High-pressure technology: application as a pretreatment technique for de-bittering and fermentation acceleration of green table olives

Abstract

An alternative approach is proposed through the application of high-pressure (HP) technology for the acceleration of table olive de-bittering processing. HP-assisted de-bittering in 8% NaCl brine for 5–20 min at 100–400 MPa was performed. The conventional “Greek-style” method (immersion in an 8% NaCl brine) and lye treatment (immersion in a 2% NaOH solution for 8 h) were also tested and compared. Oleuropein content, sensory properties, and quality characteristics, including color and texture, were evaluated immediately after treatment. Following de-bittering, all the samples underwent fermentation in an acidified brine (8% NaCl, pH 5) for at least six months to assess fermentation duration and final product quality. HP treatment resulted in up to 80% reduction in oleuropein immediately after processing, whereas NaOH and conventional brine treatments required 24 h and 8 weeks, respectively, to achieve equivalent reduction. The HP process did not alter the initial lactic acid bacteria population, allowing normal fermentation progression. Brine pH dropped below 4.2, and bitterness intensity became acceptable after approximately 101, 45, and 250 days for samples debittered by conventional, HP, and NaOH processes, respectively. No significant differences were observed in the quality characteristics of the final fermented olives. These results demonstrate that HP-assisted de-bittering efficiently minimizes processing time without compromising product quality while simultaneously reducing the use of alkali solutions, a critical concern in the table olive industry. HP technology thus represents a promising alternative for accelerating olive de-bittering and for streamlining production, maintaining desirable sensory and textural attributes in the final product. The study highlights the potential of HP as a rapid, effective, and sustainable approach for table olive processing.