Thermal and non-thermal bioprocessing: a comprehensive review on millet starch properties and digestibility

Abstract Millets are known for their unique nutritional composition and functional properties, making them a promising solution to nutritional challenges and food security. This review examines the effects of various processing techniques, both thermal (such as cooking, boiling, roasting, and extrusion) and non-thermal biological (such as fermentation and germination), on the properties of millet starch, its digestibility, and nutritional value. Thermal processing methods cause gelatinization, retrogradation, and structural changes in millets, which in turn affect their digestibility, texture, and nutritional attributes. Non-thermal bioprocessing methods, like fermentation, modify starch composition and increase the availability of bioactive compounds in millets, while germination boosts nutritional content and reduces anti-nutritional factors. This review summarizes recent research explaining the mechanisms through which these processing techniques influence millet starch properties and addresses the importance of optimizing processing parameters such as time, temperature, and moisture levels to achieve desired product characteristics while minimizing nutrient loss. Additionally, the implications of these processing methods for improving the functionality, sensory qualities, and nutritional value of millet-based products are discussed. Overall, this review provides valuable insights into processing strategies to enhance the nutritive value and functionality of millets in diverse food applications.