The researchers of the chemical laboratory “CDR Chemical Lab Francesco Bonicolini” conducted a study with the aim of developing a quick and simple system to identify the best time for the olive harvest, determined by their state of ripeness.
When to harvest olives
By choosing to start the harvest in a period slightly prior to completion of technological maturation, more importance is given to the quality and to the greater content of polyphenols. Instead, if to prioritise the oil yield, it is possible to schedule the harvest when it is completed, but seeking to limit the loss of quality.
The state of maturation
Various sets of research have been carried out which have shown how it is possible to determine the state of ripeness of olives by studying over time the evolution curve of the quantity of sugars contained in them.
During the maturation phase, in fact, it was found that the concentration of sugars in the olive decreases, while the oil content increases. When the sugars reach a constant concentration we have the maximum yield in oil and therefore technological maturation.
The two sugars most present in olives are glucose and fructose, so to study their maturation trend it is sufficient to determine the variation over time of their concentration in the drupes.
The study of the CDR laboratory
In September, October and November the following steps were taken on a weekly basis:
- from a single olive tree approximately 50 grams of olives were sampled on all sides of the plant;
- the olives were pressed with the CDR mechanical extraction system in order to obtain a homogeneous stone-free paste;
- by centrifuging the paste the aqueous part was separated;
- the aqueous part was analysed with the CDR OxiTester system determining the value of the sugars present.
It was thus found that sugars have a fairly constant decrease for about 6/7 weeks starting from mid-September. In the following weeks the value stabilises. The moment at which the sugars reach the minimum value, with a good approximation, corresponds with the maximum yield in oil.
The analysis of the results obtained has shown that the variation in the concentration of glucose and fructose is used to estimate when the fruit has reached technological maturation and gives important indications on what is the most appropriate time to carry out the harvest.
We can therefore state that the tests carried out in the laboratory confirmed the progress of this parameter during the maturation phase already determined in other studies.
Using the CDR extraction system and the CDR OxiTester analysis system to conduct the study, a simple and easily reproducible method was developed to determine the technological maturity of the olives, which can also be adopted by small companies that are not equipped with a chemical laboratory.
In fact, with the CDR extraction system the treatment of the sample is simple and does not require any chemical solvent.
In addition, the CDR OxiTester analysis system, already present in many companies in this sector for oil quality control, is easily used even by those who have no experience in laboratory techniques.
The pre-filled and ready-to-use reagents avoid contact with toxic substances and the analyser does not require any calibration.
In conclusion, with this new application, which can be easily implemented on CDR OxiTester, it is possible to check the maturation status of the olives directly in the mill or on the farm and to evaluate the most appropriate period for the harvest.