Climate-Resilient Crops as Gluten-Free Substitutes: A Systematic Review of the Nutritional, Technofunctional, and Rheological Properties of Sorghum, Pearl Millet, and Amaranth

Background: Gluten-free flours are essential alternatives for individuals with gluten intolerance, providing various nutritional benefits. Despite the increasing prevalence of gluten intolerance, there is limited systematic research on the potential of drought-tolerant grains like sorghum, pearl millet, and amaranth as gluten-free flour substitutes. Aims: This study aims to review the nutritional, functional, and baking properties of gluten-free flours derived from red and white sorghum, pearl millet, and amaranth, assessing their viability as alternatives to wheat for gluten-intolerant individuals. Methods: A systematic review was conducted following PRISMA guidelines, analyzing 30 peer-reviewed articles published between 2015 and 2024, primarily from Asia and Africa. Results: White sorghum flour had the highest zinc concentration (13.20 mg/g), while red sorghum had the highest iron levels (28.93 mg/g). Amaranth flour demonstrated the highest protein content (25.5%) and crude fiber (15.9%). In contrast, pearl millet had the lowest iron (0.11 mg/g) and crude fiber content (0.6%). Among functional properties, pearl millet showed the highest water absorption capacity (359.33% ± 1.45), whereas white sorghum had the lowest (1.07% ± 0.04). Amaranth exhibited the highest oil absorption capacity (1.88 g/g ± 0.01), while pearl millet had the highest swelling index (8.17 mL/mL ± 0.01). In terms of baking properties, specific volume was the most frequently analyzed parameter, with pearl millet presenting the highest specific volume (4.87 cm³/g). Amaranth flour was identified as the best gluten-free option, excelling in loaf volume, porosity, and firmness. Conclusion: The study suggests that utilizing traditional grains can help meet the growing demand for gluten-free products, highlighting their significant potential in the gluten-free market. Future research should focus on optimizing flour blends to enhance nutritional value and baking performance by incorporating conventional ingredients and innovative techniques to replicate the gluten network.