INFLUENCE OF DIFFERENT EXTRACTION METHODS ON THE YIELD, TECHNOLOGICAL AND THERMAL PROPERTIES, AND DIGESTIBILITY OF MONGUBA (Pachira aquatica Aubl.) SEED STARCH

Brazilian biodiversity includes non-conventional food plants such as monguba (Pachira aquatica), whose seeds are an underexplored source of starch and minerals. This study compared four starch extraction methods and characterized the resulting products regarding composition, structure, thermal and technological properties, and in vitro digestibility. Fruits were collected in Barra do Garças, Mato Grosso, Brazil, and stored at −18 °C. Starch was extracted using water, 0.1 mol/L NaOH, 0.2% SO₂, or a combination of 0.2% SO₂ and 0.1 mol/L NaOH. Extraction yield, color, proximate composition, total starch content, water absorption, solubility, swelling power, and gel clarity were evaluated. Relative mineral composition was analyzed by X-ray fluorescence (XRF). Crystalline structure, functional groups, and thermal properties were investigated using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetry (TG), and differential scanning calorimetry (DSC). Digestibility was assessed using the modified Englyst method. Aqueous extraction produced the highest lightness (L* = 78.16), whereas the combined method produced the lowest (L* = 70.75). Compared with the seeds, extracted starches exhibited higher fiber (16.61–23.26%) and protein (6.30–8.72%) contents and lower carbohydrate contents (69.04–74.32%). The combined method yielded the highest total starch content (67.68%), whereas monguba seeds had the lowest (3.31%). Aqueous extraction provided the highest water absorption capacity (203.08 ± 14.66%) and gel clarity (78.9 ± 0.05%T). Starch extracted using SO₂ exhibited the highest resistant starch fraction (63.48 ± 3.03) and the lowest rapidly digestible starch fraction (8.35 ± 3.96). XRD revealed crystalline regions, while FTIR spectra displayed characteristic polysaccharide bands and differences associated with molecular organization. Thermal decomposition began at approximately 250 °C for starch extracted using SO₂ and 320 °C for starch extracted using NaOH. XRF analysis indicated higher relative proportions of Ca following SO₂ extraction, Mg following NaOH extraction, and K and Rb following the combined method. In the ashes, aqueous extraction resulted in higher proportions of CaO, Fe₂O₃, and CuO; NaOH extraction resulted in higher proportions of MgO and P₂O₅; and the combined method resulted in a higher proportion of MnO. Differences in water absorption and gel clarity suggest distinct behaviors during gel preparation and other applications. The higher resistant starch fraction obtained with SO₂ highlights the relevance of digestibility when selecting extraction conditions. Overall, the extraction method influenced monguba starch characteristics, supporting process selection according to the intended technological application.