12 Factors that Influence the Quality of Extra Virgin Olive Oil

Premium quality extra virgin olive oil is not made in Gramma's backyard, though many would lead you to believe it is.
12 Factors that Influence the Quality of Extra Virgin Olive Oil

Olives are a fruit and just like any agricultural crop, there are factors that affect the quality.  This article is an overview of 12 main factors that impact the quality of the fruit juice (extra virgin olive oil). 

1. Variety of the olive

The variety of the olive affects the composition, texture and flavor of the oil extracted from it.  According to Tom Mueller, guru about truth in olive oil, there are more than 700 varieties of olives around the world.  Spain has 25% of the entire olive growing area with more than 260 varieties.

One of the main compositions of olive oil, —and most important in terms of health and nutrition—, is oleic acid.   As Uceda, Aguilera and Mazzucchelli point out in their book, Manual de cata y maridaje del aceite de oliva (Handbook for tasting and pairing olive oil), every variety offers different levels of oleic acid.  And even within a specific variety, the composition of oleic acid will vary depending upon region, altitude, time of harvest, and extraction process.  The Picual, and Hojiblanca varieties offer the highest level of oleic acid, compared to most other varieties.  Picual and Hojiblanca are two varieties that are grown heavily in Andalusia, Spain.

But, oleic acid is not the only important element in top quality extra virgin olive oils.  Many would argue that the sensory attributes are the most important thing.  The look, taste and feel of EVOO are hugely important, and again varies depending upon the variety of olive.  Some varieties produce a dark green oil, others an oil with a golden tone.  Each offers a different set of flavors for the taste buds and a different structure (thin to rich).  EVOOs that have a higher content of polyphenols (a fantastic natural antioxidant) also offer strong sensory attributes of bitterness, pungency and scratchiness, which may not be enjoyable to all palates.  The Picual variety offers medium-high contents of polyphenols, and Hojiblanca,  medium-low content.  Comparing a top quality picual EVOO along side a top quality Hojiblanca, you will find that the latter is a tad smoother to the palate without loosing the distinctive end bite.

Note:  GringoCool has bottled Arbequino, Picual and Hojiblanca EVOO as well as a coupage (mixture) of Picual and Arbequino.  Picual and Hojiblanca are the two varieties in Spain that have the highest composition of oleic acid (more than 70%) as well as poliphenols (known for its antioxidative qualities), which make the olive oil stable with a long shelf life. 

2. Location

The location where the olive trees grow is a factor that can affect the composition of an olive oil.  Sunny days, precipitation and soil quality are some of the ingredients leading to a successful harvest.  You can’t grow olive trees in the Artic, or at least in natural conditions.  Each agricultural crop, whether it is peanuts, potatoes, grapes or olives, has minimum requirements for the fruit or vegetable to be produced.  … I know it is pretty elementary, but some locations are better for some crops.  The Mediterranean basin is ideal for olive production.  Southern Spain especially, is ideal for olive production.  On a regular basis, more than 45% of the world’s olive oil is produced in Spain.

Some varieties are more hearty than others and location/conditions have a lower impact on the fruit production.  One of the varieties that is most affected (or least “plastic”) is Arbequino.  Studies have shown that depending upon where the tree grows can affect the content of oleic acid in Arbequino harvest from 75% (in Cataluña) to less than 55% in some orchards of Argentina.  The content of polyphenols can as much as triple from one location to another, and the polyphenols are the basis of the sensory attributes.  So in one location, you might produce a wonderful EVOO and the same variety in another location might produce an oil that doesn’t qualify as EVOO.

Note: Our GringoCool varieties of picual, hojiblanca ana arbequino are grown near Cordoba, Andalusia, in terrain and conditions that produce the highest quality of EVOO.

3. Agricultural techniques

I always get a kick out of some of the European marketing to US customers.  Many of the “Italian” and “Greek” brands of EVOO, suggest they are produced by “Gramma and Grampa Bambino”, in their back yard orchard, and the olive oil is natural because it is pressed under their feet the way their ancestors made it, etc. etc.  They market an idea that the best quality is almost artisan or homemade.  And I put “Italian” and “Greek” in quotes because there are a lot of these companies that buy Spanish EVOO in bulk and then bottle and label it as their own.

