Why is high free oleic acid undesirable?

On the other hand, olive oil undergoes hydrolysis during different phases of production (fruit ripening, harvest, processing, and storage).

Hydrolysis is a reaction that breaks the acyl chains away from the TAG structure. As a result, oleic acid is released as a free fatty acid molecule into the oil.

The amount of free fatty acids in oil is measured analytically and expressed as free acidity relative to free oleic acid.

So, a high level of free oleic acid is a negative quality indicator of olive oil.

Summary

• A high level of oleic acid bound within the triacylglycerols is desirable and contributes to the health benefits of olive oil and its oxidative stability.
• A high level of free oleic acid is an undesirable quality marker that indicates deterioration or poor processing of the oil.