Olive Oil Characteristics

 

Before industrial processes began, the olives were cold pressed, therefore decanted and filtered using a physical procedure (using paper or cotton) without using any chemical processes. The final product was called the first cold pressing, therefore, biologically alive. Oils extracted in this manner contain a relevant quantity of vitamin E and polyunsaturated fatty acids called vitamin F. These acids are: linoleic acid; alfa-e gammalinoleic acid; di-omo-gamma-linolenic acid and arachidonic acid. These five polyunsaturated fatty acids are called ‘essential’ in that they carry out vital functions in the body.

 

They interact:

 

1. On the structure and on the permeabilityof the cell membranes;

2. On the mechanisms that regulate the immune defences of the organism.

 

Linoleic fatty acids and linoleate cannot be made synthetically by man, who is obliged to assimilate them via foodstuffs.

 

Polyphenols

 

Before industrial processes began, the olives were cold pressed, therefore decanted and filtered using a physical procedure (using paper or cotton) without using any chemical processes. The final product was called the first cold pressing, therefore, biologically alive. Oils entracte in this manner contain a relevant quantity of vitamin E and polyunsaturated fatty acids called vitamin F.

 

These acids are: linoleic acid; alfa-e gamma-linoleic acid; di-omo-gamma-linolenic acid and arachidonic acid. These five polyunsaturated fatty acids are called ‘essential’ in that they carry out vital functions in the body.

 

They interact:

 

1. On the structure and on the permeability of the cell membranes;

2. On the mechanisms that regulate the immune defences of the organism.

 

Linoleic fatty acids and linoleate cannot be made synthetically by man, who is obliged to assimilate them via foodstuffs. Oil is 100% made up of fatty substances which are susceptible to oxidisation; oxidisation, which takes place gradually, causes first the aromatic substances to degrade, then free radicals are formed and finally malodorous substances. The POLYPHENOLS have the function of protecting the oil from oxidisation, in that they oxidise in place of the oil and cause the oil to retain intact its organic characteristics longer.

 

 

 

 

Anatomy of an olive tree

 

As in every arboreal plant, the olive is marked by a subterranean part and an aerial part. The subterranean part is composed of the roots system, which has the function of support and of absorption, it has the function of anchoring the tree and shares in the important phenomenon of nutrition.

 

The roots system of the olive is superficial; it terminates with the formation of capillaries equipped with “absorbent hairs”, that renew themselves continually and which are used by the tree for nutrition. The extremity of each root is covered at the tip by a kind of “cap”, which has the task of protecting the tender and delicate part of the root from the harsh soil.

 

Trunk: the area of the ‘neck’ divides the aerial part from the roots system and, in the olive, it is enlarged and thus is known as the ‘pedal’; it has numerous swellings, rich in reserve substances of dormant buds, called “ovules”, from which a shoot grows, which divides out into branches and leaves.

 

The leaves are made up of the ‘stalk’ and of the leaf itself. The leaves are usually green, due to the presence of the chemical substance known as chlorophyll. This has an extremely important function: in the presence of sunlight it transforms the raw material drawn from root absorption into processed substances, after combining them with carbon, which the plant absorbs from the atmosphere. In fact, the “raw sap”, formed by water containing various minerals (nitrogen, phosphorous, potassium, calcium, iron, etc.) in solution, being drawn up through the woody veins, rises from the roots up to the leaves where it meets with the absorbed carbon dioxide, together with the air. Therefore, in the presence of the chlorophyll and the sunlight, it transforms into “processed sap” (sugars, fats, protein substances); this descends to the roots, feeding the various organs of the plant and, in part, stopping in the nodules, in the buds, in the seeds, etc. to constitute deposits of nutriment reserves.

 

Respiration: plants, like all living things, breathe, and to carry out this important function use the roots, the branches and each part of the plant. Transpiration: the plants absorb nutritive minerals dissolved in the water; to feed themselves, therefore, they are forced to absorb enormous quantities of water, which they then eliminate by transpiration via the stomas, losing it in vapour form to the air or expelling it in liquid form via particular apertures. During certain critical periods of its life (flowering, setting, swelling, etc.), the tree must have considerable quantities of water available, otherwise production can be compromised.

