Optimization of polysaccharide extraction from foxtail millet husk and characterization of its structure and antioxidant activity

Abstract

Foxtail millet is a widely cultivated cereal crop in arid regions particularly across Asia and Africa, and has been used primarily as animal feed. Recent research has mainly focused on the nutritional value and potential health benefits of millet endosperm and bran layers, while millet husks have been little investigated. This study aimed to study the extraction of polysaccharides from foxtail millet husk (FMH) and optimize the extraction yield of water-soluble (SDF) and insoluble dietary fibers (IDF). Single-factor experiments identified key parameters, including solid-to-liquid ratio, extraction time, temperature, and solvent concentration (NaOH). Response surface methodology (RSM) determined the optimal conditions for SDF extraction, which included a temperature of 82.2 °C, a time of 5.1 h, and a solid-to-liquid ratio of 1:20 (g/mL), with 3.65 % yield. For IDF extraction, the optimal conditions were a temperature of 81 °C, a solid-to-liquid ratio of 1:20 (g/mL), a time of 5.13 h and a NaOH concentration of 0.62 mol/L, with 12.4 % yield. The molecular structures and antioxidant activities of the optimally extracted polysaccharides were analyzed to explore their potential functions. FMH fibers were found to have complex molecular structures and significant antioxidant activities, suggesting their potential application as nutraceutical and functional food ingredients to improve health.