Quality & testing
The numbers on a laboratory report: peroxide, K232 and K270
Acidity tells you one thing. These numbers tell you the rest.
18 October 2026 · 2 min read
Free acidity is the figure most often quoted, and it is useful. But a complete laboratory report carries several others, and each tells you something acidity cannot.
Why one number is not enough
Free acidity measures how far the fats in the oil have broken down into free fatty acids. It tells you about the condition of the fruit and how quickly it was processed.
But it says nothing about oxidation — a separate process that happens when oil meets air, light and heat. An oil can have low acidity and still be oxidised if it was badly stored.
Peroxide value
This measures oxidation at an early stage. Peroxides are the first compounds to form as oil begins to oxidise, before any change in taste is detectable.
The international standard sets a ceiling of 20 for extra virgin. A figure well below that indicates fresh, well-handled oil. Olivko tested at 8.0.
Peroxide value is useful because it catches a problem earlier than your palate does. By the time oil smells rancid, the peroxides are long past their peak.
K232 and K270
Both are ultraviolet absorbance readings. The oil is tested to see how much light it absorbs at two specific wavelengths, and each points to a different stage of oxidation.
- K232 indicates early-stage oxidation — closely related to peroxide value. The extra virgin limit is 2.50. Olivko tested at 2.13
- K270 indicates later-stage oxidation, and it also rises if refined oil has been blended in. The extra virgin limit is 0.22. Olivko tested at 0.15
K270 is the most interesting one for authenticity. Refining creates compounds that absorb strongly at that wavelength, so an oil labelled extra virgin but containing refined oil will show a high K270.
Moisture
Water left in the oil after separation can encourage microbial growth and speed up spoilage. A low figure indicates clean separation. Olivko tested at 0.10%.
How to read a report
- 1.Check the report is named — which laboratory, which report number, which date
- 2.Check the date is recent. A three-year-old report describes oil that is long gone
- 3.Compare each figure to the extra virgin limit, not to another brand
- 4.If a seller cannot produce a report at all, that is an answer in itself
The Olivko figures above come from ONH Tunis report N° 2025B1064, dated 17 March 2026. They are measures of quality and freshness — we make no health claims from them.
