The effect of pine and oak ash in debittering on the biological properties, fatty acids and phenolic components of brined olive fruits

In this study, geographically indicated Tarsus Sarıulak green olive cultivar obtained from the Tarsus district of Mersin were used as the experimental material. During the fermentation process of table olives subjected to debittering treatments with hot water, normal water, NaOH, oak wood ash, and pine wood ash after cracking and slitting processes, the effects of debittering methods on fermentation profile, bioactive compounds, physicochemical properties, and sensory characteristics were examined. The potential use of oak wood ash and pine wood ash treatments as an alternative to caustic solution (NaOH) was evaluated. The moisture content, oil content (dry basis), total phenolic content, antioxidant activity, and flavonoid content of the fresh olive sample were found to be 57.75%, 62.26%, 4230.57 mg GAE/kg, 10.22 mmol TE/kg, and 2365.11 mg CE/100 g, respectively. The total phenolic contents of the final products ranged from 700.00 to 2084.23 mg/kg. The greatest loss of polyphenols was observed in the samples processed with pine ash. At the end of fermentation, antioxidant activity values ranged between 1.53–9.83 mmol TE/kg in olives. The total flavonoids of the final products ranged from 312.89 to 1842.89 mg CE/100 g. The oil contents of fermented olives ranged from 65.13% to 74.23% (dry basis). The moisture contents of fermented olives ranged from 57.57% to 63.01%. A negative correlation was found between the moisture content and oil content of the olive. The main phenolic compound of the fresh olive fruit was determined to be oleuropein. Hydroxytyrosol was identified as the major phenolic compound in the final products. In this study, it was generally observed that, compared to the raw sample, the concentrations of luteolin-7-glucoside decreased in fermented samples, while the concentrations of hydroxytyrosol increased. The major fatty acids in the fresh olive fruit were found to be oleic acid, palmitic acid, and linoleic acid. The major fatty acids in fermented olives were observed to be oleic acid, palmitic acid, and linoleic acid. The salt concentrations of all brine samples reached their minimum level on the 90th day of fermentation. At the end of fermentation, the brine pH values of all samples remained above 4.5. Titratable acidity values could not be detected in the brines of all samples processed with pine ash throughout fermentation. At the end of fermentation, the odor, taste, color, texture, bitterness and overall acceptability scores of fermented olives debittered using hot water, oak wood ash, normal water and NaOH methods were determined to be ≥ 4 (good), whereas the odor, taste, color, texture, bitterness, and overall acceptability scores of fermented olives debittered with pine wood ash were generally ≤ 2 (poor). Keywords: Debittering methods, bioactive compounds, pine wood ash, fermentation period, processing technique, oak wood ash, brine, Tarsus Sarıulak cv. green olive