Freeze–ohmic thawing: A novel pretreatment strategy for cold-pressed black cumin oil production

Cold pressing is one of the most preferred techniques for producing high-quality vegetable oils; however, its relatively low extraction efficiency remains a major limitation. Although ohmic thawing has been investigated as a rapid thawing technique for frozen foods, its application as a pretreatment prior to cold-press oil extraction has not yet been reported. Therefore, this study investigated, for the first time, the potential of freeze–thawing (FT) and freeze-ohmic thawing (FOT) as pretreatment strategies to enhance the recovery and preserve the quality of cold-pressed black cumin oil. FT and FOT pretreatments were applied for one, two, and three cycles before cold pressing, and the extracted oils were comparatively evaluated in terms of oil recovery, physicochemical properties, antioxidant characteristics, FTIR, aroma profile, and fatty acid composition. Both FT and FOT significantly improved oil recovery compared with the untreated control. While FT2 increased the extraction yield to 51.68 ± 2.21%, FOT2 achieved the highest extraction yield (63.11 ± 1.50%), corresponding to a 41% increase over the control. FTIR analysis confirmed the preservation of the characteristic functional groups of black cumin oil following both pretreatments. Thymoquinone was largely preserved, with only a slight reduction in FT2. Likewise, the fatty acid profile remained stable, with no significant differences (p > 0.05) among treatments. These findings demonstrate, for the first time, that freeze-ohmic thawing can be successfully employed as a pretreatment prior to cold pressing, substantially improving black cumin oil recovery while preserving its physicochemical, structural, and compositional quality.