Seth Schrage - Jan 16 2019

Acidity

In the olive oil industry, the term “acidity” has very little to do with pH or any acidic/sour flavor. The confusing nature of this term has led to its misuse by olive oil marketers for decades. Acidity actually refers to the percentage of free fatty acids that are present in the oil. 

What is a free fatty acid?

The fat in olive oil is in the form of a triglyceride, three fatty acids connected by a glycerol backbone:

As you may have guessed, the “tri” in triglyceride refers to the three fatty acids in the triglyceride molecule. Lipase enzymes, which are present in the pulp and seed of the olive, bugs, and soil break apart triglycerides, causing one or more fatty acids to be “freed”.

Why is the acid content of an olive oil important?

The acidity of an olive represents how carefully an olive oil was handled and processed.

What factors contribute to high acidity in olive oils?

The leading causes of high free acidity are: mishandling, prolonged storage of olives before processing, prolonged contact with soil, fly or parasite attack.

The enzymatic reaction that breaks apart triglycerides [or frees fatty acids] will only occur in the presence of water. This is why good oil producers take so many steps to remove water and excess plant matter (pulp, seed, etc.) from the olive oil quickly. Processing olives immediately after harvest, decanting, centrifugation, and filtration are essential for keeping the free acidity low.

A high quality olive oil will always have a low acidity. For example, to be classified as extra virgin, acidity must be below 0.8%. Good extra virgin oil has acidity below 0.2%.

Low acidity does not represent sourness in flavor. It shows that olives are grown, handled, and processed with care.

References:

“Fatty Acid.” Wikipedia, Wikimedia Foundation, 10 Nov. 2018, en.wikipedia.org/wiki/Fatty_acid.

Peri, Claudio. The Extra-Virgin Olive Oil Handbook. Wiley-Blackwell, 2014.

“Triglyceride.” Wikipedia, Wikimedia Foundation, 19 Oct. 2018, en.wikipedia.org/wiki/Triglyceride.