Description of technology

Type of Report:
Completion Report
Period Covered:
April 17th 1998. – June 17th 2001.
Title of Project:
Investigation of optimal harvest time for high olive oil quality
in Istria.
Contract Number:
Project Start Date: April 17th 1998.
Principal Investigator:
Prof. Dr. sc. Ivo Miljković
Participating Institution:
Faculty of Agriculture University of Zagreb
Department of Pomology
(Signature of Principal Investigator)
One of the major factors of olive oil quality is the degree of fruit maturity or choosing
the optimal term of harvesting for each single cultivar in specific ecological
conditions. The goal of this research was to find optimal harvesting moments of the
most important olive cultivars in two significantly different ecological conditions of
Istria. For this experiment the following olive orchards were chosen:
1. Barbariga (the property of ‘Agroprodukt’, Pula), plantation near the sea,
Cultivars: Leccino on its own root
Leccino on the generative root
Istarska bjelica on its own root
2. Veli Mlun (near Buzet, a private plantation of Mr. Danilo Cerovac)
Plantation is 30 km distant from the sea on the level above sea 250 – 300 m
Cultivar: Leccino on its own root.
3. Pračana (near Buzet, a private plantation of Mr. Sirotić)
Plantation is 30 km distant from the sea, on the level above sea 250 – 300 m
Cultivars: Buža on its own root.
Istarska bjelica on its own root.
In each year of the three-year lasting research the harvest was performed in three
moments of ripeness. Oil extraction using small extracting machine took place
immediately after harvesting. The obtained samples were chemically analysed to
prove oil quality parameters. Details dealing with setting of the experiment and with
experimental results can be found in PhD dissertation of Đani Benčić ‘The
Influence of the Degree of Ripeness and Harvesting Term on Quality of Istrian OliveOrchards Oils.’
Description of technology
On the basis of results given by this research, we concluded that cultivars Leccino and
Bjelica reach the optimal degree of ripeness by November 10th in ecological
conditions of Buzet, when on the seaside (Pula) it is up to November 23rd. Higher
indexes of ripeness, that is later dates of harvesting decrease the oil quality, and it is
most obvious in decrease of the total phenols content. Cultivar Istarska bjelica showed
stability in quality of oil in both ecological regions as well as in later moments of
harvesting. For this reason Istarska bjelica can be harvested later – in the first half of
December – without significant degradation of oil quality. Some of the oils obtained
from cultivar Leccino growing by the sea contain up to two times higher quantity of
total phenols in comparison to oil from the same cultivar grown in continental Istria
(Buzet and its surroundings), which significantly affects sensorial characteristic. On
this basis it can be said that these oils would be essentially different in their chemical
composition and organoleptical characteristics.
It is also possible to consult additional researches that dealt with the influence of
different conditions of fruit storage on quality of cultivar’s Istarska bjelica oil, and
which were presented in scientific papers:
1. Olivera Koprivnjak, G. Procida, Đ. Benčić, T. Zelinoti (1999) ‘Effect of ‘Bjelica’
Olive Fruits Storage in Sea Water on Olive oil Quality.’ Food Technology and
Biotechnology, Volume 37 No. 3 p. 209-214; cited in: CC, 1999, Accession Number
2. Olivera Koprivnjak, Lanfranco S. Conte, Đani Benčić, Nicola Totis (2001)
‘Application of solid-phase microextraction of olive oil volatiles on varieties
characterization’. In press; American Journal of Oil Chemist Society (JAOCS).
Economical analysis (profitability)
The profitability of the mentioned technology will be fully expressed when the laws
regulating the standardization of olive oil quality are fully applied. Then the price will
be regulated by the category to which the oil belongs. For the major Istrian cultivars
this technology guarantees harvesting at the right moment. In this way it will be
possible to obtain extra quality oils that can achieve up to 100% higher prices in
relation to second and third class oils. We will be able to make a definitive
economical analysis with the application of given laws.
Applicability of optimal harvest terms for the leading Istrian olive cultivars is very
easy and it depends mainly on producers’ good will. The exception is cultivar Istarska
bjelica that can be harvested even later (till December 15th). But in some years
Istarska bjelica can loose more than 50% of fruits before the right harvest time, and in
such cases it is necessary to perform an earlier harvest time – as soon as an intensive
fruit fall is observed. Also when temperature below 0 °C are lasting more then 20
hours the fruits could be frozen, which rapidly decreases the quality of oil. In this case
it is necessary to perform the harvest immediately and/or to harvest in earlier terms.
Evaluation of olive producers
Olive producers have used our research in many cases – especially in the northern
region of Istria, and in the surroundings of Buje and Buzet, where we organized a
series of lectures and evaluation of their olive oil quality. For example, in year 2000,
60% of oil producers from upper Bujština had extra virgin quality olive oil what is
very good success if it is known that only 5% of annually world production have extra
virgin label. This success highly interested other olive producers for production of
extra quality olive oil.
Quantitative data
Oil obtained from cultivar Istarska bjelica had significantly higher total phenol
content in relationship to cultivars Leccino and Buža in all years and harvest times of
research. For instance, in third harvest term (23.11.) for all three years of research
there was the following content of total phenols:
Table 1.
Istarska bjelica
Oil obtained from cultivar Leccino grown near the sea had relatively higher content of
total phenols in relationship to oils from the same cultivar grown in the northern Istria.
On the basis of these results it is possible to plan further research with the purpose of
detail defining of oil quality specific for particular Istrian regions.
Table 2.
Leccino – Barbariga
Leccino – Veli Mlun
Qualitative data
The data in this three-year research shown the same regularity in relationship between
total phenols content and they can be considered reliable. However, it must be pointed
out that relationship between phenols significantly oscillate due to soil water supply.
Namely, in extremely dry conditions total phenols amount significantly getting
higher, and mentioned regularity can be lost then. With application of irrigation it
could be possible to satisfy the main conditions for achieving continued yields and
optimum of oil quality.
For achieving of extra quality olive oil from the main Istrian cultivars it is necessary
to perform harvest in such degree of ripeness that for cultivars Leccino and Buža
comes (by calendar) up to November 15th in Istrian conditions.
Cultivar Istarska bjelica can be harvesting also in later harvest terms, of course, with
daily observation of fruits falling.