Olive oil museum Jaen Spain

Crushing olives old school style - Museum in the Province of Jaen, Spain

Spaniards don’t buy into that because they know good quality EVOO, and they know it is not produced in Gramma’s back yard.  A good comparison is wine.  While it might be fun to taste Gramma’s backyard moonshine, if you are looking for a good quality bottle of wine, you purchase it from a respectable winery.

You will notice on all the labels of top quality Spanish extra virgins, the phrase:

“Aceite de oliva de categoría superior obtenido directamente de aceitunas y sólo mediante procedimientos mecánicos”  which translates as “Superior category olive oil obtained directly from olives and solely by mechanical means.”   No grubby hands and feet involved.

The best olive farmers produce the best extra virgin olive oil.  Good farming involves the right varieties of olives, timely and appropriate pruning, timely harrowing or disc-ing to preserve ground moisture, timely and appropriate irrigating, fertilizing and pest control.  There are few secrets to good farming, mostly it takes a lot of knowledge, experience, dedication and hard work (and a little luck and cooperation of Mother Nature).

Olive orchard in Spain
Olive orchard near Cordoba, Spain (for the production of olive oil)  

4. Harvest

The olive harvest season in Spain usually starts in October and is finished by the end of December.  The maturity rate of the fruit will vary according to conditions of the season (e.g. wet or dry) and location (e.g. altitude).  Many factors are involved in a harvest, and not the least important is the production capacity of a molino (olive oil mill).

There are many, many small property owners in Spain and olive trees are part of the culture, tradition and heritage.  Many families maintain their “link to the land” by keeping a couple of hectares of olive trees.  The harvesting is a seasonal opportunity to meet up with old friends, and stand around “swatting flies and kicking tires”.

You can smell the harvest in Andalusia.  It is a lovely time of the year.  Driving the country roads in the fall evenings, a lovely aroma drifts about, associated with the picking and transporting of the olives.

In Spain there are two types of molinos or mills where the olives are processed and turned into olive oil.  The first type is private mills.  In many cases, the private molinos are owned and operated by a family and in other instances, large corporations.  The second category of mills is ownership by an “association”.  Usually, an association is formed of many small land holders in an area, and it allows cost sharing of the purchasing and maintenance of the equipment, as well as the operation of the mill.   Also, many times the associations will take the lead on labeling, marketing and selling the product each year.  An association provides the opportunity for small land owners to make a profit.

Each mill will have a daily production capacity, like any factory.  To be profitable and to produce the best quality olive oil, the harvest must be orchestrated.  Specific varieties of olives mature more rapidly than others.  Many times, it is more profitable to produce a single variety extra virgin olive oil (such as picual, and hojiblanca), and in other instances a blend of varieties is used to produce the olive oil.  You have to imagine that each mill is surrounded by fincas (farms) and olive orchards.  There has to be a plan and a sequence to the harvesting, so that all the olives are harvested in an order that best permits the production of top quality olive oil.  This is no easy task.

This is where the “catador” comes into the picture.  Each mill will have at least one catador who acts as the director of the orchestra.  This person determines the sequence of the harvest and the sequence of olive oil production at the mill.  Prior to the harvesting (during the spring and summer), the catador visits the fincas, registering the varieties, condition, expected yields and maturity of the fruit.  This data along with logistical considerations of moving teams/equipment, is used to plan the harvest.

Olive branch in Spain

Some varieties mature earlier so they are harvested first.  If single variety olive oil is the goal, then the catador must coordinate the harvesting and delivery of the same variety from several different harvesting locations.

This grows more complicated as mills work to fill their capacity and calendar.  Usually, each private mill will have a limited number of hectares that the family owns.  So, the mill will make agreements to purchase the olive production at other fincas, not owned by the family.  Or, mid-size or larger olive orchards, may make an agreement for delivery to the mill at a specific date for the production of their specific brand of EVOO.

In the meantime, there are always a few Grampas that show up at the mill with their old tractor or jeep and one cart of olives (or several gunnie sacks).  So the mill has to plan for the reception of local production as well as the large sequenced harvests of orchards.

