Modeling the effect of physically debittered unsalted dried olive production process on total phenolics and some quality properties

The total phenolic content of pitted, unsalted dried olives obtained through physical methods (ultrasound, freezing, and drying) was determined in this thesis study. The impact of independent variables and parameters on the final product was assessed. The study material was pitted Ayvalık (Edremit) Olive variety from the 2020-2021 harvest season, and the changes in total phenolic compounds, oleuropein and hydroxytyrosol contents were investigated. In the production process of unsalted olives, ultrasound (10 min, 20 min, 30 min), freezing (-40°C, -30°C, -20°C) and drying (50°C, 60°C, 70°C), processes were applied, respectively. Response Surface Methodology (RSM), a design method for experimental studies, was applied, using a Box Behnken Design. The independent variables of model were ultrasound time, freezing temperature, and drying temperature. As a response, the total phenolic content, antioxidant activity, moisture content, ash content, oil yield, free fatty acidity, peroxide value, ultraviolet absorbance (K232-K270) values, textural properties, and color change were studied. The effects of physical methods on olive quality characteristics such as moisture content, ash content, total phenolic content, total antioxidant activity, color and texture properties were statistically evaluated and modeled. While the total phenolic content in the control sample was 16.28±0.58 mg GAE (Gallic Acid Equivalent)/g DM (Dry Matter), physical methods reduced it to a level of 3.78-9.62 mg GAE/g DM. The oleuropein and hydroxytyrosol content of the control sample were determined to be 15.39±1.70 mg/g DM and 0.544±0.06 mg/g DM, respectively. After physcial treatments, the oleuropein content were found 0.04-10.14 mg/g DM and hydroxytyrosol contents s were 0.135-0.202 mg/g DM. Physical methods reduced the total phenolic content and oleuropein content in the final products by 40.91% - 76.78% and 34.11%- 99.74% respectively.