How to Make Olive Oil: The 7 Stages of Production

If you want to know the steps, methods and process of making oil, you are in the right place. Rich in active ingredients and antioxidants, extra virgin olive oil is a noble fat. Its organoleptic properties, as well as its smell and taste, make it the best vegetable fat in the world.

Extra virgin olive oil, also known as EVO oil, is an edible oil extracted from the fruits of the olive tree and is a typical food of the Mediterranean area: a valuable and very ancient product with high economic value. We find extra virgin olive oil as the main food in the renowned Mediterranean diet, which, thanks to the amount of monounsaturated fatty acids it contains, is an important product for the well-being of the body.

Extra virgin olive oil: the 7 stages of production

But what are the processes that extra virgin olive oil goes through before it appears on our tables?

The production chain is basically divided into seven stages:

• The collection
• Storage
• Defoliation and washing
• The milling
• Gramoling
• The extraction
• Storage and bottling

Let us now go on to analyze each of them in detail:

Step 1: The olive harvest

Olive harvesting is a very important stage in oil production. From the techniques used and the period in which this operation is put in place, depends the taste of the oil and its quality. In reality, it is not as simple a process as it may seem, but it is made up of techniques and secrets that are passed down to ensure that the best end result is obtained.

The first aspect that must be taken into consideration is the type of olive to be harvested, for this factor in fact changes both the condition in which it must be harvested and the time of year in which it is considered ripe. For a good harvest it is advisable to wait until the change in the color of the fruit (the so-called veraison) changes from green to black, this is in fact the phase in which there is a greater amount of oil and nutrients that lead the final product to have a higher quality.

Each harvesting method has different effects on the fruit and the final product, so it is always best to carefully evaluate the technique according to your need.

Collection can be done in two ways:

• Handbook
• Mechanics

Handbook

The main hand-harvesting techniques are:

– Tacking
It is a very old method of “chopsticking” the olive branches with sticks so that the olives fall, and then picking them up with nets placed on the ground. This technique has the defect that the fruits after impact with the ground easily risk damage, which is why it is now considered obsolete.

– Burning
It consists of hand-picking olives directly from the branches. It has the great advantage of not damaging the olives and is suitable for producing the highest quality oils as all fruits are individually hand-selected.

– Harvesting

It simply consists of ground-harvesting the ripe olives that in a completely natural way have fallen off the branches. This method is strongly discouraged, as the olives are already overripe and that will therefore not get us high quality oil.

Mechanics

• Scroll
  In shaking, the olives are harvested using mechanical arms that wrap around the trunk or branches of the tree, which are lightly beaten to encourage the fruit to fall. Thanks to this technique, the quality of the product is not appreciably affected, as these tools are equipped with structures similar to inverted umbrellas that serve to avoid damaging the olives.

• Combing
  The branches are “combed” by special tools that detach the olives, which are then picked up by nets attached under the trees. The disadvantage of this method is that the fruits are likely to be damaged very easily by the comb-shaped tools and therefore, requires a second stage of sorting.

Step 2: The storage of olives

No less important in order to obtain a quality oil is the olive storage process. This first stage of processing should not be underestimated, in fact if the olives remain too long on the branches or are left on the ground, they can undergo a maceration process detrimental to the subsequent production of the oil.

To avoid compromising the quality of the olives, it is ideal to take them to the mill within 48 hours of harvesting. This fruit is so delicate that great care must also be taken on the type of container used for storage. The olives should be collected in special plastic “ventilated boxes” and then stored away from heat sources. This ensures that the olives do not ferment anaerobically, giving rise to the formation of aliphatic alcohols, which would produce defects in the oil such as “reheating” and in extreme cases even mold.

Sacks should definitely be avoided, where the olives are crushed giving rise to those processes that inevitably deteriorate the fruit. Another container we do not recommend is the wooden crate as it is easily attacked by mold.

Step 3: The defoliation and washing.

Before being introduced into the actual processing cycle, olives must undergo defoliation and washing operations both for sanitation and oil quality reasons.

Since oil is a food product, it is correct and proper, in compliance with the most basic health and hygiene regulations, that the raw material from which it is obtained is free of harmful substances.

In addition, removing the material that often accompanies olives is especially appropriate when the oil mill adopts the metal crusher for preparing the olive paste and the centrifugal decanter for oil separation. In this case, in fact, the presence of leaves could affect the organoleptic characteristics of the oil.

Obviously, potable water is used to wash the fruit and should be reciprocated frequently enough to achieve good olive hygiene and to avoid the appearance of bad odors that could contaminate the oil.

Finally, the washers are equipped with an additional shower sprayer that operates the final washing with mains water to remove any possible pollution hazards and to ensure the elimination of possible residues of organic substances used to defend the crop from external agents.

Read also: New Oil 2019: Guide to Safe Buying

Step 4: The milling of the olives

In the milling process, the harvested olives, after being cleaned and washed, are subjected in the mill to mechanical actions in order to cause the rupture of the cell wall and the membranes that compose them. In this way, the oil escapes from the fruit, allowing the product to be collected and move on to the next stages of processing.

