Extraction and Structural, Morphological, and Thermal Characterization of Non-Conventional Starches from Pequi, Lobeira, and Baru

The valorization of Cerrado plant materials as sources of non-conventional starches may expand the availability of regionally derived biopolymers with distinct technological properties. This study aimed to obtain starches from pequi (Caryocar brasiliense), lobeira (Solanum lycocarpum), and baru (Dipteryx alata) mesocarp and compare their extraction yields and structural, morphological, and thermal characteristics. The starches were obtained by aqueous extraction involving cleaning, grinding, filtration, and drying. Characterization comprised Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetry, and derivative thermogravimetry (TG/DTG). Phenolic compounds were also quantified using a gallic acid calibration curve. Lobeira showed the highest extraction yield (7.75%), followed by baru (1.91%) and pequi (0.97%). FTIR spectra showed bands characteristic of starch, including broad O-H stretching bands at 3279-3285 cm⁻¹, C-H stretching bands at 2924-2930 cm⁻¹, and intense absorptions in the carbohydrate fingerprint region between 1000 and 1158 cm⁻¹, with source-dependent variations. SEM micrographs revealed distinct morphologies: baru starch exhibited agglomerated particles and irregular surface regions; lobeira starch showed numerous dispersed granular structures; and pequi starch displayed larger, compact agglomerates with irregular outlines. DSC curves also differed among the samples, indicating source-dependent thermal behavior. TG/DTG curves showed an initial mass loss associated with water release and a main degradation stage at approximately 250-380 °C. Lobeira starch exhibited 87.03% total mass loss and a peak degradation temperature of 311.29 °C, whereas pequi starch showed 75.34% mass loss and a peak at 318.04 °C. Baru starch had the lowest total mass loss (63.70%), the highest residual mass, and the highest peak degradation temperature (350.40 °C). Phenolic analysis yielded gallic acid-equivalent concentrations of 0.02193 ± 0.00232, 0.02011 ± 0.00334, and 0.01691 ± 0.00121 mg GAE/mL for lobeira, pequi, and baru starch extracts, respectively. These findings demonstrate that botanical origin influences the structural organization, morphology, and thermal degradation of the starches, while residual non-starch constituents may also contribute. The three Cerrado sources therefore yielded starches with distinct physicochemical profiles, supporting further investigation for technological applications.