Technological Assessment of Unconventional Oil-Bearing Materials for Screw Pressing: Oil Recovery, Quality, Clarification, and Press Cake Characteristics

Abstract

The technological suitability of unconventional oil-bearing materials for screw pressing depends on both raw-material characteristics and their behavior during processing and subsequent oil clarification. This study comparatively evaluated black sesame seeds (BSSs), white sesame seeds (WSSs), blue poppy seeds (BPSs), black cumin seeds (BCSs), full-fat coconut flour (FCF), apricot kernels (AKs), and raspberry seeds (RSs) within an integrated framework combining screw pressing performance, oil quality, fatty acid composition, press-cake characteristics, and sedimentation behavior. Considerable differences were observed in processing efficiency, with oil yields ranging from 23.32% for BCS to 92.68% for FCF, while AK also showed high extraction efficiency (89.92%). The investigated oils differed markedly in lipid composition: RS oil contained the highest proportion of PUFA (83.45%) and the lowest ω6/ω3 ratio (1.69), whereas AK oil was characterized by the highest MUFA content (66.09%). Initial oil quality also varied substantially among materials, with very low peroxide values (0.01 mmol O2/kg) recorded for sesame and coconut oils, while BCS oil exhibited pronounced oxidative deterioration (39.37 mmol O2/kg). Press cakes contained 8.32–49.60% protein and variable amounts of residual oil, indicating differing potential for further valorization. Post-pressing clarification behavior was strongly material-dependent. RS and AK oils showed the most pronounced sedimentation, with the suspended sediment fraction decreasing by 70% and 64%, respectively, over 7 days, whereas WSS oil showed only a 13% reduction. Exploratory PCA further differentiated the investigated materials according to pressing efficiency, oil quality, press-cake composition, and sedimentation characteristics. Overall, the results revealed substantial material-dependent differences in pressing performance, oil quality, fatty acid composition, and sedimentation behavior, highlighting the importance of raw-material selection in small-scale screw pressed oil production.