 

Nutrition: Nitrogen, phosphorous and potassium are indispensable for the life of a plant. Nitrogen is the basis for protein substances, in fact, in soils lacking this substance, the plant will have stunted growth, the flowers do not set well and many fruits fall before reaching maturity. Phosphorous is recognised as an essential element for the formation of seeds and fruit. Potassium acts by activating vital functions of the organism, increasing its capacity to resist the often harsh environment.

 

Flowering: the buds inserted in the leaf axils or the tips of the branches can develop into new branches or blossom. The difference in flowering buds is favoured by another concentration of sugars in the sap, that is by an increased level of carbon

and nitrogen substances. The olive tree usually bears fruit on branches of one to two years old.

 

The Olive Flower: each flower has a cup of four light green sepals and a corolla of four yellow-white petals attached to the base. The ovary is large, divided into two loculus with a short and fat stalk which terminates in a forked ‘stigma’. The male part has two filaments attached to the corolla, which each carry an ‘anther’, containing the pollen. Germination: when the flower has bloomed and the pollen is mature, the ‘anther’ open freeing it to the wind, which carries it to the ‘stigmas’, where it germinates emitting the so called ‘pollen tube’; this penetrates the stalk until it reaches the ovary and germinates the ovule, which transforms into seed, while the ovary itself transforms into the fruit.

 

The Olive Fruit: the fruit originates from the germination of the ovule; from a botanical point of view it is a ‘drupe’ of ovoid shape more or less long or rounded depending on the variety. In the drupe it is possible to distinguish from exterior to interior: a membrane layer called “skin” or “epicarp”, a meaty pulp or “mesocarp”, and a woody stone or “endocarp”, which contains the real seed and relative embryo. The olive tree is noted for alternating heavy and light harvests, that is, one year can yield an abundant harvest and the next can be poor.

 

Characteristics of the olive

 

The drupe has a weight which varies considerably: the oil oscillates between 1g and 3g, with plus or minus values depending on the variety. On average the drupe is made up of:

 

• Vegetation water 40-55%

• Oil 15-23%

• Solid residues 25-40%

 

The oil is contained almost totally in the pulp and to a minimum extent (1-2%) in the seeds.

The histology of the drupe influences the transformation and paste production systems.

The fats are represented above all by the tri-glycerides (95-96%) and by glycerides (2-3%); they constitute the saponifiable fraction (98-99%), that is, lipids. An insaponifiable

fraction is also present in the oil (1-2%), and this represents the minor component; this is

extremely important in olive oil because gives organic properties to the oil which exalt its

good qualities.

 

Among the minor components are: tocopherol, sterol, chlorophyll, antocyanic acids, flavonoid, wax, squalene, carotene, phenols, polyphenols, alcohol, di-tertepenic and tri-terpenic composites. These give the main organic characteristics to the oil, such as: taste,

flavour, aroma. At the beginning of maturity the oil is in the form of tiny drops dispersed

and separated by a lipoprotein film; successively the drops become larger until they join

in one mass which moves the nucleus. The intercellular oil is distributed among the various

cells and this is the easiest to extract. The cells are cemented by pectin substances which tend to transform from an insoluble to a soluble form. The water content varies from 45-60% depending on the stage of maturity, the atmospheric conditions and the variety.

 

Based on weight, the varieties can be classified, as follows:

 

  • Microcarpic drupe

with weight lower than 1.5g;

  • Mesocarpic drupe

with an intermediate weight of 1.5 to 4g;

  • Macrocarpic drupe

with weight above 4g.

 

maturation phases of the olive

 

The olive has three stages of maturity which can be listed as:

 

• Herbaceous stage

• Swelling

• Maturity

 

Herbaceous stage: this is characterised by the enlarging of the green drupe, inside of

which the process of chlorophyll photosynthesis takes place with the synthesis of sugars

and organic acids. In this phase the stone can be distinguished well, which will later

become woody; there are in addition chlorophyll and glycerine.

 

Swelling: first one can observe the transformation of the colour from green to yellow, and successively the formation of reddish patches which begin to form at the opposite end of the stalk and which then spread along the whole drupe. There is then a violet pigmentation, which darkens to become black. In this phase the blush appears and the start of the formation of the oil, which for the time being is a whitish liquid. The colour is given by antocyanic acids, flavonoids and chlorophyll.

