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Everything you should know about olive oil

A brief introduction to olive oil in general

Olive oil has been one of the healthiest nutritional staples for millennia, produced at exceptional quality — especially in Crete.

A great deal has been written and said about olive oil, and in recent years more and more people around the world have shown growing interest in this precious product.

Olive oil is produced by olive growers (large and small), who typically sell it — based on the prevailing market price — to processors and traders. These, in turn, channel it to market through third parties.

A fundamental issue with this process is that the producer price does not always reflect — as is the case with many agricultural products — the true value of the product, meaning the full cost of production and a fair return for the producer. This results in reduced incentives for quality production.

Another significant issue is quality — both of the oil as produced and as bottled. Even today, there is widespread confusion among consumers about what genuine quality means and what the correct sensory characteristics of olive oil actually are.

So what does 'extra virgin olive oil' actually mean? What is seed oil? What does organic mean? And how can one distinguish, compare, and recognise the authentic hallmarks of a high-quality olive oil?

How consumers choose

The average consumer, when faced with a product on the shelf, typically relies on specific criteria, such as:

  1. Price
  2. Certifications (BIO, HACCP, etc.)
  3. Advertising
  4. Previous experience
  5. Word of mouth
  6. Other factors

These criteria are useful, given that the consumer remains largely disconnected from the production process and lacks specialist knowledge.

By contrast, for someone with experience and an understanding of the production process, many of these criteria carry less weight.

A telling example is the excessive emphasis placed on BIO, HACCP and similar certifications, which cannot by themselves convey the full picture of a product's essential quality characteristics. For instance, while an organic olive oil should largely guarantee the absence of chemical residues, it does not on its own guarantee superior quality. Conversely, a non-certified olive oil could well be qualitatively superior.

Olive Oil Quality Characteristics

The quality of olive oil is determined by measurable characteristics, assessed in specialised laboratories.

Acidity

The most widely known characteristic is acidity.

For an extra virgin olive oil, acidity must be less than 0.8%.

Acidity is a key quality indicator, as it expresses the percentage of free oleic acid. Low acidity indicates a healthy fruit and proper processing.

Olive oil quality grades

Extra Virgin Olive Oil

Acidity ≤ 0.8% — no perceptible defects

Virgin Olive Oil

Acidity ≤ 2.0% — minimal defects

Olive Oil (refined / ordinary)

A blend of refined and virgin olive oil

Other quality characteristics

Peroxide Value

Indicates the degree of oxidation (rancidity). Must be < 20.

Spectrophotometric indices (K232, K270, ΔK)

Assess oxidation, freshness, and possible adulteration:

  • K232 (indicates early-stage oxidation): for a quality olive oil should be < 2.50
  • K270 (indicates advanced oxidation): for a quality olive oil should be < 0.22
  • ΔK (indicator of adulteration): for a quality olive oil should be < 0.01

Polyphenols and health benefits

Polyphenols are natural antioxidants that contribute significantly to the nutritional value of olive oil.

According to EU Regulation 432/2012, they contribute to the protection of blood lipids from oxidative stress.

Required amount: ≥ 250 mg/kg

Recommended daily intake: approximately 20 g (1.5 tablespoons)

Key polyphenols:

  • Oleocanthal
  • Oleasin
  • Hydroxytyrosol
  • Tyrosol

Benefits:

  • Anti-inflammatory action
  • Cardioprotection
  • Neuroprotection

Factors affecting polyphenol content:

  • Harvest timing (early-harvest oil → higher content)
  • Variety (e.g. Koroneiki)
  • Processing method (cold extraction < 28°C)
  • Storage conditions (dark, cool environment, glass packaging or special metal containers)

Note on polyphenols

The polyphenol content of olive oil depends largely on the degree of ripeness of the olive at harvest. The earlier the harvest (greener, less ripe olives), the higher the polyphenol concentration.

In our region, typical polyphenol values range from approximately 220 to 280 mg/kg, depending on the year.

Polyphenols give olive oil its characteristic bitter and pungent flavour notes.

In international markets, olive oils with very high polyphenol concentrations (above 500 mg/kg) are available, considered particularly beneficial for health and sold at premium prices.

However, very high polyphenol levels can make the oil unpleasant in taste for the majority of consumers.

It should be noted that artificially boosting polyphenols — such as by milling olive leaves together with the fruit — constitutes adulteration and compromises product quality.

Chemical residue testing

Accredited specialised laboratories carry out residue testing for more than 400 chemical substances and issue the corresponding certificate.

A high-quality olive oil should show no measurable residues of any substance.

Organoleptic characteristics of olive oil

Organoleptic characteristics are the properties perceived through the senses and constitute a fundamental criterion for assessing quality — particularly in extra virgin olive oil.

