STANDARDIZATION OF PHENOLIC COMPOUND EXTRACTION AND SPECTROPHOTOMETRIC DETERMINATION IN PARTIALLY DEFATTED BARU (DIPTERYX ALATA) CAKE

The oil extraction process from baru kernels generates a substantial amount of partially defatted cake, an underutilized co-product with potential as a source of bioactive compounds. The baru fruit (Dipteryx alata), native to the Brazilian Cerrado, is valued for its edible kernel and cold-pressed oil; however, the characterization and reliable quantification of phenolic compounds in the resulting cake are challenging due to the presence of residual lipids that can interfere with spectrophotometric analysis. Therefore, this study aimed to standardize a hydroalcoholic extraction procedure for the determination of total phenolic compounds in partially defatted baru cake, incorporating a preliminary solvent-based defatting step to minimize lipid interference. Partially defatted baru cake, containing approximately 11.7% residual lipids, was milled to 48 mesh and subjected to three consecutive washing cycles with hexane under vortex agitation for 5 min per cycle, followed by complete solvent evaporation. The resulting defatted flour was extracted with 70% (v/v) ethanol at a 1:40 (w/v) solid-to-solvent ratio. Ultrasound-assisted extraction was performed for 45 min under light-protected conditions, followed by vacuum filtration using a Büchner funnel and qualitative filter paper. Total phenolic content (TPC) was determined using the Folin–Ciocalteu assay, with gallic acid as the standard (20–100 mg/L; r² ≥ 0.99). Absorbance was measured at 765 nm after incubation in the dark at room temperature. The preliminary hexane treatment produced a clear extract suitable for spectrophotometric analysis, overcoming the turbidity observed when residual lipids were not previously removed. Under the standardized conditions, the hydroalcoholic extract showed a total phenolics content of 550.83 ± 11.86 mg GAE/100 g of the original partially defatted baru cake. These findings demonstrate that preliminary removal of residual lipids is an important sample-preparation step for obtaining a clear extract and enabling reliable spectrophotometric determination of phenolic compounds in baru cake. The standardized procedure provides a practical approach for the analytical characterization and valorization of this agro-industrial co-product as a potential source of phenolic compounds.

Financial Support: The authors gratefully acknowledge the Coordination for the Improvement of Higher Education Personnel (CAPES) for financial support through a Master's scholarship.