A Review on Phenolic Compounds of Natural Olive Oils: Sensory Characteristics, Oxidative Stability and Olive Oil Processing
Muge Asan Nebioglu1, Fahri Yemiscioglu2, Onur Ozdikicierler2
1 Central Institute of Food and Feed Control, Bursa, Turkey
2Ege University Food Engineering Department, Izmir, Turkey

Phenolic compounds in olive oil gains increasing importance as regards to their nutritional functionality and as well as their contribution to sensory profile of olive oils. Hence many studies are conducted dealing with various aspects related to phenolic profile of olive oils. This review aims to summarize the effect of phenolic composition on sensory characteristics of olive oil together with the relation of phenolics with oxidative stability of olive oils. 
Studies confirm that phenolic composition is strongly determinative on bitterness and pungency of olive oils especially due to oleopeurin and ligstroside derivatives. Storage temperature and duration are also determinative on bitter and pungent sense and mouth feel probably due to interactions on stated phenolics. Bitterness is the dominant sensory characteristics at early stages of extraction. Bitterness rapidly decreases through aging in storage. Pungency also tends to decrease but it is still persistent.Phenolic compounds also effect thermal stability of olive oils due to their antioxidative characteristics. Studies showed that phenolic composition and amount of total phenolics in olive oil increase the induction period determined by Rancimat technique considerably. Bitterness index also have strong relation with oxidative stability.
Olive oil processing is also effective on total phenolics in olive oil. Especially malaxation temperature and duration together with the application affects the distribution of phenolics between olive oil and black water. Addition of hot water for increasing the oil yield must be avoided. Also total amount of phenolics tend to decrease during prolonged storage at elevated temperatures.
As a result; phenolic content and phenolic composition of olive oils is an important quality characteristic which both determines the sensory evaluations and oxidative stability.