And rain.  If it rains during the harvest season, it pushes the harvest back.  The plumpness of the olive is important to produce the best quality.  An olive overly plump after a rain will produce a lower quality EVOO.

5. Timing

The quality of EVOO produced during a harvest season follows a bell curve.  The very best extra virgin olive oil is usually produced in the middle of the season when the content of polyphenols peak.  Again, the polyphenols provide the sensory attributes of EVOO (i.e. composition, texture and flavor).  The earliest olive oil produced in the season is called “verde” or green, and usually has a fresh, green flavor that is quite strong.  Towards the end of the harvest, a lot of the olives may be overly mature and plump, reducing the content of oleic acid and pholyphenols, leading to a less flavorful EVOO.

EVOO & Mediterranean diet
Premium EVOO is the foundation of the Mediterranean diet.

Extra virgin olive oil must meet specific criteria to be classified as extra virgin.  It is only the very best quality of the harvest, offering the best flavors, consistency, and health benefits.

Virgin olive oil is the next category down.  The olive fruit will not be the same quality as those harvested to produce the extra virgin variety.  The fruit are still processed in the same way (first cold pressed), but the quality in terms of oleic acid and polyphenols, will be of lower quality.

Olive oil is the lowest quality produced during a harvest.  This is refined by using acids, alkalis and heat to extract the oil from pulp remaining of earlier production runs.  Olive oil offers little in terms of taste, aroma and natural antioxidants.   Many times this type of poor quality olive oil is sold under labels declaring “pure” or “100% pure” or “Light”.

Always, …always read the label and buy your EVOO from a source you trust! 

6. Transportation

The speed of conversion from picked fruit to fruit juice impacts the quality produced.  The shorter the period between when the olive leaves the tree and when it is cold pressed, the better and truer the quality of EVOO.  In the best mills, the olives are picked/harvested and within four hours are cold pressed at the mill and the juice stands in temperature controlled, stainless steal tanks.

To achieve the shortest transport time, it is important to have the best methods for transporting the olives to the mills and usually this involves trucks.  A lot of time, bins are used in the fields, which are then emptied into trucks, which then go to the mill and dump.

Bins of olive in Andalusia Spain
Reception of harvested olives

Smaller producers may have smaller crews and slower transporting machinery.  They may half fill a tractor/trailer unit in the afternoon, then go home for the night, coming back the next day to finish filling the trailer.  Olives begin to deteriorate when they leave the limb.

For this reason, mechanized methods are used for harvesting.  Hand picking is too slow. And mixing olives that haven fallen and lain on the ground with those picked directly from trees, lowers the overall quality of fruit.  Again, some mills will process a lot of gunney sacks (burlap bags), of olives transported to the mill by individuals or small property owners.  It is harder to control the quality of small quantity deliveries.

Olive harvest Andalusia Spain

Trucks are better than burlap bags 

7. Sorting & Cleaning

When the olives arrive to the molino they first must be sorted and cleaned.  There will always be a certain amount of leaves, twigs and branches that need to be sorted off.  And, there are always a small percentage of olives that shriveled on the tree, and they need to be sorted off before the olives are cold pressed.  The mill must have the appropriate machinery for receiving, sorting and washing the olives if top quality EVOO is the goal.  The best mills have mostly stainless steel machinery, which facilitates the cleaning between production runs.

Sorting and cleaning olive in Andalusia Spain

Olives to be cleaned

8. Storage of the Olives

First, olives should not be stored.  The olive should be cleaned and cold pressed as soon as possible after harvested from the tree.  Storing olives is a no no.  The mill has to have a clear plan for processing the olives as soon as they receive them.  They cannot sit around or they begin to ferment and the quality of the EVOO drops.

