Cactus Fruits are Promising Sources of Betalains: A Systematic Review of Extraction and Microencapsulation Strategies for Food Colorant Applications

Betalains are water-soluble nitrogenous pigments biosynthesized from L-phenylalanine or L-tyrosine that impart red–violet and yellow–orange hues to fruits and beetroot. They are chemically labile to extrinsic stressors, thereby motivating stabilization strategies. The key scientific advances related to extraction methods and microencapsulation strategies for fruit-derived betalains were elucidated, with an emphasis on the critical appraisal of knowledge gaps relevant to process optimization and industrial scale-up. Following PRISMA principles, 272 records were screened, of which 15 studies met the inclusion criteria. These studies covered four betalain-producing fruit genera, all belonging to the family Cactaceae, predominantly Hylocereus polyrhizus (red pitaya). The studies employed conventional solid–liquid extraction, mechanical juice or pulp preparation, and ultrasound-assisted extraction, with heterogeneous operating conditions that limited direct comparisons. Subsequent stabilization was most consistently achieved by spray drying using maltodextrin-based wall matrices, either alone or blended with other biopolymers. Composite protein–polysaccharide matrices expanded stabilization options, but pigment retention, thermal protection, and release required separate evaluation. Further application trials are required for bakery, dairy, sauce, and meat products, as well as for freshness-monitoring systems.