Millet Fermentation: Biochemical Transformations, Health Impacts, and Enhanced Nutritional Profiles

Abstract: Millets represent a diverse collection of small-seeded cereals, attracting increased attention due to their notable nutritional composition, environmental adaptability, and potential in the development of functional foods. They naturally contain many essential amino acids, dietary fibre, slowly digestible carbohydrates, and bioactive compounds, including flavonoids and phenolics. Their low glycaemic index and gluten-free status make them especially suitable for managing lifestyle-related conditions such as diabetes and cardiovascular diseases. However, the presence of anti-nutritional factors, including tannins, phytic acid, and enzyme inhibitors, may limit the bioavailability of essential nutrients. Millet fermentation represents a biotechnological approach that significantly enhances the nutritional, sensory, and functional properties of the grain. This review focuses on the metabolic activities of both native and introduced microbial consortia, examining the biochemical changes that occur during the fermentation of various millet species. Anti-nutritional factors are degraded, vital micronutrients become more bioavailable, protein digestibility is improved, and bioactive molecules are generated as a result of these activities. The health effects of consuming fermented millet, such as modulation of gut microbiota, antidiabetic potential, antihypertensive properties, and antioxidant activity, are rigorously assessed. Conventional fermentation techniques are discussed within the framework of emerging biotechnological strategies, such as the use of controlled fermentative systems and starter cultures. This review emphasizes the importance of millet-based fermented foods in addressing global challenges, including food security, undernutrition, and the rising burden of noncommunicable diseases.