Obtenção de amido a partir do subproduto do Feijão-caupi verde (Vigna unguiculata (L.) Walp.) e extrato hidroalcoólico da vagem do feijão: caracterização físico-química, análise toxicológica, microbiológica e utilização para produção de microesferas

Abstract

In Brazil, cowpea is a highly important food crop and is cultivated in more than 50 countries worldwide. However, its processing generates residues (pods) and by-products (slightly defective grains), which can be repurposed. Starch, a carbohydrate found in various plants and legumes, has promising industrial potential due to its biodegradability and non-toxicity. Currently, studies have explored the use of starch and plant extracts to produce microspheres, which enhance stability, bioactive compound delivery, and the nutritional value of the matrices used. Thus, the present study aimed to valorize residues and by-products from the processing of green cowpea (Vigna unguiculata (L.) Walp.), focusing on the extraction, characterization, and production of starch–extract microspheres. Four starch extraction methods were evaluated, and the starch obtained by the highest-yield method was selected. The selected starch was characterized for proximate composition, apparent amylose and amylopectin content, FT-IR, NMR, XRD, SEM, GPC, TGA, and DSC, and was subsequently used to produce pod extract microspheres using spray drying technology. The extract was characterized for total phenolic content, antioxidant activity, acute toxicity against Danio rerio, and antimicrobial activity. The microspheres were characterized by color analysis, FT-IR, XRD, SEM, TGA, DSC, antioxidant activity, acute toxicity against Danio rerio, and antimicrobial activity. Ultrasound-assisted extraction showed a yield of 43.70%, with 4.4005 ± 0.42% protein, 8.350 ± 0.095% moisture, 0.188 ± 0.11% ash, pH 6.623 ± 0.136, and amylose and amylopectin contents of 10.99 ± 2.35% and 89.01 ± 2.35%, respectively. The starch exhibited typical physicochemical characteristics of carbohydrates, high purity, preserved morphology, a crystalline pattern typical of conventional starches, and thermal stability suitable for industrial applications. The extract showed low antioxidant activity (0.1344 ± 0.0127 μmol Trolox/g sample) and low total phenolic content (TPC = 48.89 mg GAE/100 g sample), and also reduced zebrafish locomotor activity. However, it demonstrated considerable antimicrobial activity against Staphylococcus aureus, with inhibition halos ranging from 8.357 ± 1.319 to 12.567 ± 0.252 mm. The starch–extract microspheres also exhibited considerable antimicrobial activity against S. aureus, in addition to helping preserve the extract’s properties and the morphological and physicochemical characteristics of the starch. It can be concluded that the residues and by-products generated from green cowpea processing have potential to be converted into higher value-added products, contributing to the development of new products and more sustainable industrial practices.