PROTEIN CONCENTRATES FROM DEFATTED BARU NUT: INFLUENCE OF SOLUBILIZATION pH ON TOTAL PHENOLIC COMPOUNDS, ANTIOXIDANT CAPACITY, AND FUNCTIONAL PROPERTIES

The baru (Dipteryx alata Vogel) is a native species of the Brazilian Cerrado whose nut presents high potential as a source of proteins and bioactive compounds. During oil extraction, a press cake is generated with potential for use as a protein source, in which proteins may be naturally complexed with phenolic compounds. This study evaluated the effect of solubilization pH on the production of protein concentrates from baru press cake in terms of phenolic compound content, antioxidant capacity, and functional properties. Protein concentrates were obtained by isoelectric precipitation, using alkaline solubilization from defatted baru nut at pH 10 and 12, followed by acid precipitation at pH4.8 (Leonel et al., 2025). After precipitation, the protein fractions were recovered by centrifugation and freeze-dried, yielding protein concentrates from defatted baru nut at pH 10 (CPT10) and pH 12 (CPT12). The extractable and non-extractable phenolic compound fractions were obtained from the concentrates and evaluated for total phenolic content using the Folin–Ciocalteu method (Singleton et al., 1999) and antioxidant capacity using the ABTS assay (Re et al., 1999). The concentrates were also characterized in terms of their water-holding capacity (WHC) and oil-holding capacity (OHC) (Ribeiro-Sanches et al., 2025). Differences between treatments were determined using Student’s t-test, considering p < 0.05. CPT12 exhibited a higher extractable total phenolic content (305.36 ± 15.92 mg GAE/100 g) than CPT10 (247.19 ± 5.81 mg GAE/100 g), as well as a higher non-extractable total phenolic content (219.75 ± 10.08 vs. 190.09 ± 6.35 mg GAE/100 g). This behavior may be related to the higher alkalinity of the medium, which favors the solubilization and dissociation of matrix components, increasing the release of phenolic compounds. The antioxidant capacity of the extractable phenolic fraction was also higher in CPT12 (1269.81 ± 48.57 µmol TE/100 g) than in CPT10 (1023.44 ± 8.66 µmol TE/100 g), whereas the non-extractable extracts did not differ significantly (173.37 ± 13.17 vs. 150.39 ± 29.38 µmol TE/100 g). CPT12 exhibited a higher water-holding capacity (WHC) (4.43 ± 0.10 g/g) than CPT10 (0.42 ± 0.21 g/g), possibly due to conformational changes in the proteins and greater exposure of polar groups under alkaline conditions. The oil-holding capacity (OHC) was also higher in CPT12 (3.27 ± 0.05 g/g) than in CPT10 (2.93 ± 0.15 g/g), possibly due to greater exposure of hydrophobic regions of the proteins. The higher solubilization pH favored the recovery of phenolic compounds and antioxidant capacity of the concentrates, highlighting pH 12 as a promising condition for obtaining protein concentrates from defatted baru nut.