Valorization of Microalgae as Multifunctional Protein Sources in Plant-Based Systems: Structural, Functional, and Processing Challenges

The growing demand for sustainable protein sources has intensified interest in plant-based food systems. Pulses are well established and recognized as nutritious, sustainable protein sources (~15–30% dry weight), rich in lysine and limited in cysteine, methionine, and tryptophan amino acids. In contrast, Spirulina is characterized by a complete amino acid profile, high protein content (~50–70% dry weight), and bioactive potential. This comprehensive review explores the role of Spirulina as a complementary protein source in plant-based systems, with emphasis on its structural, technofunctional, and processing characteristics. A literature analysis was conducted to identify advances, trends, and gaps in their incorporation into food matrices. The findings indicate that, despite their nutritional and functional advantages, the application of microalgae and beans remains constrained by sensory and technological challenges, such as off-flavors and textural issues. The combination of microalgae with pulse-based ingredients represents a promising strategy to enhance amino acid balance, improve functionality, and develop nutritionally enriched products. Studies addressing multi-component systems remain scarce, especially in bakery and flour-based applications, as well as in understanding synergistic interactions between microalgae and pulse proteins in food matrices. This review highlights the potential of microalgae as key ingredients in next-generation food formulations. It identifies critical gaps that must be addressed to enable their broader application in food products.