Breaking is done naturally by the rubbing of the stones against the ends of the fruit, or by the collision of special mechanical tools. A “crude” olive oil is thus extracted, also called oil paste, a semi-fluid compound that is the main product of olive milling. It is often the case that in the processes of processing quality foodstuffs such as extra virgin olive oil, each stage may be carried out in different ways depending on the needs, the type of plant, the final product and the traditions or choices of the company. There are mainly two systems used for milling: classic milling and crushing.

Classical milling

It is implemented by means of the “muller,” a tool belonging to tradition and derived from the classic stone grinders. With this technique, the mechanical action is exerted with large wheels usually made of granite that perform a rotation on the fruits.
There are blades on the wheel also, which have the function of removing the oil paste adhering to the surface, improving its stirring.

Crushing

It is a technique performed by means of industrial machinery called, precisely, hammer crushers. Loading is done from above by means of belt elevators that pick up the fruits directly from the washers and pour the oil paste from below, into the gremolators. Through this type of milling, the rupture of cell walls and membranes is caused by the impacts of mechanical devices rotating at high speed, which occurs in a very short time indicating this technique is perfect for continuous and automated processing cycles.

In crushing, the enzymes present in the pulp and seed are activated by breaking the cell walls. This is not necessarily bad: it is true that oxidation is facilitated and thus the organoleptic quality of the oil is diminished, but it is also true that in this way those volatile substances responsible for its typically fruity aroma are extracted .

Classical milling, on the other hand, involves a significantly lower degree of emulsification, allowing for a higher yield. The taste will be less spicy and bitter, because polyphenols are present in lower amounts.

In summary, it can be said that the classical olive milling system lends itself to the production of higher quality oils, the selling price therefore will be higher allowing the high production costs to be recovered.

Step 5: Gramoling

It is the process that follows milling or pressing and is intended to break up the emulsion between water and oil and cause the oil micelles to flow into larger droplets that tend to separate spontaneously from the water.
It is carried out in steel tanks called gramules in which helical paddles rotate to keep the oil paste in slow stirring.

This stage is very important in determining the relationship between quantitative yield and oil quality in fact heating will increase the effectiveness of gramoling allowing the oil yield to rise, however it will negatively affect the quality.

Step 6: The extraction of the oil

Extraction is the process that finally sees the appearance of a product close to what we know: again, there are several techniques for bringing this stage of olive oil production to fruition, let’s look at them briefly:

• Pressure (classical and discontinuous method)
• Centrifugation (modern and continuous method)
• Percolation by selective filtration

Pressure

Pressure extraction is characterized by a series of well-defined steps. Pressing is applied to the gram mixture to separate the liquid portion from the pomace. The resulting fluid must then be centrifuged (centrifugation) in order to obtain an initial separation of the water from the oil. The resulting mixture is then subjected to filtration from which virgin olive oil is obtained.

Centrifugation

With centrifugation, on the other hand, all 3 final components are obtained simultaneously in one continuous process. Centrifugal extraction of the gramolate makes use of the difference in the three specific weights of the compounds by obtaining separately: pomace, virgin olive oil and water.

Percolation

Extraction by percolation and selective filtration adopts a different physical process: the higher surface tension of oil than that of water is employed:
A large steel sheet is immersed in the gram, which, due to the difference in surface tension between the two fluids, becomes predominantly wet with oil; causing the latter to be dripped into another container. The leachate will produce oil and must, later to be centrifuged to get more oil at the expense of water.

Or it can generate non-final oil and pomace, from the centrifugation of which must and pomace are obtained. Either method is applied depending on the type and effectiveness of percolation.

Step 7: The storage and bottling of olive oil.

Storage

At this point, the resulting product is ready for consumption; however, it still contains solid residue and is muddy to the eye. It therefore needs to be stored in stainless steel tanks, following chemical and organoleptic examinations. The temperature its optimal storage is 15°-17°C in the absence of sunlight.

During the storage period, the oil undergoes a sophisticated natural decanting process, without further filtration, the mucilage from the skin and suspended water particles will thus be sedimented at the bottom of the tank. This natural filtration provides the oil with greater clarity without affecting the qualitative, nutritional and organoleptic characteristics rather it allows our oil to preserve the typical tastes and sensations of the fruit.

Bottling

The final part of the oil production chain takes place on the premises adjoining the olive processing areas, observing the complex HACCP regulations.
It is certainly one of the most delicate stages precisely because it is necessary to limit contact with air during decanting. Packaging is carried out by specific equipment that allows the oil to be poured into suitable containers.

Afterwards, the oil is bottled and hermetically corked, preventing the alteration of its organoleptic properties.
Containers should be made of dark glass to avoid contact with light, or alternatively, special tinplate containers, previously treated with antioxidant materials, can be used.

Another important factor during the bottling stage is the overall time of the operation. It must, in fact, be short to safeguard the taste and flavor of the oil.

Having completed these 7 stages of oil production, one can finally enjoy an excellent New Oil.