From off-flavor mitigation to flavor engineering: Redefining marine microalgae as natural flavor modulators in food systems

Marine microalgae are promising sustainable food ingredients, offering multifunctional potential in the food industry. Despite their nutritional value, widespread commercial use of microalgae biomass remains constrained by persistent sensory challenges, including undesirable fishy, grassy, sulfurous and bitter off-flavors that compromise consumer acceptance even at low inclusion levels. Previous reviews have generally addressed volatile chemistry, off-flavor mitigation, food applications, and sensory acceptance separately. This review critically integrates these dimensions within an application-oriented flavor-engineering framework linking flavor-active compounds, technological interventions, food-matrix compatibility, and sensory evaluation. Current evidence associates major off-flavors with dimethyl sulfide derived from dimethylsulfoniopropionate degradation, trimethylamine, and lipid oxidation products. On the contrary, the compounds glutamate, aspartate, and 5′-ribonucleotides generally found in marine microalgae are responsible for umami taste with desirable savory, meaty, or brothy attributes. In addition, some carotenoid-derived volatiles may contribute positively with floral or fruity notes. Research findings indicate that selected cultivation and bioprocessing conditions can modify biochemical composition and volatile profiles, but perceptible effects remain species-, process-, and matrix-dependent. Genetic and metabolic engineering approaches, including CRISPR/Cas, remain prospective for targeted flavor modulation. Major gaps include limited quantitative VOC and odor-activity data, lacking integration of chemical profiles with sensory and consumer responses, and deficient validation across strains, processing conditions, and food matrices. In sum, this review underscores the evolution of flavor engineering applied in microalgae biotechnology as a method that guides food design, but it still needs more testing with marine microalgae, elevating the credibility of microalgae as functional ingredient in food systems.