From Millet Waste to High-value Products: A Circular Approach to Food, Nutraceutical and Biopolymer Applications

Abstract

Millet processing generates substantial quantities of underutilised by-products, including bran, husk, seed coat, germ fractions, broken grains and lignocellulosic residues. Although these materials are commonly discarded, burned or used as low-value feed, they contain valuable dietary fibre, phenolic compounds, flavonoids, proteins, peptides, lipids, minerals and other bioactive constituents. This review examines the composition and bioactive potential of millet-processing residues, emerging recovery and valorisation technologies, and applications in food, nutraceutical and biopolymer systems within a circular biorefinery framework. Recent research indicates that millet processing residues can serve as promising raw materials for the development of value-added food, nutraceutical and biomaterial products. Conventional and emerging approaches, including enzymatic hydrolysis, fermentation, ultrasound-assisted extraction and microwave-assisted extraction, can improve the recovery and functional properties of bioactive compounds from these residues. Recovered phenolics, dietary fibre and protein-derived peptides have potential applications in functional foods, beverages and nutraceutical formulations, while starch-rich fractions can be explored for biodegradable films and food-packaging materials. Lignocellulosic residues such as husk and straw can further contribute to the production of bio-based composites, biochar and energy, supporting a cascading utilisation strategy. Integrating these pathways within a circular biorefinery framework can reduce waste generation, improve resource efficiency and create additional economic value from millet-processing streams. Future research should emphasise process optimisation, scalability, safety, techno-economic feasibility, life-cycle assessment, regulatory compliance and consumer acceptance to facilitate sustainable industrial implementation.