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A
first classification, divides virgin olive oil (obtained solely by olive
mechanical press) from olive oil (obtained through chemical extraction). Among
virgin olive oil, certainly extra virgin olive oil (or virgin extra) set the
excellence and among the others it must fit within the following parameters:
A)
it shall contain a high percentage of unsaturated fatty
acids (e.g., oleic acid between 55 and 83% of all fatty acids),
B)
the free acidity value must be less than 0.8% and C)
peroxydes concentration less than 20 meqO2 /kg of oil,
C)
Polyphenols concentrartion (largely responsible for oil
taste) is regulated by DOP Origin Protected Denomination (DOP) rules, which
divides Umbria Region in five zones. This amount may change from zone to zone
and differentiates mild olive oils (polyphenols content <200 mg/kg of oil)
from oils progressively more pungent (polyphenols content >200 and
<500mg/kg of oil).
Recently,
has been introduced the DOP olive oil, based on European Regulamentations
2081/91 and 2082/92, which improves quality (e.g., Panel Test value higher than
7, free acidity and peroxydes content must be maximum 0.6% and 12 meqO2 /kg
respectively).
Then,
there are olive oils produced by organic farming according EC Reg. 2092-91. This oils are pesticides and
chemical fertilizer FREE, therefore without potencial poison substancies derived
from chemical agricolture. In the fiel of organic oil, we clearly suggest you to
purchase the extra virgin type.
At
the end, it has to be pointed out that an olive oil with 0.6% of free acidity,
12 meqO2 /kg of peroxides and 150mg/Kg
of polyphenols (when the other
criteria ad regulamentations are fulfilled) may be:
-extra
virgin
-or
extra virgin DOP
-or
extra virgin organic
as an
oil with 0.2% of free acidity, 4 meqO2 /kg of peroxides and polyphenols
between 200
and 300 mg/Kg. The second oil
shows an high quality with respect to the first one and at these levels the difference is made up and depend
upon manufacturers.
In conclusion it is important for the
consumer read the chemical analysis values prior to purchase an oil.
Making
an extra virgin olive oil with higher concentration of both unsaturated fatty
acids (principally oleic acid) and polyphenols requires:
1.
olive harvest must be done
early in the season (before 15-20th of November)
2.
harvested olives, must be
stored in small aerated containers and pressed no later than 48 hours from
the day of harvest)
3.
cold-pressed techninique
(temperature below 38°C), must be preferred over the others.
Respecting
these rules we will obtain an extra virgin olive oil having the following
features:
-
a higher content of polyphenols and oleic acid,
-
a very low peroxydes concentration,
-
a very low free acidity,
these
characteristics also limitate autoxidation a phenomenon that occurs during oil
life and leads to:
-an
increment of saturated fatty acids while unsaturated fatty acids decrease,
-a
decreament of polyphenols content.
As we said, olive oil must be conformed to EC. Reg.
(European Community Regulamentation) nevertheless, an extra virgin olive oil with:
- 0.2% of free acidity, 6 meqO2 /kg of peroxydes and
200-300mg/Kg of polyphenols
shows
an high quality and will preserve as much as possible during its
shelf-life an unaltered concentration of oleic acid and polyphenols with respect
to an oil which contain 0.6% of free acidity, 12 meqO2 /kg of
peroxydes and 150mg/Kg of polyphenols.
Our
extra virgin olive oil chemical features (click here)
In addition, it is important to elucidate
two main points:
1. The polyphenols, are molecular heterogeneous class of compounds of which they make depart different
substances. In the olive oil there are at least nine different types of it; two of these compounds tyrosol and
hydroxytyrosol in an high quality oil, product with standard good and not older than one year should not overcome the 4-5% of the total content of
polyphenols. You pay attention because no norm not even the Reg. CEE 2568/ 91 imposes of analyze the various classes of polyphenols and only the normative DOP requires the total polyphenols content
measurements. We have measured the different classes of polyphenols and the results are display in section regarding
our oil features.
