Optimizing the effects of different ultrasound parameters on some secoiridoids of olive extracts using response surface and artifical neural network methodologies

Olive (Olea europaea L.) is a fruit that originates from Mesopotamia and is widely consumed all over the world due to the different functional elements in its composition. Our country is one of the leading countries in the world olive production and comes right after countries such as Spain, Italy, Greece and Tunisia, which have an important say in olive production. The functional importance of olives stems from various minor groups in its composition and phenolic compounds play an important role among these groups. Olive phenolics are mainly composed of phenolic acids, lignans, phenolic alcohols, flavonoids and secoiridoid groups and oleuropein, oleacein and oleocanthal components in the secoiridoid group are expressed as prominent phenolic components. While oleuropein, which has many positive effects on health, has been extensively studied, there are limited references in the literature on the other two components. However, ultrasound-assisted extraction, which is accepted as an alternative to conventional extraction techniques, is a technique that stands out and attracts attention due to its advantages such as fast processing time, low temperature requirement, effective extraction efficiency. In this study, the effects of different ultrasonic treatment conditions on some physicochemical properties and phenolic content of olive extracts were investigated. For this purpose, pH, free acidity, colour index, total phenolic content and secoiridoid phenolic compound composition analyses were carried out in olive extracts subjected to ultrasonic extraction at different temperatures, power and times. The data obtained were modelled by using artificial neural networks and also by Box-Behnken, a design of response surface method, and mathematical equations were established. The pH values of the samples ranged between 4.94±0.028 and 5.23±0.120 and the average free acidity value was 0.551 (in %oleic acid). Colour index values varied between 20.46±2.869 and 83.70±2.220. Total phenolic content was found between 0.13±0.036 and 0.42±0.071 mg GAE (gallic acid equivalent)/g dry matter. In the secoiridoid phenolic compound composition analysis, oleuropein was found between 5.33±0.45 and 34.39±0.47 ng/μL, oleacein between 0.76±0.07 and 6.03±0.51 ng/μL, oleocanthal between 3.77±0.01 and 14.16±0.13 ng/μL.