Olive bin for harvesting in Spain

Bins for the sorting of varieties or quality, before the cold press


9. First Cold Pressing

“First Cold Pressed”  is a phrase that has caught the attention, if not the understanding of the US consumer.  Our GringoCool brand of Spanish extra virgin olive oil is for sale at our online store (gringocool.com), and also via amazon and several of our customers have written reviews to the effect that our EVOO is good but it is “cold pressed” and NOT “first cold pressed”.   As the owner/operator of GringoCool, I have taken the time to write back and point out that all “extra virgin olive oils” are by definition “first cold pressed”  or “cold pressed”.   This phrase refers to the fact that the EVOO is the juice produced as the olive is crushed, ground and the olive oil extracted via a centrifugal machine.   Another important detail is that at no point during the process can the temperature rise above 26 degree Celsius.

“Olive oil” on the other hand, is produced not from the first cold press, but instead from the pulp remaining from the first cold presses and it is refined at times in high temperature processes which actually change the qualities of the olive oil.

Olive oil mill in Andalusia Spain

No substitute for good machinery and cleanliness in the production of EVOO

10. Centrifugal process

There is no substitute for modern, up-to-date machinery for extracting the best quality extra virgin olive oil.

The Real Deal - premium extra virgin olive oil

The best olive mills today are computer programmed, controlled and monitored.  Each delivery is tracked from the point of reception to the final storage in temperature controlled stainless steel tanks.  The process is completely mapped, controlled and registered.  Modern mills record the harvest date and time, harvest location, as well as the processing and specifications of each litre produced.   Each year this information is more necessary to combat the olive oil fraud perpetrated by dastardly desperados that purchase in quality EVOO in bulk, and then add other oils such as canola, sunflower, etc along with coloring,  – before labeling it and selling it as extra virgin olive oil.

Modern Olive Oil Mill in Andalusia Spain

Modern mills closely monitor each procedure when extracting the EVOO.

11. Hygiene

Everyone knows that cleanliness is important to quality.  But it takes dedication and discipline to really go the extra yard and keep the mill and processing clean.  I have been in some very “iffy” mills, where you become scared to peer into corners for what you might discover.  It is very easy to let things slide in a factory environment, and only the very best mills stay disciplined and produce the highest quality of EVOO.

Cinta with GringoCool bottle of EVOO

Clean surfaces are important for quality – which means hard work and dedication to details

12. Storage of final product

Temperature controlled stainless steel – no other answer for the storage of EVOO.  Gramma’s wooden barrels just don’t cut it.  Haha.

EVOO temperature controlled storageg

Clean temperature controlled storage is key to quality.

From the reception patio to the stainless steel tanks is a path of two to three hours approximately.  The stainless steel tanks store fresh olive juice and the centralized computer registers the harvest location, time and crop attributes for each of the tanks.  Each step in the process is strictly controlled in the production of high quality EVOO.


There are many factors that impact the quality of extra virgin olive oil.  Here I have provided a breakdown of 12 factors.  There are many articles and blogs to be written about the production of EVOO.  Here at GringoCool, we are interested in diving into other areas regarding the production, bottling, exporting and selling Spanish EVOO.

Each year, I think it is more and more important that brands provide security to their customers so that they feel comfortable with their purchases.  There is so much olive oil fraud in the market that it can be tough to trust a brand without learning some of the nuts and bolts.  I believe it is important to lay out what is involved in the production of olive oil and to provide a guarantee that customers receive only the highest quality product.

GringoCool Guarantee

You will always receive top quality, Spanish extra virgin olive oil from GringoCool.  There will be no middlemen.  The EVOO will be carefully selected, bottled, and then shipped to our warehouse in Oregon, where it is sent out to our customers (or amazon fulfillment).  Rest assured you will never receive a watered down concoction, posing as an extra virgin olive oil from GringoCool.  You will always receive the real deal .

GringoCool will endeavor to provide our customers with the best information, recipes, customer service and product we are capable of bottling.

GringoCool De Sevilla 2 liter bag-in-a-box of Premium Quality Extra Virgin Olive Oil

GringoCool De Sevilla - 2 liter box of premium quality extra virgin olive oil from Spain


Thanks so much for reading.  We welcome comments and emails.

Please, if you find this article helpful, share it and also please tell your family and friends to check out gringocool.com for the "real deal" EVOO.

Happy and healthy eating!  -Steve


p.s.  If you are interested in learning about how olives are harvested from the trees, check out our youtube video! 

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