 

Maturity: Industrial maturity is reached when the maximum yield in oil is reached. Less important is the biological aspect of maturity, which, by the way, cannot be defined and determined perfectly. At maturity the colour is black and the surface of the drupe tends to become wrinkly due to water loss. Determining the point of maturity can only be carried out in a laboratory by means analysing the fat content. In this way a greater yield is obtained to that which happens in the oil mill because in the laboratory olive residue oil is also extracted which is present in the vegetation water, which, however, does not happen at the mill.  The theoretical data obtained in the laboratory should indicate the harvest time, after having examined the evolution of the fat content. If the optimum harvest time is passed, the phase of “super-maturity” is entered, which should not be confused with “extra-maturity”, which regards the processes of maturation of the fruits after the detachment from the tree. Successive analysis of the detached drupe can give an apparent increase in the fat content, due to the progressive water loss caused by transpiration or respiration; it is necessary therefore to refer to the dry weight analysis results.

 

OLIVE TREE VARIETIES

 

MORAIOLO

This variety is to be found in Umbria, but is also cultivated in other regions: Tuscany,

Lazio, Marche, Abruzzo and, to a lesser degree, in other areas. It is a vigorous tree with

upright bearing; the leaves are elliptic-lanceolate, the drupe have an ellipsoidal shape with

an average weight of 1g. the variety needs cross-pollination. Its productivity is good and the oil yield oscillates around 20-22% with excellent organic characteristics.

 

FRANTOIO

This variety is cultivated above all in Tuscany but is also to be found in other regions: Umbria, Lazio, Marche, etc. The tree is of average vigorous growth, the spread is wide and gives pendulous branches. The leaves are lanceolate, the drupes are ovoid-long and the weight is usually 2-3g. The Frantoio is a self-pollinating variety and gives high productivity; the oil is of high quality and the industrial yield is 16-23%.

 

LECCINO

This variety is to be found above all in central Italy: Umbria, Tuscany, Lazio, Marche, Abruzzo. Recently it has spread also into southern Italy. The tree is very vigorous, the leaves are elliptic-lanceolate, the drupes have an ellipsoidal shape with an average weight of 2.5g. The variety needs cross-pollination. The industrial yield is 20% on average. It matures early and gives quite good productivity.

 

 

HOW TO HARVEST OLIVES

 

Stripping: Stripping is the most traditional and rational method of harvesting the olives, even if it is the most labour intensive. Stripping is the manual picking of the olives. The harvest can be facilitated by the use of specific tools, which are used manually (rakes and combs).

 

Combing: Combing derives from stripping. Using this system, the olives are stripped

from the branches using manual tools, such as ‘combs’, they fall onto large nets, spread

out under the trees. Beating: With this system the olives are made to drop from the tree using sticks. The use of sticks, however, causes lesions to the olives, which in turn affects the quality of the oil (a notable increase in acidity).

 

Picking up: the fruits are collected directly from the ground where they have fallen naturally,

which happens when the olives are over mature, this also affects the quality of the oil (a notable increase in acidity).

 

Mechanical Harvesting: taking into consideration the high costs of manual harvesting

and the lack of manual labour in many areas, mechanical harvesting is becoming increasingly popular. In this method the olives are detached from the tree by using a kind of mechanical “shaker”, which shakes the trunk and branches, causing the olives to fall off onto large nets or “umbrellas”, this also affects the quality of the oil (a notable increase in acidity).

 

 

ENVIRONMENT

 

The Climate - olives love a mild climate, which is ventilated, not humid and where the temperature rarely drops below -5°. Particularly harmful to the life of the trees are prolonged periods of cold and violent, sudden ranges in temperature, especially in a damp environment. The type of soil and the variety of tree have a great influence the growth of the tree.

 

 

CULTIVATION TECHNIQUES

 

Cultivation procedures are the first actual and possible defence in preventing or limiting

attacks from parasites or weeds.

 

Among these are:

 

- Pruning: which must also encourage the growth of the foliage and create low leaf density

on the interior. This gives greater sunlight and heat to the foliage, preventing the formation of humidity, which is the major cause of fungal diseases.

- Fertilising: this consists in applying the correct and well-balanced ratio of fundamental

and necessary elements, to make the tree more productive, more vigorous and stronger.

- Working of the soil: working of the superficial and deeper layers of soil favour the formation of a suitable and optimum structure and texture of the soil, causing the correct

balance between micro and macro-porosity, which in turn favours the flow of water and

air circulation.

- Irrigation: this is carried out during the summer season or during the critical periods of

the first phase of development of the fruits and the hardening of the stone, reducing stress to the tree due to lack of water and making them more ready and able to assimilate the elements necessary for the productivity of the tree.

