Olive semidrying process: oleuropein degradation in relation to sensory bitterness.

Abstract

Today, treatment with brine or NaOH is the most common debittering procedures for olive industry. Although these debittering procedures are used widely, they have serious disadvantages such as high salt content of the final product, time consuming process (6-8 months required), degradation of other phenolic compounds, nutrient losses and formation of high amounts of waste water. Semidrying method has been recently introduced as a new debittering method. The aim of the present study was to evaluate the degradation of oleuropein and the sensory bitterness during semidrying of olives in a dryer at 40oC and 60oC with 1.5 m/s air flow rate. In this research, oleuropein, hydroxytyrosol and tyrosol content and sensory bitterness of olives have been determined for the first time during semi drying. An acceptable bitterness level and 88.76-91.29% oleuropein reduction was reached while 31.03-38.24% weight loss of olive was determined after semi drying process. Debittered olives were obtained with 22.41-28.61% water content. Results suggest that semi drying with piercing in combination with immersion pre-treatments could be used as an environmentally friendly olive debittering method for the production of higher nutritional value and low or free of salt table olives.