1. Aroma (smell)

  • Fruity, reminiscent of fresh olive
  • Notes of grass, olive leaf, tomato, artichoke, apple or almond

A quality olive oil has a clean and pleasant aroma, free from any off-notes.

2. Taste

  • Fruity: intensity and quality of olive character
  • Bitter: characteristic, especially in unripe fruit
  • Pungent: a burning sensation in the throat (indicative of phenolic compounds)

The three elements should be in balance.

3. Texture

  • Fluidity
  • Smoothness or body
  • Velvety or slightly rough mouthfeel

4. Appearance

Colour ranging from green to golden yellow

Colour is not a reliable quality indicator — it is influenced by variety, ripeness, and processing.

Negative organoleptic characteristics

  • Rancid (oxidation)
  • Musty or damp
  • Vinegary or sour taste
  • Metallic or 'muddy' taste

Their presence disqualifies an oil from the 'extra virgin' category.

Basic tasting procedure

  1. 1. Preparation

    • Use a small dark glass
    • Add 1–2 tablespoons of olive oil
    • Warm gently in the palm (~28°C)

  2. 2. Smell

    • Cover and swirl gently
    • Look for freshness and a fruity aroma

  3. 3. Tasting

    • Take a small sip — detect fruity, bitter and pungent character

  4. 4. Strippaggio technique

    • Draw air into the mouth to intensify the aromas

  5. 5. Evaluation

    • Balance, pleasant taste, cleanliness

What characterises a good olive oil

  • Fresh and clean aroma
  • Balance of bitterness and pungency
  • Pleasant sensation with a mild 'burn' in the throat

Common mistakes

  • Judging by colour
  • Tasting with a full mouth
  • Not warming the oil before tasting
  • Not comparing different oils side by side

Tasting 2–3 different oils simultaneously makes the differences far easier to detect.

Uses of olive oil

Consumers should be aware of the many uses of olive oil: in cooking, in pastry and baking, as a natural preservative, and even in pharmaceutical or traditional applications (e.g. soaps, herb-infused oil, etc.).

Further information: Factors affecting quality

The quality of olive oil is a function of a complex set of factors related to the environment, olive varieties and cultivation practices, and the harvesting and processing of the fruit.

1. Environmental factors

Soil composition and fertility, as well as geographic location (mountain or lowland areas), influence tree development and the chemical composition of the fruit.

Climatic conditions during each growing season (temperature, humidity, sunshine, rainfall), as well as the presence of disease or pests, significantly affect both the quality and quantity of the harvest.

2. Varieties and cultivation practices

The type of tree and cultivation practices significantly differentiate the quality of the final product:

  • The species and variety of olive tree affect the composition and organoleptic characteristics of the oil produced.
  • Natural farming is characterised by minimal interventions and is often associated with high quality.
  • Organic and biodynamic cultivation avoids the use of pesticides and chemicals, contributing to environmental balance and the production of nutritionally valuable olive oil.
  • Conventional cultivation primarily aims to maximise yields through intensive mechanisation and the use of chemical inputs.
  • Cultivation may be irrigated or rain-fed, which affects both yield and the composition of the olive fruit.

3. Harvesting methods

The harvesting method directly affects the quality of the olive oil:

  • Collecting fruit from the ground leads to increased acidity, due to the onset of fermentation and oxidative processes.
  • Mechanical or manual stripping (raking, shaking) is the most widespread practice. Modern mechanical rakes reduce damage to the fruit and tree.
  • Super-intensive cultivation systems allow for mechanical, continuous harvesting, but require specific varieties and linearly arranged trees.

Traditional methods are often associated with superior quality characteristics.

Critical factors during harvesting:

  • Avoid collecting wet fruit
  • Use ventilated transport containers
  • Minimise the time until processing
  • Avoid exposing damaged fruit to exhaust fumes

4. Processing the olive fruit

The olive fruit should be brought for pressing as soon as possible, ideally within 24 hours.

Oil extraction is carried out by mechanical means.

The malaxation temperature should not exceed 27–28°C (cold extraction), so as to preserve phenolic compounds and aromatic characteristics.

5. Storage of olive oil

  • Use of appropriate containers (e.g. stainless steel)
  • Protection from light and oxygen
  • Maintain at a stable, low temperature

The Market (the producer–consumer relationship)

Olive oil is not merely a product. It is a fundamental part of our diet. And yet its price is determined neither by its quality nor by the efforts of the producer. It is determined by 'the market.'

This brings us to a paradox:

  • The producer is squeezed
  • The consumer pays a high price
  • And the middlemen set the rules of the game

The producer–consumer relationship has been lost within an opaque supply chain.

Conclusion

Olive oil is a precious product with significant nutritional and economic value. A genuine understanding of its quality characteristics and proper consumer education can contribute to improving both the choices made and the overall value of the product in the market.