, because the natural metabolic process needs a temperature threshold for its correct functioning.
In our latitudes, between June and December the two extremes occur, very high temperatures, even many days above 36-38ºC and later, with fruits still green, frosts of up to -4 / -5ºC.
Obviously both factors stop lipogenesis for a longer or shorter period or definitely.
With pruning the vegetative response of the tree is controlled and production is regulated. This practice allows to act, with a certain margin on the size of the fruits, mainly on the pulp / bone ratio.
This, together with the improvement of the lighting and the ventilation that pruning implies, allows us to affirm that this cultivation practice favors a correct lipogenesis.
Influence of a correct fertilization. The correct use of N (Nitrogen) favors a certain delay in maturation, which, therefore, would lengthen the process of lipogenesis.
On the other hand there is a clear positive correlation between the content of K (Potassium) in fruit and the final amount of oil in it, because of the important role that this element plays in lipogenesis.
In an olive tree well endowed with moisture during the cycle, the fruits are uniform with high pulp / bone ratio and form the oil in an adequate amount.
On the contrary, the lack of moisture in the soil in the stages prior to maturity, causes the existence of small fruits with difficult lipogenesis.
Basically the influence that an adequate control of plagues can have is to avoid the presence of pests that depress the sprout, the leaf or the fruit itself, and thus hinder or interrupt the correct lipogenesis. For the same reason, diseases that directly or indirectly influence fruit development should be avoided.
Apart from other genetic issues such as susceptibility or resistance to diseases, pests, ripening season, ease or resistance to abdication, size of the fruit and its pulp / bone ratio, the variety of olives has a marked influence on the quality and final quantity of oil to obtain.
Are you ready to obtain full advantage of your olives?