Increasing the Bioactive Compound Content of Olive Oil by Acidification of Olive Paste

This study investigated the impact of acidification on olive paste to enhance the extraction of olive oil enriched in bioactive phenolic compounds, aiming to develop a novel functional food. Recognizing that acidic pH promotes the activity of β-glucosidase responsible for oleuropein and ligstroside hydrolysis, food-grade organic acids-citric, ascorbic, and acetic acid-were added prior to malaxation to improve the bioactive compound content in the resulting oils. A randomized experimental design was employed, using three different doses of each acid (1, 2, and 4%) with three replicates per dose, alongside control trials without acid addition. Acidification did not affect olive oil extraction efficiency or alter quality parameters for extra virgin olive oils. Treatment with 1% ascorbic acid significantly increased phenolic compound content by 37% compared to controls. Secoiridoids comprised 79.4% of the total phenolic content, with oleacein as the predominant compound (237.58 ± 9.18 mg/kg), representing over 50% of the total. This increased oleacein concentration led to up to a 67% enhancement in antioxidant capacity (428.63 ± 31.57 mg Trolox/kg) compared to controls. The antioxidant capacities of 3,4-DHPEA, 3,4-DHPEA-EDA, and 3,4-DHPEA-EA were determined to be 12.05, 5.80, and 4.91 µmol TE/mg, respectively. Furthermore, the 1% ascorbic acid treatment enhanced volatile compounds associated with the lipoxygenase (LOX) pathway while reducing ethanol levels.