EFFECT OF ULTRASOUND (US) AND PULSED ELECTRIC FIELD (PEF) TECHNOLOGIES ON OLIVE PROCESSING

The Spanish-Style (SS) and California-Style (CS) processes are the main methods used worldwide for table olive production. However, they are time-consuming methods that also require substantial amounts of sodium hydroxide and generate wastewater. In this context, intensifying green technologies such as ultrasound (US) and pulsed-electric fields (PEF) appears to improve processing efficiency, product quality and sustainability. Thus, the effects of US, PEF, and their combination were evaluated on texture, color and NaOH penetration rate for both production styles. For SS, debittering was performed by immersing green olives in 1% NaOH (1:2.5 m/m olive-to-lye ratio) for 8 h. For CS, turning-color olives were similarly debittered until complete lye penetration into the flesh and further exposed to oxygen for 9 h to promote oxidative darkening. US (570 W/L) was applied as assistant technology, while PEF (2.4 kV·cm⁻¹, 200 pulses) as pretreatment. NaOH penetration, texture, and color were evaluated by colorimetric reaction, puncture test, and colorimetry, respectively. For SS, two-thirds NaOH penetration was reached after 7.5 h under conventional conditions, whereas PEF, US, and PEF+US reduced this time to 4.9, 5.8, and 4.5 h, respectively. For CS, complete penetration occurred after 6 h conventionally, and after 5 h (PEF and US) and 4.25 h (PEF+US). No significant differences in lightness were observed in SS, while PEF enhanced darkening in CS after oxidation. Regarding texture, in SS, both the force required to rupture the skin and the energy needed for deformation were significantly reduced for PEF (0.171 N, 0.043 J) and PEF+US (0.171 N, 0.042 J) compared to conventional (0.219 N, 0.060J) and US treatments (0.224 N, 0.057 J). In CS, texture effects were predominantly observed for the PEF+US combination (0.152 N, 0.043 J) compared to US (0.202 N, 0.053 J), PEF (0.189 N, 0.056 J) and conventional (0.189 N, 0.056 J). Overall, for both SS and CS, the application of PEF, US, and their combination accelerated debittering through enhanced NaOH penetration without detrimental effects on color but promoting desirable darkening in CS. These results demonstrate the potential of the studied technologies, individually or in combination, to improve table olive processing efficiency.