 

STORING THE OLIVES

 

The way the olives are stored has a notable influence on the quality of the oil and the organic characteristics. Therefore, it is advisable to have the olives pressed immediately after picking, or within 24/48 hours of the harvest. Plastic, cases with holes both underneath and on the sides must be used for transport and preservation of the olives, ventilation allows the air to circulate and prevents the phenomenon of overheating. The use of sacks, of any material, in which to keep the olives must be avoided at all cost, this is because when the olives are stacked together in the sacks they crush and damage the olives, causing serious defects to the oil. Wooden cases should also be avoided because the wood can be affected by fungal growths.

 

EXTRACTION METHODS

 

Traditional Method - This is the ancient method and one which has remained unchanged

over the centuries. It involves pressing the olives between milling stones. Two heavy wheels,

arranged vertically in a circular tank, turn, reducing the olives to a paste, which is made up of an oily part, a watery part and a solid part, the olive residues. The paste is then put into the “roller-breaker” homogenising machine or decanting tank for the molecular agglomeration, which consists in a rotating bed with a horizontal propeller which amalgamates the tiny drops of oil so that they increase in size and can be extracted. The separation of the three substances to extract the oil takes place using pressure: the paste is spread onto discs of woven fibre, that are piled up one on top of the other and placed under the hydraulically operated press. This operation separates the ‘oil must’ (oil mixed with vegetation water) and the olive residues. The separation of the oil itself from the watery paste is carried out by centrifugal force, which exploits the different specific weights of the two elements.

 

Continuous Cycle System - This is an olive mill in which the processes are completely mechanical and all the working phases take place without manipulation and with the minimum intervention by manual labour: the olives enter from one side and the oil exits from the other. The pressing is carried out by mechanically operated hammers and extraction by centrifugal force. Metal plate hammers break the olives, forcing them through a grille in the internal surface of the machine. The olive paste (vegetation water, oil and residues) is stirred in the homogenising machine and is then transferred, with the addition of water, into the “horizontal axis decanter”, or rather into a centrifugal extractor that carries out the separation by exploiting the different specific weights. The vertical centrifuge, spinning faster, cleanly separates the oil from the water and eliminates the last particles in suspension. The continuous cycle system offers numerous advantages and also, in many cases, better qualitative results. The olives are not manipulated, guaranteeing a high level of hygiene. The stainless steel closed circuit installation gives less contact with the air and prevents the formation of residues on the equipment, giving protection against oxidisation, and enables the use of woven fibre discs to be eliminated, which, if not washed thoroughly or replaced frequently, can give the oil a rancid flavour.

 

Two phase integrated continuous system – Different from the traditional “three phase” (separation of the residues, of the vegetation water and finally the oil) continuous cycle  installation in the integrated continuous installation the extraction is in two phases: the oil on the one hand, residues and water, combined into one single product, on the other.

 

Mixed or Combination Mill - This is the fusion of the two systems, traditional and continuous

cycle. The granite mill stones are positioned first, in place of the mechanical press, then the

homogenising machines and finally the centrifuges in place of the woven fibre discs. According to some producers, it offers the advantages of the two systems: the mill stones give a sweeter oil, while the elimination of the woven fibre discs excludes the risk of a rancid flavour.

 

Sinolea Method - This is one of the latest generation continuous cycle mills with hammer presses and extraction by means of natural dripping of the oil. After the mechanical milling

a steel lung with blades is activated that penetrate the paste causing the percolation of

the oily part: in this way approximately 75% of the finished product is obtained, while the remaining part comes from a second extraction using a horizontal centrifuge separator. The Sinolea system has the advantage of reducing still further any contact with external agents

(water and air) and the working temperature, giving protection against oxidisation.

 

How to Keep your Oil Fresh

 

In order to prevent the oxidization or ageing of extra virgin olive oil, which results in a lowering of the health benefits of the product as well as an alteration in its taste, there are a few simple golden rules to follow:

 

Container -  The type of container used. The container must not release metals to the oil, hence stainless steel containers are highly recommended for bulk storage;

 

Air and light - Air and light are two enemies of oil. These contribute to the oxidation of the product, hence keep you oil tightly sealed and in the dark, away from direct sources of light;

 

Storage temperature - Temperature is key to keeping your oil fresh: ideal storage temperature is between 12° and 16° Celsius (53° - 60° Fahrenheit).

 


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