Modeling the Effects of Physical Methods on Olive Bitterness Components

Abstract

Olive fruit is rich in various micronutrients, especially phenolics and antioxidants, which are widely consumed as an important component of a healthy diet. In table olive production, chemical applications applied to reduce bitterness cause quality loss, salt accumulation and wastewater. Considering all these factors, within the scope of this study, the combined effects of sonication, freezing-thawing and drying processes, known as unique positive and successful applications, were investigated using RSM. For this purpose, total phenolic content (TPC), oleuropein and hydroxytyrosol content were examined while producing dry olives from ripe Edremit (Ayvalık) olives. It was found that raw Edremit olives had TPC at 16.28±0.58 mg gallic acid equivalents (GAE)/ g dry matter (DM). Oleuropein and hydroxytyrosol content at 15.39±1.70 mg/g DM and 0.544±0.06 mg/g DM, respectively. The quadratic model was found to be the most accurate in modeling and identifying TPC in experimental samples. According to ANOVA results, the most effective parameters on TPC were investigated as sonication time (A), drying temperature (C), interactive effect of sonication time and freezing temperature (AB), sonication time and drying temperature (AC) and the quadratic effect of sonication time (A2). It was evaluated that, the combination of sonication, freezing and drying reduced the oleuropein content to 0.307-0.501 mg/g DM and hydroxytyrosol content to 0.135-0.202 mg/g DM regardless of the level of parameters (p>0.05). Consequently, it was proven that sonication, freezing- thawing and drying for desired level of TPC and oleuropein can be provided. For further studies, consumer expectation and sensory evaluation are required for targeted industrial applications.