Antinutrient Dynamics in Fermented Composite Cereal–Legume Foods: A Systematic Review of Processing Effects and Nutritional Implications (2015–2025)

<ns3:p>Composite cereal–legume foods are increasingly being recognized as important dietary interventions for improving nutritional quality and addressing micronutrient deficiencies, particularly in developing countries. This systematic review evaluated the effectiveness of fermentation and associated processing methods in reducing antinutritional factors and improving nutrient bioavailability in composite cereal–legume foods reported in Nigeria between 2015 and 2025. The systematic review adopted the Preferred Reporting Items for Systematic and Meta-Analysis (PRISMA)-aligned search strategy table and screening flow diagram approach. Generally, findings from the reviewed studies indicate that fermentation is an effective approach to antinutritional reduction in composite cereal–legume foods. In addition, with respect to the influence of combined processing methods on antinutrient degradation, a major observation from the reviewed studies was that the combination of fermentation with other processing methods, such as germination, roasting, or soaking, could lead to an increase in antinutrient reduction more effectively than fermentation alone. Furthermore, synthesized studies indicate that fermentation duration and conditions influence the extent of antinutrient degradation in composite foods. From the study findings, cereal-legumes interact with antinutrient dynamics. Composite grain systems have been reported to induce complex biochemical interactions between different plant matrices. Another key observation from the synthesized studies was the variability and susceptibility of different antinutrients to fermentation. Overall, evidence from the reviewed studies revealed that fermentation is an important processing approach for improving the nutritional quality of composite grains.</ns3:p>