The 0.16% on Your Olive Oil Label Has Nothing to Do With Sourness

One of the most prominent numbers on an extra virgin olive oil (EVOO) label is an acidity figure — often something like 0.16%. A common misconception, frequently noted across the trade, is that this number describes how sour the oil tastes. Pour it and you will notice almost no sourness at all. That is because the acidity printed on an EVOO label is read not by the tongue but by a spectrophotometer or a titration instrument — it is a chemical indicator, not a sensory one.

Acidity is the proportion of free fatty acids

EVOO acidity is the free fatty acid (FFA) content expressed as a percentage of oleic acid. During pressing and subsequent storage, some of the triglycerides naturally present in the olive fruit undergo hydrolysis. Each hydrolysis event releases free fatty acids, and the proportion of those fatty acids is what gets measured and printed on the label. Acidity is therefore better understood as an indicator of deterioration than of flavour. A lower figure suggests the fruit was in good condition before pressing — fewer bruises, pest damage, or windfalls — and that oxidation was kept in check after pressing.

The grade boundary sits at 0.8%

International olive oil grading uses acidity as a primary criterion. According to the IOC Trade Standard COI/T.15/NC No 3/Rev.19, extra virgin olive oil must show a free fatty acid content at or below 0.8%, zero organoleptic defects, and must be produced mechanically without chemical treatment. Virgin olive oil allows up to 2.0% FFA and permits some organoleptic defects that would disqualify an EVOO. Lampante — named for the oil once burned in lamps — exceeds 2.0% FFA, is not fit for direct consumption, and must be refined before use. Refined grades vary by labelling convention and are essentially flavour-stripped oils.

Within the trade, 0.3% FFA has emerged as an informal threshold for high-quality EVOO. A bottle showing 0.16% or 0.14% — anything comfortably below 0.2% — is generally read as the product of precise harvesting and rapid, careful pressing.

KOH titration and automated measurement

The classical measurement method is potassium hydroxide (KOH) titration. An oil sample is dissolved in ethanol and diethyl ether, phenolphthalein is added as an indicator, and a KOH solution is introduced drop by drop until the mixture changes colour. The volume of KOH consumed is used to calculate the free fatty acid content, which is then converted to a percentage expressed as oleic acid. Modern laboratories increasingly rely on automated titrators and near-infrared (NIR) spectroscopy. The essential point is that the number on the label is generated by instruments, not by sensory evaluation.

The relationship to flavour is indirect

Acidity and flavour are not directly linked. The perceptible sourness difference between 0.1% and 0.3% FFA is, by most analytical accounts, undetectable on the palate. The connection is indirect: low acidity implies intact fruit, fast pressing, and minimal oxidation — conditions that are also associated with better retention of polyphenols and aromatic compounds.

When reading an acidity figure on a label, three reference points are broadly useful. First, 0.8% or below confirms the oil meets the EVOO standard under the IOC classification — the label itself is a guarantee of that threshold. Second, 0.3% or below is widely treated as a signal of high quality; seeing a figure below that in a shop is generally taken to mean relatively fresh, precise pressing. Third, figures below 0.2% — such as 0.14%, 0.16%, or 0.20% — are typically associated with oils that carry a laboratory certificate of analysis from the producer. That said, acidity alone is not sufficient to judge an oil: it is one data point within a broader picture. OLEA's storage guide and label-reading guide offer additional context for getting the most from the information on the bottle.

Acidity is among the most objectively stated numbers on an EVOO label. Understanding it as a measure of fruit condition and post-pressing oxidation — rather than a measure of sour taste — changes how the label reads entirely.