Valorization of carbohydrate-rich by-products through thermoplastic extrusion: A systematic review of recent advances

• High-fiber CBPs require extrusion adjustments for efficient product quality. • CBPs enhance extrudate nutrition but may reduce heat-sensitive antioxidants. • Fruit and cereal CBPs yield nutritious expanded snacks and extruded flours. • Extrusion improves CBPs' functional properties in extruded products. • Sensory challenges arise when incorporating CBPs into extruded foods. Carbohydrate-Rich By-Products (CBPs) are plant-based agro-industrial residues rich in starch and/or dietary fiber; their polysaccharide matrix (amylose/amylopectin and non-starch polysaccharides) underpins melt viscoelasticity and structure formation, making them suitable for thermoplastic extrusion. This systematic literature review synthesizes recent advances in the valorization of CBPs through thermoplastic extrusion and its impact on food manufacturing, focusing on the optimization of process parameters and the technological, nutritional, and sensory properties of extruded products. An exhaustive Scopus search (PRISMA) identified 35 studies published between 2019 and 2024. The results indicate that the most utilized CBPs originate from fruits (44%) and cereals (36%), primarily incorporated into the production of expanded snacks and extruded flours. Given the high fiber content and variable starch and protein levels in these by-products, extrusion parameters, such as feed moisture, temperature, screw speed, and extruder design, must be tailored to ensure efficient processing and product quality. Extrusion enhances the techno-functional properties of CBPs, increasing solubility and water absorption capacity, and can elevate dietary fiber and essential amino acids content. However, it may negatively affect heat-sensitive bioactive compounds like antioxidants. The developed products showed technological and nutritional improvements, although challenges were identified in sensory acceptance. Valorization of CBPs via thermoplastic extrusion is a viable strategy to reduce food waste and develop nutritious, sustainable products, provided that process parameters are carefully optimized considering the specific properties of the by-products.