Influence of extraction method on structural, rheological, and nutritional characterization of peach palm (Bactris gasipaes) fruits pulp and peel oils

Peach palm (Bactris gasipaes) is a promising tropical resource, yet its fruit oils remain poorly understood from both chemical and structure–function perspectives. This study investigated how the fruit fraction (pulp and peel) and the extraction protocol modulated the chemical composition, multiscale organization, and technological functionality of peach palm oils. Oils obtained from pulp and peel using conventional isooctane- and ethanol-based protocols were evaluated through an integrated chemical, thermal, structural, and rheological approach. The oils were characterized for fatty acid profiles, lipid quality indices, predicted triacylglycerol composition, carotenoids, thermal transitions by differential scanning calorimetry, crystal morphology by polarized light microscopy, supramolecular and crystalline organization by small- and wide-angle X-ray scattering/diffraction, and oscillatory rheology at 20 °C. Rheological measurements were performed only on samples that exhibited structured behavior at room temperature, namely, pulp oil obtained using the isooctane-based protocol and peel oil obtained using the ethanol-based protocol. All oils were rich in oleic acid, reaching up to 63.98%, and displayed favorable lipid quality indices, including low atherogenicity and thrombogenicity indices. The predicted triacylglycerol profiles suggested a predominance of mixed saturated–unsaturated species, especially palmitoyl-dioleoyl-glycerol, a monounsaturated–dipalmitoyl–oleoyl–glycerol, followed by trioleoyl-glycerol and dipalmitoyl-oleoyl-glycerol. Carotenoids, particularly β-carotene and lycopene, were detected at measurable levels, with protocol- and fraction-dependent differences; lycopene was not detected in pulp oil extracted with ethanol. Differential scanning calorimetry revealed complex crystallization and melting behavior, with room-temperature structuring that depended on the combined effects of the extraction protocol and the fruit fraction. Pulp oil obtained via the isooctane-based protocol and peel oil obtained via the ethanol-based protocol exhibited melting/crystallization events extending to approximately 20 °C and behaved as semi-solid systems. Microscopy, scattering/diffraction, and rheology supported the development of interconnected crystal networks and organized lipid domains only in these structured oils. Overall, extraction conditions and tissue fraction jointly governed lipid organization and functionality, supporting the use of peach palm pulp and peel oils as potential ingredients for future food and cosmetic formulation studies.