Important Numbers in Olive Oil: How Do Importers Read Oil Quality?

With the start of the olive pressing season to produce high-quality oil for local markets or for export, importers and professional buyers focus on a set of precise analyses to ensure the purity of the product. Among the most important of these analyses is the spectrophotometric analysis at wavelengths of 232 and 270 nanometers, which reveals the secrets of the oil's quality, whether it has been mixed with old oils or other types, and also helps determine the oil's stability against oxidation.

What do the numbers K232 and K270 mean?

In a meeting with Mr. Juan Vilar, advisor to the International Olive Council, from the Malaga region in southern Spain, he explained that the ultraviolet absorption test (K232 and K270) provides vital information about the quality of the oil and the oxidative changes it has undergone.

In simple terms:

• K232: measures the products of primary oxidation (peroxides).
• K270: measures the products of secondary oxidation (aldehydes and ketones).

The significance of high index values

K232 index: It is an important indicator of the quality of extra virgin olive oil, as its value should not exceed 2.5. This value may rise as a result of oil oxidation for reasons including:

• pressing overripe (black) olives or late harvesting.
• the use of heat during the extraction process.
• improper storage of olive fruits before pressing.

K270 index: If its value rises above 0.22, this strongly indicates that:

• the oil is old and stored from previous seasons.
• the current oil has been mixed with old oil.
• this number increases over time due to the oil's exposure to sun and heat.

How do these numbers reveal adulteration?

In cases of commercial adulteration, refined oils are often added to extra virgin olive oil. The refining process itself produces substances that absorb light at the wavelengths of 232 and 270 nanometers. Therefore, a rise in the K232 and K270 indices may indicate oil adulteration.

To confirm the result, the peroxide value index and sensory tasting are taken into account to determine whether the cause of the rise is adulteration or merely rancidity (deterioration) of the oil.

DK index (Delta K): This index indicates the mixing of extra virgin olive oil with other lower-quality oils, such as virgin olive oil or seed oils.

Conclusion: The ideal numbers for extra virgin olive oil

The golden rule is: the lower the values of K232, K270, and DK, the better the quality of the extra virgin olive oil.

The maximum limits for these indices should be as follows:

• K232: less than 2.5
• K270: less than 0.22
• DK: less than 0.01

For these reasons, the spectrophotometric measurement is a crucial tool for importers and exporters alike. As the pressing season approaches, producers must pay great attention to quality standards, press at the right time, and use cold-pressing technology to obtain a high-quality product capable of competing in the global olive oil market.

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