Extraction of monguba (Pachira aquatica) starch by different methods and evaluation of phenolic compounds and minerals after in vitro digestion

Monguba (Pachira aquatica) is a tropical species found in different regions of Brazil, including Cerrado areas. Its seeds contain starch, minerals, and phenolic compounds associated with antioxidant activity, characteristics that arouse interest in the food application of this raw material. This study aimed to compare four starch extraction methods from monguba seeds and to determine the levels of total phenolic compounds and minerals in the seed and in the obtained starches after the oral, gastric, and intestinal phases of in vitro digestion. The fruits were collected in Barra do Garças, Mato Grosso, and stored at −18 °C. Starch was extracted using four methods: water; 0.1 mol/L NaOH; 0.2% SO₂; and a combination of 0.2% SO₂ with 0.1 mol/L NaOH. The seed and the starches were subjected to in vitro gastrointestinal digestion following the INFOGEST protocol. Total phenolic compounds were quantified using a colorimetric method with Folin–Ciocalteu reagent. Mineral composition was determined by X-ray fluorescence spectrometry using Epsilon 4 equipment and expressed in mg/100 g of sample and percentage of daily reference value (%DV). Phenolic compound contents varied among samples and evaluated phases. The seed presented the highest values in the oral (61.38 ± 2.89 mg/100 g) and gastric (95.72 ± 3.98 mg/100 g) phases. Among the starches, the one extracted with NaOH showed the highest level in the oral phase (18.15 ± 0.19 mg/100 g). Starch obtained with SO₂ stood out in the gastric (35.12 ± 2.81 mg/100 g) and intestinal (42.78 ± 4.19 mg/100 g) phases. In the gastric phase, the seed presented the highest phenolic compound content among samples, while in the intestinal phase, starch extracted with SO₂ was highlighted. Starches showed distinct mineral profiles: in the oral phase, the highest %DV were for Cu in starches extracted with H₂O (858.89%) and SO₂ (696.67%), and for Mn in the combined method (895.22%) and NaOH (726.09%). In the gastric phase, besides Cl, Cu in the NaOH method (36.67%) and Mn in the same method (36.52%) were highlighted. In the intestinal phase, the highest values among starches were for Cu in H₂O (30.00%), Fe in NaOH (27.11%), and Mn in the combined method (26.09%). The results indicate that extraction methods and digestive phases are associated with differences in phenolic and mineral contents, reinforcing the interest in investigating the use of monguba for food applications.