Fermentation enhances finger millet and soybean nutritional value and functional properties in functional foods.

The ever-increasing global malnutrition, environmental degradation, and food insecurity challenges have intensified interest in sustainable food systems and underutilized crops. Fermentation improves the nutritional quality, digestibility, shelf life, and sensory attributes of plant-based foods. Finger millet (Eleusine coracana) and soybean (Glycine max) are promising for functional food development due to their complementary nutrient profiles. Finger millet is rich in minerals, fibre, and polyphenols, while soybean provides high-quality protein and bioactive compounds. Their synergistic amino acid profiles and the benefits of fermentation—such as improved micronutrient bioavailability and reduced antinutritional factors—make them suitable for developing innovative fermented foods. Therefore, this review evaluates the nutritional value, fermentation potential, and health-promoting properties of finger millet and soybean for sustainable nutrition and food security. A narrative review following PRISMA principles was conducted using Google Scholar, PubMed, ScienceDirect, and Scopus. Literature from 2000–2025 on finger millet, soybean, fermentation, and functional foods was searched, yielding 116 records. After screening, 59 peer-reviewed studies were included. Two reviewers independently extracted and analysed data through thematic synthesis on nutritional composition, fermentation methods, microbial ecology, functional properties, and health benefits. The literature shows that fermentation significantly enhances the nutritional and functional value of both crops. Fermentation reduces antinutritional factors such as phytates and tannins, improves protein digestibility, and increases mineral bioavailability. Lactic and acetic acid fermentation also enhance flavour, texture, and shelf stability. However, the review identified a major research gap: few documented fermented foods combine finger millet and soybean despite their complementary nutritional profiles. Finger millet and soybean present strong potential for developing next generation fermented functional foods that address malnutrition, lactose intolerance, and dietary protein deficiencies. Nevertheless, several challenges remain, including fermentation standardization, sensory acceptance, limited infrastructure, and insufficient characterization of microbial communities and bioactive metabolites. Advancing multi-omics research, improving fermentation technologies, and promoting supportive policies and value chains will be critical for translating these crops into scalable, sustainable food innovations.