2. Attention to the oils with low acidity. Today the technologies are able to transform when healthy old oils with acidity of 2-3%, in oils with low acidity (0.2-0.3%). It is easily understood as that goes to loss of the quality with high economic
reloads. Generally this tipology of oils is without specific olive oil taste, flat and
smooth. Sometimes low quality old olive oil may be mixed with small quantity of high quality extra virgin olive oil, so as to to hide the swindle to the consumer
and to the NAS (Nucleus Anti Sophistication, Weapon of the Police).
Unfortunately the Reg. CEE 20568-91 doesn't foresee analytical fit techniques to underline this fraud but there is unofficial elaborate analysis to defend the quality and the consumer.
With the term "unofficial" we meant that these analysis has got their scientific validity but has not contemplated from the official
law.
The analyses are based on the determination of the total dyglicerids (DAG) and on the relationship between 1/2-DAG and 1/3-DAG.
An high quality extra virgin olive oil during the first year of life show a content in DAG that goes between 1 and
2,5%, and the relationship between 1/ 2-DAG and 1/ 3-DAG should be not inferior to 80%. This means that in these oils prevail the 1/ 2-DAG respect to 1/ 3-DAG.
With the aging and the oxidation in the oil increases the DAG until 3% and prevail on the contrary the 1/3-DAG on the 1/2-DAG.
We do an example of old oil:
Acidity: 1.5%
Total DAG: >2.5%
Relationship between 1/2 and 1/3 DAG: 40-50%
Wanting to subject this oil to chemical treatment to make it extra virgin the acidity will change from 1.5% to 0.3% but what remain stable
it is the total quantity of the DAG and the relationship between 1/2 and 1/3 DAG.
Therefore an extra virgin olive with acidity about 0.3% but with a content and a relationship of DAG similar to that of the example is strongly
suspect.
II) Several epidemiological scientific studies published
on international medicine journals (see references below), such as:
-
the
Seven Country Study (1) (duration time= 10 years; number of patients
assigned to study in seven States= 12,733),
-
the
Framingham Study (2) (duration time= 10 years; number of patients assigned to
study= 5,209),
-
the
Veterans Administration Study (3) (duration time= 8.5 years number of patients
assigned to study= 846),
-
the studies: MRFIT, LCR CPPT and MFABP (4, 5, 6),
have
evaluated the effect of unsaturated fatty acids rich diet (with olive oil as
prevalent diet fat). These studies demonstrate that in patients subjected to
olive oil diet as prevalent fat:
-blood circulating LDL cholesterol levels drop down,
-the incidence of myocardial infarction and sudden
death decrease by 31% and 30% respectively
-arterial blood pressure reached lower values,
in
comparison to patients subjected to american’s diet, which on the contrary it
is rich in saturated fatty acid as derived from the prevalent use of margarine
and animal fats.
In addition from these studies it
becomes evident that polyphenols and vitamin E, contained in olive oil are
powerful antioxidants which may be effective in reduces: a) in part the risk of
developing
atherosclerosis and b) oxygen free radicals
production, which is implicated in myocardial infarction and cellular aging.
The
recommendations of these studies were: diet derived fat should not be exceed 30%
of daily caloric intake with an optimal ratio of 7%, 15% and 8% between
saturated, monounsaturated (oleic acid) and unsaturated fatty acids respectively.
Olive oil, particularly the extra virgin type is the fat which most closely
fulfill these criteria.
Marco Bettini, Bc.S.,
Division of Cardiology,
University of Perugia School of Medicine
References:
1)
A. Keys et Al., Seven Country, Harvard University Press, 1980;
2)
W. B. Kannel et Al, Ann Intern Med, 61:888-899, 1964;
3)
S. Dayton et Al, Circulation, 3-40 (Supp. 3), 1-63, 1969;
4)
MRFIT Group, JAMA 248:1465-1477, 1982;
5)
LRC Programme, JAMA, 251 351-374, 1984;
6) A. Espino et Al, Nutr. Metab.
Cardiovasc Dis, 6: 147-154, 1996;
7)
Massaro M et Al. Direct vascular antiatherogenic effects of oleic acid: a clue
to the cardioprotective effects of the Mediterranean diet. Cardiologia. 1999 Jun;44(6):507-13.
Review.
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