Papaya Seed as a Potential Protein Source: Proposed Extraction Methods and Future Recommendations

Abstract

Papaya (Carica papaya L.) seeds are an underutilized fruit-processing by-product with potential as a source of plant protein. This review evaluates the potential of papaya seed protein as an alternative protein resource, with emphasis on its composition, nutritional characteristics, extraction methods, and techno-functional properties. Available evidence indicates that papaya seeds contain a substantial protein content, although reported composition varies with ripening stage, cultivar, and processing method. Globulins have been identified as the major protein fraction, while the amino acid profile includes several essential amino acids, with methionine occurring at relatively low levels. Conventional alkaline extraction has been used to recover papaya seed protein, whereas aqueous enzymatic extraction has reported higher protein extraction rates under optimized conditions. Pulsed electric field and high-voltage electrical discharge treatments have also demonstrated potential for improving protein release. Emerging technologies, including ultrasound, microwave-assisted extraction, and deep eutectic solvent-based extraction, may offer additional opportunities to improve protein recovery and functionality, although evidence specific to papaya seeds remains limited. Overall, papaya seed protein represents a promising yet understudied plant protein resource. Further research should focus on standardized extraction methods, structure–function relationships, nutritional and safety evaluation, optimization of emerging extraction technologies, and validation in real food systems.